Deliberate profound hypotension induced with halothane: studies of haemodynamics and pulmonary gas exchange.

Haemodynamic measurements and estimates of pulmonary gas exchange have been made in 15 patients during varying degrees of deliberate arterial hypotension induced by IPPV with varying concentrations of halothane in oxygen. Used in this way, halothane caused a dose-dependent arterial hypotension, which was directly related to a reduction in stroke volume and cardiac output, raised right atrial pressures, but insignificant changes in either heart rate or systemic vascular resistance. The findings are not compatible with the concept that the hypotensive effects of halothane are due to "vasodilatation", but are compatible with the results of animal studies which indicate a dosedependent impairment of the contractile function of the myocardium.