Hip dysplasia is a significant problem in guide dogs. Fifty-two 6-month old dogs enrolled as potential guide dogs were anesthetized for early hip dysplasia diagnostic evaluation. Physical examination was performed prior to anesthesia. Acepromazine (A) or acepromazine-butorphanol (B) were randomly administered within each gender (respectively 11 and 12 males, and 14 and 14 females). Anesthesia was induced with a bolus of propofol (4.2 ± 0.6 mg/kg) and allowed intubation and spontaneous ventilation with 100% O2. Propofol was then infused at 322 ± 60 ug/kg/min according to the animal's response to anesthesia and manipulations. Heart rate, respiratory rate, indirect blood pressure, and end-tidal CO2 were monitored throughout anesthesia. Duration of anesthesia (AD) and times to various events during the recovery were recorded. Survival analysis was used to assess the effect of premedication and gender on AD and times from end of propofol infusion until ambulation. All statistical calculations were performed at the 0.05 -level. Body weight was significantly influenced by breed and gender (P = 0.0006), but preanesthesia data was not statistically different across gender-premedication groups. Induction dose was statistically similar across gender-premedication groups. Total infused dose was significantly lower in females (P = 0.04). Females were 4 times more at risk than males to need an additional bolus of propofol during anesthesia for the diagnostic evaluation to be completed (respectively 19 and 8; P = 0.02). After induction with propofol, heart rate was significantly reduced (P = 0.02), especially in females premedicated with B (P < 0.0001). End-tidal CO2 was higher in dogs in group B, especially in males (P = 0.03). Indirect blood pressure was kept constant throughout anesthesia, and was lower in group B, especially females (P < 0.0001). However, these changes did not affect the recovery of dogs, and AD and times to various events until ambulation were similar across gender-premedication groups. This study suggests that cardiovascular effects of butorphanol used in conjunction with propofol anesthesia are present and more important in female dogs.
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