[Effect of Pitressin (8-arginine vasopressin) on the lower esophageal sphincter in dogs].

The effect of vasopressin on the lower esophageal sphincter pressure (LESP) is still poorly understood. The present study was designed to determine the effect of I.V. and intra-arterial administration of 8-arginine vasopressin (Pitressin) on the LESP in dogs. A total of 16 anesthetized mongrel dogs were given a continuous perfusion of Pitressin for 20 minutes. Group A (3 dogs): Infused at 2.75 mU/kg/min into the superior mesenteric artery. Group B (3 dogs): 2.75 mU/kg/min into a peripheral vein. Group C (5 dogs): 14 mU/kg/min into a peripheral vein (equivalent to therapeutic dose in humans). Group D (5 dogs): 28 mU/kg/min into a peripheral vein. Esophageal manometry was performed using a triple lumen polyvinyl tube assembly perfused with water at 0.4 ml/min. LESP was checked by the pull-through technique before, immediately and 30 minutes later after termination of the infusion. LESP was monitored at 3 locations during the infusion. No change in LESP was noted when Pitressin (2.75 mU/kg/min) was infused intra-arterial or I.V. I.V. infusion of 14 and 28 mU/kg/min Pitressin caused a significant sustained decrease in LESP (p less than 0.001). After infusion of 28 mU/kg/min, LESP failed to return to control levels in 30 minutes. The results suggest that intravenous administration of a high dose of Pitressin predisposes to gastroesophageal reflux during and shortly after infusion.