Inhibition of Cerebral Oxygen and Glucose Consumption in the Dog by Hypothermia, Pentobarbital, and Lidocaine

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Abstract
The effect of lidocaine, 160 mg/kg and pentobarbital, 40 mg/kg, on cerebral O2 and glucose consumption was examined at brain temperatures of 37.degree., 28.degree. and 18.degree. C. Cerebral metabolic rate was measured in dogs on cardiopulmonary bypass circulation by using the sagittal sinus outflow technique. When studied separately, both drugs suppressed synaptic transmission and inhibited metabolism and a maximum effect was obtained when the EEG became flat. Using halothane 1-1.5% as the control condition, this function-metabolism coupled inhibition was .apprx. 30%. When the drugs were studied in combination, it was found that when lidocaine was given after pentobarbital, it caused an additional metabolic inhibition of 15-20%, while pentobarbital given after lidocaine had no effect. Pentobarbital has no inhibitory effect on cerebral metabolism in the absence of synaptic activity, while lidocaine suppresses synaptic transmission and has a specific membrane stabilizing effect. In analogy to its local anesthetic action, lidocaine blocks the Na+ channels and restricts the Na+-K+ leak fluxes. The load on the ion pump is reduced and metabolism is decreased accordingly. This specific effect of lidocaine was evident at brain temperatures of 28.degree. and 18.degree. C. The study supports the possibility that lidocaine, like hypothermia, may provide protection for the ischemic brain.