The cerebral arterio‐venous oxygen content differences (AVDo2) during halothane and neurolept anaesthesia in patients subjected to craniotomy

Abstract

In 20 patients subjected to craniotomy for supratentorial cerebral tumours, the haemodynamic changes during halothane and neurolept anaesthesia were evaluated by measuring mean arterial blood pressure (MABP) and cerebral arterio-venous oxygen content differences (AVDo2) repeatedly during the operation. Ten patients were given 0.5% halothane anaesthesia and ten patients neurolept anaesthesia. MABP, AVDo2 and Paco2 were measured after induction of anaesthesia, before and after incision, after opening and closure of the dura, at the time of extubation and 1 h later. Concerning MABP and Paco2, no significant difference between the two groups was found. In both groups an increase in MABP was observed after incision (P < 0.01 in the neurolept group and P < 0.05 in the halothane group) and in the neurolept group after extubation (P < 0.01). In both groups a decrease in AVDo2 was observed after incision (P < 0.01) and after extubation (P < 0.01 in the neurolept group and P < 0.05 in the halothane group). During the operation AVDo2 values were significantly higher in the neurolept group (P < 0.05). The results indicate that even a moderate increase in MABP after incision during neuroanaesthesia affects AVDo2 values, suggesting an increase in cerebral blood flow. The study suggests that autoregulation of cerebral blood flow might be better preserved during neurolept anaesthesia. A state of hyperperfusion of the brain after extubation was unveiled in both groups.