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The Exam RoomBy The VeterinaryPracticeNow Desk4 min readNovember 9, 2026
Medetomidine premedication halved hypotension rates in a randomized spay-neuter trial
The trial ran at a university teaching hospital and tracked mean arterial pressure, creatinine changes, and oliguria 24 hours post-op.
A randomized clinical trial at a university teaching hospital found that healthy dogs premedicated with medetomidine before routine spay-neuter surgery had lower rates of intraoperative hypotension and postoperative acute kidney injury compared to dogs premedicated with acepromazine.
What the study found
Researchers found medetomidine premedication reduced hypotension incidence to 51% compared to 84% with acepromazine. Hypotension episodes were shorter, 14 minutes on average with medetomidine versus 26 minutes with acepromazine, and less severe, with lowest mean arterial pressure averaging 60.0 mm Hg versus 51 mm Hg. The study defined acute kidney injury as a serum creatinine increase greater than 26.5 µmol/L at 24 hours postoperatively. AKI occurred in 9.8% of the medetomidine group versus 20.9% of the acepromazine group. The medetomidine group had zero cases of oliguric AKI, and the acepromazine group had four.
How the study was built
The trial enrolled healthy dogs six months or older, weighing at least 4 kg, with American Society of Anesthesiologists risk scores of 2 or lower and no cardiovascular or renal disease. The medetomidine group included 51 dogs, and the acepromazine group included 43. All dogs received methadone as part of premedication, with either medetomidine at 0.3 to 5 µg/kg or acepromazine at 0.01 to 0.05 mg/kg intramuscularly. Anesthesia was induced with alfaxalone and maintained with isoflurane. Researchers measured mean arterial pressure during surgery, defined hypotension as mean arterial pressure below 60 mm Hg, and measured serum creatinine before surgery and 24 hours after. Oliguria was defined as no urination with a low-volume bladder at 24 hours.
This is a single-center randomized controlled trial in healthy, low-risk dogs undergoing one type of elective surgery. The design supports causal claims about the premedication choice in this population, but the sample is small and the setting is controlled.
The number, and its error bars
The primary comparison is hypotension incidence: 51% with medetomidine versus 84% with acepromazine. The abstract does not report p-values or confidence intervals for this difference. Mean duration of hypotension was 14 minutes in the medetomidine group and 26 minutes in the acepromazine group. Lowest mean arterial pressure was 60.0 mm Hg with medetomidine and 51 mm Hg with acepromazine. Acute kidney injury incidence was 9.8% with medetomidine and 20.9% with acepromazine. The standard deviations on hypotension duration are wide relative to the means, so individual cases varied substantially.
What the authors say it cannot tell you
The abstract does not state limitations. The study enrolled only healthy dogs with ASA risk scores of 2 or lower undergoing elective gonadectomy at a single teaching hospital, so the findings do not extend to sicker patients, emergency cases, or other surgical procedures. The kidney injury assessment stopped at 24 hours postoperatively.
Who paid for it
The abstract does not state funding sources or conflicts of interest.
What this means for your practice
VeterinaryPracticeNow's read, not the study's. Everything in this section is our editorial interpretation for practice owners. The study does not claim any of it.
If you run a high-volume spay-neuter practice, this trial is worth reading in full. The hypotension difference is large enough that we'd expect it to show up in your anesthesia logs if you switched protocols. The kidney injury data is preliminary (small sample, single center, only one type of surgery) but the pattern is worth tracking if you do multiple spays a day. We'd want to see this replicated in a multi-center trial before calling it settled, but the direction is clear enough to inform your next protocol review.
For associate DVMs, this is evidence you can bring to a medical director when discussing premedication protocols. The trial used real-world dose ranges and alfaxalone induction, so the workflow transfers to general practice. For relief veterinarians walking into different protocols every shift, knowing medetomidine outperformed acepromazine on hypotension and AKI in this population gives you standing to ask about the premedication choice when you see acepromazine loaded for a healthy spay.
The study does not report drug costs, and it does not track renal outcomes beyond the immediate postoperative period. It does show that the premedication choice affected both blood pressure during surgery and early kidney markers after surgery in healthy dogs undergoing routine gonadectomy, and medetomidine performed better on both measures in this trial. Our read: if you're still defaulting to acepromazine for healthy spays, the burden of proof has shifted.
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