[Organ-specific characteristics of blood supply in the liver, kidney, and brain in acute blood loss in rats with various resistance to circulatory hypoxia].

A marked fall in arterial blood pressure, organ blood flow rates and tissue perfusion in the liver, kidneys and brain was registered by ultrasound and laser Doppler flowmetry in rats with low (LR) and high resistance (HR) to circulatory hypoxia (average life spans less than 1.5 h and more than 3 h were 42 and 58%, respectively) at the end of acute massive hemorrhage. In the posthemorrhagic period organ hemodynamics and microcirculation showed a tendency to further decrease in LR rats. In HR rats blood flow in hepatic, renal and common carotid arteries were restored for a while up to 115-120%, 85-90% and 60-65%, respectively, following bleeding arrest. At this new posthemorrhagic level the brain flow was actively maintained in the compensatory phase of the posthemorrhagic period due to autoregulatory changes in the carotid resistance. Such a peculiar reaction of the brain blood vessels in HR rats is considered as an adaptive response protecting the brain during massive hemorrhage under severe tissue hypoxia against autoreperfusion and reoxygenation-induced damage.