Assessing analgesia equivalence and appetite following alfaxalone- or ketamine-based injectable anesthesia for feline castration as an example of enhanced recovery after surgery

Abstract

Objectives The primary study objective was to assess two injectable anesthetic protocols, given to facilitate castration surgery in cats, for equivalence in terms of postoperative analgesia. A secondary objective was to evaluate postoperative eating behavior. Methods Male cats presented to a local clinic were randomly assigned to receive either intramuscular ketamine (5 mg/kg, n = 26; KetHD) or alfaxalone (2 mg/kg, n = 24; AlfHD) in combination with dexmedetomidine (25 μg/kg) and hydromorphone (0.05 mg/kg). All cats received meloxicam (0.3 mg/kg SC) and intratesticular lidocaine (2 mg/kg). Species-specific pain and sedation scales were applied at baseline, 1, 2 and 4 h postoperatively. Time taken to achieve sternal recumbency and begin eating were also recorded postoperatively. Results Pain scale scores were low and showed equivalence between the treatment groups at all time points (1 h, P = 0.38, 95% confidence interval [CI] of the difference between group scores 0-0; 2 h, P = 0.71, 95% CI 0-0; 4 h, P = 0.97, 95% CI 0-0). Four cats crossed the threshold for rescue analgesia (KetHD, n = 1; AlfHD, n = 3). At 1 h, more cats in the KetHD (65%) group than in the AlfHD (42%) group were sedated, but statistical significance was not detected ( P = 0.15, 95% CI -1 to 0). Most AlfHD cats (88%) began eating by 1 h vs 65% of KetHD cats ( P = 0.039). Time to recover sternal recumbency did not differ between groups ( P = 0.86, 95% CI -14.1 to 11.8). Conclusions and relevance These results show that AlfHD and KetHD provide equivalent analgesia as part of a multimodal injectable anesthetic protocol. Alfaxalone is associated with an earlier return to eating.

Figure 1

A Consolidated Standards of Reporting Trials Statement (CONSORT) flow diagram showing the flow of animals through the study. Treatment groups are identified as ketamine or alfaxalone, combined with dexmedetomidine and hydromorphone

Figure 2

Plot of pain scale scores for the UNESP-Botucatu multidimensional pain expression subscale (U-B MCPSpainex). The analgesia intervention threshold (>2/12) is indicated by the broken horizontal line. Symbols represent individual data points: ketamine–dexmedetomidine–hydromorphone (gray triangles, n = 26 cats) and alfaxalone–dexmedetomidine–hydromorphone (black circles, n = 24 cats). Data are median and interquartile range. BL = baseline

Figure 3

Percentage of cats eating at 1–4 h postoperatively. Stippled bars represent the ketamine-dexmedetomidine-hydromorphone group (n = 26 cats) and black bars represent the alfaxalone-dexmedetomidine-hydromorphone group (n = 24 cats)