Evaluation of different constant rate infusions of dexmedetomidine in cats undergoing elective surgery

Objectives: The objective of the study was to evaluate the effects of three constant rate infusions (CRIs) of dexmedetomidine (DEX; 1, 2 and 3 µg/kg/h) on cardiovascular, respiratory and analgesic outcomes in cats undergoing elective ovariectomy, aiming to identify an infusion rate that optimally balances analgesic benefits with minimal side effects. Methods: In a randomised, controlled, blinded study, 73 healthy female cats were assigned to one of four groups: DEX1 (1 µg/kg/h), DEX2 (2 µg/kg/h), DEX3 (3 µg/kg/h) or a control group receiving saline solution (CTRL). Anaesthesia was maintained with isoflurane, and physiological variables, including heart rate (HR), blood pressure (BP), respiratory rate (RR) and end-tidal CO2, were measured at baseline and specific time points during surgery. Intraoperative analgesia was assessed based on rescue analgesia requirements, and recovery quality was evaluated postoperatively. Results: DEX CRI reduced isoflurane requirements only in DEX3 at T30 compared with the other groups at the same time point. Blood pressure was higher in DEX3 at T15 and T30 compared with the other groups at the same times, while no differences were observed for HR across all groups at any time of the study. The percentage of cases that required rescue analgesia was significantly lower in the DEX3 group (33%) compared with the CTRL (80%), DEX1 (80%) and DEX2 (86%) groups, which were similar. Recovery quality was similar across the groups, with fewer signs of agitation and dysphoria in DEX2 and DEX3, though DEX3 showed a slightly prolonged recovery. Conclusions and relevance: This study supports the use of DEX CRI in cats as a valuable and safe option for balanced anaesthesia. Among the doses tested, 3 µg/kg/h provided the most clinically evident intraoperative analgesic and isoflurane-sparing effects with an improved quality of recovery. High blood pressure was observed, which may be considered critical in the clinical setting. Further research is needed to explore rate adjustments for more extensive procedures.