LOCAL HYPOTHERMIA DURING ISCHEMIA OR REPERFUSION IN SKELETAL-MUSCLES

A modified rat hindlimb tourniquet model was used to measure postische mic muscle necrosis. The effect of moderate local hypothermia to 20-de grees-C during ischemia and reperfusion was investigated. Eighteen ani mals were kept in an incubator at 27-degrees-C, and complete circulato ry arrest was maintained for 3.5 h before release of the vascular occl usion. After survival for 72 h the degree of necrosis in the anterior tibial muscles was measured morphometrically on histological slides. A reas of necrosis with intact capillary structure and resorption of mus cle fibers, and areas without resorption and capillary disintegration were measured separately. Three experimental groups (six animals in ea ch) were included in the series. In the first group local cooling to 2 0-degrees-C was performed during the initial 1.5 h of ischemia. The se cond group was cooled for 1.5 h during the initial phase of reperfusio n. The animals in the third group served as controls without cooling. The total areas of necrosis in the three groups were 0, 90 and 90%, an d the areas of no-resorption 0, 23 and 39%, respectively. Cooling duri ng ischemia thus had a marked effect, while no significant differences were found between the control group and the group cooled during repe rfusion. The study shows that moderate cooling during initial ischemia protects effectively against postischemic muscle necrosis, while cool ing during reperfusion has no such effect.