To determine the sedative effects and characteristics of cardiac rhythm with intravenous (IV) premedication of medetomidine, butorphanol and ketamine in dogs.Prospective, blinded, randomized clinical trial.A total of 116 client-owned healthy dogs undergoing elective surgery.Dogs were randomly allocated one of four groups: group M, medetomidine 5 μg kg-1; group B, butorphanol 0.2 mg kg-1; group MB, medetomidine 5 μg kg-1 and butorphanol 0.2 mg kg-1; or group MBK, medetomidine 5 μg kg-1, butorphanol 0.2 mg kg-1 and ketamine 1 mg kg-1 IV. Sedation was assessed using a numerical descriptive scale. Heart rate (HR) and rhythm were monitored; propofol dose (mg kg-1 IV) to allow orotracheal intubation was documented. Data were analysed using anova, accounting for multiple testing with the Tukey honest significant difference test.Sedation scores varied significantly between all groups at all time points, except between groups MB and MBK at four time points. HR decreased in all groups: most in groups M and MB, least in group B. HR was initially higher in group MBK than in groups M and MB. Arrhythmias occurred in all groups: group B showed second-degree atrioventricular blocks occasionally, all other groups showed additionally ventricular escape complexes and bundle branch blocks. Dose of propofol required for orotracheal intubation was significantly higher in group B (5.0 ± 2.0 mg kg-1) than in group M (2.6 ± 0.6 mg kg-1). Although no difference could be demonstrated between groups MB (1.4 ± 0.6 mg kg-1) and MBK (0.9 ± 0.8 mg kg-1), both groups required significantly less propofol than group M.Medetomidine-based premedication protocols led to various bradyarrhythmias. Addition of subanaesthetic doses of ketamine to medetomidine-based protocols resulted in higher HRs, fewer bradyarrhythmias and fewer animals that required propofol for intubation without causing side effects in healthy dogs.

application/pdf

Veterinary Anaesthesia and Analgesia

10

50

2

136

145

Wiley