The effect of metoprolol upon blood pressure, cerebral blood flow and oxygen consumption in patients subjected to craniotomy for cerebral tumours

Hypertension and cerebral hyperperfusion are often seen in the immediate postoperative period after craniotomy for supratentorial tumours. Metoprolol is known to attenuate the postoperative hypertensive response after hypotensive anaesthesia and this study was carried out to evaluate the effect of metoprolol on cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRo₂) before extubation and cerebral arteriovenous oxygen content difference (AVDo₂), mean arterial blood pressure (MABP), Pao₂ and Paco₂ in a 180–min period after extubation. Twenty patients anaesthetized with thiopentone, fentanyl, nitrous oxide 67%, and halothane 0.5% were randomized to receive intravenous metoprolol or placebo at the end of the peroperative period. There were no significant differences in CBF– and CMRo₂ values between the two groups. In the period between closure of the dura and 5 min after extubation, an increase in MABP was observed in the control group ( P < 0.05), but not in the metoprolol group. During the same period a decrease in AVDo₂ was observed in both groups ( P < 0.05); during the next 10 min an increase was observed, but with no difference in AVDo₂ values between the groups. A higher level of Pao₂ in the metoprolol group was observed in the postoperative period. These findings suggest that peroperative treatment with metoprolol reduces postoperative MABP but does not influence the cerebral blood flow and metabolism.