Anesthesia of the Late-Term Mare

Equine anesthesia inherently carries a higher risk than that for other domesticated animals, with reported mortality rates ranging from 0.08% to 1.8%. This chapter discusses current knowledge regarding the physiological changes during pregnancy, the anesthetic approach specific to the pregnant mare, and brief comments on neonatal resuscitation of the foal. The respiratory system undergoes several changes during pregnancy. The gravid uterus increases the intraabdominal pressure and can cause changes in gastrointestinal function. Anesthesia in the horse is associated with complications such as systemic hypotension, reduced cardiac output, hypoventilation, hypoxemia, and impaired gas exchange, myopathy, neuropathy, and complications accompanying anesthetic recovery. Ketamine is a dissociative anesthetic and remains the most common induction agent in equine anesthesia. Inhalational anesthetics have an increased potency in a variety of pregnant animals. Anesthetic monitoring requirements are no different in the pregnant mare compared to a non-gravid horse undergoing an anesthetic episode.