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Canadian Journal of Anesthesia, Vol 7, 91-99, Copyright © 1960 by Canadian Anesthesiologists' Society

The Cardiovascular Effects of Azeotropic Halothane-Ether

GORDON M. WYANT F.F.A.R.C.S.1, JOHN E. MERRIMAN F.R.C.P.(C)1, JOHN H. HARLAND M.B.1, and HARRY V. DONALDSON M.D.1

1 Departments of Anaesthesia and Medicine (Cardio-Pulmonary Laboratory), University of Saskatchewan and University Hospital, Saskatoon, Sask

Azeotropic halothane-ether has a less profound effect on the cardiovascular system than halothane alone. Consequently, less rigid control of vapour concentration is needed.

Following induction of anaesthesia, the blood pressure falls slightly to a plateau, where it tends to remain. Fall in cardiac output is proportional to the degree of hypotension. No significant changes in pulmonary artery pressure, vein-to-artery circulation time, total peripheral and total pulmonary resistance are evident at this stage. Further depression of systemic blood pressure occurs only when very deep anaesthesia is produced by deliberate overdosage. This is in marked contrast to the findings under halothane anaesthesia, where similar hypotension is associated with only moderate depth of anaesthesia. In this respect, the azeotropic mixture more closely resembles ether than halothane. Cardiac output falls to very low values as the systemic blood pressure reaches its nadir. Pulmonary artery pressure gradually rises during deepening of anaesthesia and as respiration requires assistance and later control. Vein-to-artery circulation time increases with increasing hypotension. No significant changes are apparent in the total peripheral resistance, but total pulmonary resistance rises greatly and, at the time of maximum hypotension, may be four times the control value.

During emergence from halothane-ether anaesthesia the relation of blood pressure to cardiac output is less strict than during maintenance. The development of bigeminal rhythm is a definite possibility if concentrations of the agent are grossly excessive. No significant electrocardiographic changes were observed at other times.

Note:

Presented at the Annual Meeting of the Canadian Anaesthetists' Society, Seigniory Club, Montebello, P.Q., May 4–7, 1959.






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Copyright © 1960 by the Canadian Anesthesiologists' Society.