The aim of this work was to evaluate the alterations due to butorphanol administration in desflurane anesthetized dogs over heart rate (HR) and electrocardiography (ECG).

Twenty clinically healthy adult dogs, males and females, were randomly distributed in 2 groups of 10 animals each (GS and GB). General anesthesia was induced by intravenous administration of propofol (8.4±0.8 mg/kg) and immediately, the dogs were intubated and submitted to inhalatory anesthesia with desflurane (10V%). After 40 minutes of induction, the animals from GS received saline solution at 0.9% (0.05 mL/kg) and from GB received butorphanol (0.4 mg/kg), both applied intramuscularly. Measurement of heart rate (HR), duration and amplitude of P wave (Ps e PmV), P-R intervals (PR), QRS complex duration (QRSs), R wave amplitude (RmV), Q-T intervals (QT) and R-R intervals (RR) started immediately before the application of the agents (M0). Serial measurements were carried out at 15 minutes intervals after the administration of butorphanol or saline up to 75 minutes (M15, M30, M45, M60 and M75). Data were evaluated by analysis of variance for repeated measures (ANOVA), followed by the Tukey test (p<0.05).

Heart rate decreased significantly after butorphanol administration (from 138 ± 21 to 118 ± 19 bpm; p<0.05) while RR (from 0.44 ± 0.08 to 0.52 ± 0.08 sec; p<0.05) and QT (from 0.22 ± 0.01 to 0.24 ± 0.01 sec; p<0.05) intervals increased.

These results allowed to conclude that butorphanol administration in desflurane anesthetized dogs decreases heart rate and promotes a delay in ventricular repolarization.