Premedication with medetomidine compared to acepromazine reduces the risk of hypotension and mild acute kidney injury in healthy dogs undergoing gonadectomy surgery: results of a randomized clinical trial

Objective To compare premedication with medetomidine or acepromazine in regard to hypotension and acute kidney injury (AKI) in dogs undergoing elective gonadectomy. Methods This randomized clinical trial included healthy dogs ≥ 6 months of age undergoing gonadectomy in a university teaching hospital. Exclusion criteria were weight < 4 kg, American Society of Anesthesiologists risk > 2, or cardiovascular/renal disease. Premedication consisted of methadone and medetomidine at 0.3 to 5 µg/kg or acepromazine at 0.01 to 0.05 mg/kg IM. Anesthesia was induced with alfaxalone and maintained with isoflurane. Hypotension (mean arterial pressure < 60 mm Hg) frequency, severity, and duration; recovery temperature; and vomiting and pain interventions were compared. Oliguria 24 hours postoperatively was defined as no urination with low-volume bladder. Serum creatinine was measured from blood before and 24 hours after surgery. Acute kidney injury was defined as an increase of > 26.5 µmol/L. Results The medetomidine group included 51 dogs and the acepromazine group 43. There were no differences in preoperative characteristics, anesthetic doses, or time. Hypotension was significantly less frequent (51% vs 84%), had a shorter duration (14 ± 20.2 minutes vs 26 ± 24.2 minutes), and was less severe (lowest mean arterial pressure 60.0 ± 14.9 mm Hg vs 51 ± 10.3 mm Hg) following medetomidine. Acute kidney injury was less frequent in the medetomidine group (9.8% vs 20.9%), with no oliguric AKI cases compared to 4 following acepromazine. There were no differences in postoperative hypothermia or treatments for vomiting or pain. Conclusions Premedication with medetomidine results in a lower frequency and duration of hypotension and might reduce the risk of AKI. Clinical Relevance For healthy dogs undergoing elective surgery, premedication with medetomidine is preferable to acepromazine.