Superior mesenteric blood flow in man following injection of bradykinin and vasopressin into the superior mesenteric artery.

The superior mesenteric blood flow was studied with a dye-dilution technique after catheterization of the superior mesenteric artery and vein. The investigation was performed in connection with portography in 22 patients with apparently normal small bowel function. Intra-arterial injection of 5, 10 or 20 mug bradykinin was followed within one minute by an increase, on the average, of 114, 176 and 223% respectively, in the superior mesenteric blood flow. The blood flow was dose-dependent in this range. The estimated vascular resistance decreased by 52, 61 and 67%, respectively. The portal venous pressure was increased slightly after intra-arterial injection, but the pressure was unchanged after intra-portal injection. Intra-arterial injection of bradykinin causes a highly improved venous phase at superior mesenteric angiography. This may be due not only to the increased flow but to some extent also to increased capillary permeability produced by bradykinin. Intra-arterial injection of 0.125 and 0.250 IU of vasopressin decreased the superior mesenteric blood flow by 53 and 54%, respectively, within 3 minutes of the injection. The dye-dilution method used was not applicable to blood flow below a level of about 200 ml/min. Continuous infusion of 0.05 IU/min decreased the superior mesenteric blood flow by, on an average, 58%. The portal venous pressure was decreased by 25% after the intra-arterial injection, but no change in pressure was recorded after intra-portal administration. The clinical use of intra-arterial infusion of vasopressin during gastrointenstinal bleeding is discussed.