rCBF in impending brain death.

Regional cerebral blood flow (rCBF) was measured in three patients after relief of elevated intracranial pressure and restoration of normal cerebral perfusion pressure. Two patients, studied within 4 hours after closed head injury were found to have marked impairment of cortical blood flow and elevation of cerebrovascular resistance. We suggest that this picture is indicative of impending brain death, and may be the result of a long period of severe cerebral ischemia. The third patient, who had a shorter period of intracranial hypertension occurring during anaesthetic induction, responded to reduction of ICP quite differently with a transient relative hyperaemia. The physiopathological explanations for these two different types of flow response and their possible clinical significance are discussed.