Effect of acute hypoxia on blood viscosity, red blood cell deformability and the left ventricular function in rats

Experiments were performed on SD rats anaesthetized with urethane and chloralose. The left ventricular function and the parameters of hemorrheology during acute hypoxia were investigated. It was found that during acute hypoxia of 15 min, arterial blood gas value PaO2 decreased markedly. The parameters of the left ventricular function such as +/- dP/dtmax, Peak, HR, Vce40, Vmp, Vmax, L0 (CFU), decreased markedly either. At the same time, hyperviscosity was induced and red blood cell filtration (IF) increased. All these parameters recovered to normal control level after reoxygenation of 15 min. By intravenous injection of propranolol (0.5 mg/kg) and then hypoxia, the left ventricular function were suppressed markedly; and so were to the elevation of blood viscosity and IF. Preinjection of regitine (3 mg/kg) prior hypoxia has the same effect on the blood viscosity and IF. Acute hypoxia induced hyperviscosity and elevation of IF could be suppressed by destruction of carotid sinus region with phenol, but the left ventricular function decreased markedly. These results suggest that acute hypoxia induces hyperviscosity and decreases of red blood cell deformability and left ventricular function, which is probably mediated via the sympathetic nervous system and carotid sinus region.