Effects of desflurane and mode of ventilation on cardiovascular and respiratory functions and clinicopathologic variables in horses

Abstract

Objective - To quantitate the effects of desflurane and mode of ventilation on cardiovascular and respiratory functions and identify changes in selected clinicopathologic variables and serum fluoride values associated with desflurane anesthesia in horses. Animals - 6 healthy adult horses. Procedure - Horses were anesthetized on 2 occasions: first, to determine the minimum alveolar concentration (MAC) of desflurane in O2 and second, to characterize cardiopulmonary and clinicopathologic responses to 1X, 1.5X, and 1.75X desflurane MAC during both controlled and spontaneous ventilation. Results - Mean ± SEM MAC of desflurane in horses was 8.06 ± 0.41%; inhalation of desflurane did not appear to cause airway irritation. During spontaneous ventilation, mean PaCO2 was 69 mm Hg. Arterial blood pressure, stroke volume, and cardiac output decreased as the dose of desflurane increased. Conditions of intermittent positive pressure ventilation and eucapnia resulted in further cardiovascular depression. Horses recovered quickly from anesthesia with little transient or no clinicopathologic evidence of adverse effects. Serum fluoride concentration before and after administration of desflurane was below the limit of detection of 0.05 ppm (2.63μM/L). Conclusions and clinical relevance - Results indicate that desflurane, like other inhalation anesthetics, causes profound hypoventilation in horses. The magnitude of cardiovascular depression is related to dose and mode of ventilation; cardiovascular depression is less severe at doses of 1X to 1.5X MAC, compared with known effects of other inhalation anesthetics under similar conditions. Desflurane is not metabolized to an important degree and does not appear to prominently influence renal function or hepatic cellular integrity or function.