Comparison of sedative and some cardiopulmonary effects of intramuscular medetomidine or medetomidine-tramadol in dogs

Objective: To evaluate the clinical and physiologic effects of intramuscular (IM) administration of medetomidine with and without tramadol in dogs. Study design: Prospective experimental study. Animals: A group of eight mixed breed dogs of both sexes, aged 1–2 years, weighing 16.0 ± 0.6 kg. Methods: Each dog was studied twice at ≥1 week interval. Medetomidine (5 μg kg–1; treatment M) was administered IM alone or with tramadol (4 mg kg–1; treatment MT). Sedation was scored by a system that included vocalization, posture, appearance, interactive behaviors, resistance to restraint and response to noise. Times from drug administration to ataxia, impaired walking, head drop, sternal and lateral position and standing were recorded. Sedation score, heart rate, respiratory rate, rectal temperature, end-tidal carbon dioxide (PE′CO2), hemoglobin oxygen saturation and mean noninvasive blood pressure were recorded and compared 15 minutes before and 15, 30 and 45 minutes after drug administration. Results: Dogs administered MT had higher sedation scores than dogs administered M at 30 and 45 minutes after drug administration (p < 0.05). Times to ataxia, impaired walking, head drop and sternal recumbency were not different between the treatments. Time to lateral recumbency was longer in M than in MT (21.1 ± 1.0 versus 17.6 ± 0.7 minutes, respectively; p < 0.05). Time to standing was longer in MT than in M (67.9 ± 1.4 versus 54.5 ± 1.9 minutes, respectively; p < 0.001). Measured physiological variables did not differ between the treatments, with the exception of PE′CO2, which was higher in MT than in M at all post-treatment evaluation times (p < 0.001). Conclusions and clinical relevance: Tramadol combined with medetomidine resulted in greater sedation scores (deeper sedation) than medetomidine alone in dogs, and minimal adverse changes in the physiologic variables were measured. © 2020 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia