Progressive change in cerebral blood flow during the first three weeks after subarachnoid hemorrhage.

Cerebral blood flow (CBF) was estimated from each cerebral hemisphere by the 133Xe inhalation method. Daily estimates were made during the first 3 weeks after subarachnoid hemorrhage (1265 studies in 116 patients). Some of the patients were taking adrenergic blocking drugs (propranolol and phentolamine), others were taking tranexamic acid, and the rest were taking no drugs. CBF was also studied in 67 normal subjects. The resting CBF was related inversely to age not only for normal subjects but also for patients after subarachnoid hemorrhage (SAH). The CBF fell progressively during the first 2 weeks after SAH and was abnormally low throughout the 3 weeks after hemorrhage. For any 1 day after SAH, those patients who were fully alert had the smallest reduction in CBF. The progressive changes in CBF occurred whether or not an aneurysm was present on angiograms. For aneurysms situated to one side of the midline, the changes in CBF affected both sides of the brain. The progressive decline in CBF was least in those patients who subsequently made the best clinical recovery. Arterial pCO2 seemed to influence CBF throughout the 3 weeks after SAH. During the 2nd week, CBF was especially low in SAH patients treated with tranexamic acid. The serial changes in CBF are discussed in relation to current views concerning the timing of operation for ruptured aneurysms.