Recovery quality following a single post-anaesthetic dose of dexmedetomidine or romifidine in sevoflurane anaesthetised horses

Abstract

Background: Post-anaesthetic sedation is administered to horses to improve recovery quality from inhalant anaesthesia and reduce the risk of catastrophic injury. A single dose of dexmedetomidine for this purpose has not been evaluated clinically.

Objectives: To determine whether dexmedetomidine improves recovery quality from sevoflurane anaesthesia compared to a previously studied dose of romifidine.

Study design: Prospective, randomised, masked clinical trial.

Methods: Ninety-nine, adult, client-owned horses anaesthetised for elective procedures completed the trial. Anaesthetic protocol was standardised. Horses were randomly assigned to receive either dexmedetomidine 1 mcg/kg bwt (D) or romifidine 20 mcg/kg bwt (R) intravenously at their first spontaneous breath in recovery. Recoveries were reviewed and independently assigned subjective visual analogue scale (VAS) scores (0-100 mm, worst to best) for overall quality and standing ataxia scores (1-4, none to severe) by two anaesthesiologists blinded to treatment group. Objective anaesthesia and recovery data were also recorded. Comparisons were made using the Chi-square, Wilcoxon rank sum, linear models or Welch-Satterthwaite two-sample t-test (P ≤ .05). Predictors of VAS score were analysed independent of treatment group.

Results: There were no significant differences between groups except end-tidal sevoflurane (FE´Sevo) concentration and post-induction extra ketamine dosing. Including FE´Sevo and additional ketamine in the analysis as covariates, VAS scores and time to standing were not significantly different between groups. Increased age, not receiving a nerve block, increased duration of hypotension, and having a nervous temperament were significant predictors of VAS score.

Main limitations: No universal recovery scale exists for inter-study comparisons.

Conclusions: After sevoflurane anaesthesia, sedation with dexmedetomidine or romifidine provides clinically similar recovery time and quality.

Keywords: anaesthesia; dexmedetomidine; horse; recovery; romifidine.