Hemodynamic effects of phenoxybenzamine and volume replacement in segmental ischemia of the rat small intestine

Segmental ischemia of the small intestine in the rat was established by ligating the mesenteric arterial end arcades of 1/4 of the length of the small intestine. Regional and central blood flow was measured with the microsphere technique before and 2 h after induction of the ischemia. In one series of rats an i.v. infusion of 16 ml plasma per kg body weight (b.w.) was given during the experimental period, which maintained the central circulation. However, the impairment of blood supply to the whole small intestine caused by the segmental ischemia was not normalized. Two other series of rats were treated with either phenoxybenzamine alone, 3 mg.kg-1 b.w., or the same dosage of phenoxybenzamine plus plasma infusion (16 ml.kg-1 b.w.). The central circulation was deteriorated and the blood flow to the small intestine reduced in the rats receiving phenoxybenzamine alone. Both the central circulation and the blood supply to the non-ischemic parts of the intestine were maintained in rats treated with both phenoxybenzamine and plasma. Combined treatment with phenoxybenzamine and volume replacement thus seems to be valuable for limiting the secondary hemodynamic changes caused by segmental intestinal ischemia.