Role of sympathetics in the response to acute venous occlusion

The effect of venous ligation and subsequent blockade of alpha receptors on hindlimb venous pressure, vascular resistance, oxygen extraction and carbon dioxide removal was evaluated in mongrel dogs with use of constant-flow perfusion of the extremity bed. Perfusion, metatarsal vein, femoral vein, and central vein pressures, and changes in paw and thigh circumference were recorded in mongrel dogs in which the hindlimb was perfused at a constant flow. Arterial, metatarsal venous, and femoral venous blood gases were drawn and analyzed for arteriovenous oxygen and carbon dioxide differences. Measurements were repeated following extensive ligation of veins and after subsequent alpha-receptor blockade with Dibenzyline. Findings indicated that ligation of extremity veins resulted in an active increase in total limb resistance upstream from the ligation, and an increase in volume of the limb. Following alpha-adrenergic blockade with Dibenzyline, limb volume increased and oxygen extraction decreased below control levels. The reflex constriction following ligation of veins protected against the detrimental effect of excessive accumulation of fluid in tissue spaces.