The effect of inhalational anaesthetics on hypoxic pulmonary vasoconstriction and pulmonary vascular resistance in the perfused lungs of the dog and cat

Abstract

Summary: Alveolar hypoxia produced an increase in pulmonary vascular resistance in isolated cat and dog lungs or lobes perfused at constant flow. This response was abolished for varying periods of time by the administration of high concentrations of inhalational anaesthetic agents. In these preparations 5 per cent halothane caused pulmonary vasodilatation whereas 15 per cent ether, 1.5 per cent trichloroethylene and 79 per cent nitrous oxide caused vasoconstriction. Two per cent methoxyflurane did not cause a significant change in pulmonary vascular resistance. It is postulated that the abolition of the pulmonary vasoconstrictor response to hypoxia may increase the proportion of blood flowing through shunts or areas of lung with a low ventilation/perfusion ratio and so may contribute to a decrease in arterial oxygen tension during anaesthesia. The pulmonary vasodilatation or vasoconstriction produced by inhalational agents may augment this effect. © 1972 John Sherratt and Son Ltd.