Impact of low inspired oxygen fraction on oxygenation in clinical horses under general anesthesia

Abstract

The objective was to compare the use of 0.3 and >0.95 oxygen inspired fraction during general anesthesia in horses. Forty client-owned adult horses were anesthetized in dorsal or in lateral recumbency with isoflurane in oxygen and randomly allocated to receive inspiratory fraction of oxygen >0.95 (group HIGH) or 0.3 (group LOW). Mechanical ventilation was provided using pressure controlled mode. Arterial blood gas analysis was performed before, during and after general anesthesia. The group LOW obtained lower intra-operative PaO2 values but better indices of venous admixture than the group HIGH. The PaO2 further decreased during the recovery, without significant differences between groups. Even though the use of lower oxygen inspired fraction (0.3) tended to improve pulmonary function during general anesthesia, it markedly decreased safety as a result of hypoxemia. During the recovery, no difference was observed between groups for the arterial oxygenation such that lower intra-anesthetic oxygen inspired fraction did not provide any advantages.