^In^^?i^:i^^^ff^ RK510H49^'91)Y^363 ^"' ^^e administration ( RECAP THE ADMINISTRATION OF NITROUS OXIDE & OXYGEN FOR DENTAL OPERATIONS. Commbia Winibttsiity in tije Citp of iSteto gorfe \ "^ ^cijool of Bental anb #ral ^urgerp Digitized by the Internet Arciiive in 2010 with funding from Open Knowledge Commons http://www.archive.org/details/administrationofOOhewi THE ADMINISTRATION OF NITROUS OXIDE AND OXYGEN FOR DENTAL OPERATIONS. THE ADMINISTRATION OF Nitrous Oxide and Oxygen FOR DENTAL OPERATIONS FREDERIC W. HEWITT, M.A., M.D., Cantab. Anasthetist to His Majesty the King ; Consulting AncEsthetist and Emeritus Lecturer ott Anesthetics at the London Hospital : Late Anesthetist at the I^ondon Hospital, Charing Cross Hospital, and the Dental Hospital of London SECOND EDITION XonDon CLAUDIUS ASH & SONS, Limited 5, 6, 7, 8 and 9, BROAD STREKT, GOLDEN SQUARE Philauelphia THE S. S. WHITE DENTAL MAN U FRACTURING CO. Chestnut Streict, Corner 'Iwei.fth KKS'IO ' ! 4 A m^o I TO THOSE OF THE PAST AND PRESENT SURGEONS AND ASSISTANT SURGEONS OF THE DENTAL HOSPITAL OF LONDON WITH WHOM 1 WAS ASSOCIATED WHILST MAKINc; THE OBSERVATIONS HEREIN CONTAINED, I VENTURE TO DEDICATE THIS LITTLE BOOK IN GRATEFUL RECOGNITION OF THE PATIENCE AND COURTESY WHICH THEY INVARIABLY DISPLAYED DURING THE PROGRESS OF THE INVESTIGATION. PREFACE TO THE SECOND EDITION. Since the appearance of the first edition of this little book, the system of administering oxygen with nitrous oxide has become firmly established in dental practice. The only correction, worthy of the name, which it has been necessary to make in pre- paring the present edition, will be found in the first chapter. Thanks to a reference dis- covered and kindly furnished me by Messrs. Ash and Sons, it is now perfectly clear that the credit of first employing oxygen with nitrous oxide should be given to Andrews of Chicago. The only additional matter of any import- ance is to be found in Chapter II., which contains a resume of the research to which reference was made in the Preface of the lormer edition, and also a description of a Slight modification in my apparatus, by which I am enabled at any moment during an ad- viii. Preface to the Second Edition ministration to suddenly increase the oxygen percentage to any desired extent, and so to successfully deal with exceptional cases. FREDERIC W. HEWITT. 14, Queen Anne Street, Cavendish Square, W. October, 1901. PREFACE TO THE FIRST EDITION. Eleven years have elapsed since I commenced working at this subject. The first eight years were mainly devoted to conducting prelimi- nary experimental administrations of various mixtures of nitrous oxide and oxygen, and to devising and perfecting apparatus. The last three years have been occupied in ascer- taining the precise influences exerted by this or that percentage of air or of oxygen upon the usual asphyxial phenomena of pure nitrous oxide. My original intention was to incorporate in one volume the results of both parts of the research, but I have since decided to adopt a different course, and to first place in the hands of the medical and dental professions this small treatise dealing more particularly with the practical aspects of the subjects, and subsequently to bring forward the large mass of evidence which I now possess concerning the physiological effects of different mixtures of nitrous oxide with air or oxygen. X. Preface to the First Edition Safe and thoroughly efficient anaesthesia for dental operations is of such importance that it behoves every dental practitioner to carefully consider whether he should not abandon the prevalent but comparatively crude and unscientific method of producing insensibility from nitrous oxide and avail himself of the new system. It is true that there are at present some difficulties in the way of this advance, but it is to be hoped that they may soon be sur- mounted. The principal of these undoubtedly is the difficulty of obtaining proficient anaes- thetists. Increased facilities, however, are now being afforded at most hospitals for acquiring experience in administering anaes- thetics, so that there is every reason to believe that in course of time there will not be that dearth, which now exists, of medical men capable of administering nitrous oxide in dental practice. Moreover, I hope to see the day when the immense amount of clinical material which is now being wasted, so to speak, at our dental hospitals, will be utilised, not only for the systematic instruction of dental students who are intending to qualify in medicine, but for that of extraneous students and practitioners. In this way it would be possible to efficiently train medical men in dental anaesthetics, and Preface to the First Edition xi. to keep the dental profession supplied, as it were, with proficient anaesthetists throughout the country. FREDERIC W. HEWITT. lo, George Street, Hanover Square, W. May, 1897. CONTENTS. PAGK Chapter I. — Introduction ... ... ••• i Early history of nitrous oxide ; its discovery by Priestley ; recognition of its anaesthetic properties by Davy ... ... ... ■•• ^ Colton's lectures ; Horace Wells the first to inhale nitrous oxide for a surgical opera- tion ; " Laughing Gas" ... ... ••■ 2 Early administrations of nitrous oxide; air mixed with the nitrous oxide ; symptoms due to this admixture ; Smith's and Colton's administrations ... ... ... ••. 4 Rymer's administrations ; Evans' demonstra- tion ; Clover's improvements ... ... 5 Nitrous oxide now administered free from all air ; asphyxial phenomena ; only suitable for brief operations ... ... ... ••• 6 Nitrous oxide and oxygen first used by Andrews, of Chicago •■• 7 Paul Bert's researches; his attempts to obtain anaesthetic effects without asphyxia) mani- festations, by using nitrous oxide and air under increased barometric pressure ... 7 Oxygen used'instead of air ; Bert's experiments continued ... ... ... ■•• ••• 9 Bert's method applied to practice ; the pheno- mena observed ... ... ■•• ••• 9 Klikowitsch's, Winckel's, Doderlein's and Zweifel's administrations ... ... ••• 10 Martin (of Lyons) and his trial of Bert's method 1 1 xiv. Contents PAGE Bert's attempts to obtain good effects without employing increased pressure ... ... 12 Hillischer's work; "Schlafgas"; 15,000 ad- ministrations; his regulating apparatus ... 13 Witzel's administrations ... ... ... 15 The Author's work ; early administrations ; 13 forms of apparatus devised ... ... 15 Sudden transitions in composition of mixture not desirable ; experiments with different percentages of oxygen ... ... ... 16 Necessity of absolutely excluding air ; the effect of administering the gases from a dis- tended bag ... ... ... ... ... 17 10 per cent, of oxygen found to be preferable to i2f per cent. ; but no definite percentage answered in all cases... ... ... ... 17 Difficulties in obtaining a suitable apparatus ; objections to Hillischer's apparatus ; a satis- factory apparatus eventually devised ... 18 Chapter II. — Apparatus ... ... ... ... 20 I. Gasometer methods ; the best percentages of oxygen ... ... ... ... ... 20 Resume of a research conducted by the author ; nitrous oxide administered with 3, 4, 5, 6, 7, 8, g, 10, II, 13 and 20 percent, of oxygen ; duration of inhalation ; average duration of the after-anaesthesia ; average quantity of mixture used ; degree of " jactitation " (anoxasmic convulsion) ; alterations in colour ; stertor ; phonation ; reflex and excitement- movements ; after-effects ... 21 Chart showing general results obtainable by (a) pure nitrous oxide ; (b) nitrous oxide mixed with different percentages of air ; and (c) nitrous oxide mixed with different percentages of oxygen ... ... ... 23 Objections to use of definite mixtures of nitrous oxide and oxygen ... ... ... 24 Contents I'AGE Keeping the two gases together before use ... 24 2. The Author's regulatuig apparatus; re- quirements that must be fulfilled by a regulating apparatus ... ... ... ... 25 Cylinders for the two gases ; combined stand and union ... ... ... ... ... 27 Tubes for transmitting gases from cylinders to bags 30 Regulating stop-cock and mixing chamber ; its various parts ; its flange with figures ; its oxygen inlets ... ... ... ... 30 Its valves 34 Face-pieces ... ... ... ... ... 35 Necessity for carefully handling and examin- ing the apparatus ; the relative proportions of the two gases passing through the apparatus ... ... ... ... ... 36 Slight differences in action in different models; makers of the apparatus ... 35 Chapter III. — Preparations 37 Precautions as to diet ... ... ... ... 37 Stimulants ... ... ••- ••• ■•• 3^ Everything should be in readiness before patient enters room ; appliances which should be at hand in case of emergency... 38 Necessity for the presence of a third person 39 Importance of loose clothing 39 Influence of posture ; Use of inflated air- cushion... ... ... ••• ••■ ••• 40 Mouth-props and their insertion ; treatment of retching movements excited by inserting mouth-prop ... ... ••• ••• ••■ 4^ Chapter IV.— The Administration 43 All disturbing influences to be avoided ... 43 Application of face-piece 44 xvi. Contents PAGE How the patient should breathe ; air first of all inhaled through the apparatus ... ... 44 Then nitrous oxide with a small percentage of oxygen ... Initial sensations The fitting of the face-piece ... The fulness and relative sizes of the bags The admission of oxygen Proper adjustment of the proportions; too much oxygen ; too little oxygen Characteristics of nitrous oxide and oxygen anaesthesia Signs of the anaesthesia " Respiratory calm " ... ... '..., The pulse and circulation The eyes and eyelids The delayed effects of admitting more or less oxygen ... The length of inhalation Quantity of mixture required ... Chapter V. — The Patient Different types of patients Influence of sex and age General condition of patient ... Physique... The presence of a beard or moustache Temperament Complexion; colour Alcoholic indulgence The excessive use of tobacco and other nai cotics ... ... ... ... ... Frequent administrations of nitrous oxide an oxygen ... Affections of the respiratory system ... Affections of the circulatory system ... Blood pressure under the mixed gases Affections of the nervous system Pregnancy ... ... ... ... ' .. Contents xvii. PAGE Chapter VI. — The Anesthesia 71 The available anaesthesia for a dental operation ... ... ... . ... ••• 71 The duties of the anaesthetist during the operation ... ... ... ... ... 72 Duration of the available anaesthesia ... 72 State of the patient during the operation ... 74 Reflex movement ; phonation... ... ... 74 Termination of the anaesthesia ... ... 75 Re-administrations; difficult operations ... 76 Drilling into pulp-cavities ; opening up the antrum... ... ... •.• •■• 77 Chapter VII. — Exceptional Cases 78 Laughter; singing; shouting; phonation... 78 Muscular phenomena during inhalation ; strictly voluntary movements ; uncontrol- lable nervous movements ; intoxication movements; tonic spasm ... 79 Clonic spasm; "jactitation"; fine tremor... 81 Tonic movements of deep anaesthesia ... 81 Cyanosis ... ... ■■ ... ••• ••• 82 Shallow, imperceptible, or arrested breathing, with good pulse and colour ... ... ... 83 Violent respiration ... ... ... ... 83 Coughing, crying 83 Retching and vomiting during inhalation ... 83 Dangerous symptoms ... ... •■• 84 Highly exceptional cases ... ... ... 85 Chapter VIII. — After-Effects ... ... ... 87 Important to regulate diet ... ... ... 87 Recovery usually very satisfactory : often better than after nitrous oxide perse ... 87 Protracted inhalations liable to be followed by giddiness, torpor, headache, &c. ... ... 88 Nausea, retching, and vomiting ... ... 89 i. Contents PAGE Pallor, faintness, and feebleness of pulse ... go Treatment of after-effects ... ... .. 90 Hysteria ; temporary maniacal seizures ; cataleptic states ... ... ... 91 Dreams ... ... ... ... ... ... 91 Bibliography... ... ... ... ... ... 92 LIST OF ILLUSTRATIONS. Fig. I. Chart showing comparative general results obtained by (a) pure nitrous oxide ; (b) nitrous oxide with different percentages of air, and (r) nitrous oxide with different percentages of oxygen ... ... ... ... ... 23 ,, 2. The Author's apparatus ... ... 26 ,, 3. Diagrammatic section of cylinders and of combined stand and union ... 28 ,, 4. Diagrammatic section of the india-rubber transmitting tubes and bags... ... 29 ,, 5. Regulating stopcock and mixing chamber 31 ,, 6. The administration ... ... .. 45 THE ADMINISTRATION OF NITROUS OXIDE AND OXYGEN FOR DENTAL OPERATIONS. CHAPTER I. INTRODUCTION. In reviewing the past history of nitrous oxide as an anaesthetic one cannot help being struck by the singular vicissitudes which this agent has experienced. That a quarter of a century should have passed between its dis- covery by Priestley and the recognition of its pain-relieving properties by DaYy is sufficiently remarkable. But more curious still is the fact that nearly double this length of time elapsed between Davy's observations and the first ad- ministration of the gas for a surgical operation. It was during this latter interval that nitrous oxide received the name of "laughing gas," from the power it possessed, when small quan- tities were breathed backwards and forwards, of producing hilarious excitement. I 2 Introduction In December, 1844, Dr. Golton, " an itinerant lecturer on chemistry " (to use a description given of him by one of his own countrymen)/ demonstrated these effects at Hartford, Conn., U.S.A. At this entertain- ment Horace Wells, a dentist, was present, and noticing that one of the audience who had inhaled the gas had unconsciously bruised him- self whilst under its influence, he shrewdly suspected that the so-called " laughing gas " might prove to be of valuable service in den- tistry. This brilliant idea was quickly put to the test ; Colton administered the gas to Wells ; and a friend of the latter extracted a tooth during the ansesthesia thus produced. This administration of nitrous oxide, although conducted in the crudest manner, will ever deservedly remain a memorable one ; for it laid the foundation stone, so to speak, of our present system of surgical anaesthesia. The realisation of the hopes which Wells had entertained was so complete that he naturally enough looked forward to an uninterrupted and glorious reign for the new anaesthetic whose services in surgery he had been the first to requisition. His first public demonstration, however, unfortunately proved a fiasco ; and this circumstance, coupled with the fact that intense interest soon became universally felt at the discovery, by Morton, of the anesthetic Introduction 3 properties of ether, rapidly placed nitrous oxide ag"ain upon the shelf, where it remained, more or less forgotten, for a further term of nearly twenty years. A little reflection will at once show that Wells' anaesthetic was heavily handicapped in its struggle for existence. Its physical characters were against it. Being gaseous at ordinary temperatures and pressures, it was, as compared to its liquid rivals, ether and chloroform, more or less unmanageable. It was, moreover, a difficult matter to obtain the gas in a state of purity, and in sufficiently large quantities for administration. But the chief cause of the discredit into which nitrous oxide fell was the want of knowledge which necessarily prevailed as to the principles which should be followed in its administration. The methods employed by Wells and his. fol- lowers were such as to render success or failure merely a matter of chance. The administra- tion was very simply conducted. Some of the gas was placed in a bag or bladder to which was attached a tube, and the patient breathed backwards and forwards. The results which followed were necessarily exceedingly irregular, as the chronicled accounts of Wells' demon- stration and of subsequent attempts to produce anccsthesia amply testify. In addition to the fact that much of the nitrous oxide which was employed itself contained air, it must be 4 Introduction remembered that the re-breathing of a small quantity of the gas necessarily led to its dilu- tion by the air already present in the respira- tory passages. The early administrations of nitrous oxide were, indeed, administrations of nitrous oxide mixed with considerable propor- tions of nitrogen, oxygen, and carbonic acid gas, to say nothing of the impurities other than air which may or may not have been present in the anaesthetic employed for inhalation. Loud and prolonged laughter, crying, shout- ing, praying, semi-maniacal excitement, and many grotesque and amusing phenomena manifested themselves — phenomena which we now know to have been produced by the too free dilution of the gas with the oxygen of atmospheric air. In some of the cases in which teeth were removed no pain was ex- perienced ; in others the pain was only miti- gated ; in many the pain was felt with the usual or even with more than the usual acute- ness. It was not until 1863 that nitrous oxide again began to emerge from the seclusion into which it had been forced by reverses of for- tune. , In this year a dentist named Smith, of New Haven, Conn., took upon himself the responsibility of submitting one of his patients to its influence, and the results were this time so satisfactory that Colton, who was again Introduction 5 the administrator, forthwith proceeded to New York, where, with several influential dentists, he established an Association bearing his name for the painless extraction of teeth. Writing" in March, 1881, Dr. Colton stated that no less than 121,709 administrations of nitrous oxide had been conducted by the Colton Dental Association since July, 1863, when the Asso- ciation was founded, and that no accident had occurred. The news of Colton's success soon crossed the Atlantic, and in January, 1864, Mr. Rymer, a London dentist, reported^ some experi- mental administrations of nitrous oxide which he had undertaken at the National Dental Hospital. In these experiments either a bladder or an india-rubber bag was used, and the patient breathed the gas backwards and forwards through a tube of large calibre. According to the interesting paper published by Mr. Rymer, the results were very satisfac- tory. So far as I am able to ascertain, the first apparatus which possessed valves to prevent re-breathing, was that used by Dr. Evans, of Paris, at a very successful demonstration which he gave at the Dental Hospital of London in 1868. The introduction of this improved method of administration was quickly followed by the manufacture of liquefied nitrous oxide ; and, for the first time since Horace Wells' ex- periment, nitrous oxide began to occupy an unassailable position amongst its rivals in the great field of therapeutics. Clover, whose in- genuity in devising other anaesthetic apparatus had already become conspicuous, quickly im- proved upon the still rough nitrous oxide inhalers, and laid down rules to be observed in administration. The complications which had attended the earlier administrations of nitrous oxide, if such they can be called, had been due to the pre- sence of atmospheric air in too large quantities ; those which now began to appear, with the more perfected apparatus, were of an exactly opposite nature. The recognition of the effects produced by the admission of air now led to its most stringent exclusion. The pendulum, in fact, began to swing just as far in this direc- tion as it had swung in the other. It was thought that because air produced excitement it should necessarily be wholly excluded — a view which subsequent experience has taught us to modify. With this new system of ad- ministration, it soon became clear that a more or less continuous inhalation was impossible. Given that the gas was mixed with no air or oxygen, that no re-breathing was possible, and that the inhaling apparatus fitted and worked accurately, nitrous oxide could not be given for Introduction 7 more than a very brief space of time. After the inhalation had lasted a minute or so, certain phenomena arose which necessitated the with- drawal of the anaesthetic and the admission of air. It therefore became clear that nitrous oxide was/^r excellence the anaesthetic for very- brief operations. Prolonged operations could only be accomplished under its influence, and these not very satisfactorily, by intermittently allowing air to be respired. The next step in the development of nitrous oxide ansesthesia was taken by Professor E. Andrews,^ of the Medical College, Chicago, who, after making experiments upon lower animals, succeeded in anaesthetising human beings by means of mixtures of nitrous oxide and oxygen. Andrews found that by the use of such mixtures he was able to render nitrous oxide continuously respirable, and to prevent the usual asphyxial accompaniments of the anaesthesia. Little or no notice appears to have been taken of the interesting cases published by Andrews. At all events, it was not until several years later, when the French physi- ologist, Paul Bert, began to devote attention to the subject, that the advantages of oxygen in conjunction with nitrous oxide again at- tracted attention. In a communication which Bert made to 8 Introduction the Societe de Biologic, on Feb. 9th, 1878, he stated'^ that he found the effects of toxic gases upon Hving organisms to be dependent upon their tension when breathed. Nitrous oxide was a gas which, at the ordinary atmospheric pressure, would only produce anaesthesia when administered pure, i.e., free from air. Un- fortunately, however, in administering nitrous oxide free from all air, asphyxial phenomena soon become developed. But if a mixture of one half nitrous oxide and one half air were administered in a closed chamber in which the ordinary barometric pressure could be doubled, then the blood would receive just as much nitrous oxide as when the gas was adminis- tered pure at ordinary pressures, and just as much air as would be breathed under natural circumstances. In this way prolonged anaes- thesia would be possible and asphyxia pre- vented. As we shall subsequently see, Bert's original proposition as to the necessity of em- ploying perfectly pure nitrous oxide for the production of anaesthesia was not true. He soon saw, moreover, that by using oxygen instead of air it would be unnecessary to dilute the nitrous oxide to anything like the extent above indicated, so that a compara- tively small increase in barometric pressure would be needed. On the nth May, 1878, Bert stated^ that Intvoduction g he had successfully anaesthetised a dog with a mixture of 80 per cent, of nitrous oxide and 20 per cent, of oxygen, under an additional barometric pressure of 20 cm. There was no excitement, and no material disturbance of the normal functions of respiration and circulation. The anaesthesia was everything that could be desired. On the 13th of July following he announced^ that, by his method, he had kept a dog anaesthetised, and free from asphyxial symp- toms, for half an hour ; that a manometer, placed in an artery, had not shown any per- ceptible variations in tension ; that the blood pressure had been raised by irritating exposed nerves ; that irritation of the peripheral end of the vagus had stopped the heart ; and that irritation of its central end had stopped the respiration. On Nov. nth of the same year Bert made^ a preliminary report of his results to the Academie des Sciences. On Feb. 15th, 1879, he announced^ to the Society de Biologie that two days previously his method of producing anaesthesia had been for the first time tried upon the human subject. A large air-tight metal chamber in which, by means of pumps, the barometric pressure could be raised, had been employed, and a mixture of 85 per cent, of nitrous oxide and 15 per lo Introduction cent, of oxygen had been administered from a bag by means of a face-piece with two valves, the barometric pressure in the chamber being 92 cm. (= an increase of 17 cm.). The opera- tion, which was the avulsion of a toe nail, had been a complete success. There had been no pain, very little movement, no excitement, a quiet pulse, and no loss of colour. The ten- sion of the nitrous oxide had been 85 x |f — 104 ; and that of the oxygen 15 x ff = 18*4 ; in other words, that of the nitrous oxide had been a little higher than when the pure gas was given at ordinary pressures, and that of the oxygen a little lower than that of the air (20"9). Incidentally Bert remarked that such a mixture as that which he employed would not produce anaesthesia at ordinary pressures — a point to which I shall have to refer later on. Bert's next communication^ is dated Feb. 2ist, 1880. On this occasion he advocated a total barometric pressure of 89* 5 cm. and a mixture of similar proportions to those before described. The almost ideal type of anaesthesia pro- duced by Bert's method attracted such atten- tion, especially on the Continent, that attempts were soon made to obtain similar results with- out the employment of the costly and cum- brous apparatus which Bert had devised. Thus Klikowitsch,'° Winckel," Doderlein, and Introduction 1 1 Zweifel employed a mixture of 80 per cent, of nitrous oxide and 20 per cent, of oxygen m obstetric practice, administering the gases as nitrous oxide itself is customarily administered. In most of the cases of which records are available an analgesic effect seems only to have been produced, the patient's conscious- ness having remained more or less intact whilst her pains were relieved. The first systematic application of Bert's method to dental practice was made by Dr. C. Martin, of Lyons, whose monographs'" upon the subject are of interest. Having pro- vided himself with an air-tight metal chamber and with the necessary machinery for raising the barometric pressure, he proceeded to carry out Bert's directions. He found, however, that by carrying them out to the letter he met with considerable excitement, and a "dis- turbed sleep, barely anaesthetic." The results were, in fact, inferior to those obtainable with nitrous oxide as ordinarily given. He there- fore tried an increase of barometric pressure, raising it to 95 cm., 100 cm., and even to 125 cm., but without success. He next tried 12 per cent, of oxygen instead of 15 per cent., as recommended by Bert. Anaesthesia now more rapidly ensued ; there was less excite- ment, there was no cyanosis, and recovery was satisfactory. These results were obtained with 12 Intvodiiction a pressure of 105 cm. He next raised the pressure to no cm., and for the first time obtained results comparable to those described by Bert. When any excitement began to manifest itself an increase in the barometric pressure quickly arrested it. Martin found it best to wait from 2 to 3 minutes before operat- ing, and in the event of a long anaesthesia being necessary he administered the mixture for four or even five minutes before beginning the extraction. It is interesting that he found that if the pressure w^ere only 100 cm. or 105 cni., the patient recovered more quickly than with a pressure of 115 or 120 cm. After- nausea was more frequent in the prolonged administrations than in the others. I have elsewhere'3 described an interesting experiment which Dr. Martin made upon a dog. He kept the animal breathing a mixture of 85 per cent, of nitrous oxide and 15 per cent, of oxygen under a pressure of from no to 120 cm. for three consecutive days without any untoward effects during or after the insensibility. Nothing could more forcibly demonstrate the harmlessness of the mixture than such an experiment. On April 30th, 1883, Bert read his final paper on the subject.'* Having reviewed his previous work, he stated that he had been endeavouring to produce prolonged nitrous Introdtiction 1 3 oxide anaesthesia without the employment of increased atmospheric pressure, and that he had been successful in the case of the lower animals. He regarded the alternate adminis- tration of nitrous oxide and air as objectionable. He first tried administering nitrous oxide and oxygen alternately, but the rapid elimination of the former gas in the presence of the latter led to a too sudden recovery. He next adminis- tered alternately pure nitrous oxide and a mixture of nitrous oxide and oxygen similar to that which he used in his pressure cases. He was thus able to keep a dog unconscious for half an hour. At the time of his paper he had not tried this method in human beings, nor can I find any record of his having subsequently done so. He urged surgeons, however, to give it a trial, and stated that he intended to make further experiments as to the best percentages for the mixture. Dr. Hillischer, of Vienna, a well-known dentist, was the first to systematically employ nitrous oxide and oxygen, at ordinary atmo- spheric pressures, in dental surgery. His first paper appeared"^ in 1886; his second'^ and third'7 i,-, igg^^ and his fourth'^ and fifth'^ in 1890. He suggested that the gaseous mixture should be termed " Schlafgas," from the sleep- like state into which patients passed under its inHuence, Dr. Hillischer has administered 14 Introduction nitrous oxide and oxygen in upwards of 15,000 cases, and the facts which he has brought forward fully justify him in entertaining such high opinion of the mixture he employs. In his earlier cases he used gasometers, but in latter years he has employed a regulating apparatus by which the proportion of oxygen can be increased or diminished during the administration. He very properly directs attention to the necessity of this plan, for patients vary very considerably in the per- centage of oxygen needed to secure a good type of anaesthesia. Dr. Hillischer states that he has adminis- tered " Schlafgas " to patients of all ages, to those suffering from advanced affections of the heart, to those with diseases of the lungs, and to the subjects of epilepsy and other nervous diseases. He further states that he looks upon the gaseous mixture as absolutely without con- tra-indication — that he administers it to every patient irrespective of any morbid state which may be present. He admits that far more experience is needed in administering "Schlaf- gas " than in giving any other anaesthetic with which we are acquainted ; and there can be no doubt that here, again, he is perfectly correct. As to the percentage of oxygen, he finds it best, in most cases, to commence with 10 per cent, and to gradually increase this to 15 or even 20 Introduction 15 per cent. With regard to alcoholic subjects and others who are rebellious to the influence of nitrous oxide with 10 per cent, of oxygen, he reduces the proportion to 5 per cent, or even less. On the other hand, if he finds that the breathing becomes laboured, or that the features assume a cyanotic appearance, he increases the percentage of oxygen. Dr. Witzel, of Essen-on-the-Ruhr, has also administered nitrous oxide and oxygen for a large number of dental operations, and in some interesting lectures which he published^" in 1889, he strongly urged the advantages of the mixture and the correctness of Hillischer's views. In 1886 I commenced, at the Dental Hos- pital of London, a series of experimental ad- ministrations of nitrous oxide and oxygen, at ordinary atmospheric pressures, with the object of ascertaining the best method for general use. It would serve no useful purpose to describe, on the present occasion, the numerous procedures which were adopted. No less than 13 distinct plans were tried, each of which necessitated a different form of apparatus. Those who are specially interested in the matter, however, will find, in another publi- cation,"' a full description of the stages by which I arrived at the apparatus which I brought out in 1894 — and which is fully i6 Introduction described in the following chapter. That it should have taken so long to devise a work- able method may appear remarkable. But the fact is that, as the experiments proceeded, so it became more and more clear that attention had to be paid to the minutest possible details. One of the first points that became obvious was that sudden transitions in the composition of the oases breathed were to be avoided. o For example, no good results could be obtained by suddenly changing from ordinary nitrous oxide to a mixture containing a considerable percentage of oxygen ; or from one containing a small to one containing a large percentage ; or vice versa. I then endeavoured to ascertain whether any definite percentage of oxygen with nitrous oxide would answer in every case. I found that in most cases a mixture containing i2f per cent, of oxygen answered admirably. By its use all asphyxial phenomena were avoided ; there was no stertor, jactitation, or lividity ; breathing continued without the slightest embarrassment ; the natural colour was pre- served ; and in most cases the anaesthesia was perfect and tranquil. In a certain number of cases, however, excitement and screaming arose, and it was necessary to let some pure nitrous oxide into the mixture in order to terminate the case satisfactorily. My results Introductory 1 7 with this mixture were published in the The next point that proved to be of import- ance was the necessity of absolutely excluding air during the inhalation. There can be no doubt that in administering nitrous oxide in the usual manner a small quantity of air is very likely to gain access to the lungs, either under the face-piece, or at the expiratory valve. If nitrous oxide, with or without oxygen, be administered in such a way that the inhaling bag is kept distended, it is obvious that no such admixture of air can occur. I was at a loss for some time to account for the better results obtained in administering nitrous oxide and oxygen (the oxygen being present to the extent of 1 2^ or 10 per cent.) when the gases issued from the gasometer under slight pressure ; but there is little doubt that the explanation given is the true one, and that when the gases were given with a half-full bag small quantities of air gained access and disturbed the anaesthesia. The admixture of a small quantity of air during an ordinary administration of nitrous oxide is an advantage, at all events in most cases ; but it is not so with nitrous oxide and oxygen. I next came to the conclusion that 10 per cent, of oxygen was preferable to 12^ per 2 1 8 Intvodtictovy cent., and when this mixture was administered from a distended bag very good results occurred in most cases. It soon became clear, however, that there was no definite percentage of oxygen which in every case would prevent all traces of asphyxia, and yet would in no way interfere with anaes- thesia. Patients varied too widely for the employment of any method of this nature. It was obviously necessary to have control over the percentage of oxygen, so that it could be increased or diminished during the adminis- tration in accordance with the needs of the case. I therefore tried various kinds of resfu- lating apparatus which I devised. I also tried Hillischer's apparatus ; but the results which I obtained with it were not satisfactory. Its chief fault seemed to be that it did not allow of fine enough adjustment in its oxygen inlet. The channels through it, moreover, were of very small calibre, the bags were too far from the mouth-piece, and the valves did not work with that perfect freedom which is essential. The first apparatus with which I obtained reliable results was described by me before the Odontological Society in 1892,^' and I demonstrated''^ the results which could be obtained with it at the meeting of the British Dental Association at Manchester in the same year. I need not refer to its mechanism here Inti'oductovy 19 as the apparatus was similar in its main prin- ciples to that which is fully described in the following chapter. There were two separate bao-s. one for nitrous oxide, the other for oxvo'en. The oxygen was admitted to the nitrous oxide through thirteen small circular holes, any number of which could be opened. I found four flap valves necessary ; two pre- vented re-breathing, and two prevented any diffusion of the gases before they were mixed. The expiratory valve was found to be much more efficient in preventing air gaining access during its closure when a chimney was fitted to its orifice. If the valve were not thus guarded. a small quantity of atmospheric air was very liable to be drawn in during its closure. The apparatus which I now use was brought before the notice of the British Dental Asso- ciation at Newcasde-on-Tyne in 1894.'^ I propose, however, to fully describe it again here, and when this has been done, to consider in detail the effect which it produces. By this plan we shall, I think, l3e in a favourable position to realise the immense advantages of obtaining an anaesthesia which, when properly established, may be regarded as absolutely safe, and certainly far more satisfactory, from the operator's point of view, than that which we have been accustomed to meet with when employing nitrous oxide gas in the usual manner. 20 CHAPTER 11. APPARATUS. I. Gasometer Methods. Whilst it is true, as already stated, that there is no definite percentage of oxygen which will answer satisfactorily in every case, and that to obtain the best results a regulating apparatus is essential, it is equally true that a continuous administration, by means of a gasometer, of certain known mixtures of the two gases, will produce better results than can be obtained by nitrous oxide alone. The question hence arises : What percent- age of oxygen should be used in gasometer administrations ? In the course of an investigation^^ which I conducted at the Dental Hospital of London, one object of which was to settle this question, I administered nitrous oxide with the following percentages of oxygen. CASES Nitrous oxide with 3 per cent, of oxygen 5 ,, M 4 >' " 10 > < » > 5 > ' " ^7 .1 If *-' 1 » ♦ » A -* Apparatus 21 CASES Nitrous oxide with 7 per cent, of oxygen 11 8 ., „ [8 5 10 9 [O 1 1 20 100 These mixtures were accurately prepared and accurately administered under precisely similar circumstances by means of an apparatus with accurately working valves, great care being- taken to exclude all atmospheric air. Records were taken with regard to : — ( i ) The duration of inhalation necessary for the production of anaesthesia for a short dental operation; (2) the average duration of after-anaisthesia ; (3) the average quantity of the mixture used ; (4) the degree of jactitation (anoxsemic convulsion) ; (5) alterations in the colour of the features ; (6) stertor ; (7) phonation ; (8) reflex and excite- ment movements ; and (9) after effects. The duration of inhalation increased in proportion to the amount of oxygen in the mixture. Thus, with 3 per cent, of oxygen the average inhalation period was 96-6 seconds ; whereas, with 20 per cent, of oxygen it was 223-5 seconds. Deep anaesthesia was obtainable 22 Apparatus even when the proportion of oxygen was as great as in atmospheric air. The after- anaesthesia was longer than when mixtures of nitrous oxide and air were employed. The best results, so far as a lengthy available anaesthesia was concerned, were met with when using 7 per cent, of oxygen, the average duration of after-anaesthesia with this mixture being 50* i seconds. Anoxaemic convulsion was readily prevented even by comparatively small percentages of oxygen. During the inhalation of nitrous oxide, either pure or with oxygen, up to 4 per cent., some degree of " jactitation was very common ; but when once 5 per cent, of oxygen was reached very little convulsive movement was observed, and with 6 per cent, and over, no such move- ment was obtained. I found that with less than 1 1 per cent, of oxygen some degree of lividity of the features was usually present ; but with this percentage and over, the normal colour was retained. The effects of even small percent- ages of oxygen in preventing stertor were very marked. Thus with 3 per cent., 4 per cent., and 5 per cent, of oxygen the ordinary stertor met with under pure nitrous oxide lost its irregu- lar character and became replaced by a regular snoring sound, similar in its type to that of ether or chloroform anaesthesia. With 20 per cent, of oxygen snoring altogether vanished. Apparatus 23 Phonated sounds were less common under nitrous oxide and oxygen than under nitrous oxide and air mixtures. They were commonest with very small and with very large percentages. Reflex and excitement movements were un- common with small percentages of oxygen, but often asserted themselves and occasionally became inconvenient when the proportion of oxygen rose to 10 per cent, or more. Stamp- Pure N i trou5 Oxide Perc A ir wit :e n L ages of NiLrousOxid e Percen \Jxyser\\j\l\\ \|i bus Oxide 3 5 6 7 10 12 14 15 16 18 20 P^ 25 3C 3 A 5 6 7 8 9]l0!li 20 1 — 1 i 20; 25] 35 40 45 50 55 60 65 70 75 80 85 90 95 A \/\ 1 A / V \ / n; i 1 \ t I \ A / \, < / / V l\ \ / j \ Vj-I ~^ \ ''\/ / V /^ M ^ y 1 i • 1 / 1 -J J.._ .. ,.:. ~ ■^ Fig. I. — Chart showing comparative general results obtained by {a) pure nitrous oxide, (/j) nitrous oxide with different percentages of air, and (c) nitrous oxide with dfferent percentages of oxygen. Arbitrary Numeri- cal Scale. — Perfect type — o ; failure to produce anaesthesia = 200. ing, kicking, side to side movements, &c., were common with from lo to 20 per cent, of oxygen. As regards the general result, the best mixtures for adult males were those con- taining 5, 6, or 7 per cent, of oxygen ; and 24 Apparatus mixtures containing 7, 8, or 9 per cent, were best for females and children. The accompanying chart shows the com- parative general results obtained by {a) pure nitrous oxide, [b) nitrous oxide mixed with different percentages of air, and [c] nitrous oxide mixed with different percentages of oxygen. The chief objections to the use of definite mixtures of nitrous oxide and oxygen are : (i) That they are difficult to prepare with accuracy and in sufficiently large quantities ; {2) that different subjects require different percentages ; and (3) that the proportion of oxygen cannot be increased or decreased to meet special conditions arising during the ad- ministration. At the same time, it is important to have a clear idea of the effects produced by different proportions of oxygen, in order that we may correctly understand all the phenomena which may arise during the use of varying per- centages of the two gases by means of the apparatus to be presently described. A word of caution is perhaps necessary with regard to keeping nitrous oxide and oxygen together, in gasometers, for any length of time. Hillischer states that traces of the higher oxides of nitrogen were detected, at the end of a week, in a mixture which had been kept in Ludwig's laboratory. The two gases should therefore be mixed as required. Apparatus 25 2. The Author's Regulating Apparatus. Before describing this in detail it may be well to briefly enumerate the various require- ments which must be fulfilled by any regulat- ing apparatus for the administration of nitrous oxide and oxygen. They are as follows : — (i) There must be a plentiful supply of the two gases from easily and quietly working cylinders : (2) The bags into which the gases pass must be capable of being kept partly and equally distended during the administration : {3) The bags must be as close as possible to the face-piece : (4) The channels throughout the apparatus must be sufficiently large to avoid any stress whatever being thrown upon respiration : (5) The regulating portion of the apparatus must allow of very small increments and decre- ments in the proportion of oxygen breathed with the nitrous oxide : (6) There must be accurately working- valves : {a) for preventing all re-breathing, and {b) for preventing diffusion between the contents of one bag and the contents of the other : (7) The expiratory valve must not allow of any air being sucked back during its closure in the inspiratory phase : 26 Apparatus (8) The apparatus must be so constructed that, v/hen first applied to the face, air will be Fig. 2. — The Author's apparatus. breathed freely through it, and through the same valves that will be subsequently used when the mixture is turned on : Apparatus 27 (9) The apparatus must admit of being readily taken to pieces without the use of tools', so that its various parts may be in- spected from time to time : (10) The inhaling portion of the apparatus must admit of being thoroughly cleansed, and of being treated with antiseptic solutions should occasion require : (11) The whole apparatus must be suffi- ciently portable to be carried in a hand-bag. (See fig. 6, p. 45.) Fig. 2 represents the complete apparatus. It consists of two nitrous oxide cylinders, one oxygen cylinder, a combined stand and union, double india-rubber tubes (one run- ning inside the other) for conducting the tw^o gases from the cylinders to the bags, two india-rubber bags joined together by a sep- tum common to both, a combined regulating stop-cock and mixing chamber, and a face- piece. The two nitrous oxide cylinders, the single oxygen cylinder resting upon them, and the combined stand and union, are shown in diagrammatic section in fig. 3. Each nitrous oxide cylinder will furnish 50 gallons of nitrous oxide gas ; and each oxygen cylinder about 1 5 gallons of oxygen. The combined stand and union is so made that the cylinders can be connected together 28 Apparatus or disconnected without the aid of spanners or other appHances. In order to prevent undue strain to the union when the foot-key is being used upon the oxygen cyHnder, an adjustable screw pillar, fixed to the stand below, is made to engage that part of the under surface of the oxygen cylinder upon which foot-pressure directly tells. In this way all foot-pressure is transmitted to the stand. Fig. 3. — Diagrammatic section of cylinders, and of combined stand and union. When the foot-key is placed upon one of the nitrous oxide cylinders, and is turned, the liberated nitrous oxide passes to its bag through brass and india-rubber tubes of com- paratively large calibre. When oxygen is similarly released from its cylinder it passes to its bag through brass and india-rubber Apparatus 29 tubes which are so much smaller than the nitrous oxide tubes that they are made to travel inside the latter. Thus, in fig. 3, it Fig. 4. — Diagrammatic section of the india-rubber transmitting tubes and bags through which the two gases pass on their way to the regulating stop-cock and mixing chamber. will be seen that, in the combined stand and union, the metal transmitting tube for the oxygen is inside that for the nitrous oxide. Fig. 4 shows, in diagrammatic section, the 30 Apparatus two india-rubber transmitting tubes, one in- side the other, conveying their respective gases to the two india-rubber bags. These bags are of about equal capacity, and are so made that a rather thick india-rubber septum is common to both. When full they have the out- ward appearance of a single bag. Care is needed to prevent the india-rubber from be- coming punctured or otherwise injured. Even if only one or two minute punctures exist, they may be quite sufficient to allow of an admixture of atmospheric air. The bags, moreover, must not be too small ; otherwise it may be difficult or impossible, during the administration, to keep the nitrous oxide bag equal in size to the oxygen, especially if the patient should breathe very deeply. The regulating stop-cock and mixing cham- ber is shown in detail in fig. 5. The nitrous oxide bag (see fig. 4) is attached to the tube NOT, the orifice of which, NOO, is shown. The oxygen bag is attached to OT, which communicates above with a little oxygen cham- ber OC. There are ten minute holes between the oxygen chamber OC and the mixing chamber. Only three of these ten holes, OO, appear in the figure. All the ten oxygen orifices are of the same size except the first, and by means of the supplementary stop-cock SS, this can either be made of the same size Apparatus 31 as the other nhie (first position of SS), or it can be made equal to the V^n orifices collectively Fig. 5. — Ko^iilalin^ slo[)-C)ck and mixing chamber. (second position of SS), or to twenty such orifices (third position of SS). The 'i'tubes, OT and NOT, arc furnished with removable 32 Apparatus valves, iv and iv\ wHich act during inspira- tion, and which prevent diffusion between the gases of the two bags. AH is the air-hole. IV is the main inspiratory valve. EV is the expiratory valve, with its chimney C. PD, shown in dotted outline, is a partial diaphragm, mounted upon a removable inner tube, which serves to direct the expirations towards the expiratory valve EV. In the absence of this partial diaphragm there is a tendency for the expirations to pass back again beneath IV, and so to throw the valve-action completely out of gear. The chimney C is essential in preventing air being drawn back through EV during its closure at each inspiration. The inner drum, ID, which is made to revolve by means of the handle H, has a large portion of its circumference cut away to form a long slot S. The handle H is prolonged into an indicating point or indicator. To the circumference of the stop-cock and mixing chamber is fixed a flange with " AIR," " N2O," and "N2O + O," engraved upon it. There are also figures, from " i '" to " 10 " in- clusive, belonging to the "NgO-fO" part of the flange. When the indicator of the handle H points to "AIR," as in fig. 2, the slot S of the drum ID allows air to pass through AH and IV during the act of inspiration ; but by Apparatus 33 reason of the other part of the drum covering the orifices NOO and OO nothing' but air is breathed. When the indicator is moved to '• N2O," the drum closes AH and opens NOO, the oxygen orifices still remaining covered. Pure nitrous oxide is therefore inhaled. When the indicator reaches " i " on the " N2O + O " part of the flange, the nitrous oxide orifice NOO still remains open, but in addition, the first oxygen orifice OO becomes uncovered by the revolution of the inner drum. When " 2 " is reached, two oxygen holes are open, and so on up to " 10," the nitrous oxide orifice remaining patent throughout. It may thus be said that directly the in- dicator is made to point to " NgO," there passes through the stop-cock a continuous and large stream of nitrous oxide, and that as the indicator is moved to i, 2, &c., any number of small streams of oxygen (from i to 10 inclusive) may be added to this continuous stream of nitrous oxide. As the first of the oxygen orifices may be made ten or twenty times its ordinary size, it follows that the administrator can add, at will, quantities of oxygen corresponding to i, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 23, 24, 25, 26, 27, 28, or 29 orifices. A very fine adjustment in the oxygen supply is thus effected. As the indicator reaches the various 3 34 Apparatus points on the flange an audible click is pro- duced by means of a spring attached to the handle. All the Yalves are made of thin sheet india- rubber, and it is important to keep them in good order. Should they become inelastic from age, or in any way fail to act, as they are intended to act, with perfect accuracy, the apparatus will not produce good results. For example, an apparatus may let through much larger proportions of oxygen than usual if the nitrous oxide valve iv should happen to adhere, along a part of its circumference, to the rim upon which it rests ; the explanation •being that the suction exerted by the inspira- tions of the patient would have a greater influence than usual in drawing oxygen from the oxygen bag owing to the abnormal resist- ance at the nitrous oxide valve. The valves of the apparatus are so arranged as to act most efficiently when the main expiratory valve is kept as horizontal as possible. If the whole apparatus be much tilted during use, as would be the case if the patient's head should be thrown very far back, the valves may not act efficiently. The apparatus may be taken to pieces with the utmost readiness by simply removing, with the finger, the screws which connect the handle H to the inner drum ID. In this way the Apparatus 35 drum may be removed and the valves and oxygen orifices inspected. The latter may occasionally require to be freed from dust. Three or four face-pieces of different sizes should be at hand. The air cushion of the face-piece employed should be only moderately inflated, otherwise it may not fit as well as is desirable. In order that good and reliable results may be obtained, it is important that the whole apparatus should be carefully handled. The process of anaesthetising with nitrous oxide and oxygen is a more delicate process than that involved in the ordinary administration of nitrous oxide alone ; and trifling defects in the apparatus are liable to interfere with results. The connections must be tested ; the baos inspected frequently ; the stop- cock taken to pieces occasionally — in fact, the "anaesthetist must take a personal interest in his apparatus if he wishes to succeed with it. A word may here be said as to the relative proportions of nitrous oxide and oxygen which the apparatus is capable of furnishing. As will be pointed out in the following chapter, much will depend upon the state of the bags during the inhalation, and especially upon whether they are kept of equal size throughout. But it is necessary to mention, in the present connection, that each apparatus possesses slight 36 Apparatus peculiarities of its own. It is a difficult matter to produce two models which will act in pre- cisely the same way. The result is that the anaesthetist must observe what his particular apparatus is capable of doing. With one model it may not be possible to reach " 8 " upon the flange without excitement arising ; whilst with another model "9" or "10" may be reached in nearly every case without any such symptoms occurring. But when once the anaesthetist has found out how far he can go with his particular apparatus he will always be able to depend upon it working in the same way, provided, of course, that he keep its valves, oxygen holes, bags and other parts in good order. The apparatus is manufactured by Messrs. Barth & Co., of Poland Street, Oxford Street, to whom I am much indebted for the patience and skill they have shown in carrying out my designs. It may either be obtained from them or from Messrs. Ash & Sons, Broad Street, Golden Square. 37 CHAPTER III. PREPARATIONS. The old adage, " Everything that is worth doing is worth doing well," forcibly applies to the use of anaesthetics in dental practice. It is only by attention to detail that success can be achieved in every case. The dentist who regards preparations and precautions as un- necessary, and who expects his colleague to entertain similar views, has only himself to thank when difficulties arise. There is no known method of anaesthetising which will succeed when the corsets are tightly laced, the stomach full, or the posture faulty. It is, I think, a mistake to suppose that patients are made nervous by the few preparations which are essential to success. I would rather say that most patients gain assurance when they see that pains are being taken to obtain the best results. When practicable, an interval of about four hours should have elapsed between the last meal and the administration. The middle of the day (from 12 to 2 o'clock) is a very o8 Preparations convenient time for the extraction of teeth under anaesthetics. Precautions as to diet are especially important in the case of children, and when a long anaesthesia is needed (see p. 89). Stimulants should, as a rule, be avoided. In very feeble subjects, however, and in those inclined to faint, an exception may be made if desired. I have notes of a child who was given by his parents some brandy and water before starting for the dentist's. A very unsatisfactory anaesthesia followed, and the little patient retched violently. In the case of children, and even in that of adults, when circumstances permit, it is well that the bladder should be empty. Micturition during the administration is, how- ever, exceedingly rare. Whenever circumstances are favourable, it is a good plan to have CYerything in readi- ness before the patient enters the room. The anaesthetist should see that his apparatus is in working order ; he should fill the bags with their respective gases to the extent of about two-thirds, so that they are equally and moderately distended ; and he should leave the foot-key on one of the nitrous oxide cylinders ready for use. The following appliances should always be in readiness : Mouth props of various sizes, Preparations on a Mason's gag, a pair of tongue forceps, some nitrite of amyl capsules, and instruments for performing tracheotomy. Although I have never had occasion to use tongue forceps, nitrite of amyl, or tracheotomy instruments in connection with this form of ansesthesia, it is nevertheless important to be fully prepared for all contingencies. A third person should always be present in the room from the time the inhalation is begun till the patient's consciousness is fully restored. The administration should not be under- taken by the same person who performs the operation. The importance of loose clothing cannot be too strongly insisted upon. In order that the induction of anesthesia may be successfully accomplished, it is necessary that the air in the lungs should be exchanged as quickly as possible for the anaesthetic gas. In order that this may be effected, the bases of the lung must expand by diaphragmatic action. If there be tightly-fitting corsets or waist-bands, the diaphragm cannot descend fully ; the breath- ing will be restricted, and to a great extent, or entirely, thoracic ; interchange between the air in the lungs and the anaesthetic will only take place freely in the upper parts of the lungs ; and the onset of anaesthesia will there- 40 Preparations fore be delayed. Patients who are tightly laced may do their best to quickly fill their lungs with the anaesthetic gas, but they will fail. All constricting clothing about the upper part of the chest and neck should also be loosened with the object of allowing respira- tion to proceed perfectly freely. It is not a bad plan for ladies to come to the dentist's loosely attired, so that no further preparation in this direction need be made. The posture of the patient has a very decided influence in modifying the phenomena of anaesthesia. I have elsewhere entered at length into this subject, and I would refer the reader to my paper^^ specially dealing with it. Whenever circumstances permit, the patient should be allowed to assume a comfortable and unrestrained posture, and his head should be permitted to retain its natural position in regard to the body, being neither flexed upon the chest nor extended towards the spine (see fig. 6, p. 45). Good results cannot be expected if the administration be beorun when the patient's head is thrown back upon the spine. Should the operator wish to have the head thrown more backwards than is represented in the figure, the best plan is to anaesthetise the patient in the posture depicted, and to tilt the whole chair backwards just before the face- piece is removed for the commencement of the Preparations ± i operation. In this way the proper angle for the operation will be obtained without disturb- ing the normal relations of the head to the trunk. Should the chair not admit of this movement, an inflated air pillow should be placed under the head before commencine the administration, and, just before the face-piece is removed, the air may be allowed to escape. In this way the head will fall into the ex- tended position ready for the operation, and the comfort of the patient, as well as the con- venience of the operator and of the anaesthetist, will have been provided for. Should relatives or friends express a desire to be present during the operation, they should not be permitted to stand near the chair, nor to hold the patient's hand, as such attentions will almost certainly have an opposite effect to that which is intended, and introduce a disturbino- element into the anaesthesia. In many cases friends wish only to be present during the induction stage, and there is little to be said against this ; directly consciousness has been lost, a signal should be given them in order that they may retire during the actual opera- tion. Owing to the fact that by the use of oxygen with nitrous oxide a far more tranquil and sleep-like anaesthesia is produced than with nitrous oxide alone, there is less objection to 42 Preparations friends being present than under other circum- stances. A suitable mouth-prop should be inserted immediately before the administration is begun. The prop which I employ is fully described elsewhere.'^ It is made of aluminium, and is so shaped that it rarely if ever slips when once put into position. It is important in fixing the prop that the mouth should be opened as widely as possible, except when stretching the lips would inconvenience the operator, or when widely opening the mouth would give the patient great discomfort, or excite retching movements. In the extraction of wisdom teeth it is usually a good plan not to open the mouth to its fullest extent. Should the in- sertion of the prop excite retching movements, the remedy which usually answers is an ex- ceedingly simple and efficient one. The prop having been inserted, the patient should be re- quested to breathe deeply through the open mouth, to count his respirations to himself, and to concentrate his whole attention on the counting. The face-piece is then quickly applied ; the gases admitted ; and if the patient continues to fix his attention as suggested, he will pass into anaesthesia without the recur- rence of any retching movements. 43 CHAPTER IV. THE ADMINISTRATION. With the object of making this part of the subject as clear as possible, it will be well to confine our attention in the present chapter to the details of an ordinary or average ad- ministration, and to the effects which such an administration produces in an ordinary or average patient. As the majority of those who require anaesthetics in dental practice are women, it will be advisable to take as our normal type, a young woman of medium height and build, of medium complexion, and not markedly nervous. When we have fully considered the method which should be adopted in anaesthetising such a patient we shall be in a position to discuss, in a subse- quent chapter, the slight modifications in pro- cedure which are essential in dealing with other types of patients. An endeavour should be made to avoid all disturbing influences during the adminis- tration. The room should be kept quiet. Friends should not be permitted to hold the 44 The A patient's hand. There is no objection to the operator holding the hand of a nervous patient if confidence is hkely to be gained in this way. The anaesthetist should say a few words to the patient during the first moments of the inhala- tion, but not a word should be uttered after this until the operation has been completed. With nervous subjects it is often a good plan for the anaesthetist to count aloud, as the patient breathes. Under any circumstances he should instruct the patient how to breathe. The anaesthesia is likely to be disturbed by any conversation, loud noises, the comments or questions of anxious friends, &c. Even feeling the pulse at the wrist is likely to in- duce nervousness, and should be avoided. In a word, the patient should be left as much as possible to herself. When considering, in Chapter III., the pre- parations which are necessary before an ad- ministration is commenced, it was stated that the bags containing the nitrous oxide and oxygen should, if possible, be charged with their respective gases, and that the foot-key should be placed upon one of the nitrous oxide cylinders, before the patient enters the room. The patient having assumed a perfectly comfortable posture, and a mouth-prop having been adjusted, the face-piece is applied. Air will now be breathed through the ap- The Admiuistration 45 paratus, each expiration escaping at the ex- piratory valve. The anaesthetist should request his patient Fig. 6. — The adminUtralion. to take lontr deep breaths, backwards and forwards, through the mouth. Nasal breathing should be avoided. If there is any " holdine^ 46 The Administration the breath " or hesitation in breathing, this must be corrected before proceeding further. The most absolute co-aptation of the face- piece is essential. The sound made by the flapping of the valves is the best proof that the face-piece is fitting well ; and this sound should always be heard before the mixture is turned on. When it is clear that the face-piece fits accurately, the indicator, which has hitherto been pointing to "AIR," should be turned to " 2." At the same moment the foot should slightly turn the foot-key in order to quickly replace the nitrous oxide which the patient is breathing. It is impossible to state, with precision, what percentage of oxygen will come through when the indicator is thus turned to *' 2," for one apparatus will be found to differ slightly from another, and much will depend upon the relative sizes of the bags at the moment. It is sufficient for our purpose that quite a small percentage — roughly about i or 2 per cent. — will be first breathed. The percentage is so small, indeed, that the oxygen bag hardly appears to alter in size throughout, and no further addition to it from the oxygen cylinder is usually necessary in dental administrations, even in the case of long inhalations. The initial sensations of the patient are The Administration 47 similar to those experienced under nitrous oxide itself. There is, however, one import- ant difference, viz., that the small quantity of oxygen usually prevents all feelings of suffoca- tion. There is, moreover, less tinnitus than with the pure gas. It may be said, in fact, that provided the clothing be absolutely loose and that the patient breathe freely through the mouth, the administration of nitrous oxide and oxygen may be conducted without any dis- comfort to the patient. Consciousness is not lost quite so quickly as with nitrous oxide alone ; but in other respects the early sensa- tions are identical, and need not therefore be described. The anaesthetist has now to pay attention to three points at the same time. He has (i) to keep the face-piece very accurately applied ; (2) to keep the two bags equally and only partly distended ; and (3) to increase or diminish the proportion of oxygen according to the symptoms of the patient. It will there- fore be advisable to consider the remainino- part of the administration under these three heads. (i) The fitting of the face-piece. Whilst there is much to be said in favour of the face- piece, as opposed to the mouth-tube, for nitrous oxide inhalation, there can be no doubt that it is more difficult, when employing the former, to 48 The Administration completely exclude atmospheric air than when using the latter. There are, however, several objections to mouth-tubes. The idea of hold- ing between one's lips a tube that has just been used by another patient is not a pleasant one, even though the most scrupulous cleanliness may have been enforced. Moreover, it is essential, in using a mouth-tube, that the nose should be clipped or held, in order to prevent any air entering the nasal passages. And, lastly, breathing is liable to be impeded by the tube necessarily being of small calibre. Tak- ing everything into consideration, therefore, the face-piece has distinct advantages. But considerable practice is required before perfect co-aptation can be secured in all cases. Un- fortunately, when employing the mixed gases, any want of co-aptation cannot be met by increasing the pressure at which the gases enter the face-piece, for distension of the bags would at once throw the regulating mechanism out of orear. (2) The fulness and relative sizes of the bags. In order that the regulating mechanism may work properly it is necessary that the two bags should be kept as nearly as possible of equal size throughout, and only partly dis- tended. The anaesthetist has, in fact, to use his foot as much as his hand, and to let in nitrous oxide to its bag in such quantities that The Administration 49 the bag- remains the same size as the oxygen bag. The latter necessarily grows gradually smaller, and the anaesthetist, therefore, has to keep the nitrous oxide bag less and less full. (3) The admission of oxygen. Given that the apparatus works satisfactorily and in the usual manner, the anaesthetist must regulate the admission of oxygen in accordance with the type of his patient, and with the symptoms displayed. There is, unfortunately, no rule which will apply to every case. After some experience the administrator will recognise that he has at his disposal an apparatus by which he can, if he wish, obtain two totally different groups of symptoms. If very little or no oxygen be given, the ordinary phenomena of nitrous oxide narcosis will present themselves, viz., blueness, lividity, or duskiness of the features, epileptiform muscular twitchings of the trunk, extremities and face, and obstructive stertor. If too much oxygen be admitted, there will be no alteration in colour, no epilepti- form convulsive movements, and no stertor, but violent mental and muscular excitement (laughter, shouting, kicking, stamping and struggling) may attend the administration, and will be almost as objectionable as the asphyxial phenomena produced by pure nitrous oxide. There are thus two extremes — two ends of 4 50 The Administration the scale — and each extreme must be avoided. The anaesthetist has, in fact, to steer a middle course, and to keep a sharp look-out. A little practice will enable him to avoid the Scylla of asphyxia on the one hand, and the Charybdis of excitement on the other. He will find, after a time, that he is able to detect even sligrht deviations from the proper course, almost before such deviations have taken place. Generally speaking, a gradual and progres- sive increase in the percentage of oxygen is advisable. In such a case, for example, as that which we have pictured to ourselves, the best results will be obtained by starting the inhalation, as already mentioned, with about i or 2 per cent, of oxygen, and then progressively increasing the proportion to 8 or 9 per cent. It seems to me that it is a mistake to adopt the plan which is customary in Germany, and to begin with as much as 10 per cent, of oxygen. It is surely more rational to make an allowance for the oxygen present in the lungs when the administration begins, and we should therefore commence with a very small per- centage of this gas. As the lungs lose the air they contained, so the percentage of oxgyen in the mixture may be increased, provided that no symptoms of excitement arise. If a 10 per cent, mixture be used from the commencement, excitement is liable to ensue from the undue The Administration 51 proportion of oxygen. Witzel,^° for example, who followed this course in his administrations, found it necessary to employ arm-rings, foot- straps, and other appliances to restrain the patient's movements, and to have at hand, on all, occasions, strong and trained assistants. Such precautions are unnecessary when the method here advocated is followed. I find it best, as a general rule, to allow two or three inspirations of the mixture to take place with the indicator at " 2 " ; two or three more with it at " 3 " ; two or three more with it at "4" ; and so on till "6" or "7" is reached. When the breathing is shallow the admission of oxygen must be more gradually effected than when the breathing is deep. Usually by the time the indicator has reached " 6 " or " 7 " the anaisthetist will be able to recog- nise the existence of one of three conditions. There will either be evidence to show — (a) That the proportions of the two gases are properly adjusted ; (j8) That the proportion of oxygen is rather in excess of that which is needed, and should therefore be diminished ; or, (y) That this proportion is rather less than that required, and should therefore be in- creased. (a) The absence of any indications of ex- citement on the one hand, or of asphyxia on 52 The Administration the other, will prove that the proportions of the two gases are properly adjusted. Under such circumstances the indicator may either be kept at " 6 " or " 7 " for several breaths, and then gradually turned to "8," "9," or " 10," or it may be allowed to remain at "6" or '' 7 " till anaesthesia is fully and satisfactorily established. [^) Should there be an unaltered colour, associated either with slight phonation, hardly perceptible breathing, a tendency to laughter, or slight restless movements of the head, trunk, or extremities, the oxygen indicator should be turned back slightly; for these symptoms in- dicate that too much oxygen is being inhaled. (y) Should the breathing be loudly snoring in character, or the colour rather dusky, or should slio-ht oeneral clonic movement of the body, head, or extremities be evident, the oxygen indicator must be moved on ; for such symptoms indicate a deficiency of oxygen. In one or other of these three ways the patient will pass into deep and satisfactory ansssthesia characterised by certain definite phenomena. The experience of recent years has convinced me that in administering nitrous oxide and oxygen we should endeavour to obtain an anaesthesia similar in most of its features to the best types of ether or chloroform anaesthesia. If we aim at inducing a perfectly The Administration 53 sleep-like state in which the colour of the features is absolutely unaltered or is even heightened, and the breathing is so tranquil that it is inaudible, we shall not only be liable to meet with excitement, but the ansestliesia will, at all events in many cases, be less pro- found than is desirable Moreover, it is not an easy matter, when the breathing is inaudible, to estimate the depth of anaesthesia. We should therefore, I think, endeavour to bring about an ancesthesia characterised by softly snoring breathing, a good pulse, a colour as near the normal as possible, an insensitive ocular conjunctiva, relaxed eyelids, a fixed condition of the globes, and the absence of muscular rigidity in the extremities. Sometimes, and especially after a pheise of rapid breathing, or when a good deal of oxygen has been given, the respiration may come almost or completely to a standstill without there being the slightest need for alarm. The apnoeic state is associated with a good pulse and colour, and will quickly pass off when the proportion of oxygen is reduced. The pulse is always as quick as, or quicker than, it was immediately before the adminis- tration. In most cases the initial accelera- tion from nervousness gradually increases to a maximum, and then declines somewhat, though it never falls below its initial acceleration rate. 54 The Administration I am unable to aoree with Hillischer's observa- tion that the pulse-rate sinks to normal during anaesthesia. Dr. Oliver^^ observed, in using his arteriometer, that the pulse calibre was not reduced as in the case of pure nitrous oxide. The small, feeble, and exceedingly rapid pulse which not unfrequently may be felt at the acme of an ordinary nitrous oxide inhalation, is not met with when oxygen is present with the nitrous oxide in sufficient quantities. I have never, in fact, come across any indications of circulatory failure during the administration of the mixed gases. The tongue and adjacent structures are less engorged than when nitrous oxide is administered free from oxygen. The eyes are generally closed throughout. Some patients, however, prefer to keep them open when the inhalation begins, but as it proceeds the globes gradually cease to fix themselves on surrounding objects, and the lids become approximated. During the first minute or so of the inhalation any attempt on the part of the administrator to raise the upper lid will be resisted by the patient ; but after the first minute the lid will gradually relax, and when it can be raised without any resistance, and the conjunctiva can be touched without reflex response, it may generally be assumed that sufficient anaesthesia is present. Sometimes fine oscillatory movements of the globes may The Administration 55 be seen on raising the upper lids. The pupils are generally of medium size or moderately dilated. There is a striking" contrast between the closed lids of this form of anaesthesia and the open and turned-up eyes so often seen in ordinary nitrous oxide narcosis. Amongst the numerous points to which attention must be paid in conducting the ad- ministration, there is one which is of consider- able importance. It is that the anaesthetist must allow for what may be termed the delayed effects of admitting more or less oxygen. For example, let us suppose that slight phonation occurs when the indicator points to "7." By turning it to "3" or "4" the phonation will in the course of a few moments subside. But if the indicator be kept at "3" or "4" till the patient is perfectly quiet, the anaesthetist will probably have gone too far in the asphyxial direction. He should turn to "3" or "4" for a few breaths only and return to "5," "6" or "7" before the phonation has ceased. In other words, he must bear in mind that a little interval must necessarily elapse before the effects of an increase or decrease in oxygen admission will become manifest. As regards the length of inhalation re- quisite for the production of the typical pheno- mena of anaesthesia, I have found that it is, on 56 The Administration the average, iio seconds, i.e., nearly twice the length of the average nitrous oxide inhalation. The juncture at which the administration should be terminated must, however, depend upon the circumstances of each case, such, for example, as the susceptibility or insus- ceptibility which the patient has displayed, the nature of the proposed operation, and the length of time that has elapsed since food was taken. The quantity of the mixture required to produce anaesthesia will likewise vary con- siderably, being dependent upon the propor- tion of oxygen employed, the depth and rate of respiration, the length of inhalation, the type of patient, and other factors. 57 CHAPTER V. THE PATIENT. In studying" the effects produced in the human subject by nitrous oxide and oxygen, one of the first facts which becomes apparent is that, although the constitution of the mixture, the method of administration, and other sur- rounding circumstances may remain the same, different individuals will display very different phenomena. To say, however, that every case has its own special peculiarities is hardly correct. By careful observation it becomes possible to group cases together into classes, and to say that patients of this or that class will display this or that set of symptoms. We are in this way led to speak of different types of patients. It is true that our knowledge of this interesting aspect of the subject is still very meagre ; but it is rapidly increasing. Success in administering aneesthetics is largely depen- dent upon the power the administrator possesses of correctly foretelling what effects this or that method will produce in the patient before him ; and it is this kind of knowledge which is 58 The Patient essential in deciding upon the particular lines of treatment which should be adopted in anaes- thetising patients by the method now under consideration. In the preceding Chapter we discussed the plan which should be followed in dealing with those types of subjects most commonly met with. We have now to consider what modi- fications in that plan are advisable when anaesthetising patients of other types. Sex and age. — In anaesthetising small children, more oxygen than usual may be admitted. Should crying take place, it is best to commence the administration with the indicator at "8," "g" or 10" ; for the crying tends to introduce an asphyxial element. I have anaesthetised two or three children of three years of age by means of the mixture, but with moderate success only, the anaesthesia being very transient in such small subjects. In older children the indicator may usually be placed at " 3 " or " 4 " to commence with, and moved on rather" more quickly than usual to " 5," " 6," &c. By the time " 10" is reached, the breathing will probably have become so tranquil that some doubt as to the presence of anaesthesia may be felt ; the indicator should therefore now be turned back to " 5," *' 4," or even "3," when snoring will be certain to com- mence. In this way a more satisfactory anaes- The Patient 59 thesia may be induced than if the face-piece be removed during the inaudible breathing. Taken as a class, women are better subjects than men. They are more tolerant of con- siderable proportions of oxygen, they are more susceptible to the mixture, and, by reason of their being less muscular, they are less prone to inconvenient rigidity and movement. Middle- aged women are almost invariably good sub- jects. I have, for example, notes of several cases in which 60-90 seconds' anaesthesia resulted after an ordinary inhalation of the mixed gases. Old persons of both sexes are always very favourably affected by the mixture. I have anaesthetised, by its means, several patients over 80 years of age. One of these, a gentle- man of 88, had an intermittent heart: the administration was conducted until the con- junctiva became insensitive, and an excellent anaesthesia was obtained. The absence of that temporary respiratory embarrassment which is so often induced by nitrous oxide free from oxygen, and which, in the case of elderly persons with rigid chests, cannot be regarded as free from risks, is a very distinct gain. General Condition. — The better the patient's state of health the more aneesthetic will he require, and vice versa. The proportions of 6o The Patient oxygen In the mixture, moreover, should be rather smaller in a case of a perfectly healthy subject than in that of a debilitated individual. An. exuberance of health and spirits is not always conducive to the most tranquil form of anaesthesia. It may be said, in fact, that patients of a weakly constitution, and those who have recently been suffering from some depressing malady, more often approach our ideal standard of anaesthesia than patients of opposite types. Physique. — Other things being equal, the more powerfully built the patient the greater will be the quantity of the mixture required. Men of an athletic physique, who have led out-door lives, and who are in a state of perfect health, often give slight trouble by becoming rigid during the administration and operation. Speaking in general terms, one may say that rather smaller proportions of oxygen should be used in the case of men than of women. Thus it is best, as a rule, to start the administration with the indicator at " I " and to very gradually move it onwards. If oxygen be admitted at the same rate as in anaesthetising women, a long inhalation will be necessary before good anaesthesia is estab- lished ; and in attaining this anaesthesia excite- ment will be liable to arise. Men of slim build and rather weakly constitution may be The Patient 6i treated in precisely the same way as women. Very stout subjects, and especially those with thick, short necks, or double chins, tend to become unusually stertorous, so that, in such cases, it is generally advisable to slightly increase rather than to diminish the usual proportions of oxygen. Very stout elderly women, with feeble heart action and possibly bronchial symptoms, are remarkably good subjects for nitrous oxide and oxygen adminis- tered in this way. The presence of a beard or moustache. — When the hair is so distributed about the lips and chin that even a small quantity necessarily intervenes between the cushion of the face- piece and the skin, allowance must be made for the unavoidable ingress of a small propor- tion of air with the mixture. The best plan in such cases is to secure as accurate a co- aptation of the face-piece as possible, and then to surround the air-cushion of the latter with a wet cloth. In this way I have been able to obtain very good results. In many cases the long inhalation which has resulted from the unavoidable admission of small proportions of air, has led to remarkably long anaesthesia. It is impo.ssible, however, in these cases, to be as sure of one's results as in others. Temperament.— Other factors remaining the same, the best subjects for this as for 62 The Patient Other anaesthetics, are patients with placid, equable temperaments. Highly excitable and emotional persons are liable to give slight trouble. They sometimes voluntarily hold the breath, or scream, before the anaesthetic is actually breathed. They often, moreover, require considerable quantities of the mixed gases before the conjunctival reflex vanishes. In many cases, indeed, this reflex will not disappear, and the anaesthetist has to judge by other signs that his patient is ready for the operation. Highly neurotic persons usually display a shorter available anaesthesia than others. Thin, pale, dark-complexioned young women, of nervous temperament, are particularly liable to prove difficult of management. With nitrous oxide alone the full effects of the gas are produced in a few respirations ; the asphyxial element is conspicuously present ; and the resulting anaesthesia is disturbed and brief. Much better results may be obtained, however, with the mixture if the administra- tion be conducted properly. Oxygen should be rather sparingly admitted at first ; it should then be somewhat more freely given, and a long inhalation secured. With regard to hysterical women, we may say that, although one cannot always depend upon obtaining perfect results, such patients are, as a rule. The Patient 63 remarkably good subjects for the mixture, provided that oxygen be not too freely ad- mitted. When such subjects are anaesthe- tised bv nitrous oxide alone, the anaesthesia is so short that during recovery nightmare- dreams and other distressing sensations are likely to arise, and to induce screaming and emotional attacks. The anaesthesia being deeper when the mixture is used, the result- ing unconsciousness is quieter and longer, and the recovery is usually unattended by any emotional disturbances. The difference be- tween the two methods of anaesthetising dental patients was very obvious in the administrations I conducted at the Dental Hospital. I found that with nitrous oxide and oxygen patients rarely make any sound at all, either during or after the administration ; whereas with nitrous oxide alone, phonation was exceedingly common. Complexion - colour. — Plethoric, florid patients are more liable than anaemic- looking persons to evince some duskiness during the inhalation. Of all subjects, however, those of a congested, bloated aspect are the most prone to become dusky in appearance. It is not advisable to be guided entirely by the patient's colour in deciding whether more or less oxygen should be given ; for if this course be adopted in the case of patients who quickly and readily show slight duskiness, but who are naturally 64 The Patient excitable, imperfect anaesthesia from too much oxygen may arise. In most cases it is possible to retain the patient's normal colour throughout the administration. Curiously enough, I have notes of one or two cases in which no very distinct alteration in colour occurred even though, as was obvious from the presence of " mild oscillation," the patient was at the moment breathing a mixture containing very little oxygen. These cases are very ex- ceptional. Should the patient be pale from nervous apprehension, the pallor will become replaced by the natural colour as the inhala- tion proceeds. Generally speaking, anaemic subjects are very tolerant of oxygen, and in their case this gas should be admitted more freely than usual, the indicator being placed at "3" or "4" at the beginning of the administration. Alcoholic indulgence. — In anaesthetising alco- holic subjects the administration should be as prolonged as is considered advisable, in order to produce as deep an anaesthesia as possible. As with other anaesthetics, difficulties are liable to arise, and the anaesthetic state is often short and imperfect in character. Movements of the head, arms, or legs are not uncommon during the earlier part of the inhalation, so that care should be taken at this stage not to give more oxygen than is needed to keep asphyxial phe- The Patient g_ nomena at bay. At the same time it must be remembered that alcohoh-c patients are singu- larly intolerant of oxygen starvation, evincing convulsive movements with great readiness. The best Hne of treatment, apparently, is at first to be somewhat sparing in the oxygen supply, and then, when the excitement stage has presum- ably passed, to be more liberal with the oxygen keepmg a close watch for any convulsive spasm The excessive use of tobacco and other narcotics.-I have found that patients who smoke mordinately are not the best subjects lor nitrous oxide, even when given with oxygen. They are inclined to movement, hesitating or suspended breathing, and rigid- ity during the inhalation, and to a short anaesthesia afterwards. All that we can say is that one can obtain, by means of the mixture, a better result than with nitrous oxide alone Patients who habitually take chloral or mor- phmealso become comparatively insusceptible to this as to other anaesthetics. I have only once met with a temporary maniacal seizure after nitrous oxide and oxygen, and this was m the case of a young man who, for six con- secutive nights, had taken sleeping draughts of chloral and of opium. I have notes of several cases in which I have administered nitrous oxide and oxygen to the same patient on several occasion.'T at 5 66 The Patient intervals of from one to ten days. I have almost invariably noticed, under such circum- stances, a progressive insusceptibility to the anaesthetic. Affections of the respiratory system. — Should any affection of the respiratory sys- tem exist, care must be taken to allow for this, so to speak, in conducting the administra- tion, otherwise asphyxial phenomena similar to those met with when nitrous oxide is ad- ministered in the customary manner will be liable to arise. If the air-way be partly obstructed by large tonsils, adenoid growths, or other conditions ; if the patient be the subject of chronic bron- chitis, emphysema, phthisis, or other allied diseases ; or if breathlessness from some cardiac affection be present ; more oxygen than usual must be given in order to neu- tralise, as it were, the unusual asphyxial ele- ment in the case. If this be done, nitrous oxide anaesthesia may be safely induced in nearly every case. There are, however, a few highly exceptional conditions in which some other form of anaes- thesia is preferable. I refer particularly to patients suffering from such dyspnoea that no tightly-fitting mask can be tolerated — patients, for example, who are the subjects of aneurysmal The Patient 67 or other pressure upon the trachea, very ad- vanced phthisis, hydrothorax, and other grave respiratory conditions. Putting such excep- tional cases on one side, we may safely administer nitrous oxide and oxygen to all other patients. Affections of the circulatory system. — It is well known that patients with diseases of the heart are good subjects for anaesthetics, pro- vided that care be taken in selecting appropriate methods. I have administered nitrous oxide and oxygen to patients with all the commoner forms of morbus cordis. Amonost these have been three cases of aortic regurgitation, one of advanced mitral and aortic disease, and one of congenital valvular disease (? pulmo- nary). In all of these cases excellent results were obtained, and no anxiety was experienced. Although nitrous oxide, as ordinarily adminis- tered, is generally regarded as safe even in advanced heart disease, I must confess that I prefer not to adopt the customary plan of administration in such subjects. The case is (juite different when nitrous oxide is given with oxygen, for the temporary impairment of respiration, with its consequent temporary general venous engorgement, is prevented, so that no undue strain is thrown upon the ric^ht side of the heart. I have notes of an 68 The Patient interesting- case which occurred at the Dental Hospital, which is perhaps worth quotino-. The patient was a pale, thin, breathless man, who had been an in-patient at Charing Cross Hospital with oedema of the legs and cardiac symptoms following rheumatic fever. He was stated to have double aortic and mitral disease. The heart's action was very tumultuous and irregular. Nitrous oxide, free from oxygen, was administered to him by a skilled anaes- thetist on two occasions. On one of these his pupils became enormously dilated, his breathing very difficult, and his conjunctiva insensitive. His appearance was so alarming that no operation was performed. The tongue was drawn forwards, and gradually the threatening symptoms vanished. I sub- sequently administered nitrous oxide and oxygen to this patient. The pupils never became widely dilated, and no trouble what- ever occurred. In the case of a lad with aortic regurgitation, who was pale, probably from fright, before the administration, the pulse markedly improved as the inhalation proceeded, and the pallor lessened ; during the operation the normal florid colour was completely restored. I have observed exactly the same train of symptoms in a patient who, at the time of the administration, had an ex- ceedingly feeble pulse, and was pale from The Patient 6g shock produced by fruitless attempts to ex- tract a tooth without an anaesthetic. One patient to whom I administered the mixture was the subject of a large intra-thoracic aneurysm ; no bad effects followed. In elderly persons with atheromatous vessels, it is better to administer nitrous oxide and oxygen than nitrous oxide alone. Dr. Leonard Hill finds that blood pressure under nitrous oxide and oxygen either rises slightly or remains constant ; whereas as Kemp has shown, there is a considerable rise in tension when nitrous oxide is administered in its pure state. '^ Affections of the nervous system. — I have anaesthetised numerous epileptics, and have not yet met with a case in which an epileptic attack has arisen during or immediately after the inhalation, I have, however, had experi- ence of one case in which a well - marked seizure took place during the administration of pure nitrous oxide ; but as the attack came on very early in the administration it would be wrong, I think, to assume that the absence of oxygen had any influence in its causation. Pregnancy. — Nitrous oxide and oxygen may be safely given to patients during the latter months of pregnancy. Although nitrous oxide, free from oxygen, is generally regarded as admissible, it certainly seems to me that 70 The Patient it is wiser to adopt a non - asphyxiating method in these cases, I have on more than one occasion administered nitrous oxide and oxygen, for a dental operation, within a week of the expected confinement, and without any difficulty or subsequent trouble arising. This plan of obtaining anaesthesia, indeed, is of great value in such cases, for on the one hand we are able to avoid the asphyxial accompani- ments of an ordinary nitrous oxide inhalation, and, on the other, the possible after-vomiting of ether or chloroform narcosis. 71 CHAPTER VI. THE ANAESTHESIA. The anaesthesia which is available for a dental operation commences at the moment the face-piece is removed, and should be re.- garded as terminating at the first indications of returning semi-consciousness. Nothing has contributed more to the unfavourable opinions held by the public concerning " laughing gas " than the practice of continuing the operation whilst the patient is emerging, or has emerged, from deep ansesthesia. With pure nitrous oxide the available unconsciousness is com- paratively short, and the transitional zones between deep ansesthesia, semi-aneesthesia, and normal consciousness are so narrow that errors of judgment as to whether or not the patient is capable of feeling pain at a given moment are to a certain extent excusable. But with nitrous oxide and oxygen the avail- able anaesthesia is distinctly longer, and the transitional zones are distinctly broader, so that operations which do not admit of being perfectly painlessly performed under nitrous 72 The Anesthesia oxide as customarily administered, may be conducted with an absolute freedom from pain and discomfort under nitrous oxide and oxygen. Immediately the anaesthetist has removed the face-piece he should direct his attention to supporting the patient's lower jaw, or steady ing the head, according to the nature of the operation. He should at the same time keep a sharp look-out for teeth or fragments of teeth falling or shooting backwards towards the fauces. It is generally customary for lower teeth to be removed before upper. If both sides of the mouth are to be operated upon, and if the order of events is a matter of indifference to the surgeon and to his patient, it is better for the left side to be first dealt with, for it is easier to introduce the Mason's gag, should one be required, from this, i.e., the side upon which the anaesthetist stands, than from the other. The duration of the available anaesthesia varies somewhat in different cases. The average duration is about 44 seconds. Other things being equal, the longer the inhalation the longfer will be the resultino- anaesthesia. On many occasions, for example, I have con- tinuously administered the mixed gases for three minutes, and have thus been able to The Anesthesia 73 secure an available aneesthesia of 50, 60, or even 70 seconds. But although the duration of the inhalation has a very marked influence in determining the length of the subsequent unconsciousness, there are numerous other factors. The type of subject occupies a pro- minent position amongst these. Children, excitable and neurotic patients, alcoholics, and inveterate smokers, generally remain a shorter time than usual under the influence of the anaesthetic. On the other hand, anaemic, non- excitable young men and young w^omen, middle-aged women of spare build, and persons of both sexes who are in indifferent health, may remain tranquilly anaesthetised for a comparatively long time. The amplitude and rate of the breathing immediately after the face-piece is removed is another factor. Should the operation be such that the lower jaw becomes depressed towards the sternum, temporarily obstructed respiration may ensue and this, by preventing the exit of the imprisoned anaesthetic and the entrance of atmospheric air, will lead to a prolongation of the anaesthesia. The same result may be brought about by sudden alterations in the posture of the head, by which respira tion becomes mechanically obstructed. A somewhat similar lengthening of the usual anaesthesia is occasionally observed in stout, 74 The AncBsthesia wheezy subjects, and in those with chronic bronchitis and emphysema ; imperfect expan- sion of the bases of the lungs in these subjects being favourable to the retention of the anaes- thetic gas for a longer time than usual. Generally speaking, the patient remains perfectly quiet and passive during the opera- tion, provided that a proper limit be placed upon the latter. At the first application of the. forceps or elevator, there is, however, in many cases, a very slight and not incon- venient reflex moYement of the body. In exceptional cases the movement is greater. Should the colour have been slightly dusky or paler than the normal when the face-piece was removed, it will quickly become natural when air is admitted. But if the operator should depress the lower jaw, or in any other way drive the tongue backwards, and thus temporarily arrest the breathing, some duski- ness will necessarily be produced.. Phonation at the beginning of the operation is hardly ever evoked. Should the patient have been making phonated sounds during the inhalation they may increase somewhat during the operation ; but it is not uncommon for the exact reverse of this to take place, and for such sounds to be suddenly arrested when the tooth is grasped by the forceps. The available anaesthesia is far quieter and The AncBsthesia 73 of a better type than when nitrous oxide has been given free from oxygen. In exceptional cases, and more particularly in children and very nervous subjects, reflex phonation may occur, but as is well known, such phonation does not necessarily indicate the perception of pain or, indeed, any knowledge of ' the operation being performed. It is, moreover, usually not remembered. There are unfortunately no systematic rules by which we can invariably tell when the available anaesthesia has come to an end. An endeavour should be made to so adjust the administration and the operation that after the latter has been completed there shall still remain a slight reserve of anaesthesia. In the event, however, of unexpected difficulties arising in the operation, the anaesthetist is rightly expected to give the signal for discon- tinuing the extraction. It is by no means always an easy matter to say whether, at a particular juncture, the operation should be terminated or continued. Nothing but practical experience is of any avail in deciding- points of this kind. The general aspect of the patient, the state of the eyes and pupils, the character of any sounds that may be uttered, and the nature of any movements that may take place — these and other indications have to be taken into careful consideration. 76 The Anesthesia The most successful cases are those in which the operation is performed at the acme of anaesthesia, so that not only is there an absence of all pain, but the patient experiences none of those unpleasant sensations which are likely to arise when an operation takes place during semi-consciousness. A re-application of the face-piece before consciousness has been regained is not to be recommended, except under certain circum- stances, for such a plan of procedure is almost certain to be followed by inconvenient if not by objectionable asphyxial effects. If, how- ever, the patient's head be nearly vertical, if the attempt to remove a tooth or teeth should have led to no haemorrhage, and if the face- piece be applied before inconvenient movement has taken place, there is but little objection to the re-application. Generally speaking it is better, in the event of an extraction proving exceptionally difficult, to desist from the operation, to allow the patient to recover consciousness, to request him to thoroughly wash out his mouth with water, possibly containing a small quantity of sulphate of zinc or some other astringent, and to administer the mixture a second time. The circumstances will in this way be far more favourable than if a hurried attempt to extract a difficult tooth be made during imperfect The Anesthesia 77 anaesthesia. Re-administrations of the mixture during partial or complete anaesthesia, as well as those conducted after an interval of several minutes' consciousness, are liable to induce nausea and vomiting, so that, whenever pos- sible, they should be avoided. In concluding this chapter it may be men- tioned that there is no better anaesthetic than that under consideration for such operations as drilling into pulp cavities and opening up the antrum. The absence of all jactitation and irregular breathing renders such operations far easier of performance than when nitrous oxide is used free from oxvoen. 78 CHAPTER VII. EXCEPTIONAL CASES. Although the method of producing anaes- thesia which has been described is the safest of all those at present known to us, it is un- doubtedly the most complex. From this it follows that partial or complete failure to bring about typical non-asphyxial nitrous oxide anaes- thesia will be liable to occur to everyone who has not had much experience of the method. As more and more experience is gained, it will be found that difficulties and exceptional cases are less and less frequently met with, and that eventually such a state of proficiency will be gained that cases displaying any unusual departure from the normal type will be rare. Laughter, singing, and articulate shouting. Inarticulate phonation. — The occurrence of such symptoms during the administration usually indicates either that air is gaining admission with the mixture, or that the oxygen proportion is too high. Muscular phenomena during inhalation. — Exceptional Cases 79 These may comprise: (i) Strictly voluntary movements at the outset of the administration, as, for example, putting up the hands with the object of removing the face-piece, &c. Some patients imagine that by moving their fingers, hands, or feet, at the beginning of the administration, they may afford valuable assist- ance to the anaesthetist by providing him with a reliable sign that consciousness is present. Unfortunately, movements originally voluntary not only tend to become automatic as conscious- ness becomes lost, but they may even increase to such a degree that the patient's whole body shares in the movement. (2) Uncontrollable nervous movements, also at the outset of the administration, e.g., tremor of the legs, or fidgety movements of arms, hands and fingers. (3) Intoxication - movements, such as move- ment of the head from side to side, stamping, alternate thrusting out of the arms, &c. Such movements as these are often associated with laughter or shouting, and like the latter are usually due to air or too large a percentage of oxygen in the mixture. I have notes, how- ever, of one highly exceptional case — that of a young lady about 20, who after four or five breaths of the mixture began to move so in- conveniently that it was impossible to continue the administration. A second inhalation was attempted. Precisely the same phenomena 8o Exceptional Cases appeared ; but by obtaining- assistance anses- thesia was eventually induced. Two teeth were painlessly removed. There was nothing abnormal in the patient's appearance, nor did she seem to be hysterical. She gave a history of having had "gas" given to her by a dentist who broke the tooth and said he had never before seen a case similar to her own. So far as I could judge, the patient seemed anxious to help us, and implicitly obeyed our instructions as to breathing, posture, &c. (4) Tonic spasm. Some degree of tonic spasm is not uncommon, especially in men, but extreme conditions, such as those to which the terms opisthotonos and emprosthotonos have been applied are very rare. Sometimes the tonic spasm affects the neck muscles, and the head gradually becomes turned to one or other side. It is difficult to say what these movements depend upon. In many cases they occur when the percentage of oxygen is rather less than usual, but this is not always so. Indeed, if the patient be a vigorous, athletic man, and too much oxygen be admitted with the nitrous oxide, excitement will arise, and marked rigidity may be occasioned. It is on such occasions as these that some degree of respira- tory spasm, from contraction of thoracic and abdominal muscles, is prone to occur. In this way a primary excess of oxygen may lead to Exceptional Cases 8i secondary cyanosis, or even to jactitation. (5) Clonic spasm. Epileptiform twitchings always indicate a diminution in the normal oxygen supply. When the diminution is but slight the clonus may be so mild that it may escape detection. The most marked clonic spasm (jactitation) is met with in children when nitrous oxide free from oxygen is rapidly inhaled. The epileptiform movements may affect all parts of the body. Whenever the anaesthetist detects any such movements com- mencing during the use of nitrous oxide and oxygen, he should at once increase the oxygen supply and the movements will quickly vanish. (6) Fine tremor of arms and legs occurring during unconsciousness. This is rare ; I have only seen it in three or four cases, and it came on when anaesthesia was fairly well estab- lished. {7) Certain peculiar tonic movements of deep anaesthesia. These are very remarkable. After a lonij inhalation of the oases, and when anaesthesia is well established, as may be seen from the state of the eyes, patients sometimes display peculiar movements of the arms, legs, neck and body. The arms and legs will slowly move in a certain direction ; the head will slowly turn to one side, or the whole body may begin to turn gradually in one direction or another. The movements often suo-Cfest a return of consciousness ; but this is not so. 6 82 Exceptional Cases When the face-piece is removed a long and perfectly tranquil anaesthesia follows. The tonic movements differ from those referred to in (4), for they come on after relaxation of the muscular system has been produced. For want of a better term I have called the condition " secondary rigidity." Cyanosis. — This always depends upon want of oxygen. It may either be brought about by the nitrous oxide bag becoming distended, so that little or no oxygen passes from the oxygen bag ; or it may arise from respiratory spasm incidental to laughter, crying or coughing ; or the so-called "holding the breath" may take place during or immediately after the inhalation of the gases, and thus induce cyanosis. This " holding the breath " is a misnomer, for the patient is not conscious at the time. Certain patients, especially men who are alcoholics or iriveterate smokers, are prone to muscular spasm, and when this spasm affects the chest and abdomen, temporarily arrested breathing necessarily occurs. There is no occasion for alarm in these cases, as the breathing quickly regains its normal rhythm. Cyanosis may also occur in connection with the presence of morbid states, such as enlarged tonsils, nasal polypi, post-nasal adenoid growths, bronchitis, &c. And, lastly, a faulty posture of the patient may induce it (see remarks, p. 40). Exceptional Cases 83 Shallow, imperceptible, or arrested breath- ing, associated with a oood pulse and colour. This condition, which should not alarm the anaesthetist, is discussed on p. 53. Very violent respiration at the outset of the administration may generally be corrected by requesting the patient to breathe more quietly. Should consciousness have been lost when this kind of respiration occurs, an attempt may be made to check it by adminis- tering rather less oxygen. Generally, how- ever, the condition subsides spontaneously, to be followed by "respiratory calm" (see p. 53). In some instances, and especially when patients are very nervous, the whole body may move backwards and forwards synchronously with the exaggerated breathing. Coughing, crying. — Each of these is liable to be followed by asphyxial manifestations, even if the mixture contain a considerable percentage of oxygen. The former may be dependent upon faulty posture, and is to be treated by tilting the head forwards. Retching or vomiting during the adminis- tration. — Retching at the very outset of the administration is to be treated as described on p. /|2. .Should retching occur towards the end (jf an administration, the inhalation should be discontinued. Retching movements are most likely to come on in protracted administrations. 84 Exceptional Cases and when a considerable percentage of oxygen has been used. They are not necessarily followed by vomiting, even though food be present in the stomach. When the patient has abstained from food for several hours, both retching and vomiting are very exceptional. Micturition. — I have only known this to occur twice in the ] 5 years during which I have administered nitrous oxide and oxygen, and in these cases no such accident would have taken place had the usual precautions been adopted. Dangerous symptoms. — When sufficient oxygen is administered with nitrous oxide to prevent asphyxial complications there is every reason to believe that the anaesthesia produced is free from risk to life. A careful study of every fatality which has been recorded in connection with the use of nitrous oxide oras o shows that in most, and probably in all cases in which this agent has caused death,' absence of oxygen has been primarily responsible for the occurrence. A similar explanation is doubtless applicable to those reported cases in which alarming symptoms have taken place during the administration of nitrous oxide by the customary method. The addition of oxygen to nitrous oxide renders this agent respirable, and robs it of its chief, if not its only, risk. There has not yet been recorded a single Exceptional Cases 85 fatality from nitrous oxide and oxygen. Al- though I have now used nitrous oxide with oxygen in several thousand cases, I have only met with two which have given me the slightest anxiety. In each case the patient was a powerfully built thick-necked man, and breathing became temporarily obstructed by the tongue being spasmodically drawn towards the pharyngeal wall. It was only necessary to separate these structures by means of the finger in order to re-establish breathing. Highly exceptional cases. — It is only right to state, before concluding this chapter, that although exceptional cases are, in most in- stances, traceable either to some error in the preparation of the patient, or to some fault in the actual administration, they are not always referable to such causes. Thus there are some patients who, whatever plans may be adopted in administering the mixed gases, cannot be made to pass into the tranquil state of anaesthesia which it is desired to establish. Under such unusual circumstances, the admin- istrator must be satisfied with an anaesthesia which ap^proacKes to, or is identical with, that ordinarily obtainable with nitrous oxide alone — in other words, he has to cut off the oxygen supply and terminate the case with the usual phenomena of nitrous oxide narcosis. Then there are other patients who, although they 86 Exceptional Cases can be made to exhibit the usual signs of nitrous oxide and oxygen anaesthesia, remain such a short time under the influence of the anaesthetic that one cannot help feeling dis- satisfied with the result. With regard to such cases as these, all one can say is that with nitrous oxide alone they would certainly have been even less satisfactory. Fortunately, they are extremely exceptional, so that we need not further consider them here. 87 CHAPTER VIII. AFTER-EFFECTS. A CAREFUL consideration of the circum- stances under which after-effects are likely to arise is of special importance ; for the one weak point, if such it may be termed, in nitrous oxide and oxygen anaesthesia, is that this anaesthesia is associated with a somewhat greater liability to unpleasant after-effects than that resulting from the administration of nitrous oxide free from oxygen. Provided, however, that the diet of the patient has been properly regulated, and that the inhalation has not been protracted, re- covery from the effects of nitrous oxide and oxygen usually takes place without the slig"htest discomfort. I have notes of several cases, indeed, in which the patient's condition immediately after the operation was more satisfactory than after a similar operation previously performed under nitrous oxide free from oxygen. Thus I have known a patient experience severe headache after an ordinary administra- 88 After -Effects tion of pure nitrous oxide, and to suffer from no such discomfort after the inhalation of this gas with oxygen. In another of the cases of which I have notes the administration of nitrous oxide per se had been followed by numbness of the arms and legs, and blueness of the hands, the symptoms persisting for some time. Recovery was, however, perfect after nitrous oxide and oxygen. In another case, that of a healthy-looking lad, the boy looked much better after the administration of the gas with oxygen than after an administra- . tion which had previously been conducted in the ordinary way. In a fourth case, that of a man ^2) years of age, who had on a previous occasion experienced temporary loss of vision after Inhaling pure nitrous oxide, no such symptoms were noted after the use of nitrous oxide and oxygen. The infrequency of dis- tressing dreams when oxygen is used with nitrous oxide Is referred to below. Should the inhalation have been some- what protracted, recovery will probably not be quite so satisfactory as after nitrous oxide alone. On such occasions as these, the patient may remain dazed and torpid for a few minutes, or he may complain of sleepi- ness and wish to be left undisturbed. In some cases, giddiness, headache, or feelings of numbness and tingling In the limbs may be After -Effects 89 experienced. Nausea, with or without actual retchinor movements, mav also be induced by prolonged administrations, and if there be food present in the stomach, or if blood has been swallowed, vomiting may occur. As already mentioned (p. 38), it is very important, when a rather difficult dental opera- tion has to be performed and as long an anaesthesia as possible is desired, to carefully regulate the patient's diet. If this be done, inhalations lasting from two to three minutes mav generally be conducted without any sub- sequent nausea occurring. I find, on looking through my note books, that, of the cases in which retching or vomiting occurred after inhalation, there are eleven in which the interval between the takine of food and the administration is re- corded. Of the retching cases, one was a female of 43 — interval 2'i hours ; another was a female of 45— interval 3 hours ; the third was a male of 23 — interval 3 hours. Of the vomiting cases, one was a female of 35 — interval 4|- hours ; one was a female of 13— interval 2^ hours ; one was a female of 10 — - interval 2\ hours. The rest of the vomiting cases were males. Four were aged 15 — in- tervals 2| hours, 2f hours, 2 hours, and |- an hour respectively ; one was aged 12 — interval 3} hours. Although these facts are very go Apev-Effects meagre, they bring into relief two interesting clinical points. One of these is that, of the cases in which vomiting occurred the average interval after food was 2^ hours. The other is that, of all subjects, boys from 10 — 16 are most likely to suffer from vomiting after nitrous oxide and oxygen. The lesson to be learnt from these observations is that, if we wish to avoid unpleasant after-effects, a long interval after food must be enforced, particu- larly in the case of young male subjects. Transient feelings of faintness, pallor, and feebleness of pulse are very rare, and are in most, if not in all cases, associated with nausea or impending vomiting. A word may be said as to the treatment of nausea, retching, and vomiting. Slight nausea generally subsides spontaneously after a few minutes. The patient should not be permitted to lie back in the chair, otherwise the swallowing of blood and saliva may favour vomiting. He should bend forwards, keep his eyes closed, and frequently wash out his mouth. Should the feeling of nausea be considerable, half a tumbler of water, so hot that the finger can hardly be immersed in it, should be given to the patient to drink. The relief afforded by this simple measure is often remarkable. If retching movements should be present, they will usually quickly subside After -Effects 91 after this treatment. Even if vomiting have taken place, a draught of very hot water may be given with advantage. Should pallor and faintness attend these gastric disturbances, the patient should be placed horizontally, prefer- ably in the lateral posture. Hysterical outbursts, crying, laughing, and similar emotional disturbances are less common than after nitrous oxide free from oxygen. The one case in which I met with a temporary maniacal seizure is referred to on p. 65. I have also once met with curious rigidity of a cataleptic character after the administration. The patient was a female, aged 26. She displayed the typical phenomena of nitrous oxide and oxygen anaesthesia ; but after the operation was over she sat for a few minutes with outstretched hands, open mouth, and closed eyes. Her colour was unaltered. Distressing dreams are less common after nitrous oxide and oxygen than after nitrous oxide alone. The cause of this difference is difficult to define, but it is probably connected with the deeper form of anaesthesia which undoubtedly follows the inhalation of the mixture. Generally speaking, either no dream whatever is experienced, or the dream is of a pleasant description. 92 BIBLIOGRAPHY. 1. Lyman, Henry M. : "Artificial Anaestliesia and Anaesthetics," 1883. 2. Rymer, Samuel Lee: "Remarks upon the Use of Nitrous Oxide in Dental Operations " : " The Dental Review : A Quarterly Journal of Dental Science," Jan., 1864. 3. Andrews, E. : "Chicago Medical Examiner:" See- also " Brit. Journ. Dental Science," 1869, p. 22. 4. Bert, Paul : " Comptes Rendus de la Societe de Biologic," 1880, Tom. v., 6eme Ser., p. 40. 5. Bert, Paul: " Anesthesie par le protoxyde d'azote employe sous tension" : " Comptes Rendus de la Societe de Biologic," Tom. v., 6eme Ser., 1880, p. 152. 6. Bert, Paul: " Du protoxyde d'azote sous tension; son action a doses anesthesiques ne s'etend par sur le systeme nerveux sympathique ": " Comptes Rendus de la Societe de Biologic," 1880, Tom. v., 6eme Ser., p. 233. 7. Bert, Paul : " Sur la possibilite d'obtenir, a I'aide du protoxyde d'azote, une insensibilite de longue duree, et sur I'innocuite de cet anesthesique " : " Comptes Rendus de I'Academie des Sciences," 1878, Tom. 87, p. 728. 8. Bert, Paul : " Anesthesie par le protoxyde d'azote " : "Comptes Rendus de la Societe de Biologic," Ser. 7, Tom. i, Pt. 2, p. 19. 9. Bert, Paul : " De I'emploi du protoxyde d'azote dans les operations chirurgicales de longue duree " : " Le Progres Medical," No. 9, Feb. 28, 1880, p. 161. Bibliography go 10. Klikowitsch, Stanislaus : " Ueber das Stickstoff oxydul als Anaestheticum bei Geburten " : "Archiv. fur Gynaskologie," 1881, Band xviii., p. 81. 11. Winckel, F. : "A text-book of Obstetrics" (Trans- lated by Edgar), 1890, p. 187. 12. Martin, Claude : " De I'Anesthesie par le protoxyde d'azote avec ou sans tension," Lyons, 1883. 13. Hewitt, Frederic: Anaesthetics and their Adminis- tration, 2nd edition, igoi, 14. Bert, Paul : " Anesthesie prolongee obtenue par le protoxyde d'azote a la pression normale " : " Comptes Rendus de I'Academie des Sciences," Tom. 96, 1883, P- 1271. 15. Hillischer, H. T. : "Ueber die allgemeine Ver- wendbarkeit der Lustgas-Sauerstoffnarkosen in der Chirurgie " (Paper read at the 59th meeting of German Natural Philosophers and Physicians at Berlin, Sept. 21, 1886), 16. Hillischer, H. T. : " Ueber Lustgas und Lustgas- Sauerstoff (Schlafgas) " (Paper read before the Royal Society of Physicians in Vienna, May 27, 1887). 17. Hillischer, H. T. : "Ueber die Verwendung des Stickoxydul-Sauerstoffgemenges zu Narkosen " (Paper read at the Annual Meeting of the Central Union of German Dentists in Berlin, 1887). 18. Hillischer, H. T, : " Neue Apparate fur Schlafgas" : " Correspondenzblatt f. Zahnarzte," Oct., 1890. 19. Hillischer, H. T. : " Wie soil man mit Schlafgas narkotisiren ? " : " Oesterr-ungar. Vierteljahres- schrift fur Zahnheilkunde," Oct., 1890. 20. Witzel, Adolph : " Deutsche Zahnheilkunde, in Vortriigen," Wein, 1889. 21. Hewitt, Frederic: "The anaesthetic effects of Nitrous Oxide and Oxygen when administered at ordinary atmospheric pressures, with remarks on 800 cases": "Trans. Odont. Soc. Gt. Britain," June, 1892. 94 Bibliography 22. Hewitt, Frederic : " On the Anaesthesia produced by the Administration of Mixtures of Nitrous Oxide and Oxygen " : " Lancet," April 27, 1889, 23. Hewitt, Frederic : " A new and portable apparatus for the Administration of Oxygen with Nitrous Oxide " : " Journ. Brit. Dental Association," Oct. 15, 1892. 24. Hewitt, Frederic : " Further Observations on the use of Oxygen with Nitrous Oxide": "Journ. Brit. Dental Association," June, 1894. 25. Hewitt, Frederic : See " Trans. Roy. Med. and Chir. Soc," vol. Ixxxii. 26. Hewitt, Frederic : " On some essential points in Administering Anaesthetics for Dental Operations ; with special reference to the subject of Posture": "Journ. Brit. Dental Association," Oct., 1896. 27. Oliver, George : " Pulse-gauging," p. 83. 95 INDEX. Adenoid growths of nasopharynx, patients with, 66, 82. Adjustment of Proportions in administering nitrous oxide and oxygen, 51. Administration, in ordinary or average cases, 43 et seq. ; duration of, 55. Admission of Oxygen during administration, 46, 49, 50, 51. 55. 59> 60, 62, 66. After-effects, 21, 87 et seq. Age, influence of, 14, 58, 73. Air, necessity for excluding, in administering nitrous oxide and oxygen, 17, 48 ; mixed with nitrous oxide in early cases, 4, 6 ; total exclusion of, considered necessary, 6. Air-cushion, use of, in obtaining proper posture, 41. Air-way, obstructive affections of the, 66. Alarming symptoms (see Dangerous symptoms). Alcoholic subjects, 15, 64, 73, 82. Anemic subjects, 64, 73. An/ESTHESIa, available for dental operations, 21 ; characteristics of nitrous oxide and oxygen, 53 ; duration of, 59, 72, 86; termination of, 75. Andrews, Prof. E., the first to use nitrous oxide and oxygen, 7. Aneurysm, patients suffering from, 66, 69. Anox>emic convulsions (see Epileptiform movements). Antiseptics, application of, to regulating apparatus, 27. Antrum, opening up the, 77. Aortic disease, patients suffering from, 67, 68. Apncea, physiological, 52, 53. 96 htdex Apparatus for administering nitrous oxide and oxygen : Bert's, g ; Hillischer's, 14, 18 ; the author's earlier forms, 15, 19; the author's present, 19, 25 et seq. ; necessity for examining occasionally, 34. Appliances which should be in readiness, 38. Arterial tension under nitrous oxide and oxygen, 9, 69. AsPHYXiAL PHENOMENA, absence of, when oxygen is used, 8, 9, II, 16, 51 ; in patients with respiratory affections, 66 ; induced by nitrous oxide, 7, 49, 83 ; from too little oxygen, 49, 52 ; in alcoholic subjects, 64 ; induced by coughing or crying, 82. Atheromatous vessels, patients with, 69. Athletic subjects, 60, 80. Available anesthesia for dental operations, 71. Average or ordinary cases, the administration in, 43. et seq. Bags for administering the gases, 25, 27, 30 ; fulness and relative sizes of, during administration, 48. Beards, patients with, 61. Bert, early work of, in connection with use of oxygen, 7, 8, 9 ; his apparatus, 9 ; his experiments at ordin- ary atmospheric pressures, 13 ; his method used by Martin, 11. Bladder, advisability of emptying, 38, 84. Blood, Bert's views as to solubility of nitrous oxide in, 8. Blood-pressure (see Arterial tension). Blueness of the features (see Cyanosis). Breathing, amplitude and rate of, 45, 73 ; at outset of administration, 45, 48, 82 ; cessation of, associated with good pulse, 53, 83 ; diaphragmatic, 39 ; em- barrassment of, 59; hardly perceptible, 52, 53, 58, 83 ; of deep anaesthesia, 53 ; patients suffering from difficulty of, 66 ; provisions for free, 39 ; restricted, 39, 46 ; snoring, 52, 53, 58 ; temporarily obstructed, 73> 74» 83 ; violent, 83. Breathlessness, cardiac, 66. Bronchial affections, patients with, 61, 66, 74. Index 97 Cardiac affections (see Heart). Cataleptic state after inhalation, 91. Characteristics of nitrous oxide and oxygen anaes- thesia, 52. Children, suggestions for anaesthetising, 58, 73. Chloral, patients addicted to, 65. Circulatory system under nitrous oxide and oxygen, io> 53) 67, 90 ; affections of, 67 (see also Heart). Clonic muscular movements, 52, 81 (see also Epilep- tiform movements) . Clothing, importance of loose, 39. Clover's improvements in early apparatus for nitrous oxide, 6. Co-aptatiox of face-piece, 46, 47. Colour of features, 10, 11, 21, 52, 53, 62, 63, 74. CoLTON Dental Association, 5. Colton's administrations of nitrous oxide, 25. Combined stand and union for nitrous oxide and oxygen cylinders, 27. Complexion, 62, 63. Conjunctival reflex, 53, 54. Contra-indications to nitrous oxide and oxygen, 14, 66. Coughing, 82, 83. Crying, 4, 58, 82, 83 ; as an after-effect, 91. Cushion, use of inflated air, 41. Cyanosis, ii, 15, 22, 49, 81, 82 (see also Duskiness and Lividity). Cylinders for nitrous oxide and oxygen, 25, 27, 28. Dangerous symptoms, appliances for treatment of, 39; occurrence of, 84. Davy, discoverer of anaesthetic properties of nitrous oxide, II. Dazed feelings after inhalation, 88. Definite mixtures of nitrous oxide and oxygen, effects of, 21 ; objections to, 23. Delayed effects of admitting more or less oxygen, 55. Diet, regulation of, 37, 38, 87, 89, go. Disturbing influences during administration, 43. DoDERLEiN, 10. 7 g8 Index Dreams, 91. Drilling into pulp-cavities, 77. Duration of inhalation, 21, 55; of anaesthesia, 21, 59, 72, 85. ■ Duskiness of the features, 21, 49, 52, 63 (see also Lividity and Cyanosis). Dyspncea, patients suffering from, 66. Early administrations of nitrous oxide, 2 ei seq. ; of nitrous oxide and oxygen, 7. Elderly persons, 59, 6g. Emergencies under nitrous oxide and oxygen, appliances for treatment of, 38. Emphysema, patients with, 66, 74. Emprosthotonos, 80. Epilepsy, patients suffering from, 14, 69. Epileptiform movements, absence of, when oxygen used with nitrous oxide, 16, 49; presence of when oxygen supply diminished or cut off, 21, 49; conse- quent upon want of oxygen due to respiratory spasm, 79 (see also Muscular phenomena — clonic). Evans' demonstration, 5 ; his apparatus for nitrous oxide, 5. Exceptional cases, 78 et seq. ; highly exceptional cases, 85- Excitable subjects, 62. Excitement, absence of, 51 ; in early nitrous oxide administrations, 4 ; under nitrous oxide and oxygen, II, 49, 50, 53- Expiratory valve of regulating apparatus, 25, 32. Extension of head upon the spine, objections to, 40. Eyes and eyelids, state of, during anaesthesia, 53, 54. Face-pieces, 25, 35 ; fitting of, 47, 48 ; re-applicatioh of, 76. Faintness as an after-effect, 90. Fitting of face-piece, 47, 48. First administration of nitrous oxide, 2 ; of nitrous oxide and oxygen, 9. Food, regulations as to, 37, 38, 87, 89, 90. Frequent administrations, 65. Index 99 Fulness and relative sizes of bags during administra- tion, 48. Gasometer methods, 17, 20. General condition of the patient, 59. General results obtained by using different percentages of air or oxygen, 21. Giddiness as an after-effect, 88. Hair about face, patients with, 61. Headache as an after-effect, 87, 88. Head, adjustment of, 40. Health, general state of, 59, 73. Heart affections, patients with, 14, 61, 66. Hill, Dr. Leonard, on blood pressure, 69. Hillischer, Dr., first to employ nitrous oxide and oxygen in dentistry, 13 ; his apparatus, 14 ; his method, 14; his views as to the pulse, 54; objec- tions to his apparatus, 18. History of nitrous oxide, i et seq. ; of nitrous oxide and oxygen, 7 et seq. " Holding the breath," 48, 82. Hot water, in the treatment of after-nausea and vomiting, 90. Hydrothorax, patients suffering from, 66. Hysteria as an after-effect, 91. Hysterical subjects, 62. Inhalation, length of, 55. Insusceptibility to nitrous oxide and oxygen, 85 et seq. Intermittent action of heart before administration, 59. Intermittent administrations of nitrous oxide and air, 7. Intoxication-movements, 79. " Jactitation " (see Muscular phenomena (clonic) and Epileptiform movements). Keeping nitrous oxide and oxygen together, 24. Kicking, 49. Klikowitsch, 10. loo Index Laboured breathing, 15. Laughter, 4, 49, 52, 78, 79; as an after-effect, 91. Length of available anaesthesia, 59, 71, 86; of inhala- tion, 55. LiviDiTY of the features, 11, 49 (see also Duskiness and Cyanosis). Loose clothing, importance of, 39. Lungs, diseases of, 14. Mania, temporary, as an after-effect, 65, 91. Martin, Dr., administrations of, 11. Men as subjects for nitrous oxide and oxygen, 59, 73. Micturition, 38, 84. Morphine, patients addicted to, 65. Mouth-props, 38, 42. Mouth-tubes for administration, disadvantages of, 47. Movements (see Musculav phenomena). Muscular phenomena, 23, 53, 78; clonic or epileptiform, 16, 49, 52, 81 ; in alcoholic subjects, 64 ; inconve- nient, 78 ; in habitual smokers, 65 ; intoxication, 79; reflex, 74, 82; restless, 52; tremulous, 8r, 82 ; tonic, 53, 65, 80, 81 ; uncontrollable nervous, 79; voluntary, 79. Narcotics, habitual use of, 65. Nausea, as an after-effect, 89 ; treatment of, 90, Nervous and neurotic subjects, 62, 64, 73. Nervous movements, 79. Nervous system, diseases of the, 69. Nitrogen, higher oxides of, produced when nitrous oxide and oxygen kept together, 24. Numbness of the extremities, as an after-effect, 88. Obesity, 61, 73. Objections to the use of definite mixtures, 23. Obstructed breathing during operation, 73. Obstructive respiratory affections, 66, 82. Old age, nitrous oxide and oxygen in, 59, 69. Oliver, Dr., pulse observations by, 54. hidex loi Operation, the anaesthetist and the, 72, 75. Operations, difficult, 76, 89. Opisthotonos, 80. Ordinary or average cases, the administration in, 43 et seq. Oxygen, admission of, during administration, 46, 49, 50, 51, 55, 59, 60, 62, 66; delayed effects of admitting more or less, 55 ; percentage of (see Percentage) ; symptoms due to too large a proportion of, 49 ; symptoms due to too little, 49. Pallor from nervousness, 64, 68 ; as an after-effect, 90. Patient, the, 57 et seq. Patients, different types of, 57. Percentage of oxygen in Bert's administrations, 8, 9, 10, 12 ; in Klikowitsch's, Winckel's, Doderlein's, 10 ; in the various mixtures used by the author in his "gasometer" cases, 20; and Zweifel's ad- ministrations, 11; in Martin's administrations, 11; in Hillischer's administrations, 14 ; in the author's administrations, 16, 17, 18 ; in the author's regu- lating apparatus, 34, 35, 46. Pronation, 21, 52, 63, 65, 74, 78. Phthisis, pulmonary, 66. Physiological apncea, 52, 53, 82. Physique of patient, influence of, 60. Posture, influence of, 40, 73, 82, 83. Precautions (see Preparations). Pregnancy, nitrous oxide and oxygen in, 69. Preparations necessary, 37 et seq. Priestley, nitrous oxide discovered by, i. Prolonged administrations of nitrous oxide and oxygen, 12, 55, 87, 88, 89. Proportions of oxygen (see Percentage of oxygen). Props (see Mouth-props). Pulmonary affections, patients with, 66. Pulp-Cavities, drilling into, 77. Pulse, feeble, after inhalation, 90 ; under nitrous oxide and oxygen, 53. I02 Index Pupils, state of, 55. Quantity of mixture required to produce anaesthesia, 21, 56. Re-administrations, 73. Re-application of face-piece, 76. Recovery from nitrous oxide and oxygen anaesthesia, 63 (see also After-effects). Reflex, conjunctival (see Conjunctival) ; movement during operation, 74, 82. Regulating apparatus, necessity for, in administering nitrous oxide and oxygen, 14, 19. Regulating stop-cock and mixing chamber (the author's), 30 et seq. Requirements for a regulating apparatus, 25. Respiration, administration to patients with impaired, 60, 61, 66 (see also Breathing). " Respiratory calm," 53, 83. Respiratory spasm, 80, 82, 83. Retching and vomiting, as after-effects, Sgetseq.; treat- ment of, 90. Retching movements, caused by inserting mouth-prop, 42 ; occurring during inhalation, 83. Rigidity, muscular, 53, 65, 79 ; of deep anaesthesia (" secondary rigidity "), 82. Rymer's administrations of nitrous oxide, 5. Safety of nitrous oxide and oxygen, 12, 84. " Schlafgas," 13. " Secondary rigidity," 82. Sensations of the patient, 46. Sex, influence of, 58. Shouting, 4, 49, 78. Signs of nitrous oxide and oxygen anaesthesia, 52. Singing, 78. Sleep-like state, 53 (see also " Schlafgas "). Sleepy feelings after inhalation, 88. Simth's early administration of nitrous oxide, 4. Snoring breathing, 22, 52, 53, 58. Index 103 Spasm, clonic (see Clonic viuscular movements, Epileptifovm movements, and Mnsciilay phenomena) ; respiratory, 80, 82, 83 ; tonic (see Rigidity and Musculay phenomena). Stamping, 49. Stand for nitrous oxide and oxygen cylinders, 27. Stertor, absence of, when oxygen used, 16 ; obstructive from too little oxygen, 49 ; moderate, 22, 52 (see also Snoring). Stimulants before administration, 3S. Stop-cock and mixing chamber (the author's), 30 et seq. Stout subjects, 61, 73. Struggling, 49. Suffocative sensations, 47. Supply of nitrous oxide and oxygen, 25, 27, 28. Temperament, influence of, 61. Tension, arterial, 9, 69. Termination of administration, 55; of anaesthesia, 75. Tight lacing, disadvantages of, 39. Tobacco, excessive use of, 65, 73, 82. Tonic spasm (see Rigidity). Tonsils, enlarged, 66, 82. Trachea, patients suffering from pressure upon, 66. Treatment of emergencies under nitrous oxide and oxygen, appliances for, 38 ; of nausea, retching, and vomiting after inhalation, 90. Tremor, 79, 81. Types of patients, 57, 73. Typical anaesthesia from nitrous oxide and oxygen, 52. Valve, expiratory, of regulating apparatus, 25, 31 ; inspiratory, of regulating apparatus, 31. Valves of regulating apparatus, 25, 31, 32. Violent breathing, 83. Vision, temporary loss of, as an after-effect, 88. Voluntary muscular movements, 79. Vomiting, occurring during the administration, 83 ; as an after-effect, 8g et seq. ; treatment of, 90. I04 Index Wells, Horace, the first to use nitrous oxide in surgery, 2. WlNCKEL, 10. WiTZEL, 15. Women as subjects for nitrous oxide and oxygen, 43, 59. 73- ZWEIFEL, II. COLUMBIA UNIVERSITY LIBRARIES This book is due on the date indicated below, or at the expiration of a definite period after the date of borrowing, as provided by the rules of the Library or by special arrange- ment with the Librarian in charge. DATE BORROWED nR^^ °"^ DATE BORROWED DATE DUE Mn 1 l!g*»r» i 1 C28(tl4t)M100 RK510 Hewitt H49 1901 Administration of nitrous oxide and oxygen for dental operations. RK5S"H4Tl90"i!'r'"'"*' ^^^ ^'?,n,L",lE^.3'!2n,.o'..a.".raus oxide and 2002448840 w iii^M 'MW. :'<:;,!:<■ ■> ;'!;k'i' ■'!iV.-"',vMki,'ii.';' W'S.i y,'>