THE EFFECT OF ETHER ANESTHESIA ON THE ALKALI RESERVE
Archives of internal medicine (Chicago, Ill. : 1908)
The alkali reserve can best be determined by measuring the capacity of the blood for combining with carbon dioxid. Many of the observations to determine the influence of anesthesia on the alkali reserve have been made on patients after surgical operations. The alkali reserve may be decreased by the restricted diet or fasting preparatory to surgical operations, and the same condition is usually present in surgical shock, so that ether anesthesia produced experimentally in animals offers the
... als offers the advantage of eliminating these contributing factors. Caldwell and Cleveland 1 studied the influence of different kinds of anesthesia on the alkali reserve in more than 100 patients, including fifty-five for whom ether anesthesia was used. In those latter cases they found a slight decrease, varying from 4.5 to 7.7 volumes per cent. in the combining capacity for carbon dioxid, but acidosis approaching dangerous proportions was noted only in the case of a diabetic patient who had acidosis before the operation. Austin and Jonas 2 determined the carbon dioxid combining capacity of blood in sixteen patients after ether anesthesia for various surgical operations. The maximal decrease was 10 volumes per cent, and the lowest amount observed was 47 volumes per cent. The reduction seemed proportionate to the duration of the anesthesia and was maximal at the close of the anesthesia. When a decrease occurred, it apparently persisted with little alteration for about five hours. Cannon 3 made a number of observations on soldiers who had been wounded in battle and were suffering from varying degrees of shock. In a series of nine cases of moderately severe shock, there was a decrease of approximately 12 volumes per cent, on the average, the maximal reduction being 16 volumes per cent. He found the decrease occurred rapidly when the capacity of the blood for combining with carbon dioxid was low (below 50 volumes per cent.) before the From the Laboratory of Physiology of the University of Texas. operation. The maximal decrease following operations when nitrous oxid and oxygen were used for anesthesia was 8 or 9 volumes per cent. Cannon expressed the opinion that the alkali reserve is below normal in shock, and that the reduction is in direct proportion to the degree of shock. W. H. Morris 4 made a number of observations on patients before and after gynecologic operations. He also made a few experiments on dogs with prolonged ether anesthesia but without any surgical operation which could produce shock. He found that a reduction of the carbon dioxid combining capacity of the blood usually but not invariably occurs and that it "does not bear any relation to the duration of the anesthesia. In one case in which the anesthesia only lasted twenty minutes, there was a decrease of 10 volumes per cent. ; in another case lasting two hours for a hysterectomy, the decrease was 7.7 volumes per cent. The greatest decrease was 22 volumes per cent., while the least was 0.4 volumes per cent., and in the latter the operation lasted one and a half hours. Comparing a series of ten patients to whom from 15 to 20 gm. of bicarbonate of sodium had been given intravenously before operation, with the same number who had not received such preliminary treat¬ ment, he found the decrease in the carbon dioxid combining capacity of the blood averaged 5.7 volumes per cent, as compared with an average of 9 in those who had not been given sodium bicarbonate. He etherized two dogs for two hours or more, making carbon dioxid determinations every half hour. He found a reduction of from 10 to 12.5 volumes per cent., that is, from 22 to 24 per cent, of the normal amount. In one dog, the greatest reduction occurred in the third half hour ; in the other, the most rapid fall took place during the first half hour. Prolonged chloroform anesthesia in one dog caused a reduction of 24 volumes per cent., or 47 per cent, of the normal amount, which was considerably greater than that caused by ether. Yandell Henderson 5 investigated the subject by experiments on dogs and reached the conclusion that the reduction in the carbon dioxid combining capacity of the blood is due to increased dissociation of the carbon dioxid from the blood, caused by the hyperpnea or increased respiratory activity produced by the irritant ether vapor. He contends that the decrease in the carbon dioxid content and capacity of the blood is due to increased ventilation of the lungs and not to actual reduction in the alkali reserve of the body. Previous observations had been.made by the Van Slyke apparatus with the plasma alone. Henderson used the whole blood and deter-4. mined by means of his own apparatus the carbon dioxid content as well as its combining capacity when exposed to an atmosphere con¬ taining a uniform amount (5.5 per cent.) of carbon dioxid. He found the maximal decrease in the carbon dioxid content during ether anesesthia was from 14 to 19 volumes per cent., while the greatest decrease in the carbon dioxid combining capacity was from 12 to 15 volumes per cent. A state of hyperpnea was maintained by artificial respiration in dogs narcotized by chlorbutanol and he states that this produces as great a reduction in the carbon dioxid content and capacity of the blood as that seen in ether anesthesia, although the chlorbutanol alone does not produce that effect. He produced the opposite condition of decreased ventilation of the lungs by morphinizing dogs so as to, reduce the respiratory activity, and he found an increase in the carbon dioxid content and capacity of the blood. When he produced light anesthesia with ether, so as to cause an acceleration of the respira¬ tion, he found a decrease in the carbon dioxid content and capacity of the blood ; when he produced deep ether narcosis with feeble respiratory activity he found that both were increased. In another series of experiments dogs inhaled ether vapor in an atmosphere containing from 6 to 7 per cent, of carbon dioxid, to which oxygen was added, and Henderson found there was no decrease in the carbon dioxid content or capacity of the blood, although the anes¬ thesia was continued from three to five hours. This last series of experiments is open to the criticism that the animals were compelled to breathe an artificial atmosphere containing a higher percentage of carbon dioxid than that of the alveolar air. Under such abnormal circumstances it is not surprising that there was an increase in the carbon dioxid of the blood. EXPERIMENTS Series 1.-The first series of experiments was made with blood plasma obtained by Van Slyke's method. The jugular vein was exposed after the animal became unconscious at the beginning of ether anesthesia and the first sample of blood was taken as the normal. Other samples were taken after half an hour, one hour, or one and a half hours of anesthesia and the carbon dioxid determinations were made with Van Slyke's apparatus. Uniform anesthesia was maintained throughout each experiment by causing the animal to breathe ether vapor from a Mason jar of one liter capacity with an adjustable inlet tube and a respiratory valve in the top of the jar (Fig. 1) , so that the vapor from the jar entered· the cone with each inspiration, while the expired air escaped into the open without entering the jar. The jar was kept in a wooden box, the air of which was warmed by one or two eight-candle power Downloaded From: http://archinte.jamanetwork.com/ by a New York University User on 05/30/2015 electric lamps, so that the air containing ether vapor was warmed before it entered the lungs. The results are shown in Table 1. Only one out of twelve dogs did not show any decrease in the carbon dioxid combining capacity of the blood. Eleven showed a decrease varying from 5.6 to 23.3 volumes per cent., or from 15 to 46 per cent, of the normal. The average decrease at the end of the anesthesia was 10.8 volumes per o Fig. 1.-Sectional view of ether jar with respiratory valve on top. The continuous lines show the position of the light aluminum disks of the res¬ piratory valve during inspiration, while the broken lines show the position of these disks during the phase of expiration. cent. The anesthesia lasted one hour in three experiments and one and a half hours in nine experiments. Very little decrease occurred during the first half hour; the greatest decrease occurred during the second half hour, with a further fall during the third half hour period. The same dog was used in Experiments 4, 5 and 6 on three con¬ secutive days. There was no fall on the third day although there was a decrease on each of the first two days.