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Canadian Journal of Anesthesia, Vol 23, 408-424, Copyright © 1976 by Canadian Anesthesiologists' Society

A Comparison of Eleven General Anaesthetics Administered With 7.5 Per Cent Carbon Dioxide during Spontaneous Breathing

ALLEN B. DOBKIN 1, PETER H. BYLES 1, BENJAMIN F. AFRICA 1, and ASHLEY A. LEVY 1

1 Department of Anesthesiology, State University of New York, Upstate Medical Center, Syracuse, New York, 13210, U.S.A.

General anaesthesia with enflurane, isoflurane, seven other inhalational agents and two parenteral anaesthetics was administered to dogs, together with nitrous oxide, oxygen and 7.5 per cent carbon dioxide. Breathing was spontaneous throughout. Each of the tests lasted 90 minutes.

Arterial blood gases, urine output, blood chemistry (including electrolytes, biogenic amines, lactate and pyruvate), pulmonary ventilation, electrocardiogram, blood pressure and heart rate were measured by standard laboratory procedures before and after the tests.

The administration of carbon dioxide augmented pulmonary ventilation with all the anaesthetics tested. Marked tachypnoea developed with chloroform, trichlorethylene and diethyl ether. Other effects observed were the development of mild respiratory acidosis (pH ~ 7.20; PaCoCo2 ~ 65) with all anaesthetics. Metabolic acidosis also occurred with some anaesthetics, but was prominent only with diethyl ether. A rise in blood sugar and serum inorganic phosphorus and a reduction in serum potassium was seen consistently, but changes in other laboratory tests were not significant. Mean recovery of steady ambulation occurred in all animals in less than one hour. Slowest recovery occurred with methoxyflurane, isoflurane and enflurane, due to their muscle relaxant effect, and with thiopentone, due to its hypnotic effect.

The addition of carbon dioxide to most general anaesthetics administered with 50 per cent nitrous oxide does not prevent the development of hypotension, but cardiac arrhythmias may be suppressed. Myocardial oxygen requirements are probably not increased except with trichlorethylene, diethyl ether, fluroxene and thiopentone.

It appears that, in the absence of chronic obstructive lung disease, intracranial lesions or increased intracranial pressure, the administration of a low concentration of carbon dioxide may be innocuous during inhalation or parenteral anaesthesia when spontaneous breathing may be desired. It may be useful to support pulmonary ventilation and oxygenation of the blood and tissues, and to reduce cerebral vasoconstriction in hypertensive patients.






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Copyright © 1976 by the Canadian Anesthesiologists' Society.