Effect of clonidine, by infi ltration and by intravenous route, on scalp block for supratentorial craniotomy

Background: The aim of this research was to study and compare the haemodynamic and analgesic effects of (A) scalp block with bupivacaine 0.25%; (B) scalp block with bupivacaine 0.25% plus clonidine 2 mu g/kg; and (C) scalp block with bupivacaine 0.25%, plus intravenous (IV) clonidine 2 mu g/kg in supratentorial craniotomies. Method: Sixty patients divided into three equal groups (A, B and C) were administered one of the above combinations. All the patients received propofol-based general anaesthesia. Propofol infusion was started at 25 mu g /kg/minute, adjusted with an increment or decrement of 5 mu g/kg/minute to obtain an A-line ARX index (AAI) of between 20 and 30 throughout the surgery, and stopped after dural closure. Fentanyl 0.5 mu g/kg IV was given if a 20% increase in either heart rate (HR) and/or blood pressure (BP) was observed. HR and BP were monitored throughout the surgery and recorded on pin application, incision (planned 15 minutes after pins), at 15-minute intervals thereafter until dural closure, and every 've minutes after dural closure. Propofol and fentanyl requirements were recorded for the duration of the surgery. Results: There was a significant fall in HR, SBP (systolic blood pressure), MAP (mean arterial blood pressure) and RPP (rate-pressure product) after pin application in group B (HR p = 0.018, SBP p = 0.003, MAP p = 0.0042, RPP p = 0.000) and group C (HR p = 0.412, SBP p = 0.01, MAP p = 0.0084, RPP p = 0.001) when compared to group A. Propofol and fentanyl requirements were significantly lower in group B (propofol 67.9% and fentanyl 34.85% less) and group C (propofol 59.21% and fentanyl 36.36% less) when compared to group A. Conclusions: The addition of clonidine, either to the scalp block or intravenously, offers better haemodynamic stability intraoperatively, and reduces analgesic and anaesthetic requirements.