John Hubbell, DVM, MS, Dipl. ACVA, professor of anesthesiology in the College of Veterinary Medicine at The Ohio State University, presented a historical perspective on equine anesthesia at the 50th annual American Association of Equine Practitioners (AAEP) Convention in Denver, Colo., Dec. 4-8, 2004. He highlighted the rapid, recent advances in anesthetic drugs and monitoring procedures. In the 1800s, veterinary care of horses, including anesthesia, was left to untrained individuals, with the advent of modern anesthesia coming in the 1940s. It wasn't until the 1960s and 1970s that inhalant anesthesia began to be commonly used in horses, and xylazine and ketamine made their introduction to the veterinary tool box.

Since then, more advanced drugs including new inhalant anesthetics have been developed to reduce stress on horses being put under anesthesia, and during recovery. Since the 1980s, research into the importance of monitoring blood pressure, respiration, and blood gases during anesthesia has also been documented.

While these improvements in induction and maintenance of general anesthesia are laudable, every anesthetic event has inherent risks. G. Mark Johnston, MRCVS, PhD, of Vetstream, Inc., from England was part of a team effort in a study of non-colic surgery cases in 148 veterinary clinics in 19 countries to determine mortality associated with equine anesthesia. This study reported a 1% mortality rate (1 in 100 cases) of death within seven days of non-colic surgery. Over 40,000 surgical cases were studied, and it was reported that foals were generally at lowered risk, while equine fracture cases were at increased risk of death.

William Muir, DVM, PhD, Dipl. ACVA, ACVECC, also a professor of anesthesiology at The Ohio State University College of Veterinary Medicine, reviewed many of the drugs currently used for anesthesia, emphasizing that the "ideal" drug would decrease stress, provide pain relief and muscle relaxation, and produce unconsciousness. While this ideal drug does not exist, the veterinary practitioner has combinations of drugs that can be used to produce close to "ideal" anesthesia. The drug combination needs to be individualized to the horse, its physical condition, surgical procedure, and other factors.

About the Author

Roberta Dwyer, DVM, MS, Dipl. ACVPM

Roberta Dwyer, DVM, MS, Dipl. ACVPM, is a professor within the University of Kentucky's Maxwell H. Gluck Equine Research Center and editor of Equine Disease Quarterly.

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