Relationship of early cerebral blood flow and metabolism to outcome in acute head injury

Abstract

Cerebral blood flow (CBF) measurements were obtained acutely in 96 comatose patients with closed head injury, using the intravenous 133Xe technique. Arteriojugular venous oxygen differences and cerebral metabolic rate for oxygen (CMRO2) were determined in a subgroup of 66 patients. The relationship between each of these variables and outcome at 6 months was analyzed, using the Glasgow Outcome Scale. The CMRO2 was significantly depressed in patients who subsequently died or remained in a vegetative state, whereas higher values were obtained in patients who later regained consciousness. Although CBF was not predictive of outcome in the total sample, omission of patients with acute hyperemia resulted in a significant relationship that paralleled the metabolic findings. Follow-up studies in the survivors revealed a correlation between CBF and degree of functional recovery, the lowest blood flows being obtained among patients with severe disability. Age, initial Glasgow Coma Scale score, and occurrence of intracranial hypertension were each found to be predictive of outcome, thus confirming previous reports. When these variables were combined with CMRO2 in a logistic regression analysis, the probability of recovery was correctly predicted in 82% of the cases. The CMRO2 was relatively independent of the other prognostic indicators and, next to age, contributed most to the prediction.