Randomized, blinded, controlled clinical trial to assess gastroesophageal reflux and regurgitation in dogs undergoing general anesthesia after hydromorphone premedication with or without acepromazine or dexmedetomidine

OBJECTIVE: To investigate whether premedication with hydromorphone alone or combined with acepromazine or dexmedetomidine affects the incidence of gastroesophageal reflux (GER) and regurgitation in dogs undergoing general anesthesia for elective orthopedic surgery. ANIMALS: 39 healthy client-owned dogs undergoing general anesthesia for elective orthopedic surgery between November 2016 and November 2018. PROCEDURES: For this prospective, randomized, controlled, blinded clinical trial, dogs were randomly assigned to be premedicated with hydromorphone (0.1 mg/kg, IM) alone (group H [control group]) or with either acepromazine (0.05 mg/kg, IM; group AH) or dexmedetomidine (6 μg/kg, IM; group DH) before undergoing general anesthesia induced with propofol and maintained with isoflurane. A pH sensor-tipped probe was used to identify episodes of GER (esophageal pH < 4 or > 7.5 for ≥ 30 seconds). Results for GER, regurgitation, vomiting, propofol dose, and durations of food withholding and anesthesia were compiled and compared across groups. RESULTS: There were 13 dogs in each group, and no meaningful differences were detected in age, body weight, sex, breed, or durations of anesthesia or food withholding across groups. Overall, 16 of the 39 (41%) dogs developed GER: 9 in group H, 6 in group AH, and 1 in group DH. The incidence of GER was significantly lower for group DH versus group H. Six of the 39 (15%) dogs regurgitated: 4 in group H and 2 in group AH. CONCLUSIONS AND CLINICAL RELEVANCE: The combined use of dexmedetomidine and hydromorphone as premedication may be a better choice to reduce GER in healthy dogs undergoing orthopedic surgery than would the use of hydromorphone with or without acepromazine. Additional research is warranted.