Use of viscoelastic coagulation testing to monitor low molecular weight heparin administration to healthy horses

Abstract

Although correlations were modest, serial measurement of TEG variables may be used to monitor LMWH therapy in horses; however, further research is required in sick horses.

Assessment of thrombin generation in horses using a calibrated automated thrombogram

“…A few studies have been conducted on LMWH pharmacodynamics in horses. One showed that the parameters from two viscoelastic tests (thromboelastography and Sonoclot) and anti‐factor Xa activity were affected by the administration of dalteparin (50 U/kg subcutaneously q 12 hours or 24 hours for 3 days) 29 . Another study showed that enoxaparin (80 U/kg q24 hours for 2 days), but not unfractionated heparin, consistently increased anti‐factor Xa activity 9 .…”

Evaluation of contact activation of citrated equine whole blood during storage and effects of contact activation on results of recalcification-initiated thromboelastometry

“…24 Maximal activation of the contact system in equine blood stored in siliconized tubes was subjectively slow over the 30-minute evaluation period, with maximal procoagulant activity detected at the 30-minute time point, which is a commonly reported sample holding period. 6,7,12,13,16 In comparison, strongly anionic surfaces such as kaolin or ellagic acid can be expected to maximally activate the contact pathway within 3 to 5 minutes, a time frame generally used for aPTT assays. 25 Considering that factor XIIa is slowly inhibited by factors present in plasma (primarily C1 inhibitor, less so α 2 -antiplasmin, α 2 -macroglobulin, and antithrombin), 23 holding periods > 30 minutes would presumably lead to a gradual decrease in coagulability in the whole blood sample.…”

“…The kinetic nature of the assay systems also allows for observation of clot formation and lysis in real time, and results are consequently reflective of factors contributing to thrombin generation that occurs over time after initial fibrin polymerization. 5 There have been numerous descriptions of the clinical and experimental application of thromboelastometry and thromboelastography in human and veterinary medicine, and recent studies have involved use of these techniques in the evaluation of blood from horses used for research purposes [6][7][8][9] and from client-owned equine patients with various disease conditions. 10-14,a Methodology used for performance of thromboelastography or thromboelastometry has varied widely in regard to sample handling and coagulation initiator use.…”

“…10-14,a Methodology used for performance of thromboelastography or thromboelastometry has varied widely in regard to sample handling and coagulation initiator use. Some reports 15 describe immediate use of samples, but holding of samples for ABBREVIATIONS aPTT Activated partial thromboplastin time SBTI Soy bean trypsin inhibitor 30 minutes is common, 6,7,12,13,16 and holding for 2 to 20 hours prior to initiation of thromboelastography or thromboelastometry has also been described. 11,17 Initiation of coagulation in thromboelastography or thromboelastometry of equine whole blood samples has included use of tissue factor 6,11,12,15,16,18 or contact activators 11,18 and simple recalcification of citrated blood.…”

“…Some reports 15 describe immediate use of samples, but holding of samples for ABBREVIATIONS aPTT Activated partial thromboplastin time SBTI Soy bean trypsin inhibitor 30 minutes is common, 6,7,12,13,16 and holding for 2 to 20 hours prior to initiation of thromboelastography or thromboelastometry has also been described. 11,17 Initiation of coagulation in thromboelastography or thromboelastometry of equine whole blood samples has included use of tissue factor 6,11,12,15,16,18 or contact activators 11,18 and simple recalcification of citrated blood. 9,10,13,14,16 Recalcification in the absence of a trigger for coagulation allows for thrombin formation as a downstream effect of activation of the contact system that occurs during sample collection and processing.…”