Isoflurane, sevoflurane and desflurane are suitable for maintenance of anaesthesia in horses. This cross-over study compares recovery from each. Six mares, median weight 414 (range 323–490) kg, were anaesthetised three times. Following premedication (acepromazine 0.04 mg kg)1), induction used detomidine 20 mcg kg)1 followed by ketamine 2.2 mg kg)1 and diazepam 0.02 mg kg)1 then, thiopental 1 mg kg)1. Anaesthesia was maintained in lateral recumbency with one of the three agents. Breathing was spontaneous. Administration of anaesthetic was terminated after two hours, the endotracheal tube removed immediately, 0.02 mg kg)1 xylazine given intravenously, and the horse left quietly. Recovery was timed. Quality of recovery was scored from films by a ‘blinded’ observer using a scale of 1 (perfect) to 5 (Young and Taylor 1993). Qualitative data were evaluated with Chi squared and Fishers exact tests. Quantitative data were analysed with two way ANOVA and the Bonferroni correction. End-tidal agent concentrations at 120 minutes were: isoflurane 1.6–1.9%; sevoflurane 2.4–2.8%; desflurane 7.7–8.0%. Time in minutes to first movement, sternal recumbency and standing (mean ± SD) respectively were: isoflurane 17.5 ± 3.3, 25.8 ± 7.6, 37.7 ± 10.6; sevoflurane 24.8 ± 4.6, 28.5 ± 4.4, 42.7 ± 15.5; desflurane 18.0 ± 6.8, 22.8 ± 4.4, 33.0 ± 10.3. Recovery times were slowest following evoflurane, but this was significant (p = 0.03) only for first movement. Quality of recovery did not differ signficantly between agents (p = 0.9). Median(range) scores were: isoflurane 3(1–4); sevoflurane 3(1–4); desflurane 2(1–5). Independent of agent, the first anaesthetic recovery for each horse was worst; median score (range) first, 4(1–5) subsequent 2(1–4) (p = 0.04) and the number of attempts to rise was higher than at later attempts (median (range) first 5(1–5); subsequent 2(1–3) (p = 0.01). The study concluded that the ‘learning’ factor from multiple anaesthetics may mask any drug differences in recovery characteristics. The Horserace Betting Levy Board funded this study.
An experimental comparison of the characteristics of recovery from anaesthesia maintained with isoflurane, sevoflurane or desflurane in horses.
DE BENEDICTIS, GIULIA MARIA;BELLINI, LUCA;
2010
Abstract
Isoflurane, sevoflurane and desflurane are suitable for maintenance of anaesthesia in horses. This cross-over study compares recovery from each. Six mares, median weight 414 (range 323–490) kg, were anaesthetised three times. Following premedication (acepromazine 0.04 mg kg)1), induction used detomidine 20 mcg kg)1 followed by ketamine 2.2 mg kg)1 and diazepam 0.02 mg kg)1 then, thiopental 1 mg kg)1. Anaesthesia was maintained in lateral recumbency with one of the three agents. Breathing was spontaneous. Administration of anaesthetic was terminated after two hours, the endotracheal tube removed immediately, 0.02 mg kg)1 xylazine given intravenously, and the horse left quietly. Recovery was timed. Quality of recovery was scored from films by a ‘blinded’ observer using a scale of 1 (perfect) to 5 (Young and Taylor 1993). Qualitative data were evaluated with Chi squared and Fishers exact tests. Quantitative data were analysed with two way ANOVA and the Bonferroni correction. End-tidal agent concentrations at 120 minutes were: isoflurane 1.6–1.9%; sevoflurane 2.4–2.8%; desflurane 7.7–8.0%. Time in minutes to first movement, sternal recumbency and standing (mean ± SD) respectively were: isoflurane 17.5 ± 3.3, 25.8 ± 7.6, 37.7 ± 10.6; sevoflurane 24.8 ± 4.6, 28.5 ± 4.4, 42.7 ± 15.5; desflurane 18.0 ± 6.8, 22.8 ± 4.4, 33.0 ± 10.3. Recovery times were slowest following evoflurane, but this was significant (p = 0.03) only for first movement. Quality of recovery did not differ signficantly between agents (p = 0.9). Median(range) scores were: isoflurane 3(1–4); sevoflurane 3(1–4); desflurane 2(1–5). Independent of agent, the first anaesthetic recovery for each horse was worst; median score (range) first, 4(1–5) subsequent 2(1–4) (p = 0.04) and the number of attempts to rise was higher than at later attempts (median (range) first 5(1–5); subsequent 2(1–3) (p = 0.01). The study concluded that the ‘learning’ factor from multiple anaesthetics may mask any drug differences in recovery characteristics. The Horserace Betting Levy Board funded this study.
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