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

Abstract

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.

Management of perioperative hypertensive urgencies with parenteral medications

“…In a study investigating metoprolol and perioperative hypertension during extubation, the administration of intravenous metoprolol safely blunted the expected rise in BP 31. Similar findings were demonstrated in neurosurgical patients 32…”

Middle cerebral artery blood velocity depends on cardiac output during exercise with a large muscle mass

“…This discrepancy makes it unlikely that the reduced MCA V mean during cycling is attributed to a direct effect of β‐adrenergic blockade on the vessels. β receptors in peripheral vasculature are mainly of the β 2 type and non‐selective β‐blocking agents like propranolol will cause vasoconstriction ( Dahlgren et al 1981 ), but β 1 selective agents do not influence the cerebral circulation ( Griffith et al 1979 , Felding et al 1994 ). Also with β‐adrenergic blockade, the reduction in MCA V mean during cycling could not be attributed to a fall in P a co 2 ( Linkis et al 1995 ).…”

Acute Arterial Hypertension in Patients undergoing Neurosurgery

“…With such tenuous cerebral autoregulation in the perioperative period, any hypertension might increase the blood flow to the brain and result in a tendency to develop postoperative hematoma. 60 Hence, additional studies are needed to elucidate the mechanisms of post-craniotomy intracranial hematomas and elucidate whether a better control of hemodynamics could improve overall neurological outcomes. It is possible that there are other mechanisms apart from hypertension that might have a more telling effect on intracranial hemorrhage after craniotomy.…”