Reactivity and participation of the vascular bed of a limb in the compensatory vasoconstriction during haemorrhage.

Haemorrhage was performed by free bleeding from the cannulated right femoral artery in a heated glass vessel in which pressure of 50-60 mm Hg was maintained. The left hind limb was auto-perfused by a roller pump with a constant flow. The haemorrhage was performed in a normal state of the animal, after intravenous infusion of phenoxybenzamine and after intraarterial injection of papaverine. Bilateral carotid occlusions were performed in a series of experiments before haemorrhage, in the course of haemorrhagic hypotension and after retransfusion of the drawn blood. The systemic arterial pressure and the perfusion pressure in the limb were controlled with electronic manometers. The changes in the vascular resistan-e in haemorrhage after papaverine show that considerable dilatatory influences do not reduce the reactivity of the vascular muscle and do not contribute to the non-maintenance of the resistance vessels constriction caused by the haemorrhage. The experiments with bilateral carotid occlusion permit the assumption that the passive/active tension ratio, which is changed after haemorrhage, is an important factor conducive to the non-maintenance of the post-haemorrhagic vasoconstriction. The extent of the post-haemorrhagic vasoconstriction caused by non-adrenergic constrictory agents in the blood is determined.