Cerebral blood flow and metabolism following subarachnoid haemorrhage: effect of subarachnoid blood.

The amount of effused blood following a subarachnoid haemorrhage (SAH) was estimated in 48 patients by cerebral computerized tomographic scanning. The cerebral oxygen consumption (CMRO2) was calculated as arteriovenous difference for oxygen multiplied by mean cerebral blood flow measured by the 133-Xe inhalation technique. A significant negative correlation was observed between CMRO2 and amount of subarachnoid blood, with additional reduction in CMRO2 in case of ventricular bleeding. Cerebral blood flow on admission, opposed to CMRO2, showed no correlation to amount of blood on CT scan. A correlation was observed for blood flow measured at day 5 and further on, indicating a restored coupling between flow and metabolism. The clinical (Hunt) grade on admission and the outcome correlated to the amount of blood. These observations suggest that the acute reduction in CMRO2 following a SAH is mainly determined by the amount of blood escaping during the aneurysm rupture, and that the cerebral blood flow level a few days after SAH mainly is determined by the initial reduction in oxygen uptake.