Horse Colic Prognosis Using Blood Lactate Levels (AAEP 2010)

Monitoring lactate levels in samples of peritoneal fluid, the fluid surrounding and lubricating the abdominal organs, can help a veterinarian predict which colicky horses require surgery. John G. Peloso, DVM, MS, Dipl. ACVS, presented a study on peritoneal lactate levels and colic prognoses at the 2010 American Association of Equine Practitioners convention, held Dec. 4-8 in Baltimore, Md.

Tissues use glucose as their energy source. When the supply of oxygen to tissues is plentiful, glucose is converted to water and carbon dioxide (aerobic metabolism) . When the supply of oxygen is lacking (anaerobic metabolism) glucose is converted to lactate. When lactate levels are high, it is inferred that oxygen levels are low. Recognizing that tissues need oxygen to survive, a high lactate level tells veterinarians that tissues are not receiving oxygen. In other words, if they hear "high" lactate, they should think "low" (no) oxygen.

"In human medicine, blood lactate levels are routinely measured in patients to determine if there is an adequate supply of oxygen to the tissues. While blood lactate levels are also used routinely in horses to determine if tissues are being adequately oxygenated, peritoneal fluid lactate levels give us an earlier indication of poor oxygen delivery to the intestines," explained Peloso, an owner/partner at the Equine Medical Center of Ocala in Florida.

Veterinarians need an accurate and rapid method of diagnosing intestinal lesions that cut off the blood supply to the intestine in colicking horses. Thus, to determine if serial measurements of lactate levels in abdominal fluid would help fill this void, Peloso and Noah D. Cohen, VMD, MPH, PhD, Dipl. ACVIM, from Texas A&M's College of Veterinary Medicine, reviewed the medical records of 95 Ocala horses that presented with colic signs and had a second peritoneal fluid lactate sample measurement 1 to 6 hours after the first measurement.

Peloso and Cohen found that an increase in peritoneal fluid lactate levels in abdominal fluid samples (sample 2 - sample 1 > 0.5) was significantly associated with the presence of a strangulating lesion. "In other words, if the lactate levels increase from one sample to the next, then the underlying cause of the horse's colic is likely due to the blood flow to part of the intestinal tract being cut off and surgery is likely indicated," summarized Peloso.

In these 95 Ocala horses, using an increasing lactate level over time as a guide, veterinarians were able to correctly identify horses with strangulated bowel 88% of time (showing sensitivity of the method) and correctly identified horses that did not have strangulated bowel 79% of the time (specificity). Thus, lactate levels may be important because they can help a veterinarian detect surgical lesions early, which will ultimately improve a horse's chance of survival.

Now practitioners, don't run and grab your lactate analyzer too quickly. Peloso and Cohen identified that these results are based on a population of Ocala horses.

"A repeat of this study at different referral hospitals around the U.S. and Canada would substantiate these results," Peloso concluded.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.