Cerebral surface pH changes during asphyxia, hypotension, and circulatory arrest in the dog

A technic is described for the measurement of cerebral surface pH in acute experiments in anesthetized dogs. During asphyxia and circulatory arrest, cerebral surface pH fell promptly and more profoundly than arterial blood or muscle surface pH; during hypovolemic hypotension (30 to 50 torr) cerebral surface pH declined later and less than muscle surface pH. The cerebral surface pH reflects the pH of the cortical interstitial fluid. Since the blood brain barrier is effectively impermeable to lactate, the changes recorded in the cerebral surface pH are a useful index of cortical intracellular metabolism.