A comparison of dexmedetomidine, and alpha 2-adrenoceptor agonist, and midazolam as i.m. premedication for minor gynaecological surgery

Abstract

The effects of i.m. dexmedetomidine 1.0 micrograms kg-1, a new alpha 2-adrenoceptor agonist, were compared with those of i.m. midazolam 0.08 mg kg-1 and placebo on vigilance, anaesthetic requirements, haemodynamic state and plasma catecholamine concentrations in a double-blind placebo-controlled study in 107 healthy (ASA physical status I-II) women undergoing cervical dilatation and uterine curettage. The premedicants were administered i.m. 60 min before induction of anaesthesia with thiopentone. Nitrous oxide 70% in oxygen and thiopentone were used for maintenance. Both premedicants were tolerated well and no serious haemodynamic or other adverse events occurred. Dexmedetomidine caused moderate reductions in arterial pressure (maximally by 20%) and heart rate (maximally by 15%). Atropine was administered to two dexmedetomidine-premedicated patients because of bradycardia less than 45 beat min-1. Both premedicants decreased the plasma concentrations of noradrenaline by about 50%, but only dexmedetomidine attenuated the catecholamine response to anaesthesia and surgery. The thiopentone requirements were decreased significantly (P = 0.003) by both dexmedetomidine (17%) and midazolam (19%). Recovery times were 11.3 (SD 4.2) min after midazolam, 8.5 (5.2) min after dexmedetomidine and 5.6 (11.4) min after placebo (P = 0.006 between midazolam and placebo groups, other differences ns).