The study compares the cardiopulmonary effects of maintenance of anaesthesia with isoflurane, sevoflurane or desflurane following anaesthetic induction with intravenous agents in a cross-over study. Six mares, median weight 441 (range 323–490) kg, were each anaesthetised three times. Following premedication (intramuscular acepromazine 0.04 mg kg)1), anaesthetic induction used detomidine 20 mcg kg)1 followed by ketamine 2.2 mg kg)1 and diazepam 0.02 mg kg)1 then, after recumbency, thiopental 1 mg kg)1. Anaesthesia was maintained in lateral recumbency for two hours with one of the inhalation agents, breathing spontaneously. If mean arterial pressure fell below 60 mmHg, dobutamine was infused. Heart and respiratory rates, arterial and pulmonary blood pressures and inspired and end-tidal oxygen, carbon dioxide and anaesthetic agent were measured continuously. Cardiac output (by thermal dilution) was measured, and arterial and venous blood sampled for blood-gas analysis at 15 minute intervals. Data were analysed to compare agent differences over the two hour time period with repeated measures ANOVA followed by the Bonferroni correction. Within 30 minutes of induction of anaesthesia, end-tidal isoflurane was 1.6–1.8%, sevoflurane 2.5– 2.7% and desflurane 7.7–8.0%. Dobutamine infusion was required in 3 horses receiving isoflurane and 3 receiving desflurane. Systolic, diastolic and mean pulmonary arterial pressures (PAP) were lowest with isoflurane (p = 0.04 for mean PAP). End-tidal carbon dioxide tended to be lower with desflurane (p = 0.06). No agent differences for other parameters over the full time period were significant. Three horses breathed rapidly with desflurane, and one of these horses also with sevoflurane; all these became hypoxic. The study concluded that, after intravenous induction, the cardiovascular effects of the three inhalation agents are similar, but there is concern over the tachypnoea and hypoxia seen in some cases, most commonly with desflurane anaesthesia. The Horserace Betting Levy Board funded this study.
A comparison of cardiopulmonary parameters during maintenance of anaesthesia with isoflurane, sevoflurane or desflurane in horses.
DE BENEDICTIS, GIULIA MARIA;BELLINI, LUCA;
2010
Abstract
The study compares the cardiopulmonary effects of maintenance of anaesthesia with isoflurane, sevoflurane or desflurane following anaesthetic induction with intravenous agents in a cross-over study. Six mares, median weight 441 (range 323–490) kg, were each anaesthetised three times. Following premedication (intramuscular acepromazine 0.04 mg kg)1), anaesthetic induction used detomidine 20 mcg kg)1 followed by ketamine 2.2 mg kg)1 and diazepam 0.02 mg kg)1 then, after recumbency, thiopental 1 mg kg)1. Anaesthesia was maintained in lateral recumbency for two hours with one of the inhalation agents, breathing spontaneously. If mean arterial pressure fell below 60 mmHg, dobutamine was infused. Heart and respiratory rates, arterial and pulmonary blood pressures and inspired and end-tidal oxygen, carbon dioxide and anaesthetic agent were measured continuously. Cardiac output (by thermal dilution) was measured, and arterial and venous blood sampled for blood-gas analysis at 15 minute intervals. Data were analysed to compare agent differences over the two hour time period with repeated measures ANOVA followed by the Bonferroni correction. Within 30 minutes of induction of anaesthesia, end-tidal isoflurane was 1.6–1.8%, sevoflurane 2.5– 2.7% and desflurane 7.7–8.0%. Dobutamine infusion was required in 3 horses receiving isoflurane and 3 receiving desflurane. Systolic, diastolic and mean pulmonary arterial pressures (PAP) were lowest with isoflurane (p = 0.04 for mean PAP). End-tidal carbon dioxide tended to be lower with desflurane (p = 0.06). No agent differences for other parameters over the full time period were significant. Three horses breathed rapidly with desflurane, and one of these horses also with sevoflurane; all these became hypoxic. The study concluded that, after intravenous induction, the cardiovascular effects of the three inhalation agents are similar, but there is concern over the tachypnoea and hypoxia seen in some cases, most commonly with desflurane anaesthesia. The Horserace Betting Levy Board funded this study.
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