[The organic macro- and microhemodynamics and the systemic circulation under the combined action of hypoxia and hypothermia]

Abstract

In regimen of the constant blood flow perfusion of shank and small intestine of cat combined effect of hypoxia (10% O2 in N2) and hypothermia (about 30 degrees C) involved a decrease in precapillary resistance, an increase in capillary filtration coefficient in both vascular regions, an increase in postcapillary resistance and in mean capillary pressure in the intestine, and their decrease in the shank. In hypothermia, the hypoxic stimulus induced insignificant shifts in all the parameters under study in both organs. Dependence of hypoxic changes of macro- and microhemodynamics on the activity of adrenergic receptors in the cooled organism was studied on decentralized shank of cat. After cooling of cat and blockade of alpha-adrenoreceptors hypoxic hypoxia caused much greater reduction of precapillary resistance of shank, more striking (by 3 times) increase of capillary filtration coefficient and the increase of capillary pressure and postcapillary resistance in contrast with their decrease to hypoxia under hypothermia before alpha-blockade. Beta-adrenoreceptor blockade had no influence on the changes of the resistance and exchange function of skeletal muscle (shank) blood vessels evoked by hypoxia under cooling. Systemic arterial pressure are diminished during hypoxia under the normothermic conditions of animals. Such kind shifts caused especially by the decreasing of the total peripheral resistance; cardiac output are small raised in this situation. But combined influence of hypoxia and hypothermia evoked the pressor shifts of the systemic arterial pressure because of less decrease of total peripheral resistance and more remarkable rise of cardiac output. Hypoxic stimulus caused both in normothermia and hypothermia conditions caused the rising of venous return.(ABSTRACT TRUNCATED AT 250 WORDS)