Risks of General Anesthesia

Q: Are there health risks simply from the anesthesia for a horse undergoing surgery? If so, what are these risks, and how common are complications from them?        via e-mail

A: Equine anesthesia has made dramatic safety advances in the last 20 years, including better sedatives, induction agents, and inhalant anesthetics, and improved monitoring. However, it remains perilous, especially compared to other species. One recent study suggests that the risk of death due to any cause within seven days of elective surgery is approximately 1%. While potential complications other than those directly linked to anesthesia might contribute to mortality, anesthesia is clearly a significant stress for horses. Other reports suggest significantly less risk, but the risk remains.

The reason that horses are harder to anesthetize than other animals is multifaceted. One problem is the reluctance of horses to remain lying down for long periods. Horses spend most of their time standing, and their natural reaction to many unfamiliar situations is to flee. This makes recovery the most crucial part of anesthesia. Ideally, a horse recovering from anesthesia would gradually awaken, roll from his side to his chest, remain lying down on the chest for a few minutes, then stand squarely on all four feet without excitement. However, horses' acceptance of strange surroundings and circumstances varies--thus it's hard to predict a horse's reaction. Another factor is the effort it takes for horses to stand. They toss their heads to generate momentum, which requires considerable energy and coordination. The great force generated in this effort to stand and the potential for residual incoordination associated with anesthesia further increase the risk of accidents during recovery.

Many anesthesiologists are working on reducing the risks of anesthesia in the horse.

About the Author

John Hubbell, DVM

John A.E. Hubbell, DVM, MS, Dipl. ACVA, is Professor of Veterinary Anesthesiology in the Department of Veterinary Clinical Sciences at the College of Veterinary Medicine at The Ohio State University.

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