Thromboelastometric evaluation of horses submitted to experimental thrombosis and jugular thrombectomy

Avaliação tromboelastométrica de equinos submetidos a trombose e trombectomia jugular experimental

Abstract:

Jugular thrombosis in horses occurs commonly in iatrogenic situations, secondary to endotoxemic clinical condition and disseminated vascular coagulation, potentially leading to death. Thus, hemostatic evaluation becomes necessary and extremely important for monitoring the risks of systemic hypercoagulability and for the efficiency of allopathic and surgical treatment. This paper describes the hemostatic behavior in experimental jugular thrombosis of ten healthy equines, subsequently submitted to two thrombectomy techniques and receiving heparin sodium as anti-rethrombosis therapy. These animals were evaluated for 20 days by thromboelastometry (TEM), platelet count, hematocrit and fibrinogen, at four moments: pre-induction to phlebitis (D0-MPF); three days after thrombophlebitis induction (D3-MFM); 6 days after, - moment of thrombophlebitis - (D9-MT); and 54 (D16) and 126 (D19) hours after thrombectomies (PTM). Thrombectomy was performed via a Vollmar Ring (group 1, n=5) and Fogarty catheter (group 2, n=5). All the animals received heparin (150 UI/kg, SC) every 12 hours, for ten days after the respective thrombectomies. Through the blood samples were evaluated TEM, activated partial thromboplastin time (aPTT) and prothrombin time (PT), dosing of fibrinogen, hematocrit and platelet count at the abovementioned moments. For comparison between groups and moments the t test was applied at 5% significance level. No significant difference was verified between treatment groups at any of the moments. There were reductions in clotting time (CT) and clot formation time (CFT), with increase in maximum lysis (ML) until the moment D9-MT. Evaluation through INTEM^® reagent presented prolongations of CT and CFT with reduction of α angle and ML starting from D16 and D19. Similarly, aPTT presented significant differences between moments pre- (D0, 3 and 9) and post- (D16 and 19) anticoagulant and surgical treatment. The platelet numbers were diminished at moments D16 and D19. In evaluation with EXTEM^® reagent, prolongation of CT and CFT occurred only between the moments D0 vs. D3 and vs. D9. O PT did not present significant differences. The results obtained demonstrate that experimental jugular thrombophlebitis leads to local clinical alterations, with impairment of tissue and of the extrinsic coagulation pathway (EXTEM^® ), but without evidence of systemic hypercoagulability status, since there was no increase of the alpha angle or maximum clot firmness (MCF). Furthermore, TEM was shown useful and more sensitive than conventional coagulation tests (PT, aPTT and fibrinogen) for the monitoring of anticoagulant therapy, as demonstrated in other works.

Index Terms:
Thromboelastometry; jugular thrombophlebitis; horses; Vollmar Ring; Fogarty Catheter.