Tissue Oxygenation in Normal and Edematous Brain Cortex During Arterial Hypocapnia

Abstract

Since arterial hypocapnia causes a cerebral blood flow decrease, hypocapnic conditions are induced in patients with severe traumatic brain injury by controlled hyperventilation in order to reduce the intracranial pressure (Gordon, 1971). Beneficial effects on the clinical course of patients, however, can be observed only under conditions of moderate hypocapnia. As shown by animal experiments severe arterial hypocapnia results in insufficient oxygen supply conditions in brain tissue (Grote et al., 1981), which subsequently influences the brain metabolism (Granholm et al., 1969, 1971) and counteracts the influence of hypocapnia on cerebral blood flow regulation (Grote et al., 1981). The present experiments were performed to study the effects of a stepwise decrease in PaCO₂ on rCBF, tissue PO₂ and tissue metabolism in the brain cortex after afflicting a local brain edema.