Relation of cerebral blood flow to neurological status and outcome in head-injured patients

Abstract

Noninvasive studies of regional cerebral blood flow (CBF) were performed on 36 head-injured patients in varying degrees of coma, using the i.v. method. Serial examinations, averaging 4/patient, were begun during the acute phase of illness and continued until death or recovery of normal consciousness. Comparison of the initial and final studies revealed that CBF declined to very low levels in all 9 patients who died and remained subnormal in a patient with persistent vegetative state. Of 26 patients who recovered consciousness 25 showed increases in blood flow. Because of the presence of both reduced and elevated blood flows on the initial study, CBF was not predictive of outcome. Absolute or relative hyperemia in 9 acute cases, was associated with either diffuse cerebral swelling (observed on computerized tomography) or recovery from systemic shock. Cerebral metabolic studies in hyperemic patients yielded a very low O2 uptake and arteriovenous O2 difference, indicating that the high blood flow was a true luxury perfusion. When instances of presumed luxury perfusion were excluded, CBF was positively correlated with level of consciousness, assessed on a 4 point coma scale.