Haemodynamic and regional blood flow changes after acute pulmonary microembolism in conscious rabbits

The central and peripheral haemodynamic effects of pulmonary embolisation with microspheres were measured in conscious rabbits in which the autonomic and central nervous systems were functioning normally. Sufficient microspheres were given to reduce cardiac output (measured by thermodilution) by one half. This fall in cardiac output was accompanied by a severe fall in arterial pressure and an increase in heart rate and right atrial pressure. Under these conditions cardiac output responded less than normally to an increased right atrial pressure imposed by an infusion of saline. Changes in regional blood flow and resistance were measured with radioactive microspheres injected into the left ventricle. Myocardial blood flow was unaffected by pulmonary embolisation. Cerebral flow was slightly increased. Renal, intestinal, dermal, and skeletal muscle blood flows were all reduced. Myocardial and cerebral tissue vascular resistances decreased; splenic and dermal vascular resistances increased; and renal and skeletal muscle vascular resistances were unchanged.