Colic Surgery Risk Factors

There are always risk factors when horses undergo surgery and anesthesia. Researchers have found that these risks are greater in horses than any other animal species. Studies have also shown that colic surgery mortality rates are higher than that of any other surgical procedure--most likely because the horse's system is already compromised when the animal is anesthetized.

To better understand this, researchers at the University of Liverpool in Neston, Wirral, United Kingdom, identified risk factors associated with mortality rates in emergency colic surgeries.

Chris Proudman, MA, VetMB, PhD, CertEO, FRCVS, a professor of equine studies at the university, and his fellow researchers recorded data for 637 horses that underwent colic surgery. They identified significant risk factors that affected the horses' survival rates such as PCV (packed cell volume), and heart rate--which are measurements of endotoxemia (endotoxins from the intestines are released into the bloodstream)--age, breed, and level of pain. Of the 637 study horses, 88 (approximately 14%) died or were euthanatized during surgery.

Heart rate, PCV, age, and breed type were directly related to the study horses' mortality rate. "Age was significantly associated with the post-op death; there was a small increase in risk for each year of age," Proudman explained.

Thoroughbreds, Thoroughbred crosses, and draft-type horses displayed a higher post-operative mortality rate than other breeds. "This may be related to size of the animal. Shires (draft horses) are at five times the risk of death (than average size horses). The bigger the animal, the more difficult anaesthesia can be, especially keeping the lungs oxygenated."

Another important discovery was that the level of pain was inversely related to the study horses' survival, meaning the greater the pain level, the more likely the horse would survive.

Proudman said, "I suspect that increased survival with severe pain is because these horses were operated on sooner than horses with mild pain. Also, severe endotoxemia generally results in depression rather than colic pain."

The study results showed that the degree of endotoxemia at the time of surgery was a major factor for the horse's survival.

"This is an important finding for veterinary anesthetists and confirms previous work stressing the importance of early referral prior to the development of endotoxemia," he explained.

Researchers in the study published in the January issue of The Veterinary Journal were Proudman; A.H.A. Dugdale, MA, VetMB, DVA, Dipl. ECVA, MRCVS; J.M. Senior, BVSc, Cert VA, Dipl. ECVA, MRCVS; G.B. Edwards, BVSc, DVetMed, FRCVS; J.E. Smith; M.L. Leuwer, DM; and N.P. French, BVSc, PhD, MRCVS.

About the Author

Chad Mendell

Chad Mendell is the former Managing Editor for .

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