Minimum Cerebral Blood Flow and Metabolism During Craniotomy. Effect of Thiopental Loading

Abstract

Cerebral blood flow and metabolism were measured repeatedly during surgery for cerebral tumors by a modification of the classical Kety et. Schmidt method using 133Xe infusion i.v. Standard procedure for neuroanesthesia (pentobarbitone-fentanyl induction, halothane-nitrous oxide maintenance) reduced blood flow from 47.1-24.2 ml .cntdot. 100 g .cntdot. ml-1 and metabolism from 3.30-1.83 ml O2 .times. 100 g-1 .cntdot. ml-1. PaCO2 [partial pressure of CO3] was reduced by hyperventilation from 5.3-3.6 kPa. Additional thiopental loading and maintenance using 4+4 mg .cntdot. kg-1 (n =5) or 8+8 mg .cntdot. kg-1 (n = 5) reduced cerebral metabolism by an additional 15% (P < 0.01) and blood flow by 16.5% (P < 0.001), while mean arterial blood pressure fell from 11.0-9.9 kPa (P < 0.05). Paco2 remained unchanged. This additional reduction in cerebral metabolism and blood flow is small, but it may well be of clinical interest to the problem of protecting the brain in case of episodes of focal cerebral ischemia which may arise peroperatively during intracranial surgery.