Leukocyte-depleting effect of hypothermia on muscle flap microcirculation following ischemia-reperfusion injury.

The aim of this study was to determine the effect of leukocyte-endothelial interaction and capillary perfusion on the microcirculation of muscle flaps submitted to ischemia in normothermic and hypothermic conditions. The cremaster muscle flap model was employed. Sixty rats were studied in six groups: normothermic and hypothermic control groups and groups that underwent reperfusion after 4 and 6 hours of ischemia in both normothermic and hypothermic conditions. In each group the following measurements were made: main vessel diameters, red blood cell velocities, the number of perfused capillaries, and the number of leukocytes rolling and sticking in the postcapillary venules. Hypothermia decreased the flow rate significantly and eliminated leukocytes from the microcirculation. Six hours of ischemia under normothermic conditions proved to be lethal for these muscle flaps, whereas hypothermia preserved flap viability.