Partial intravenous anesthesia (PIVA) seems to be a good alternative to either inhalational or total intravenous anesthesia regarding their adverse cardiopulmonary, respiratory, and other body systems effects. Many protocols have been recently investigated in order to find a safer, more effective one. The aim of the present study was to evaluate whether the addition of dexmedetomidine constant rate infusion (CRI) to sevoflurane anesthesia would have any beneficial influence on sevoflurane requirements, cardiorespiratory function, acid-base status, blood gases, hemocoagulation and recovery in healthy horses. Six horses were submitted to either sevoflurane anesthesia (group S) or PIVA using sevoflurane and dexmedetomidine (group SD). The main cardiovascular and respiratory parameters were recorded every 5 minutes throughout 3 hours. Acid-base and hemocoagulation variables, and blood gases were measured at the beginning and in the end of each anesthesia. Times to recovery and its quality were scored. Analysis of variance (ANOVA) for repeated measurements, t-test for normally distributed data or Mann-Whitney test for not normally distributed variables, one-way ANOVA, post-hoc Fisher test, and Wilcoxon signed rank test were used for statistical analysis. In conclusion, PIVA using dexmedetomidine CRI decreased slightly sevoflurane requirements in healthy horses. Sevoflurane anesthesia with or without dexmedetomidine CRI maintained stable cardiovascular status. Respiratory depression, increased blood lactate levels and unchanged coagulation parameters (except for APTT) were observed in the two anesthesia protocols. The recovery times were short and comparable in both groups but recovery quality was better in the SD group.

Key words: CRI, Dexmedetomidine, Horses, PIVA, Sevoflurane