Comparison of the effects of different doses of acepromazine-xylazine on the electrocardiogram in dogs

Seventy seven adult large mixed breed dogs of either sex were included in this study. The animals were randomly divided into four groups and received the following drug combinations intramuscularly: Group 1 xylazine (0.5 mg/kg) and acepromazine (0.05 mg/kg), Group 2 xylazine (0.8 mg/kg) and acepromazine (0.03 mg/kg), Group 3 xylazine (0.3 mg/kg) and acepromazine (0.08 mg/kg) and Group 4 xylazine (0.5 mg/kg) acepromazine (0.05 mg/kg) and atropine (0.04 mg/kg). Results showed no significant differences in the P-wave and QRS complex durations, PR interval and R waves among the 4 groups. QT interval significantly decreased following drug administration in group 4 compared to groups 1 (P = 0.03) and 3 (P = 0.004). There were significant increases in the QT interval in groups 1 (P = 0.001) and 3 (P = 0.01) after drug injections. Heart rate (HR) significantly decreased in groups 1, 2 and 3 after drug injections (P = 0.004, 0.01 and 0.03, respectively). There was a significant negative correlation between HR, PR and QT intervals, and a positive correlation between HR and P-wave amplitude. There were no significant differences between all groups in the incidence of first and second degree AV blocks.