Intravenous iloprost increases mesenteric blood flow in experimental acute nonocclusive mesenteric ischemia

Objective: To evaluate the effect of an intravenously administered synthetic epoprostenol analog, iloprost, in nonocclusive acute mesenteric ischemia induced by cardiac tamponade. Design: Prospective, randomized, controlled experimental study. Setting: Animal research laboratory at a university medical center. Subjects: Ten Yorkshire pigs (weight range, 20-25 kg). Interventions: Nonocclusive acute mesenteric ischemia was induced by pericardial tamponade. Pigs were randomized to receive either a low-dose, continuous intravenous infusion of iloprost (0.075 μg/kg/min) or an equivalent volume of normal saline to serve as the control. Infusion of iloprost or saline was continued after pericardial tamponade was reversed. Methods: Ten anesthetized and ventilated pigs underwent laparotomy and thoracotomy. A pulmonary artery catheter was inserted, a magnetic flow probe was positioned around the superior mesenteric artery (SMA), and cannulation of the pericardial space was performed. Pericardial tamponade was induced by injecting 5% dextrose in water into the pericardial space until blood flow in the superior mesenteric artery decreased to half of baseline. After 60 mins, animals received either a continuous intravenous infusion of iloprost at 0.075 μg/kg/min (n = 6) or an equal volume of normal saline (n = 4) for 60 mins. Pericardial fluid was then removed, and iloprost or normal saline infusion was continued for another 60 mins. Measurements: Heart rate, blood pressure, cardiac output, oxygen delivery, oxygen consumption, SMA blood flow, ileal PCO₂, ileal intramucosal pH, and serum lactate levels of mixed venous blood and mesenteric venous blood were recorded at baseline, after pericardial tamponade was induced, during the iloprost or normal saline infusion with pericardial tamponade, and after removal of pericardial fluid (reperfusion period). Results: Iloprost infusion increased SMA blood flow by 60% in this model of nonocclusive mesenteric ischemia (from 168 ± 41 to 269 ± 76 mL/min; p < .05). The effect of iloprost infusion was more prominent after the tamponade (422 ± 87 mL/min in the iloprost group vs. 232 ± 111 mL/min in the control group; p < .05). Increased mesenteric perfusion decreased intestinal mucosal nypercarbia, leading to improvement of intramucosal pH.