Effects of a single pre-operative dexmedetomidine dose on isoflurane requirements and peri-operative haemodynamic stability.

In a double-blind, placebo-controlled study we investigated the effect of a single pre-induction intravenous dose of dexmedetomidine 2 micrograms.kg-1 on anaesthetic requirements and peri-operative haemodynamic stability in 50 patients undergoing minor orthopaedic and general surgery. Patients were anaesthetised with nitrous oxide/oxygen/fentanyl, supplemented if necessary with isoflurane. The mean (SD) intra-operative isoflurane concentration was lower in the dexmedetomidine-treated patients than controls (0.01 (0.03)% compared to 0.1 (0.1)%; p = 0.001) although six of the 25 treated patients required isoflurane at some stage. The haemodynamic response to tracheal intubation and extubation was reduced in the dexmedetomidine group as was intra-operative heart rate variability; postoperative analgesic and anti-emetic requirements and peri-operative serum catecholamine concentrations were lower in the dexmedetomidine group. Hypotension and bradycardia occurred more frequently after dexmedetomidine.