Effects of acute anoxia on cardiac contractility

Abstract

Ventricular contractile force and arterial blood pressures were measured in anesthetized, vagotomized dogs rendered hypoxic by respiration with 100% nitrogen. Marked increments in heart force and blood pressures were observed: a) during brief nitrogen exposure and b) during the period of reoxygenation following substitution of room air for nitrogen. Experiments in animals subjected to 1) bilateral adrenalectomy, 2) thoracic sympathectomy and 3) total preganglionic sympathetic block indicate that the responses to acute oxygen lack are mainly due to stimulation of the sympathetic nervous system, while the responses to reoxygenation are dependent upon both the adrenal medullae and the sympathetic nerves.