Fibrinolytic Responses of the Equine Peritoneum to Abdominal Surgery, Surgical Trauma, and Intraperitoneal Sodium Hyaluronate

Postoperative abdominal adhesions are known to present clinical challenges to the surgeon. Adhesion formation is a balance modulated by the fibrinolytic system. The key components involved are the tissue plasminogen activators (tPAs) and plasminogen activator inhibitors (PAI-1 and PAI-2). Sodium hyaluronate (HA) has been shown to reduce the incidence and severity of adhesions in horses. The objectives of this study were to measure tPA and PAI-1 activity in equine peritoneum and evaluate the effect of 0.4% HA solution on local tPA and PAI-1 activity. An exploratory laparotomy was performed and local serosal trauma was induced by using an established abrasion model. Our study involved two groups: in the first group (n = 6) 0.4% HA was used in all intestinal manipulations, whereas in the second group (n = 6) sterile saline was used. Parietal peritoneum, jejunal seromuscular biopsies at abraded sites (AJ) and nonabraded sites, and peritoneal fluid samples were taken at time 0- and at 30-minute intervals up to 120 minutes. Peritoneum tPA activity was significantly decreased at 60 and 90 minutes. Interestingly, AJ contained significantly higher tPA activity than nonabraded sites at 30-, 60-, 90-, and 120-minute intervals in control horses. The increase in tPA activity with AJ in treated (HA) horses was significantly attenuated as compared with the control (saline). Detectable levels of PAI-1 activity could not be identified in our samples. The results of our study indicate that exploratory celiotomy in horses is associated with a significant decrease in peritoneal tPA activity, and HA significantly decreases the fibrinolytic response of the jejunum to surgical trauma. Further characterization of these responses will hopefully lead to new pharmacologic strategies for adhesion prevention.