Mild and Moderate Hypothermia (α-Stat) Do Not Impair the Coupling Between Local Cerebral Blood Flow and Metabolism in Rats

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Abstract
Background and Purpose —The effects of hypothermia on global cerebral blood flow (CBF) and glucose utilization (CGU) have been extensively studied, but less information exists on a local cerebral level. We investigated the effects of normothermic and hypothermic anesthesia on local CBF (LCBF) and local CGU (LCGU). Methods —Thirty-six rats were anesthetized with isoflurane (1 MAC) and artificially ventilated to maintain normal Pa co 2 (α-stat). Pericranial temperature was maintained normothermic (37.5°C, n=12) or was reduced to 35°C (n=12) or 32°C (n=12). Pericranial temperature was maintained constant for 60 min until LCBF and LCGU were measured with autoradiography. Twelve conscious rats served as normothermic control animals. Results —Normothermic anesthesia significantly increased mean CBF compared with conscious control animals (29%, P P P r =0.93), anesthetized ( r =0.92), and both hypothermic groups (35°C r =0.96, 32°C r =0.96, P P P Conclusions —Anesthesia and hypothermia induce divergent changes in mean CBF and CGU. However, local analysis demonstrates a well-maintained linear relationship between LCBF and LCGU during normothermic and hypothermic anesthesia.