The objective of this study was to compare three analgesic protocols for feline castration. Prospective, randomized clinical study. Forty-nine client-owned cats. Cats were injected with intramuscular (IM) dexmedetomidine (15 μg kg-1) and alfaxalone (3 mg kg-1) and assigned randomly to one of three treatment groups. Group ITL (n = 15) were administered intratesticular 2% lidocaine (0.05 mL each testicle), group SCL (n = 15) a sacrococcygeal epidural injection of 2% lidocaine (0.1 mL kg-1) and group IVM (n = 19) intravenous (IV) methadone (0.3 mg kg-1), before surgery. Cardiorespiratory variables were recorded. In case of autonomic nociceptive response, IV fentanyl (2 μg kg-1) was administered. During recovery, time from IM atipamezole (75 μg kg-1, administered at the end of surgery) to sternal recumbency and to active interaction was recorded. Quality of recovery was assessed using a simple descriptive scale. Postoperative analgesia was evaluated using a visual analogue scale and the UNESP-Botucatu multidimensional composite pain scale (MCPS) at return of active interaction and then 1, 2 and 3 hours later. The three analgesic protocols were comparable in terms of intraoperative fentanyl and propofol requirement. Cardiorespiratory variables stayed within normal ranges in the majority of the cases, although group IVM had the lowest intraoperative respiratory rate (p = 0.0009). No differences were detected between groups in UNESP-Botucatu MCPS scores (p = 0.21). However, group ITL showed higher visual analogue scale score than group IVM (p = 0.001). Four cats enrolled in group ITL, as well as three of group SCL and one of group IVM, required rescue analgesics before the completion of pain assessment. Intratesticular and sacrococcygeal epidural lidocaine injections could be regarded as good alternatives to systemic opioids in cats undergoing castration, although the benefits of these techniques seem to be of shorter duration than IV methadone.

To compare the duration, quality of anaesthesia and analgesia, and quality of recovery of dexmedetomidine and methadone combined with either ketamine or alfaxalone. Randomized, prospective clinical trial. A group of 44 healthy client-owned cats presenting for ovariectomy. Cats were randomly assigned to one of the two treatment groups: DAM (n=22), which was administered intramuscularly (IM) dexmedetomidine (15 μg kg-1), methadone (0.3 mg kg-1) and alfaxalone (3 mg kg-1), and DKM (n=22), which was administered IM dexmedetomidine (15 μg kg-1), methadone (0.3 mg kg-1) and ketamine (3 mg kg-1). During anaesthesia, heart rate, respiratory rate and systolic arterial pressure were measured every 5 minutes. Cats that moved or had poor muscle relaxation were administered an additional 1 mg kg-1 of either alfaxalone (DAM) or ketamine (DKM) intravenously (IV). In cases of increased autonomic responses to surgical stimulation, fentanyl (2 μg kg-1) was administered IV. At the end of the surgery, atipamezole (75 μg kg-1) was administered IM, and the times to both sternal recumbency and active interaction were recorded. Quality of recovery was evaluated with a simple descriptive scale. The UNESP-Botucatu multidimensional composite pain scale and a visual analogue scale were used to evaluate postoperative analgesia at the return of active interaction and 1, 2 and 3 hours later. The additional anaesthesia and rescue fentanyl requirements were similar between groups. The quality of recovery was better in the DAM group than in the DKM group [simple descriptive scale scores: 0 (0-1) and 1 (0-3), respectively; p=0.002]. Postoperative pain scores decreased progressively over time in both groups, with no significant differences (p=0.08) between them. Both protocols provided comparable quality of anaesthesia and analgesia and were suitable for cats undergoing ovariectomy. In combination with methadone and dexmedetomidine, alfaxalone and ketamine showed comfortable and reliable recoveries.