Hypothermic cerebral reperfusion and recovery from ischemia

The effect of transient postischemic hypothermia (30°C) on recovery of cerebral blood flow (CBF), oxygen consumption (CMRO₂) and somatosensory-evoked potentials (SEPs) was determined in anesthetized dogs. Ischemia was produced for 20 min by intracranial pressure (ICP) elevation while core temperature was lowered by cooling externalized blood. Epidural temperature was controlled at 37.6 ± 0.2°C during ischemia, lowered to 30.0 ± 0.1°C during the first hour of reperfusion, and then rewarmed to 38.0 ± 0.1°C in experimental dogs (n = 8) and maintained at 38.0 ± 0.1°C in control dogs (n = 8). ICP was lower throughout reperfusion in experimental as compared with control animals. By 240 min of reperfusion, CBF was ~70% of control in both groups. CMRO₂ was 60% of preischemic values in control animals and 74% in experimental animals (P = 0.077). A persistent uncoupling of CBF and CMRO₂ was observed throughout reperfusion only in the control group. Recovery of SEP amplitude was significantly improved in the experimental group (26 vs. 11% of preischemic values). These data suggest that transient hypothermia reduces ICP and facilitates recovery of electrophysiological function after cerebral ischemia.