Comparison of two injectable anesthetic regimes in feral cats at a large-volume spay clinic

Abstract

Same-day mass sterilization of feral cats requires rapid onset, short-duration anesthesia. The purpose of this study was to compare our current anesthetic protocol, Telazol–ketamine–xylazine (TKX) with medetomidine–ketamine–buprenorphine (MKB). Feral female cats received either IM TKX (n = 68; 0.25 mL cat−1; tiletamine 12.5 mg, zolazepam 12.5 mg, K 20 mg, and X 5 mg per 0.25 mL) or MKB (n = 17; M 40 µg kg−1, K 15 mg kg−1, and B 10 µg kg−1). Intervals measured included time from injection to recumbency, time to surgery, duration of surgery, and time from reversal of anesthesia (TKX: yohimbine 0.50 mg cat−1 IV; MKB: atipamezole 0.50 mg cat−1 IM) to sternal recumbency. Following instrumentation (Vet/Ox 4403 and Vet/BP Plus 6500), physiological measurements were recorded at 5-minute intervals, and included rectal temperature, heart rate (HR), respiratory rate (RR), SpO2 (lingual or rectal probes), and indirect mean arterial blood pressure (MAP) (oscillometric method). Nonparametric means were compared using Mann–Whitney U-tests. Parametric means were compared using a two-factorial anova with Bonferroni's t-tests. The alpha-priori significance level was p < 0.05. Values were mean ± SD. Body weight (TKX: 2.9 ± 0.5 kg, MKB: 2.7 ± 0.7 kg), time to recumbency (TKX: 4 ± 1 minutes, MKB: 3 ± 1 minutes), time to surgery (TKX: 28 ± 7 minutes, MKB: 28 ± 5 minutes), and duration of surgery (TKX: 11 ± 7 minutes, MKB: 8 ± 5 minutes) did not differ between groups. In contrast, MKB cats required less time from reversal to sternal recumbency (TKX: 68 ± 41 minutes, MKB: 7 ± 2 minutes) and were recumbent for shorter duration (TKX: 114 ± 39 minutes, MKB: 53 ± 6 minutes). Temperature decreased during the study in both groups, but overall temperature was higher in MKB cats (38.0 ± 0.95 °C) than in TKX cats (37.5 ± 0.95 °C). RR, HR, and SpO2 did not change during the study in either group. However, overall HR and RR were higher in TKX cats (RR: 18 ± 8 breaths minute−1, HR: 153 ± 30 beats minute−1) compared to MKB cats (RR: 15 ± 7 breaths minute−1, HR: 128 ± 19 beats minute−1). In contrast, overall SpO2 was lower in the TKX group (90 ± 6%) compared to the MKB group (94 ± 4%). MAP was also lower in the TKX group (112 ± 29 mm Hg) compared to that in the MKB group (122 ± 20 mm Hg). However, MAP increased in the TKX group during surgery compared to pre-surgical values, but did not change in the MKB group. The results of this study suggested that MKB might be more suitable as an anesthetic for the purpose of mass sterilization of feral female cats.