A systematic review of the use of peri-operative systemic ketamine in cats and dogs for analgesia.

Abstract

OBJECTIVES: Ketamine is a non-competitive N-methyl-D-aspartate antagonist widely used in veterinary medicine for analgesia peri-operatively, in polytrauma and anecdotally for chronic pain. This systematic review aimed to provide an overview of the veterinary literature available on systemic ketamine administration for acute analgesia in dogs and cats. This will include, a discussion on ketamine's impact on pain scores and rescue analgesia requirements and will correlate these with ketamine plasma concentrations and nociceptive threshold changes. METHODS: A literature search was conducted over three databases (GoogleScholar, PubMed and Veterinary Anaesthesia and Analgesia Journal) with definitive search terms and inclusion criteria between 1980 and 2024. Quality of evidence was assessed with the 'Grading of Recommendations, Assessment, Development, and Evaluations' and the Cochrane Collaboration Bias tool to assess study bias. RESULTS: Studies that met eligibility criteria included 11 dogs, three cats; 14 in total. These included prospective randomised controlled trials, crossover trials, case series and laboratory experiments. Quality of evidence was moderate, with low risk of bias, moderate-good study design, moderate indirectness due to predominantly soft tissue procedures studied and underpowered, small population studies. CONCLUSION: Ketamine may influence pain scores > 12 hours post operatively. Ketamine does not influence rescue analgesia requirements post-operatively. Plasma concentrations > 200 ng mlcorrelate with nociceptive threshold changes. When doses are extrapolated from humans, plasma concentrations are lower than expected. Plasma concentrations quickly decline after cessation of intravenous infusion or bolus. Future studies with higher doses of ketamine in a variety of clinical procedures are needed to evaluate ketamine's analgesic effect peri-operatively.