Regional cerebral blood flow, intracranial pressure, and brain metabolism in comatose patients

Abstract

✓ Cerebral blood flow (CBF), intracranial pressure (ICP), brain metabolism (CMRO2), systemic arterial pressure (SAP), and arterial blood gases were measured in comatose patients, most of whom had suffered a head injury. The patients were divided into two groups according to whether a mass lesion was or was not demonstrated by bilateral carotid angiography. In the majority of patients a control run measuring regional cerebral blood flow (rCBF) was followed by a test of cerebral autoregulation; hypertonic mannitol was then administered. During the control period there was marked and unpredictable variability in all of the parameters recorded. There was no correlation between ICP or CBF and neurological status or CMRO2 except at very high levels of ICP. Autoregulation was intact in some patients and defective in others, and there was no correlation between the status of autoregulation on the one hand and CBF or survival on the other. Mannitol increased CBF in nearly all patients, to twice the control value in a few, and CMRO2 increased with CBF in several patients. The change in CBF was independent of the initial ICP or the response of ICP to mannitol. Thus, the relationship of these parameters was unpredictable in acutely brain-damaged patients; the status of autoregulation was also unpredictable.