The effects of medetomidine on the action of vecuronium in dogs anaesthetized with halothane and nitrous oxide
Article first published online: 5 MAY 2008
© 2008 The Authors. Journal compilation © 2008 Association of Veterinary Anaesthetists
Veterinary Anaesthesia and Analgesia
Volume 35, Issue 5, pages 400–408, September 2008
How to Cite
Kariman, A. and Eddie Clutton, R. (2008), The effects of medetomidine on the action of vecuronium in dogs anaesthetized with halothane and nitrous oxide. Veterinary Anaesthesia and Analgesia, 35: 400–408. doi: 10.1111/j.1467-2995.2008.00401.x
- Issue published online: 7 AUG 2008
- Article first published online: 5 MAY 2008
- Received 19 July 2006; accepted 15 October 2007.
- neuromuscular blockade;
- alpha-2 agonists
Objective To quantify the effects of medetomidine on the onset and duration of vecuronium-induced neuromuscular blockade in dogs.
Study Design Randomized, prospective clinical study.
Animals Twenty-four, healthy, client-owned dogs of different breeds, aged between 6 months and 10 years and weighing between 5.0 and 40.0 kg undergoing elective surgery.
Methods Dogs were randomly allocated to two groups. Pre-anaesthetic medication in group M+ was intramuscular acepromazine (ACP) 25 μg kg−1, morphine 0.5 mg kg−1 and medetomidine 5 μg kg−1. Group M− received ACP and morphine only, at the same dose rate. After induction with thiopental, anaesthesia was maintained with halothane in oxygen and nitrous oxide. End-tidal halothane concentration was maintained at 1.1%. Neuromuscular blockade was produced with intravenous vecuronium (50 μg kg−1) and monitored using a train of four stimulus applied at the ulnar nerve. The times taken for loss and reappearance of the four evoked responses (twitches [T]) were recorded. Normal and nonparametric data were analysed with an independent t-test and Mann-Whitney’s U-test, respectively.
Results The fourth twitch (T4) disappeared at similar times in each group: 107 ± 19; [72–132] (mean ± SD; [range]) seconds in M+ and 98 ± 17 [72–120] seconds in M− dogs. The first twitch (T1) was lost at 116 ± 15; [96–132] seconds in group M+ and 109 ± 19; [72–132] seconds in M−. The fourth twitch returned significantly earlier in M+ dogs: 20.8 ± 3.8 [14–28] minutes compared with 23.8 ± 2.7 [20–27] minutes (p = 0.032). The duration of drug effect (T4 absent) was significantly shorter (p = 0.027) in M+ (18.9 ± 3.7 minutes) compared with M− dogs (22.2 ± 2.9 minutes). The recovery rate (interval between reappearance of T1 and T4) was significantly more rapid (p = 0.0003) in medetomidine recipients (3.0 ± 1.2 versus 5.2 ± 1.3 minutes).
Conclusion and clinical relevance Medetomidine 5 μg kg−1 as pre-anaesthetic medication shortened the duration of effect of vecuronium in halothane-anaesthetized dogs and accelerated recovery, but did not affect the onset time. These changes are of limited clinical significance.