Young foals are notoriously difficult to anesthetize because of their extreme sensitivity to most anesthetic drugs. Ideally, foals are anesthetized using only an inhaled anesthetic. One inhalant, isofluorane, has proven itself easy to use with relatively mild adverse effects. A newer inhalant, sevofluorane, has been successful in adult horses which are poor candidates for anesthesia. Recently, researchers from Saskatchewan, Canada, designed a study to compare sevofluorane with isofluorane for its ease of use in foals and adverse effects on the cardiovascular system.

Five foals received sevofluorane at one month of age, and isofluorane at three months of age. A sixth foal received the anesthetics in reverse order, for statistical comparison. Minimal restraint was used while the anesthetic was delivered via nasotracheal tube. Once the foals were anesthetized, an arterial catheter was placed to allow for monitoring of cardiovascular function during the 60-minute study period.

None of the foals had any problems associated with anesthesia. Induction and recovery were smooth. There was a cardiovascular abnormality–a decrease in blood pressure–which was noted consistently at the beginning of the anesthetic period. This problem was equally evident for both sevofluorane and isofluorane and resolved without any medical intervention. There were no other significant differences between the two anesthetics nor any additional adverse effects. The authors concluded that sevofluorane is comparable to isofluorane for general anesthesia of young foals.

Read, M.R.; Read, E.K.; Duke,T.; Wilson, D. Journal of the American Veterinary Medical Association, 221(3): 393-398, 2002