Hemorrhagic myelomalacia following general anesthesia in a horse.

The study describes a case where a horse developed hemorrhagic myelomalacia, a severe spinal cord condition, after general anesthesia for surgery. The condition led to paralysis and the horse was euthanized due to the lack of improvement.

Clinical Procedure and Observations

• The research involved an 18-month-old male horse undergoing cryptorchidectomy, a surgery performed to remove undescended testicles.
• Anesthesia was induced and maintained using xylazine for sedation, guaifenesin with thiamylal for induction, and halothane for maintenance. This allowed the horse to be placed in dorsal recumbency, a position lying on its back, for the surgery.
• During the anesthesia period, complications including second-degree atrioventricular blocks (a type of heart rhythm disorder), hypoventilation (abnormally slow and shallow breathing), and a minute-long surge in mean arterial pressure were noted.

Post-Anesthesia Complications

• The horse showed signs of flaccid paralysis in its hind limbs on recovery from anesthesia — indicating a serious neurological issue. Its movement was limited to shifting to a dog sitting position; full standing was impossible.
• Despite veterinary intervention, there was no improvement in the horse’s condition in the 22-hour postoperative period which led to the decision to euthanize the animal humanely.

Post-Mortem Findings

• Upon examination of the horse’s spinal cord after euthanasia, the researchers discovered hemorrhagic poliomyelomalacic lesions.
• These lesions represent severe damage to the spinal cord, specifically a type of necrosis or cell death called myelomalacia, with added hemorrhaging.
• This condition, hemorrhagic myelomalacia, was considered the main cause of the horse’s paralysis and subsequent adverse health state, arguably brought on by the stresses and complications during anesthesia.