Cardiopulmonary effects of desflurane in horses

Abstract

ObjectiveTo determine the cardiopulmonary effects of desflurane (DES) in horses. AnimalsSix healthy adult horses, three males and three females, aged 9 ± 4 (mean ± SD) years and weighing 370 ± 36 kg. Materials and methodsAnaesthesia was induced with an O2 (10 L minute−1) and DES mixture (vaporizer setting 18%). After oro-tracheal intubation, horses were positioned in right lateral recumbency. Anaesthesia was maintained with DES in O2 (20 mL kg−1 minute−1) delivered through a large animal circle breathing system. The minimum alveolar concentration of DES (MACDES) that prevented purposeful movement in response to 60 seconds of electrical stimulation of the oral mucous membranes was determined for each horse. The delivered concentration of DES was then increased to achieve end-tidal concentrations corresponding to 1.5 × MACDES, 1.75 × MACDES, and 2.0 × MACDES. Heart rate (HR), mean arterial blood pressure (MAP), respiratory rate (fr), tidal volume (Vt), minute volume (Vm) and core temperature were determined, and blood samples for arterial blood gas analysis taken at each DES concentration. All data were analysed by two-way anova for repeated measures and Fisher's test for multiple comparisons. A probability level of p < 0.05 was applied. ResultsDesflurane concentrations of 2.0 × MACDES increased HR whereas lower concentrations did not. Mean arterial pressure was not affected by 1.0 × MACDES 1.5 × MACDES or 1.75 × MACDES, whereas it decreased at 2.0 × MACDES. All concentrations of DES examined significantly depressed fr, Vt and Vm. Conclusions and clinical relevanceDesflurane concentrations between 1.0 and 1.75 × MACDES reduces fr and Vm but does not affect HR or MAP in horses.