A Theory of Anesthesia : Part 2

Origin and Nature of Emotions
by George W. Crile, M.D.

(Page 9 of 9)

That is, as the acidity produced by muscular action increases and threatens life, the respiratory action, by which carbon dioxid is eliminated and oxygen supplied, is increased, while the driving power of the brain, which produces acidity, is diminished or even inhibited entirely; that is, the state of unconsciousness or anesthesia is reached. We conclude first that, without this life-saving regulation, animals under stress would inevitably commit suicide; and, second, that it is probable that the remarkable phenomenon of anesthesia - the coincident existence of unconsciousness and life - is due to this antithetic action of the cortex and the medulla.

In the human, as in the animal, the degree of acidity parallels the depth of inhalation anesthesia.

Within a few seconds after beginning nitrous oxid anesthesia the acidity of the blood is increased. This rapid acidulation is synchronous with almost instantaneous unconsciousness and increased respiration. If the oxygen in the inhaled mixture be increased, a decrease in acidity is again synchronous with lighter anesthesia and a decrease in the respiratory rate.

If these premises be sound, we are justified in asserting that the state of anesthesia is due to an induced acidity of the blood. If the acidity is slight, then the anesthesia is slight and the force of the nerve impulses is lessened, but the patient is still conscious of them. As the acidity increases associative memory is lost, and the patient is said to be unconscious: the centers governing the voluntary muscles are not inhibited, however, and cutting the skin causes movements. If the acidity is further increased, there is loss of muscular tone and even the strong contact ceptor stimuli of a surgical operation do not cause any muscular response, and, finally, the acidity may be increased to the point at which the respiratory and circulatory centers can no longer respond by increased effort, and anesthetic death - that is, ACID death - follows.

Certain clinical phenomena are clarified by this theory and serve to substantiate it. For example, it is well known that inhalation anesthesia precipitates the impending acidosis which results from starvation, from extreme Graves' disease, from great exhaustion, from surgical shock, and from hemorrhage, and which is present when death from any cause is imminent.

We see, therefore, that anesthesia is made possible, first, by the fact that inhalation anesthetics cause acidity, and, second, by the antithetic adaptation of the higher centers in the brain and of the centers governing respiration and circulation.

In deep contrast to the action of inhalation anesthetics is that of narcotics. Deep narcotization with morphin and scopolamin is induced slowly; the respiratory and pulse-rate are progressively lessened - and there is no acidity.

By our researches we have established in what consists the generic difference between inhalation anesthetics and narcotics. In our experiments no increase in the H-ion concentration was produced by morphin or by scopolamin, no matter how deep the narcotization. In animals already narcotized by morphin the production of acid by any of the acid-producing stimuli was delayed or prevented. On the other hand, in animals in which an acidity had already been produced by ether, by shock, by anger, or by fear, the later administration of morphin delayed or inhibited entirely the neutralization of the acidity. In other words, morphin interferes with the normal mechanism by which acidity is neutralized possibly because its inhibiting action on the respiratory center is sufficient to overcome the stimulating action of acidity on that center, for, as we have stated, the neutralization of acidity is in large measure accomplished by the increased respiration induced by the acidity itself.

Summary

Acidity inhibits the functions of the cerebral cortex, but stimulates those of the medulla. This antithetic reaction to the stimulus of increased H-ion concentration is an adaptation to prevent animals from committing suicide by over-activity, for the mechanism for the initiation and control of the transformation of energy is in the higher centers of the brain, while an essential part of the mechanism for the neutralization of acidity - the centers governing circulation and respiration - is in the medulla.

This explains many clinical phenomena - why excessive acidity causes paralysis, why there is great thirst after inhalation anesthesia, after excessive muscular activity, excessive emotion - after all those activities which we have found to be acid-producing, for water, like air, neutralizes acids. The excessive use of alcohol, anesthetics, excessive work, intense emotion, all produce lesions of the kidney and of the liver. The explanation is found in the fact that all these stimuli increase the acidity of the blood. and that, if long continued, the neutralizing mechanism must be broken down and so the end-products of metabolism are insufficiently prepared for elimination.

In view of these considerations we may well conclude that the maintenance of the normal potential alkalinity of the blood is to be estimated as the keystone of the foundation of life itself.

About the Author

George Washington Crile (1864 - 1943) was a significant American surgeon. Crile is now formally recognized as the first surgeon to have succeeded in a direct blood transfusion. He also contributed to other procedures, such as neck dissection.