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Pharmacological action of sodium amytal; including a study of its effects upon respiration and circulation in relation to local, regional, and general anesthesia

1930; Elsevier BV; Volume: 9; Issue: 1 Linguagem: Inglês

10.1016/s0002-9610(30)91293-7

1879-1883

Robert M. Isenberger,

Sleep and Wakefulness Research

Throughout the foregoing experiments emphasis has been placed on three aspects of the function of respiration as affected by narcotizing agents. 1.1. The degree of impairment of the normal cooperation and coordination between the intercostal muscles and the diaphragm in the ventilatory process. 2.2. Variations in the minute volume as determined by accurate measurement of the rate and dept of breathing. 3.3. The degree to which the respiratory center is affected in its ability to respond to the stimulating effect of therapeutic doses of carbon dioxide. With methods such as herein described and with suitable tests for determining the degree of anesthesia and analgesia, it is possible that the most advantageous proportions of morphine or other opiate, barbituric acid compounds, and local or general anesthetics, for the production of basal narcosis and anesthesia, could be established. Further study is to be made of the effect of larger doses of the narcotics reported; of combinations of other narcotics; and of the influence of various degrees of stimulation and depression as a result of surgical procedures. The following summary and impressions seem justified at this time. 1.1. Sodium amytal was found to be very active in preventing and stopping the convulsions, and thereby the spastic paralysis of the respiratory muscles which accompanies experimental novocame poisoning. With the convulsions eliminated, however, it did not protect against central respiratory paralysis following overwhelming doses of the novocame. By the addition of well controlled artificial respiration, life of the animals with an efficient circulation was sustained for long periods in the instances in which central respiratory paralysis followed the large doses of novocaine, and in which animals the convulsions were prevented by the use of sodium amytal. Furthermore, preliminary medication of sodium amytal alone, or better in combination with small doses of morphine was observed to reduce the frequency and severity of untoward reactions of patients to local and regional novocaine anesthesia. 2.2. In the experimental work on sodium amytal as a basal narcotic for general inhalation anesthesia, quantitative determinations were made of the minute volume of respiration and of the ability of the respiratory mechanism to respond to therapeutic doses of carbon dioxide. Such determinations were considered to be of value in estimating the vital reserve, of the animals which were subjected to the effects of the various narcotizing agents. 3.3. Sodium amytal and other soluble barbiturates should be considered largely if not entirely as only an aid in the preparation of patients for true anesthesia which is to be induced and graduated by the use of local or inhalation anesthetics. For this purpose, complete loss of consciousness, accompanied in many cases by a variable degree of analgesia and relaxation, apparently can be safely and promptly induced by the use of a moderate amount of sodium amytal, particularly if it is preceded by a small dose of morphine or other opiate. The preliminary morphine seems to render the sodium amytal action more uniform as well as more intense, and thereby minimizes the amount of sodium amytal required. By maintaining the minimal doses of both morphine and sodium amytal postoperative unconsciousness and restlessness may be reduced. The preliminary morphine and sodium amytal together materially reduce the amount of local or inhalation anesthetic required for full surgical anesthesia, and also render induction and maintenance of the effects of the inhalation anesthetics more rapid, quiet and uniform. Postanesthetic nausea and vomiting are extremely uncommon. 4.4. The use of sodium amytal or other soluble barbiturate in suitable combination and sequence with morphine, or alone for the production of basal narcosis may be accompanied by a higher degree of vital reserve than prevails when local or general anesthesia is induced without preliminary medication. This is indicated by the fact that experimentally, in the presence of such basal narcosis, full surgical ether anesthesia was accompanied by a comparatively slight reduction in the minute volume of respiration, a slow but deep and efficient type of breathing, and only a slight reduction in the carbon dioxide irritability of the respiratory center. The fact that minimal amounts of a number of similarly acting drugs were used in combination, with probably slightly different sites of most intense action, rather than relatively large and depressant amounts of any one narcotizing agent, may be of importance in this connection. The elimination of apprehension and induction excitement in patients might also play a part in lessening an often unrecognized or unexpected tendency to shock reaction. On the other hand, it should be remembered that the combined effects of similarly acting drugs may assume alarming proportions, especially if the dose of each drug is not carefully curtailed and regulated to its desired effect. 5.5. Basal narcosis as a result of the proper administration of sodium amytal in combination and sequence with morphine, and unaccompanied by morphine in many instances, is followed by amnesia on the part of the patient for the anesthetic and surgical- procedures, and for a large part of the preoperative and postoperative discomfort. This action alone is worthy of intensive study and application. Finally, it may be said that in view of both experimental and clinical evidence, intravenous anesthesia in its broad sense, unsupplemented, uniform, safe and satisfactory to the best interests of the patient, surgeon and anesthetist, is not yet an established fact. Nevertheless, by the use of a judicious combination and sequence of hypnotics, narcotics, local and inhalation anesthetics, it is possible to accomplish every desirable purpose that could be fulfilled by any intravenous anesthetic. I desire to express my appreciation to Dr. Rowntree, Dr. Lundy, and the Mayo Clinic for their invaluable assistance in the conduct of this investigation, and for the privilege of doing the work in their laboratories.