Changes of blood pressure and cerebral arterio-venous oxygen content differences (AVDo2) with and without bupivacaine scalp infiltration during craniotomy

In 20 patients subjected to craniotomy for supratentorial cerebral tumours, the effect of scalp infiltration with bupivacaine before incision was evaluated by measuring mean arterial blood pressure (MABP) and cerebral arterio-venous oxygen content differences (AVDO2) repeatedly during the operation. All patients were given halothane 0.5% anaesthesia. Ten patients were given bupivacaine 0.25% and ten patients were given normal saline for scalp infiltration prior to incision. The study was performed in a double-blind randomized fashion. Significantly higher values of MABP (P less than 0.0005) after incision were found in the saline group compared to the bupivacaine group. Significantly lower values of AVDO2 (P less than 0.0005) after incision were seen in the saline group compared to the bupivacaine group. The results indicate that the increase in MABP associated with a decrease in AVDO2, suggesting an increase in CBF and cerebral hyperperfusion, is reduced by using bupivacaine scalp infiltration prior to incision.