Acute paraplegia in a thoroughbred racehorse after general anaesthesia.

This research paper involves a study regarding a Thoroughbred racehorse that developed acute paraplegia after undergoing general anesthesia for a castration procedure. The paper explores the consequential complications that arose from the procedure, namely pelvic limb paralysis due to spinal cord hemorrhages, and discusses potential theories that could explain the pathogenesis of this uncommon syndrome.

Case Background

• The research revolves around a 2-year old Thoroughbred colt that was presented for castration at Belmont Horse Hospital. The horse was otherwise healthy, aside from being slightly overweight.
• General anesthesia was induced using an intravenous injection of 600 mg of xylazine and 1,200 mg of ketamine. The operation of castration was performed routinely.
• About two hours after recovery, there was observed some excessive bleeding from the surgical wound. Examination of the wound was tough as the horse displayed aggressive behavior.

Post-Surgery Complications

• Five hours after recovering from the anesthesia, the horse collapsed and was unable to move its hind legs. On examination, the paralysis of the pelvic limbs, tail and anus was noted.
• Despite providing several treatments, including 150 mg of dexamethasone and 6 litres of intravenous fluids over 10 hours, no change in neurological status was observed after 16 hours of the onset of the clinical symptoms.
• The horse was then euthanized due to potential diagnoses of acute traumatic myelopathy, fibrocartilaginous embolic myelopathy, or an infarction.

Necropsy and Pathological Findings

• Darker areas of tissue were found on the right side of the spinal cord, including the last thoracic, lumbar, and lumbosacral segments. Histological examination of these areas revealed significant venous congestion and edema and extensive perivascular hemorrhages throughout the grey matter.
• The most severe hemorrhages were found in the caudal lumbar segments, and there were occasional individual chromatolytic neurons present in some tissue sections.
• Moreover, the sublumbar muscles showed pronounced venous congestion, edema and hemorrhages throughout the perimysium, mild infiltration with neutrophils in some places, and signs of acute degeneration and swelling of individual muscle fibres. Some small arterioles and venules showed signs of smooth muscle necrosis in their walls.

This study emphasizes that general anesthesia and surgeries, even routine ones like castration can lead to serious, unforeseen complications. As such, practitioners are encouraged to inform their clients about possible risks and complications associated with such procedures.