Evolution of blood myeloperoxidase in the perioperative period of horses undergoing emergency celiotomy.

Colic can cause an activation of neutrophils with release in the blood flow of myeloperoxidase (MPO), a specific enzyme with strong oxidative activity. The aim of this study was to describe the evolution of plasma MPO after colic surgery. Materials included 13 adult horses that underwent an emergency celiotomy for acute intestinal obstruction. Venous blood samples were collected into EDTA anticoagulated tubes before surgery, during surgery after correction of the intestinal lesion and during the recovery of anaesthesia. In the postoperative period samples were taken every 4 hours during the first 4 days (from day 0 until day 4), every 12 hours during the days 4 and 5 and every 24 hours until day 10. MPO was assayed with a specific enzyme-linked immunosorbent assay. Statistical analysis was performed by one way Anova with student- Newman-Keuls post test on data obtained for each time point. Significance was set at p < 0.05. The horses were operated for an obstruction strangulated or not of the small or the large intestine. In six cases the postoperative period was uneventful, the 7 remaining developed one or 2 severe complications. Eight horses were discharged and 5 died during the hospitalization.The general aspect of the curve of mean plasmatic MPO can be described as follow: An increase was observed from the admission on until a peak of concentration occurring generally during the time of recovery from the anaesthesia with the highest mean value reaching 740.84 +/- 507.61ng/ml. This was followed by a progressive decrease until the lowest value, usually near to day 2 after the recovery from anaesthesia corresponding to 171.79 +/- 76.21 ng/ml of MPO. Afterwards, the mean concentrations increased slowly until postoperative day 10. In the majority of cases a stable and low MPO value (plateau) was observed during approximately 2 days (from day 1 to day 3 postoperatively).The initial peak of MPO after surgery could be associated to the neutrophil activation consequent to the intestinal disorder and the intense stimulation of the coeliotomy. The following significant reduction in concentration could be attributed to MPO infiltration into the tissues with a critical point at approximately 2 days after surgery. This study may contribute to a better understanding of the role of the MPO and neutrophils in the pathophysiology of horses in the postoperative period after colic surgery.