RESUMO
OBJECTIVES: To determine the frequency, severity and duration of adverse events including myoclonus, pain on injection, hypersalivation, regurgitation and apnoea after administration of midazolam or saline followed by etomidate in hydromorphone premedicated dogs. MATERIALS AND METHODS: Dogs undergoing elective dental prophylaxis or soft tissue surgeries were enrolled in this randomised trial. Dogs were premedicated with hydromorphone 0.1 mg/kg IV. Sixty seconds later, midazolam 0.3 mg/kg or saline at an equivalent volume was administered IV. Sixty seconds after that, etomidate 1.5 mg/kg IV was administered over 60 seconds. Additional doses of 0.5 mg/kg etomidate were administered until endotracheal intubation was successful. Observers were blinded to the treatment. Frequency, duration and a severity score of 0 to 3 were recorded for myoclonus, pain on injection, hypersalivation and regurgitation. Duration of apnoea and frequency of any additional complications was recorded. RESULTS: Forty variable breed healthy dogs were enrolled in the study. Myoclonus, pain on injection, regurgitation, hypersalivation, gagging, tachypnoea and pigmenturia occurred, respectively, in 10%, 40%, 0%, 15%, 35%, 25% and 5% of dogs in the saline group and 0%, 65%, 0%, 10%, 45%, 15% and 5% of dogs in the midazolam group. Apnoea occurred for 115 seconds (range 0 to 660 seconds) and 160 seconds (range 0 to 600 seconds) in the saline and midazolam groups, respectively. Two dogs developed pigmenturia. The trial was stopped early due to the occurrence of pigmenturia. CLINICAL SIGNIFICANCE: Due to early stopping of the trial, the predefined sample size was not reached. Further investigation is needed to determine if midazolam reduced the incidence of adverse events or improved the induction quality when combined with hydromorphone and etomidate.