Effects of brain hypoxia on pulmonary hemodynamics.

The effects of acute brain hypoxia on pulmonary hemodynamics were investigated in anesthetized dogs with the vagus and carotid sinus nerves intact and cut. Following ligation of collateral vessels, brain hypoxia was induced by pumping arterial blood through a ventilated extracorporeal lung to the external carotid arteries for 5 min. In the intact-nerve group brain hypoxia caused no change in pulmonary and systemic vascular pressures and resistances. In the cut-nerve group brain hypoxia caused an increase in mean pulmonary artery, left atrial, pulmonary artery pulse, and mean aortic pressures. Cardiac output, dP/dt, central blood volume, and total peripheral resistance increased but pulmonary vascular resistance and lung extravascular thermal volume were unchanged. It is concluded that acute brain hypoxia does not increase pulmonary vascular resistance but may increase pulmonary blood volume resulting from increased left ventricular afterload.