Sedative Effects of Intramuscular Dexmedetomidine and Ketamine at Sub-Anesthetic Dose Alone or in Combination with Methadone in Healthy Dogs

The aim of the present study was to compare sedation quality and cardiorespiratory parameters in healthy dogs after intramuscular injection of dexmedetomidine and ketamine with or without methadone. Forty client-owned dogs were randomly divided into two groups and received IM dexmedetomidine (5 µg kg−1) and ketamine (1 mg kg−1), associated (DKM group) or not (DK group) with methadone (0.2 mg kg−1). Sedation, heart rate (HR), respiratory rate (ƒR), mucous membrane and rectal temperature were recorded at baseline (T0) and after 5 (T5), 10 (T10) and 20 (T20) minutes. From T10, cardiac rhythm was monitored with a continuous lead II electrocardiogram. Ease of venous catheter placement, total propofol dose and any apnea episodes were recorded. Sedation was significantly greater in the DKM group, and a significant increase from T5 to T20 within DKM (P = .0002) and DK (P = .008) was also observed. Within each group, HR was significantly lower at all time points compared to baseline. No significant differences between groups were found in the number of arrhythmogenic events (atrioventricular blocks). In both group ƒR decreased over time. The propofol dose required for anesthesia induction was significantly lower (P = .027) in the DKM group. In conclusion, a good level of sedation was achieved in both groups, although this was greater in DKM. Smooth animal-operator interaction and ease of venous catheter placement showed that DK was a useful sedative protocol in healthy patients.