EFFECTS OF DIFFERENT DURATIONS OF TOTAL WARM ISCHEMIA OF THE GUT ON RAT MESENTERIC MICROCIRCULATION

Background: Gut injury due to ischemia and reperfusion (I/R) plays a p ivotal role in many clinical conditions, such as small bowel transplan tation, heart or aortic surgery in adults, and necrotizing enterocolit is in neonates. The influence of ischemic events on microcirculatory m echanisms is not well understood, Therefore, we studied, in vivo, loca l perfusion and leukocyte-vessel wall interactions before and after di fferent periods of total warm ischemia of the whole gut and subsequent reperfusion in mesenteric microvessels. Materials and Methods: Groups of pentobarbital-anaesthetized Lewis rats were subjected to 15 (n = 9 ), 30 (n = 12), or 60 min (n = 5) of total warm gut ischemia and 2 h r eperfusion. As control a sham group (n = 10) was included, After ligat ing the inferior mesenteric artery, total warm ischemia was induced by clamping the superior mesenteric artery. Before and at different time periods after start of reperfusion intravital video microscopic measu rements were performed, Results: Rats subjected to 60 min ischemia die d during the early reperfusion phase, Fifteen, 30, and 60 min ischemia induced in venules a significant decrease in blood flow, while diamet er changes were not observed, This flow decrease was severe in the 15- and 30-min ischemia groups, dropping to 40 and 25% of control, respec tively. Following 60 min ischemia blood flow did not exceed 10% of con trol. The total number of interacting leukocytes, a parameter which in cludes both leukocyte rolling and adhesion in venules, increased up to 5 or 10 times its control value following 15 or 30 min ischemia, resp ectively. Leukocyte-vessel wall interactions could not be studied in t he 60-min ischemia group, due to the low blood flow. Conclusions: Even short periods of total warm ischemia of the whole gut induce severe a ttenuation of venular blood flow with an increase in leukocyte-vessel wall interactions. These changes increase with prolongation of the isc hemic period. A 60-min period of total warm ischemia is fatal during t he early reperfusion phase. (C) 1997 Academic Press.