Effects of Moderate & Severe Hypoxia on Functions of Two Ventricles / 第三军医大学学报

ABSTRACT

This experiment was designed to observe the changes of the functions of the two ventricles during acute hypoxia and to determine the efficacy of sodium ni-troprusside on the pressor response of the pulmonary artery under hypoxic condition. 14 piglets were anesthetized and force to inspire a gas mixture containing 10% or 5 %O2 in nitrogen respectively.During moderate hypoxia, there were increase of the dp/dt max, the systolic pressures and the develope pressures of the two ventricles, and shortening of the R-dp/dt time but there was no significant change of the end diastolic pressures of the ventricles. At the end of the ten-minute hypoxia, 7 piglets were given intravenous infusion of sodium nitroprusside. Then the pressures in the pulmonary artery and aorta were found to be reduced promptly but no change occurred in the dp/dt max and the systolic pressures of the ventricles.During severe hypoxia, 4 piglets showed a progressive falling of the cardiac functions while the remaining 9 showed a preliminary compensatory augmentation followed with a gradual falling of the cardiac functions. The survival time of the latter was longer than that of the former.These results indicate that the contractility of the myocardium is augmented during moderate hypoxia, the existence of cardiac compensatory response is one of the important factors determining the survival time of the animal, and sodium nitroprusside can markedly reduce the pulmonary arterial hypertession due to hypoxia.