Monitoring bivalirudin therapy in children on extracorporeal circulatory support devices: Thromboelastometry versus routine coagulation testing

Introduction: Bivalirudin is an alternative to heparin anticoagulation in infants and children in the setting of extracorporeal life support (ECLS). While activated partial thromboplastin time (aPTT) is widely accepted as the standard test to monitor bivalirudin therapy, the usefulness of thromboelastometry (ROTEM) to monitor bivalirudin infusion in the setting of ECLS is unknown. Objective: We aimed to assess the utility of ROTEM in monitoring hemostasis and bivalirudin effect in children on either extracorporeal membrane oxygenation (ECMO) or ventricular assist devices (VAD) compared to standard plasma based coagulation assays. Methods: A retrospective study of children undergoing bivalirudin infusion for ECMO/VAD support from a tertiary care pediatric hospital (January 2017-June 2018) was performed. ROTEM assays for extrinsic (EXTEM) and intrinsic (INTEM) coagulation pathways, INTEM with heparinase (HEPTEM), fibrin formation (FIBTEM) with measurement of the clotting time (CT) and maximum clot firmness (MCF) were compared to routine hemostasis testing including: aPTT, aPTT Hepzyme (HPTT), prothrombin time (PT), fibrinogen and platelet count. Results: One hundred and six blood samples from 18 children were tested. There was a strong positive correlation between HPTT and HEPTEM CT, and moderate correlation between aPTT and INTEM CT. The bivalirudin dose did not correlate with any test, but displayed strong age-dependence, with infants requiring higher doses of bivalirudin to maintain therapeutic targets. Excellent correlation was found between FIBTEM MCF values and fibrinogen, but FIBTEM overestimated fibrinogen level when platelet count was > 300 x 10(9)/L. Heparin-like effect was identified in 39% of specimens, and an improved correlation between aPTT and INTEM CT was observed in specimens without heparinoids. Conclusions: In the setting of bivalirudin therapy, prolongation of CT on INTEM and HEPTEM showed moderate to strong correlation with aPTT and HPTT, and therefore, may provide a good alternative to these assays. In addition, HPTT and HEPTEM CT might be preferable for monitoring bivalirudin in the setting of ECLS due to frequent detection of heparin-like effect.