The effects of an intravenous bolus of dexmedetomidine following extubation in a mixed population of dogs undergoing general anaesthesia and surgery.

An observer blinded, placebo controlled study evaluated the effects of 62.5 μg/m(2) dexmedetomidine administered IV on recovery from isoflurane anaesthesia in dogs. Forty-four healthy dogs, weighing 1.8-19.95 kg, presented for surgery that was expected to cause mild to moderate pain were studied. All were premedicated with 125 μg/m(2) dexmedetomidine and 20 μg/kg buprenorphine IM. Anaesthesia was induced with propofol and maintained with isoflurane. Non-steroidal anti-inflammatory drugs and local anaesthetics were administered as appropriate. Immediately prior to extubation dogs were treated with dexmedetomidine 62.5 μg/m(2) (group D) or an equivalent volume of heparinised saline (S). Assessments of heart rate, respiratory rate, pain (short form Glasgow composite pain scale [SF-GCPS], dynamic interactive visual analogue scale [DIVAS]), sedation (simple descriptive scale [SDS], DIVAS) and mechanical nociceptive threshold (MNT) were performed immediately before premedication, 20 min later, at the time of test drug administration (T0) and at 15-30 min intervals for four hours (T240 min). Recovery quality was scored 0 - 3 (SDS). Data were analysed with Student's t and Mann-Whitney U tests, two-way ANOVA and Fisher's exact test. Significantly fewer poor quality recoveries were observed in group D (D 2 [1-3]; S 2 [0-3]; P=0.02), however, sedation was increased in group D compared to group S from T15 to T150 min (P=0.0001). Pain scores were lower in group D compared to group S from T15 to T120 min (P=0.001), but the requirement for additional analgesia in the first 4h following extubation was not different between groups. Dexmedetomidine may decrease the incidence of poor quality anaesthetic recoveries in dogs.