Effects of hypothermia and rewarming on the mucosal villus microcirculation and survival after rat intestinal ischemia-reperfusion injury.

Abstract

To determine the effects of hypothermia and rewarming on changes in the villus microcirculation induced by intestinal ischemia-reperfusion (I/R). The small intestine is extremely sensitive to I/R injury, and although hypothermia can reduce cellular injury, its capacity to influence the villous microcirculation after intestinal I/R is unclear, especially after the return to normothermic conditions. Core body temperature of PVG rats was maintained at either 36 degrees to 38 degrees C (n = 12) or 30 degrees to 32 degrees C (n = 24) and then subjected to 30 minutes of intestinal ischemia. A subgroup of hypothermic animals (n = 12) were returned to normothermic conditions 120 minutes after clamp removal. The mucosal surface was visualized in an exteriorized ileal segment and macromolecular leak (MML) and leukocyte adhesion were monitored using in vivo microscopy (n = 6 in each group). MML from individual villi and numbers of adherent leukocytes within villi were determined for 2 to 4 hours after clamp removal. Heart rate and mean blood pressure were monitored in all animals. Control animals underwent sham surgery (n = 12). Ten of 12 normothermic animals failed to survive the reperfusion period, whereas all hypothermic animals and 11 of 12 of the hypothermic animals that were returned to normothermic conditions survived. MML was significantly increased in all animals subjected to I/R, although leakage was more marked in animals subjected to continuous normothermia. Enhanced leukocyte adhesion and decreased blood flow were observed only in normothermic animals. Hypothermia might prove to be an effective strategy for preventing adverse side effects in clinical settings in which intestinal I/R can be predicted.