Cerebral blood flow, cerebral metabolic rate of oxygen and relative CO2 reactivity during neurolept anaesthesia in patients subjected to craniotomy for supratentorial cerebral tumours

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Abstract
In 10 patients subjected to craniotomy for supratentorial cerebral tumours in neurolept anaesthesia, cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRo2) were measured twice peroperatively by a modification of the Kety & Schmidt technique, using 133Xe. The relative CO2 reactivity was assessed indirectly as the % change of the arterio–venous oxygen difference (AVDo2) per mm change in Paco2. The patients were premedicated with diazepam 10–15 mg perorally. For induction, thiopentone 4—‐6 mg/kg, droperidol 0.2 mg/kg and fentanyl 5 μg/kg were used, and for maintenance N2O 67% and fentanyl 4 μg/ kg/h. During the first flow measurement the median and range of CBF was 30 ml/100 g/min (range 17–45), of AVDo2 8.0 vol % (range 4.1–9.5), and of CMRo2 2.28 ml O2/100 g/min (range 1.57‐2.84). During tin–second CBF study, AVDo2 increased to 9.3 vol % (range 3.4–11) (P < 0.05), and CMRo2 increased to 2.51 ml O2/100 g/min (range 1.88‐3.00) P < 0.05, while CBF was unchanged. The CO2 reactivity was present in all studies, median 1.8 %/mmHg (range 0.5–15.1). The correlation coefficients between jugular venous oxygen tension/saturation, respectively, and CBF were high at tensions/saturations exceeding 4.0 kPa and 55%, indicating that hyperperfusion is easily unveiled by venous samples from the jugular vein during this anaesthesia.