Temperature Influences on Arteriovenous Anastomoses

A technique is described which employs radioactive microspheres injected into the femoral artery of the dog to quantitate the fraction of blood flow passing through precapillary arteriovenous shunts. The lung serves to retain all the spheres reaching the venous circulation through arteriovenous anastomoses. In the control state very little shunting is detectable. With rises in body temperature, there is an increase in flow through arteriovenous anastomoses. Local limb heating does not consistently enhance arteriovenous anastomotic blood flow. With cooling, either systemic or local, shunt flow diminishes to nearly zero. Cooling is associated with a significant redistribution of tissue blood flow in the limb away from the paw and away from the skin.