Pilot dose-finding and safety study of bivalirudin in infants <6 months of age with thrombosis

Heparin induced thrombocytopenia and re-thrombosis associated with warfarin and fondaparinux in a child

An 11-year-old female developed heparin induced thrombocytopenia (HIT) with thrombosis during therapy for lower extremity deep vein thrombosis and pulmonary embolism. Transition from bivalirudin, a direct thrombin inhibitor (DTI), to warfarin resulted in extensive re-thrombosis, and fondaparinux therapy similarly failed. She was then treated with argatroban, and transitioned successfully to warfarin after 9 weeks. The risk of re-thrombosis was ultimately reduced by allowing time for the thrombogenic potential to abate. The argatroban/warfarin transition was monitored with chromogenic factor X levels. This case highlights several difficult problems in pediatric thrombosis.

The evaluation and management of neonatal coagulation disorders

Neonatal hemostatic abnormalities can present diagnostic and therapeutic challenges to the physician. Developmental deficiencies and/or increases of certain coagulation proteins, coupled with acquired or genetic risk factors, can result in a hemorrhagic or thromboembolic emergency. The timely diagnosis of a congenital hemorrhagic or thrombotic disorder can avoid significant long-term sequelae. However, due to the lack of randomized clinical trials addressing the management of neonatal coagulation disorders, treatment strategies are usually empiric and not evidence-based. In this chapter, we will review the neonatal hemostatic system and will discuss the most common types of hemorrhagic and thrombotic disorders. Congenital and acquired risk factors for hemorrhagic and thromboembolic disorders will be presented, as well as current treatment options. Finally, suggested evaluations for neonates with either hemorrhagic or thromboembolic problems will be reviewed.

Bivalirudin for anticoagulation in children

BACKGROUND

Thromboembolism in children is typically treated with unfractionated heparin (UH) or low molecular weight heparin (LMWH). Both rely on antithrombin (AT) for their action. In addition, heparin-induced thrombocytopenia (HIT) is a potentially serious complication of heparin use in children. Bivalirudin or other direct thrombin inhibitors may be a useful alternative to heparins in treating thrombosis in children.

PROCEDURE

We report a retrospective review to assess the efficacy and safety of bivalirudin in pediatric patients with thrombosis.

RESULTS

Sixteen children received bivalirudin for thrombosis or prevention of thrombosis at the Children's Hospital of Illinois from January 2005 to January 2007. Patients received a bolus dose of 0.25 mg/kg followed by a continuous infusion (0.16 +/- 0.07 mg kg(-1) hr(-1)) titrated to 1.5-2.5 times the baseline activated partial thromboplastin time (aPTT). Positive correlation between the bivalirudin average infusion rate and aPTT was observed in twelve patients. Ultrasonographic evidence of thrombus regression was noted at 72 hr in 10 of 10 patients. One patient experienced hematuria after catheterization of the urethra.

CONCLUSION

Bivalirudin was effective and well-tolerated in these patients. Further studies should be conducted to better define safety and efficacy of bivalirudin in pediatric patients.

Successful use of bivalirudin for superior vena cava recanalization and stent placement in a child with heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a potentially life-threatening, adverse effect of heparin therapy. Patients with this complication require an alternative approach to anticoagulation. Bivalirudin is a direct thrombin inhibitor with an efficacy comparable to that of heparin, a short half-life, and reduced bleeding complications in adults. We present the case of a 2-year-old boy with HIT Type II who underwent recanalization of an occluded superior vena cava and stent placement, utilizing bivalirudin as anticoagulant.

Venous thrombosis in children

The advances in pediatric tertiary care have resulted in a decrease in the mortality of children with serious underlying conditions. Consequently, there has been an increase in previously rare complications of therapy in children, including venous thrombosis. Although there is a paucity of properly designed trials in the field of pediatric thrombosis, many advances have been made over the past 15 years. Venous thrombosis in children has been the subject of many reviews. This review is an update of the available evidence in the management of venous thrombosis in children, excluding thrombosis of the CNS.

New Anticoagulants in Children

Thromboembolic complications are increasing in children and the use of anticoagulation has seen a dramatic increase despite the lack of randomized clinical trials. The most widely used agents in children are heparin, low-molecular-weight heparins (LMWH), and warfarin. These agents, however, have significant limitations that are exaggerated in children. Novel anticoagulants such as direct thrombin inhibitors and the selective factor Xa inhibitor, fondaparinux, have been approved for use in adults and have properties that suggest they may be safer and more efficacious than the standard agents; however, until recently, publications using these agents in children were limited to case reports. Recently, clinical trials for two direct thrombin inhibitors, bivalirudin and argatroban, have been completed and a clinical trial of fondaparinux is under way. This review will compare the standard agents with the novel agents and briefly review the results of the clinical trials.