Effects of profound hypotension on cerebral blood flow during surgery for intracranial aneurysms

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Abstract
In the majority of grade I patients, CBF [cerebral blood flow] remained above 30 ml/100 g per min during profound hypotension at MABP [mean arterial blood flow] of 40 mm Hg. Those patients in whom CBF fell below 30 ml/100 g per min were protected from cerebral ischemia, probably through the combined effects of halothane (or enflurane), mannitol and the relatively short duration of the flow reductions. Postoperatively, there was evidence of trauma at the site of retraction, most pronounced in those patients with a low intraoperative CBF and no postoperative reactive hyperemia. There were no associated neurological abnormalities. The major clinical significance of arterial spasm may be the result of hemodynamic instability. Although these patients were protected from ischemic damage during surgical hypotension, autoregulatory impairment persisted well into the postoperative period and the patients were susceptible to ischemic deficits of late onset when subjected to a superimposed hemodynamic stress. Characteristic CBF abnormalities were identified at all 3 stages of their clinical management: preoperatively, intraoperatively and postoperatively.