Abstract

Vasopressin(Pitressin), when used to control gastrointestinal bleeding, has been shown to significantly reduce coronary flow. Our purpose was to determine if Nifedipine could be used to counteract Vasopressin's coronary effect. Six mongrel dogs, weighing approximately 25 kg, underwent laparotomy and left thoracotomy under Pentobarbital anesthesia. Electromagnetic flowmeter probes were used to measure blood flow in the circumflex coronary artery(CCF), the superior mesenteric artery(SVAF) and portal vein(PVFP). Portal venous pressure(PP), femoral arterial and Swan-Ganz catheters were inserted. After baseline control psrameters were recorded, Pitressin was administered at a continuous rate of 0. 04 U/kg/min. When all parameters stabilized., Nifedipine was infused at 0,3μg kg/min. Under Pitressin infusion PVP, PP, SMAF, CCF and cardiac output decreased by an average of 43.4, 73.1, 56.8, 54.8 and 59.1% respectively. When Nifedipine was added to Pitressin infusion, CCF and cardiac output increased significantly, averaging 105 and, 83.5% of control, respectively; SMAF also increased moderately to an average of 76% of control value. However, both PVF and PP remained lower than control by average of 59. 7 and 78.1% respectively. These data indicate that with Pitressin and. Nifedipine infusion PVP and PP were reduced significantly while CCF and cardiac output were preserved