Effects of Hyperventilation on the Rate of Cerebral Anesthetic Equilibration

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Abstract
The effects of hyperventilation, increase in VA and decrease in cerebral blood flow (CBF), on the rate of cerebral anesthetic equilibration have been studied using a mathematical model. Increase in VA increases the alveolar (arterial) anesthetic partial pressure. The degree to which increase in arterial partial pressure will rise is proportional to the anesthetic solubility in blood. A simultaneous effect of hyperventilation is the reduction of PaCO2 and CBF. It is predicted that with anesthetic agents of high solubility in blood, the effect of increased ventilation partially compensates for the effect of a decreased cerebral circulation on the attainment of the cerebral partial pressure of anesthetic. With anesthetic agents relatively insoluble in blood, the effect of ventilation is reduced so that achievement of cerebral anesthetic equilibrium may be unchanged or even prolonged.