Cerebral metabolic rate ischemia

When mild hypothermia was first shown to be beneficial, the assumption was that a substantial portion of its neuroprotective effect stemmed from a reduction in cerebral metabolism. However, studies on cerebral metabolic rate (CMR) made it clear that the degree of neuro-pathological injury following ischemia with mild hypothermic treatment did not correlate with the magnitude of metabolic depression observed (42). A reduction in temperature from 37°C to 34°C produces a 15-20% reduction in cerebral metabolism (approx 5-7% per °C), which is far less than the 50% decrease seen with electroencephalogram (EEG) silence. Furthermore, reductions in metabolism produced by anesthetics vs hypothermia are not equally neuroprotective (43). Thus, hypothermic neuroprotection cannot be explained by alterations in metabolic rate alone. 

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