Prediction of late ischaemic complications after cerebral aneurysm surgery--use of a mobile microcomputer system for the measurement of pre-, intra- and postoperative cerebral blood flow.

Patients with defective autoregulation of cerebral blood flow are at much greater risk of developing late cerebral ischaemia after intracranial aneurysm surgery. This finding was based on data derived from the intraoperative measurement of the response of the cerebral circulation to hypotension, deliberately induced to assist dissection and clipping of the aneurysm. A preoperative test which gave the same information as the intraoperative measurements might be helpful in predicting the optimal timing of aneurysm surgery. However, the original intraoperative intravenous 133Xenon injection method was limited both by the need to analyse the data off-line and the restricted number of runs (up to 6). This paper describes the modifications used, based on the Apple II microprocessor, to obtain values of cerebral blood flow within 6 minutes of the injection of 133Xenon with up to 15-20 runs per patient.