Systemic haemostatic alterations during no-flow ischaemia and reperfusion of the ascending colon in ponies

Naturally occurring and experimentally induced ascending colon volvulus (ACV) result in transmural compression, increased microvascular permeability and thrombosis and necrosis of the intestinal mucosa analysis of haemostatic variables in horses with naturally occurring ACV have identified changes in plasma antithrombin III (AT III) activity as the most reliable for diagnosing hypercoagulation and predicting survival. In an experimental pony model of no-flow ACV, which results in microvascular injury and thrombosis, systemic haemostasis was evaluated during ischaemia and reperfusion to determine whether selected haemostatic assays consistently yield results suggestive of altered haemostasis (hypercoagulation). Ten normal adult ponies were randomly divided into two equal groups (Group 1, control; Group 2, experimental volvulus). All experiments were performed under general anaesthesia and were terminal. Haemostatic variables (prothrombin time, PT; activated partial thromboplastin time, APTT, platelet count, fibrinogen concentration, and plasma AT III activity) were measured prior to general anaesthesia, immediately before colonic volvulus, at 60 and 120 min of ischaemia, and at 60 and 120 min of reperfusion. Mean plasma AT III activity decreased in both the control and experimental groups after induction of general anaesthesia. Mean plasma AT III activity continued to decrease after reperfusion in Group 2 ponies and differed significantly (p<0.05) from control ponies at 120 min of reperfusion. Prothrombin time, APTT, platelet count and fibrinogen concentration values were not significantly different between groups. The decreased plasma AT III activity following the experimental procedures in this model of no-flow colonic ischaemia and reperfusion was suggestive of systemic hypercoagulation.