Figure 21-3 The effect of temperature reduction on the cerebral metabolic rate of oxygen (CMRO₂ ). Hypothermia reduces both of the components of cerebral metabolic activity identified in Figure 21-1 : that associated with neuronal electrophysiologic activity ("Function") and that associated with maintenance of cellular homeostasis ("Integrity"). This effect is in contrast to anesthetics that alter only the functional component. The ratio of CMR at 37°C to that at 27°C, the Q₁₀ ratio, is shown in the graph. EEG, electroencephalogram. (Adapted from Michenfelder JD: Anesthesia and the Brain: Clinical, Functional, Metabolic, and Vascular Correlates. New York, Churchill Livingstone, 1988.)