Sepsis Treatment in Horses, AAEP 2009

Sepsis is a systemic inflammatory response syndrome (SIRS) in which the whole body is in an inflammatory state due to the presence of a known or suspect bacterial infection. The evolution and future of sepsis treatment in the horse was described by Pamela Wilkins, DVM, PhD, Dipl. ACVIM, ACVECC, at the 2009 American Association of Equine Practitioners (AAEP) convention, held Dec. 5-9 in Las Vegas, Nev.

Severe sepsis can lead to organ dysfunction, low blood pressure, or insufficient blood flow to one or more organs, potentially resulting in septic shock, multiple organ dysfunction, and death. Clinical signs of SIRS include elevated heart and respiratory rates, purplish to muddy-colored mucous membranes, a purplish gingival (gum) line above the teeth, delayed capillary refill time and jugular refill, injected sclera (meaning the sclera of the eyes are peppered with broken blood vessels), and fever or hyperthermia (elevated temperature), potentially leading to hypothermia.

Laboratory data are often telling in sepsis cases. Wilkins remarked that horses with diarrhea and a positive bacterial blood culture are less likely to survive than horses with diarrhea and abnormal coagulation profiles (which check for the blood components that contriubte to clotting). In adult horses with gastrointestinal (GI) disease (colic, or abdominal pain), horses with high blood glucose levels are less likely to survive. If excess blood glucose is spilling into the urine as the kidneys "filter" the blood, attempts at correcting dehydration can be more difficult.

She described bacterial sepsis as a frequent initiator of severe sepsis, particularly in young foals. In neonates, this might be due to failure of passive transfer from colostral antibodies, and/or translocation of bacteria through the bowel wall, rather than having umbilical infection as the primary source. In adult horses sepsis is commonly related to GI disturbances that can lead to diseases such as colic, proximal enteritis (inflammation of the upper GI tract), or colitis (inflammation of the colon).

Previously, SIRS was thought to be a result of excess circulating bacterial products, such as endotoxin, rather than solely related to bacterial infection. It now appears that any inflammatory bowel disease or GI obstruction disturbs the intestinal barrier, allowing bacteria to move to intestinal lymphoid tissue, where inflammatory cells can be activated to elicit SIRS. This results in multiple organ failure and more gut damage, and the cycle is then ongoing.

Foal diarrhea historically has been treated with antimicrobial drugs. Wilkins pointed out the tendency to avoid treating adults with diarrhea using antimicrobial drugs. But, she says this strategy in adults is being reconsidered; attacking the secondary disease process (bacterial translocation across the intestine) early on is a sound medical approach, requiring frequent and thorough patient monitoring, aggressive fluid therapy, cardiovascular support, appropriate antimicrobial drugs, and nutritional support, regardless of the animal's age. Anti-endotoxin therapy remains important in cases of GI disturbances and other severe illnesses, such as retained placenta and metritis (uterine inflammation).

Wilkins encourages early goal-directed therapy, since there appears to be a narrow window in which therapeutic intervention can stop progression toward shock and death. The aim is to maintain the cardiovascular system as normal as possible. She also suggests intensive insulin therapy to control hyperglycemia (excess sugar in the blood), particularly in neonates. She noted that veterinarians might see more insulin-resistant critical care patients in the future.

And, contrary to previously considered sepsis therapy, Wilkins proposes that low-dose corticosteroids might provide an important protective mechanism to control acute inflammation; veterinarians have not yet defined exact recommendations. Low-dose corticosteroid treatment (hydrocortisone or fludrocortisone) has decreased the 28-day mortality rate in septic people and might improve the outcome in both foals and adult horses.

About the Author

Nancy S. Loving, DVM

Nancy S. Loving, DVM, owns Loving Equine Clinic in Boulder, Colorado, and has a special interest in managing the care of sport horses. Her book, All Horse Systems Go, is a comprehensive veterinary care and conditioning resource in full color that covers all facets of horse care. She has also authored the books Go the Distance as a resource for endurance horse owners, Conformation and Performance, and First Aid for Horse and Rider in addition to many veterinary articles for both horse owner and professional audiences.

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