Discovery of Inhalation Anesthesia.

aDiscovery of Inhalation Anesthesia

BY ROBERT A. STEVENSON, D.D.S., R. Ph.

Dental Therapy Editor

 

                “The fierce extremity of suffering has been steeped in the waters of forgetfulness and the deepest furrow of the knotted brow of agony has been smoothed forever”—Prof. O.W. Holmes.

Humanity, ever the hardiest and bravest portion of it—instinctively shrink from the pair attending upon the deliberate cutting of the living flesh by surgical instruments.

History is full of accounts that tell of men who have proved themselves in battle and have no fear of death in its gastly form shrink from the surgeon’s knife or dentist’s forceps in almost childish fear.

Numberless instances have been related, of women that have concealed their maladys from their nearest friends and have deliberately preferred the misery of a fatal disease, than submit to the apprehended torture of an operation.

From time immemorial, means had been sought to relieve and even destroy pain during the manipulations of practical surgery. For this purpose opium, Indian hemp, alcohol, mesmerism and other substances were used with only partial success.

It was reserved for the simple inhalation of a certain gas to achieve in surgery that for which surgeons had for centuries labored and labored in vain.

To whom the credit is due for first discovering of the use of inhalation anaesthesia in surgery has long been a bitterly discussed question.

The discovery involves the names of four Americans: Crawford W. Long of Georgia, William T. Morton of Hartford, Horace Wells of Hartford and Charles T. Jackson of Boston.

In the spring of 1842 Dr. Long used the vapors of sulphuric ether to render a patient unconscious while removing two small tumors painlessly. About this time Dr. Wells, a dentist, had a tooth extracted painlessly under the influence of nitrous oxide. While serving as a medical student under the perceptorship of C.T. Jackson the latter suggested that he use ether in place of nitrous oxide and gave several successful demonstrations at the Massachusetts General Hospital in October 1846.

A short time after the demonstration, Morton and Jackson patented ether and called it letheon.

Chloroform was introduced in England in the year 1847 by Sir J.Y.  Simpson.

The employment of nitrous oxide as an anaesthetic by H. Wells in 1844 foreshadowed the use of nitrous oxide and oxygen by E. Andrews in 1868.

For the brief notes on nitrous oxide anaesthesia we are indebted to “The Art of Anaesthesia” by Paul J. Flagg, M.D. 5th Edition, 1932, Lippincott Company. We strongly recommend this late work on anaesthesia to those interested.

Nitrous oxide, laughing-gas or nitrogen monoxide is prepared by heating ammonium nitrate NH4NO3, the result being N2O and 2H2O.

Nitrous oxide is non-irritating to the respiratory tract, is possessed of a sweet taste and an odor like that of burnt sugar.

Nitrous oxide is marketed as a liquid. It is stored in especially made vanadium steel cylinders.

The pressure of the liquid gas enclosed in the cylinder is about 1000 lbs. to the square inch, at room temperature. If the cylinders be allowed to remain against a hot radiator for some time there is great danger of explosion from the increased pressure.

There is one way, and only one way, of estimating the amount of gas in a cylinder at any given time, and that is by weighing the cylinder. One will always find a label pasted on the side of the cylinder, on which is written:

The weight of the cylinder full of gas.

The weight of the cylinder empty.

The difference in these two weights represents the weight of the liquid N2O in the cylinder. One ounce of N2O is equal to four gallons of the gas at room temperature and pressure. The weight of the liquid N2O in a full 100-gallon cylinder is therefore 25 ounces, or one pound nine ounces.

Some hospitals have become so enthusiastic over gas oxygen anaesthesia that they installed small plants for the manufacture of the gas. At the Lakeside Hospital, Cleveland, a plant is in operation which supplies all the nitrous oxide in that institution.

The cost of N2O is about three and one-half cents a gallon.

With nitrous oxide alone, one can obtain only incomplete anaesthesia. The length of the administration is definitely limited by the physiological reaction of the organism to the drug. This reaction is as follows:

When N2O is breathed to the total exclusion of air, the patient experiences a sense of exhilaration. The extremes tingle and quickly grow numb. A necessity to breathe or “besoin de respire” makes itself felt and the respiration automatically becomes full and deep. Consciousness is completely lost in less than half a minute in the ordinary case. This may be, accompanied or immediately followed by flashes of light or loud sounds. Many patients experience no sensations whatever. If the administration is continued, air and oxygen being excluded, the patient rapidly becomes pallid, then blue or gray, the muscles of the face and limbs are thrown into convulsions known as jactitation, the respiratory movements become irregular and finally cease.

Immediately upon the admission of air the patient resumes normal respirations and color. Consciousness returns in less than two minutes.

Nitrous oxide has been administered hundreds of thousands of times to a degree of partial asphyxia. The procedure is indeed so common among dentists and occasionally among house officers that many men have come to look upon N2O anaesthesia as implying lividity. It is true that in order to obtain the longest “available anaesthesia,” it is necessary to push gas to an asphyxia degree where oxygen is not employed. Such a procedure is bad taste to say the least, and should not be practiced. On should manage to get along with a shorter anaesthesia, reapply the mask or add oxygen to the mixture.

When N2O is used to induce ether anaesthesia (this administration is a routine procedure in most large hospitals). When we use N2O for induction we accomplish three results:

1, 2. We destroy consciousness and render the mucous membranes less sensitive to ether vapor.

3. We induce deep breathing which permits us to rapidly reach the desired concentration of ether in the patient’s blood.

Since hearing is one of the last senses to disappear it is unwise to ask the patient whether or not he is asleep. A semi-conscious response may result.

When nitrous oxide is used alone. This type of administration is the method usually employed in dental work. When a tooth is to be extracted a mouth prop of cork or other material, made especially for the purpose, must be placed in position before the administration is begun. The patient furthermore is ordinarily in a sitting position. The head must not be extended but should be on a straight line with the body. The administration is carries out precisely as in the case of N2O induction for ether except that (oxygen not being used) we carry on the administration until slight jactitation of the arms or legs takes place.

If anaesthesia be then discontinued, a period of available anaesthesia amounting to about fifty seconds will result.

During this period any painful procedure may be carried out, such as the extraction of teeth, opening of abscesses, etc. When longer anaesthesia is desired with this method the face piece may be reapplied before complete consciousness returns. If the operation be elsewhere than in the mouth one breath of air should be administered after every four or five breathes of rebreathed N2O. This will give a longer period of available anaesthesia, but does not result in anything like a smooth anaesthesia offered by the addition of oxygen gas to the mixture.

Nitrous Oxide Oxygen Anaesthesia

This mixture was first employed by Dr. E. Andrews of Chicago in 1868.

Perhaps no other type of anaesthesia at the present day has received as much attention as has the combination of gases popularly spoken of as gas oxygen.

In order to produce complete anaesthesia, N2O must be delivered in a concentration of about 90 percent. (The limits being 75 to 90 percent.) If the additional 10 percent be replaced by air, the patient will suffer from oxygen starvation (only 1/3 of air being oxygen). If, however, the additional 10 percent be supplied by pure oxygen, no such asphyxia result will follow. This condition holds in practice and explains the great difference seen in N2O anaesthesia with air, and with oxygen. The difficulty then which confronts us in gas oxygen anaesthesia is the necessity of giving N2O of sufficient concentration to produce anaesthesia, and at the same time supply adequate oxygenation.

The permissible variations take place within narrow limits. The anaesthesia is induced quickly and recovery takes place with astounding rapidity.

The exceedingly evanescent effects of the anaesthetic make it by far the most difficult to administer. The anaesthetist must not only be constantly alert to the ordinary signs of anaesthesia, but he must have learned to distinguish shades of lightness and depth, which are of little consequence in anaesthesia by other agents, i. e., ether, chloroform, etc. In the administration of gas oxygen the personal equation is without doubt the most important element.

Anaesthesia by nitrous oxide and oxygen is characterized by muscular rigidity of varying intensity. This rigidity is sometimes present in an apparently complete and otherwise entirely satisfactory anaesthesia.

Some patients become very easily controlled, others remain rigid no matter how much the anaesthetic is pushed. In this connection one should always remember that relaxation will never occur in the presence of cyanosis. If the desired result cannot be obtained without the presence of asphyxia then ether should be employed.

With gas oxygen anaesthesia, more than with any other agent, we wish to go on record as insisting that the patient be the criterion of the mixture delivered. An anaesthetist, who will not give additional oxygen because his apparatus indicates a certain theoretical percentage, even though the patient be dying of asphyxia, certainly has no business to use this method. The author has seen a patient positively gray, crying out for oxygen by every possible sign, ignored by the anaesthetist, who was sure that all was safe because his apparatus showed such and such a percentage mixture in process of delivery. If preconceived and prearranged mixtures do not fit the needs of the patient, these must be thrown to the winds and suitable percentages employed.

The administration of gas and oxygen is gradually beginning to find its place. It has thrown off many of its early excrescences, such as positive pressure, heated vapors, and the like. Numberless apparatus of beautiful design and workmanship have died of complexity. Unskillful enthusiasts have fortunately lost interest, and are no longer forcing methods where they are contraindicated. Unfortunately, however, their blunders live on in the minds of the surgeons whom they chanced to assist. These experiences naturally give rise to prejudice against a method which is invaluable in its place.

As the symptoms and signs of gas oxygen anaesthesia change with great rapidity, we must make use of an apparatus which will be sufficiently elastic to meet these changes of state as they appear. We must be able to produce N2O effects or oxygen effects without delay.

The Signs of Nitrous Oxide Oxygen Anaesthesia

COLOR—The most important sign which we have in gas oxygen anaesthesia is the color. As with ether, duskiness is more liable to occur in the full-blooded, muscular individual. With ether, however, duskiness or cyanosis is usually directly dependent upon obstructions to the respiration, while with gas oxygen the condition frequently depends upon the mixture of the gases offered to the patient. As has been pointed out under general considerations, complete anaesthesia and a normal color are obtained only when oxygen is employed. Those who are unfamiliar with gas oxygen anaesthesia, but who have had some experience with N2O alone are very likely to purposely avoid a pink color fearing that the patient will “come out”. A good color is especially desirable where the best relaxation is required. By pushing the N2O to a degree of asphyxia, we not only do not overcome the rigidity but we superimpose the rigidity which accompanies imperfect oxygenation.

For the above reason gas oxygen anaesthesia, per se, cannot be satisfactorily administered in the dark, i.e., for nose and throat and for cystoscopic examinations. To employ this method under these conditions is to court failure and to risk the life of the patient.

The color of the patient is the only reliable index of the amount of oxygen which should be delivered. Any apparatus which does not accept the color of the patient as the criterion for the increase or the diminution of the oxygen supply is pernicious. Where such apparatus is employed as will delivered definite mixture of N2O and oxygen there must be some provision made for the immediate and copious admission of oxygen, should such treatment be found necessary. The margin of safety in gas oxygen anaesthesia is narrow, much more narrow than with ether and we cannot force out methods as we may occasionally do with the latter.

RESPIRATION—Next to the color sign the respiration is the most important sign of gas oxygen anaesthesia. During the early part of induction the respirations are very likely to be more rapid and deeper than normal. In some athletic patients this may amount to a hypercapnia, which will seriously disturb our induction. If the color is held under good control by sufficient oxygen, however, the breathing soon becomes less rapid and more shallow. A soft snore is one of the first signs of good anaesthesia. If this continues, and the respirations remain regular and somewhat deeper than normal, the preparation of the field of operation may be begun. A patient whose respirations are shallow and slow is not anaesthetized. Air has probably leaked in under the face piece and manipulations begun at this time will result in trouble. One has to “feel out” each patient and determine the approximate amount of oxygen which is required. The reaction of the respiration to vigorous “scrubbing up” is valuable. If the rhythm is not affected, the incision may safely be made. During the maintenance of the anaesthetic, the rhythm and the depth of the respirations, in conjunction with the color, form our chief guide as to the condition of the patient. The most important factor in the control of the respiration if the extent to which rebreathing is permitted. The stimulating effect of the CO2obtained is more active than where ether is employed.

RELAXATION—With gas oxygen anaesthesia there is no true relaxation. We expect and usually find more or less rigidity. The muscle tone is prone to persist. The impossibility of obtaining true muscular relaxation when gas oxygen is the anaesthetic is being borne in upon us by repeated failures where these gases alone are employed for abdominal work.

When induction has been completely brought about, the lid will be sluggish. Slight muscular movements of the limbs occasionally occur but as a rule the patient is absolutely quiet. Masseteric relaxation is never complete where the gases are employed without ether.

THE PULSE—A slow pulse, fifty or less, under gas oxygen anaesthesia is a danger sign. Rebreathing should be diminished and the general condition of the patient carefully watched.

THE EYE SIGNS—When anaesthesia is fully induced the globes are fixed, looking forward, downward of upward. (The sign is a guarantee that consciousness is lost.)

During the state of maintenance the light reflex is active; the pupils are contracted; the conjunctive palpebral reflex is active; the corneal reflex is always snappy.

THE ANAESTHETIST—Gas oxygen anaesthesia by far the most difficult of all anaesthetics to administer. From the aspect of mere labor, the method is unpopular for those who simply give “dope,” but for the man who can catch the spirit of the work, for the man who is interested in the art of anesthesia the method is fascinating. The recovery in a case of gas oxygen anaesthesia properly administered is a triumph in itself.

THE PATIENT—From the point of view of the patient the method is the most satisfactory yet devised. After-symptoms are conspicuous by their absence. The patient is scarcely over sick although retching before consciousness returns is frequently seen. The disadvantage of a rapid return of consciousness is so far outbalanced by the benefits as to be of little consequence. To see a patient pass in two minutes from a stage of deep anaesthesia, in which he has been maintained for an hour or more, to complete consciousness is the marvel of present-day anaesthesia. And by consciousness which is capable of calmly surveying immediate past experiences and which fully understands existing conditions.