Sepsis: Understanding the Systemic Inflammatory Response to Infection

Researchers are seeking to identify accurate markers for the condition so that veterinarians can develop realistic treatment plans and prognoses. Sepsis is a systemic inflammatory response to infection, which can affect the prognosis of horses in emergency situations. Clinical signs of sepsis include: elevated heart rate, elevated respiratory rate, fever or hypothermia, abnormal mucous membranes, cold extremities, alteration in white blood cell counts or neutrophil counts, an increased blood lactate level.

Dr. Marie-France Roy, DVM, PhD, DACVIM-LA, assistant professor, Department of Veterinary Clinical and Diagnostic Sciences, at the University of Calgary’s Faculty of Veterinary Medicine, explained, “Basically, when you have an infection somewhere, ideally, it would remain local and resolve without “systemic” or “whole body” effects. When the infection, or the effect of bacterial toxins, is severe enough though, the [localized] inflammatory response “spills” into the circulation and sets up a “whole body” inflammatory response.”

When horses are admitted to equine clinics in emergency situations, and they present with signs of sepsis, their chances of survival decrease significantly, according to a study by Dr. Roy. In fact, the survival rate for the sepsis cases is half of that (44 per cent) of the non-sepsis cases (88 per cent). Dr. Roy is conducting the study in partnership with Moore Equine Veterinary Centre in Balzac, Alberta. In June 2012, she began collecting information on emergency admissions at the private referral centre and comparing the survival rates of the horses with sepsis to a control group of horses without. At the conclusion of the study (which is slated to wrap-up at the end of 2013), Dr. Roy expects to have data on at least 400 horses.

Scroll to continue with content

The purpose of the study is to find ways of identifying, on admission, the horses that have a poor prognosis. “This is important because knowing the horse has a poor prognosis can help the treatment team being more aggressive with their treatment to save the horse’s life and prevent complications or, if the owner’s budget does not allow for treatment, to make a decision for euthanasia sooner rather than later,” explained Dr. Roy.

Currently, clinicians can only give a prognosis based on their own experiences and on what is known already from published literature. Dr. Roy explained, “One marker that is used a lot in human medicine, but also in equine medicine, is blood lactate. A high level of blood lactate on admission is associated with lesser chance of survival, especially if the level does not quickly come back to normal. Our study confirms this observation. Of course, the clinician will also rely heavily on the physical examination findings, blood work and initial response to treatment.

“In surgical colic cases, for example, decisions are often made quite rapidly and depend on the willingness of the owner to go through surgery with the horse given the prognosis given by the attending clinician as well as the anticipated cost. For medical cases, the owner may often elect to treat for a day or two and see how the horse is responding to therapy. These cases are often difficult for the owners because after a day or two of treatment, the bill is usually already quite high, but the horse is not out of the woods yet, making it even harder for the owner to decide [whether to keep treating or euthanize].This is where our study could help, by giving a better idea to the owner as to the prognosis for the horse, based on progress or deterioration noted on physical examination and various biomarkers that we may develop.”

Dr. Roy said the final part of the study will look at the blood gene expression pattern of horses that present with colitis (inflammation of the colon), a disease often associated with sepsis. She explained, “During inflammation, and especially during systemic inflammation, as seen in sepsis, the white blood cells circulating in the blood may increase or decrease the expression of various genes. By studying the changes in gene expression in the blood of horses during acute colitis and by comparing sepsis and controls as well as survivors and non-survivors, we are hoping to get a better understanding of the horse’s response to colitis and identify responses that are more appropriate than others. This may give us clues into potential treatments that could be tried or for the validation of additional biomarkers.”