Effects of anesthetic protocol, procedure, and recovery stall and interval on the quality of recovery in repeatedly anesthetized horses.

Abstract

The objective of this prospective study was to investigate whether repeated consecutive general anesthesia in horses undergoing 2 different anesthetic protocols could lead to improved recovery scores. Six healthy female Standardbred horses (453 ± 57 kg; 6.5 ± 4.2 y old) underwent 4 anesthetic protocols over 12 to 13 wk. Procedures 1 and 4 were arthroscopic surgeries [induction: xylazine, diazepam, and ketamine; and maintenance: Fe'Isoflurane (1.1%), lidocaine (2 mg/kg body weight [BW], 50 to 100 μg/min per kg BW), dexmedetomidine (2.5 μg/h per kg BW)]. Procedures 2 and 3 were preparation for magnetic resonance imaging (MRI) [induction: xylazine, guaifenesin, and ketamine; and maintenance: Fe'Isoflurane (1.3%)], as well as mechanical ventilation during all events. For recovery, horses were placed in 2 different recovery stalls, one for procedures 1 and 4, and a different one for procedures 2 and 3, and received xylazine, 0.15 to 0.25 mg/kg BW, IV. Recovery was scored using a numerical score and descriptive scale. A 1-way analysis of variance (ANOVA) was used to compare recovery scores, cardiopulmonary variables, anesthetic times, and drug dosages between procedures (P < 0.05). Anesthetic protocols for procedures 3 (10.5 ± 2.5) and 4 (10.2 ± 3.1) had better (P = 0.0348) recovery numerical scores than those for procedure 2 (14.3 ± 1.9) and were similar to those for procedure 1 (11.5 ± 2.3), but overall descriptive scores were not significantly different (1 = 1.7 ± 0.5, 2 = 1.8 ± 0.4, 3 = 1.3 ± 0.5, 4 = 1.3 ± 0.5). Balance and coordination (P = 0.0172) and knuckling (P = 0.0193) were associated with worse recovery in procedure 2. Anesthesia time was longer (P < 0.0001) in procedures 2 (157 ± 11 min) and 3 (96 ± 5 min) than in procedures 1 (72 ± 9 min) and 4 (60 ± 5 min). In conclusion, the quality of recovery is influenced by anesthetic protocol and in this study, quality improved in procedures 3 and 4 compared to procedure 2.