Bivalirudin for anticoagulation in children

Intravenous Direct Thrombin Inhibitors for Acute Venous Thromboembolism or Heparin-Induced Thrombocytopenia with Thrombosis in Children: A Systematic Review of the Literature

Intravenous direct thrombin inhibitors (DTIs) are used for thromboembolic disorders. This systematic review aims to characterize intravenous DTI agents, dosing, monitoring strategies (or use), bleeding, and mortality, in pediatric patients with acute venous thromboembolism (VTE) or heparin-induced thrombocytopenia with thrombosis (HITT). MEDLINE, Embase, and Cochrane's CENTRAL were searched from inception through July 2023. Case series, retrospective studies, and prospective studies providing per-patient or summary data for patients < 18 years of age with VTE or HITT treated with an intravenous DTI were included. Selection and data extraction were conducted independently by two reviewers. Sixteen studies (7 case reports, 1 case series, 5 retrospective studies, 3 prospective studies) with 85 patients were included. Target conditions included acute VTE in 54 (64%) and HITT in 31 (36%) patients. Bivalirudin, argatroban, and lepirudin were used in 52 (61%), 27 (32%), and 6 (7%) patients, respectively. Fifty-two (61%) patients received a bolus dose, and weighted mean infusion rates for bivalirudin, argatroban, and lepirudin were 0.2 mg/kg/hr, 1.2 mcg/kg/min, and 0.15 mg/kg/hr, respectively. The activated partial thromboplastin time was utilized for monitoring in 82 (96%) patients. Complete or partial thrombus resolution was reported in 53 (62%) patients, mortality in 6 (7%) patients, and bleeding complications in 14 (16%) patients. In this systematic review involving 85 pediatric patients treated with an intravenous DTI for acute VTE or HITT, bivalirudin was the most commonly utilized agent, with a rate of resolution over 60% despite a high acuity in the population studied. Prospective collaborative studies are warranted to establish optimal dosing and further characterize VTE and bleeding outcomes.

Venous Thromboembolism in Premature Neonates

While the incidence of venous thromboembolism (VTE) is lower among children than adults, the newborn period is one of two bimodal peaks (along with adolescence) in VTE incidence in the pediatric population. Most VTE cases in neonates occur among critically ill neonates being managed in the neonatal intensive care unit, and most of these children are born premature. For this reason, the presentation, diagnosis, management, and outcomes of VTE among children born premature deserve special emphasis by pediatric hematologists, neonatologists, pharmacists, and other pediatric health care providers, as well as by the scientific community, and are described in this review.

Prospective Exploratory Experience With Bivalirudin Anticoagulation in Pediatric Extracorporeal Membrane Oxygenation

OBJECTIVES

Objective of this study was to determine if bivalirudin resulted in less circuit interventions than unfractionated heparin. A secondary objective was to examine associations between bivalirudin dose and partial thromboplastin time, international normalized ratio, and activated clotting time.

DESIGN

Prospective observational.

SETTING

Medical-surgical and cardiac PICUs.

PATIENTS

Neonatal and pediatric extracorporeal membrane oxygenation patients who received bivalirudin anticoagulation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Twenty extracorporeal membrane oxygenation runs in 18 patients used bivalirudin; 90% were venoarterial. Median (interquartile range) age was 4.5 months (1.6-35 mo). Thirteen patients (72%) had an underlying cardiac diagnosis. Of the 20 runs using bivalirudin, 16 (80%) were initially started on unfractionated heparin and transitioned to bivalirudin due to ongoing circuit thrombosis despite therapeutic anti-Xa levels (n = 13), ongoing circuit thrombosis with unfractionated heparin greater than or equal to 40 U/kg/hr (n = 2), or absence of increase in ACT after bolus of 100 U/kg of unfractionated heparin and escalation of unfractionated heparin infusion (n = 1). Initial bivalirudin dose ranged from 0.2 to 0.5 mg/kg/hr; no bolus doses were used. Median (range) bivalirudin dose was 0.9 mg/kg/hr (0.15-1.6 mg/kg/hr). Median (interquartile range) time on extracorporeal membrane oxygenation was 226.5 hours (150.5-393.0 hr) including 84 hours (47-335 hr) on bivalirudin. Nonparametric results are as follows: the rate of circuit intervention was significantly lower in patients on bivalirudin than on unfractionated heparin (median [interquartile range]: 0 [0-1] and 1 [1-2], respectively; Wilcoxon p = 0.0126). Bivalirudin dose was correlated to PTT (rs = 0.4760; p < 0.0001), INR (rs = 0.6833; p < 0.0001), and ACT (rs = 0.6161; p < 0.0001). Four patients had a significant bleeding complication on bivalirudin. Survival to hospital discharge was 56%.

CONCLUSIONS

Bivalirudin appears to be a viable option for systemic anticoagulation in pediatric extracorporeal membrane oxygenation patients who have failed unfractionated heparin, but questions remain namely its optimal monitoring strategy. This pilot study supports the need for larger prospective studies of bivalirudin in pediatric extracorporeal membrane oxygenation, particularly focusing on meaningful monitoring variables.

Description of Bivalirudin Use for Anticoagulation in Pediatric Patients on Mechanical Circulatory Support

BACKGROUND

Although heparin has previously been the anticoagulant of choice during mechanical circulatory support (MCS), there is a lack of consistency in dose-response in pediatric patients. Bivalirudin offers more consistent dose-response in adults; however, there are limited data for pediatrics use.

OBJECTIVE

The purpose was to characterize the usage, dosage, and safety profile of bivalirudin when used for pediatric MCS in a tertiary care pediatric hospital.

METHODS

A retrospective review of pediatric patients receiving bivalirudin for extracorporeal membrane oxygenation/ventricular assist device (ECMO/VAD) anticoagulation was conducted. The primary outcome was the average dose of bivalirudin. Additional outcomes included initial and maximum bivalirudin dose, time to first therapeutic activated partial thromboplastin time (aPTT), time within goal aPTT range, bleeding and clotting complications, and cost. Data were compared between ECMO and VAD patients.

RESULTS

Thirty-four patients were included. The median dose of bivalirudin was 0.37 mg/kg/h (interquartile range [IQR] = 0.21-0.56), with a maximum dose of 0.62 mg/kg/h (IQR = 0.33-0.91). VAD patients had a higher median and maximum dose as compared with ECMO patients. Patients achieved their therapeutic goal in a median of 6.1 hours and averaged 61.9% time within therapeutic aPTT. One patient had significant hemorrhage, whereas 3 patients had clotting requiring a circuit change. Bivalirudin acquisition cost was higher than heparin.

CONCLUSION AND RELEVANCE

Bivalirudin dosing in ECMO and VAD patients is consistent with dosing seen in previous reports but may be higher in VAD patients. Comparative studies between heparin and bivalirudin are necessary to compare cost-effective outcomes for pediatric patients.

The Use of Bivalirudin in Pediatric Cardiac Surgery and in the Interventional Cardiology Suite

Anticoagulation is an essential component for patients undergoing cardiopulmonary bypass or extracorporeal membrane oxygenation and for those with ventricular assist devices. However, thrombosis and bleeding are common complications. Heparin continues to be the agent of choice for most patients, likely owing to practitioners' comfort and experience and the ease with which the drug's effects can be reversed. However, especially in pediatric cardiac surgery, there is increasing interest in using bivalirudin as the primary anticoagulant. This drug circumvents certain problems with heparin administration, such as heparin resistance and heparin-induced thrombocytopenia, but it comes with additional challenges. In this manuscript, the authors review the literature on the emerging role of bivalirudin in pediatric cardiac surgery, including its use with cardiopulmonary bypass surgery, extracorporeal membrane oxygenation, ventricular assist devices, and interventional cardiology. Moreover, they provide an overview of bivalirudin's pharmacodynamics and monitoring methods.

Deep vein thrombosis in pediatric patients

Due to advances in caring for critically ill children and those with chronic diseases, rates of deep vein thrombosis (DVT) are increasing in children. Risk factors consist of central venous catheters, chronic medical conditions, thrombophilia, and various medications. Compression Doppler ultrasonography is the method most commonly used to diagnose DVT, and patients will usually present with pain and swelling of the affected limb. Anticoagulation via subcutaneous injection is the most common treatment regime for children with DVT, and the new, direct oral anticoagulants are currently under investigation. Prevention techniques are not established, but clinical studies are addressing this need.

Thromboprophylaxis in Extracorporeal Circuits: Current Pharmacological Strategies and Future Directions

The development of extracorporeal devices for organ support has been a part of medical history and progression since the late 1900s. These types of technology are primarily used and developed in the field of critical care medicine. Unfractionated heparin, discovered in 1916, has really been the only consistent form of thromboprophylaxis for attenuating or even preventing the blood-biomaterial reaction that occurs when such technologies are initiated. The advent of regional anticoagulation for procedures such as continuous renal replacement therapy and plasmapheresis have certainly removed the risks of systemic heparinization and heparin effect, but the challenges of the blood-biomaterial reaction and downstream effects remain. In addition, regional anticoagulation cannot realistically be applied in a system such as extracorporeal membrane oxygenation because of the high blood flow rates needed to support the patient. More recently, advances in the technology itself have resulted in smaller, more compact extracorporeal life support (ECLS) systems that can-at certain times and in certain patients-run without any form of anticoagulation. However, the majority of patients on ECLS systems require some type of systemic anticoagulation; therefore, the risks of bleeding and thrombosis persist, the most devastating of which is intracranial hemorrhage. We provide a concise overview of the primary and alternate agents and monitoring used for thromboprophylaxis during use of ECLS. In addition, we explore the potential for further biomaterial and technologic developments and what they could provide when applied in the clinical arena.

Anticoagulation Therapies in Children

Venous thromboembolism is occurring with increasing frequency in children resulting in the more widespread use of anticoagulation in pediatrics. Antithrombotic drugs in children can be divided into the standard and alternative agents. This review discusses standard and alternative anticoagulants. Because standard anticoagulants have significant limitations, including variable pharmacokinetics, issues with therapeutic drug monitoring, frequency of administration, efficacy, and adverse effects, it is expected that the use of alternative anticoagulants will increase over time. With their improved properties and recent prospective clinical trial data, the current and future use of these agents will likely slowly replace of the standard anticoagulants.

Anticoagulation in children: Making the most of little patients and little evidence

Thrombotic complications are increasing at a steady and significant rate in children resulting in the more widespread use of anticoagulation in this population. Anticoagulant drugs in children can be divided into the standard agents (heparin, low molecular weight heparin, and vitamin K antagonists) and alternative agents (argatroban, bivalirudin, and fondaparinux). This review will compare and contrast the standard and alternative anticoagulants and suggest situations in which it may be appropriate to use argatroban, bivalirudin, and fondaparinux. Clearly, the standard anticoagulants all have significant shortcomings including variable pharmacokinetics, issues with therapeutic drug monitoring, frequency of administration, efficacy, and adverse effects. The alternative anticoagulants have properties which overcome these shortcomings and prospective clinical trial data are presented supporting the current and future use of these agents in place of the standard anticoagulants.

How We Manage Pediatric Deep Venous Thrombosis

Over the past two decades, the incidence and recognition of venous thromboembolism (VTE) in children has significantly increased, likely as a result of improvements in the medical care of critically ill patients and increased awareness of thrombotic complications among medical providers. Current recommendations for the management of VTE in children are largely based on data from pediatric registries and observational studies, or extrapolated from adult data. The scarcity of high-quality evidence-based recommendations has resulted in marked variations in the management of pediatric VTE among providers. The purpose of this article is to summarize our institutional approach for the management of VTE in children based on available evidence, guidelines, and clinical practice considerations. Therapeutic strategies reviewed in this article include the use of conventional anticoagulants, parenteral targeted anticoagulants, new direct oral anticoagulants, thrombolysis, and mechanical approaches for the management of pediatric VTE.

Perioperative care in an adolescent patient with heparin-induced thrombocytopenia for placement of a cardiac assist device and heart transplantation: case report and literature review

Heparin-induced thrombocytopenia (HIT) can cause life-threatening complications following the administration of heparin. Discontinuation of all sources of heparin exposure and the use of alternative agents for anticoagulation are necessary when HIT is suspected or diagnosed. We present the successful use of bivalirudin anticoagulation in an adolescent patient during cardiopulmonary bypass who underwent both placement of a left ventricular assist device and subsequent heart transplantation within a 36-hour period. The pathophysiology and diagnosis of HIT are reviewed, previous reports of the use of direct thrombin inhibitors for cardiac surgery are presented, and potential dosing regimens for bivalirudin are discussed.

Bivalirudin as an Alternative to Heparin for Anticoagulation in Infants and Children

Bivalirudin, a direct thrombin inhibitor, is a useful alternative to heparin for anticoagulation in infants and children. It has been found to be effective in patients requiring treatment of thrombosis, as well as those needing anticoagulation during cardiopulmonary bypass, extracorporeal life support, or with a ventricular assist device. While it has traditionally been used in patients who were unresponsive to heparin or who developed heparin-induced thrombocytopenia, it has recently been studied as a first-line agent. Bivalirudin, unlike heparin, does not require antithrombin to be effective, and as a result, has the potential to provide a more consistent anticoagulation. The case reports and clinical studies currently available suggest that bivalirudin is as effective as heparin at reaching target activated clotting times or activated partial thromboplastin times, with equivalent or the lower rates of bleeding or thromboembolic complications. It is more expensive than heparin, but the cost may be offset by reductions in the costs associated with heparin use, including anti-factor Xa testing and the need for administration of antithrombin. The most significant disadvantage of bivalirudin remains the lack of larger prospective studies demonstrating its efficacy and safety in the pediatric population.

Anticoagulants in children and adolescents

Thrombotic complications are increasing at a steady and significant rate in children, resulting in the more widespread use of anticoagulation in this population. Anticoagulant drugs in children can be divided into the older multitargeted agents (heparin, low-molecular-weight heparin, and warfarin) and the newer targeted agents (argatroban, bivalirudin, and fondaparinux). This review will compare and contrast the multitargeted and targeted anticoagulants and suggest situations in which it may be appropriate to use argatroban, bivalirudin, and fondaparinux. The various agents differ in their pharmacokinetics, requirements for therapeutic drug monitoring, frequency of administration, efficacy, and adverse effects. The targeted anticoagulants have properties that may make them more attractive for use in specific clinical situations. Prospective clinical trial data are presented supporting the current and future use of these agents in children.

Anticoagulants in children and adolescents

Thrombotic complications are increasing at a steady and significant rate in children, resulting in the more widespread use of anticoagulation in this population. Anticoagulant drugs in children can be divided into the older multitargeted agents (heparin, low-molecular-weight heparin, and warfarin) and the newer targeted agents (argatroban, bivalirudin, and fondaparinux). This review will compare and contrast the multitargeted and targeted anticoagulants and suggest situations in which it may be appropriate to use argatroban, bivalirudin, and fondaparinux. The various agents differ in their pharmacokinetics, requirements for therapeutic drug monitoring, frequency of administration, efficacy, and adverse effects. The targeted anticoagulants have properties that may make them more attractive for use in specific clinical situations. Prospective clinical trial data are presented supporting the current and future use of these agents in children.

UNBLOCK: an open-label, dose-finding, pharmacokinetic and safety study of bivalirudin in children with deep vein thrombosis

BACKGROUND

Direct thrombin inhibitors offer potential advantages over unfractionated heparin but have been poorly studied in children.

OBJECTIVES

To determine appropriate dosing of bivalirudin in children and adolescents and the relationship between activated partial thromboplastin time (APTT) and plasma bivalirudin concentration.

PATIENTS/METHODS

The UNBLOCK (UtilizatioN of BivaLirudin On Clots in Kids) study was an open-label, single-arm, dose-finding, pharmacokinetic, safety and efficacy study of bivalirudin for the acute treatment of deep vein thrombosis (DVT) in children aged 6 months to 18 years. Drug initiation consisted of a bolus dose (0.125 mg kg(-1) ) followed by continuous infusion (0.125 mg kg h(-1) ). Dose adjustments were based on the APTT, targeting a range of 1.5-2.5 times each patient's baseline APTT. Safety was assessed by specific bleeding endpoints and efficacy by repeat imaging at 48-72 h and 25-35 days.

RESULTS

Eighteen patients completed the study. Following the bolus dose and the initial infusion rate, most patients' APTT values were within the target range. The infusion rate bivalirudin correlated more closely with drug concentration than the APTT. At 48-72 h, nine (50%) patients had complete or partial thrombus resolution, increasing to 16 (89%) at 25-35 days. No major and one minor bleeding event occurred.

CONCLUSIONS

Bivalirudin demonstrated reassuring safety and noteworthy efficacy in terms of early clot resolution in children and adolescents with DVT. Although a widely available and familiar monitoring tool, the APTT correlates poorly with plasma bivalirudin concentration, possibly limiting its utility in managing pediatric patients receiving bivalirudin for DVT.

A guide to the use of anticoagulant drugs in children

Increasing thrombotic complications in children with complex medication conditions have led to more widespread use of anticoagulants [Raffini et al. in Pediatrics 124(4):1001-8, 2009]. While current guidelines for the management of antithrombotic therapy in neonates and children exist, they are based on low- and very low-quality evidence [Monagle et al. in Chest 141(2 Suppl):e737-801S, 2012]. Despite numerous differences, current anticoagulation practice is largely extrapolated from adult studies. This is sub-optimal, particularly in neonates who have a rapidly evolving hemostatic system. The majority of pediatric patients have underlying medical conditions that may significantly influence drug choice and bleeding risk. This article reviews the use of anticoagulants in children with thrombosis, focusing on practical aspects such as dosing, monitoring, and complications. Low molecular weight heparin has become the preferred anticoagulant in children, although unfractionated heparin and warfarin remain frequently used. Other anticoagulants, including fondaparinux, direct thrombin inhibitors, and the newer target-specific oral anticoagulants are also discussed. Given the many unique challenges surrounding the use of anticoagulants in children, pediatric hospitals should have written practice guidelines as well as experienced providers to care for children with thrombosis. This is an evolving field, and further studies of the use of anticoagulants in neonates and children are greatly needed to help optimize care.

Trends in Parenteral Direct Thrombin Inhibitor Use in Pediatric Patients: Analysis of a Large Administrative Database

Context.—Parenteral direct thrombin inhibitors (DTIs) may be used in pediatric patients with contraindications to heparin therapy, such as heparin-induced thrombocytopenia. Few data exist regarding the use of DTIs in pediatric patients.

Objective.—To characterize the use of DTIs in pediatric patients, including monitoring strategies and bleeding complications.

Design.—A retrospective descriptive study was designed and the Pediatric Health Information System database was queried from 2004 to 2011 for pediatric patients receiving a parenteral DTI. Patient demographic and hospital data, mortality, disease state, and procedure information (from International Classification of Diseases, Ninth Revision codes) were collected from the query. DTI monitoring information was also collected. Patients were divided into 2 time periods (2004–2007, 2008–2011) to evaluate trends.

Results.—Two hundred eight patients met study criteria (50.9% male, 64.4% white), and children (2–12 years of age) represented 34.6% of the population. Congenital heart disease was present in 43.8% and cardiovascular surgical procedure occurred in 28.4%. Argatroban was most commonly used (73.1%) and bivalirudin use increased (P &lt; .001). Bleeding complications were present in 37.9% of patients and mortality was 19.7%. Bleeding complications were associated with lepirudin (62.5%) and argatroban (41.7%) more often as compared with bivalirudin (18.8%) (P &lt; .001). Activated partial thromboplastin time and prothrombin time were used more often in patients receiving argatroban and lepirudin in comparison with bivalirudin, and thrombin time was used more often in patients receiving lepirudin (P &lt; .001). Activated clotting time use increased over time (5.1% versus 17.5%, P = .02).

Conclusion.—Pediatric use of DTIs is infrequent and occurs in patients with high morbidity and mortality.

The pediatric cardiology pharmacopeia: 2013 update

The use of medications plays a pivotal role in the management of children with heart diseases. Most children with increased pulmonary blood flow require chronic use of anticongestive heart failure medications until more definitive interventional or surgical procedures are performed. The use of such medications, particularly inotropic agents and diuretics, is even more amplified during the postoperative period. Currently, children are undergoing surgical intervention at an ever younger age with excellent results aided by advanced anesthetic and postoperative care. The most significant of these advanced measures includes invasive and noninvasive monitoring as well as a wide array of pharmacologic agents. This review update provides a medication guide for medical practitioners involved in care of children with heart diseases.

Updates in thrombosis in pediatrics: where are we after 20 years?

The incidence of venous thromboembolism (VTE) in the pediatric population is increasing. Technological advances in medicine and imaging techniques, improved awareness of the disease, and longer survival of life-threatening or chronic medical conditions all contribute to the increase in VTE rates. There is a paucity of data on management of VTE based on properly designed clinical trials, but there is significant advancement in the last 2 decades. This review summarizes the progress made in pediatric thrombosis, including epidemiological changes, advances in anticoagulant agents, and outcomes of VTE.

Bivalirudin use in an infant with persistent clotting on unfractionated heparin

Bivalirudin is a direct thrombin inhibitor approved for use in adult patients with heparin-induced thrombocytopenia (HIT) undergoing percutaneous coronary intervention. Recently, its use in the pediatric population has increased due to its anti-thrombin-independent mechanism of action. As heparin products produce great inter- and intraindividual variability in pediatric patients, often due to decreased anti-thrombin concentrations in the first year of life, some practitioners have turned to direct thrombin inhibitors, such as bivalirudin, for more predictable pharmacokinetics and effects on bound and circulating thrombin. We report our experience using bivalirudin in a 2-month-old female with recurrent systemic thrombi despite continuous unfractionated heparin infusion. Due to the patient's inability to maintain therapeutic activated partial thromboplastin time (aPTT) values during heparin infusion, bivalirudin was initiated at 0.1 mg/kg/h and increased due to subtherapeutic aPTTs to a maximum of 0.58 mg/kg/h. Therapeutic aPTTs were achieved at the increased dose; however, the patient's worsening renal impairment with resultant drug accumulation and overwhelming sepsis on day 5 of therapy led to discontinuation of the infusion and the initiation of comfort measures.

Venous thrombosis in children: an emerging issue

More and more cases of venous thrombosis are diagnosed in children thanks to newer imaging modalities. Central venous catheters have become commonplace in the care of critically ill children and have contributed to the increased rate of thrombotic events. Lastly, children who develop life-threatening or chronic medical conditions are surviving longer because of advanced medical therapies; these intensive therapies can be complicated by events such as thrombosis. Over the last 10 years, specific guidelines for treating thrombosis in children have become available. Nevertheless, in many situations anticoagulant treatment is specially tailored to each individual patient's needs. Some new antithrombotic drugs which have undergone clinical testing in adults might be beneficial to paediatric patients with thromboembolic disorders; unfortunately, clinical data and reports on the use of these drugs in children, when available, are extremely limited. The aim of this review is to provide physicians with enough background information to be able to manage thrombosis in children. First, by helping them detect a thrombotic event in a child. Upon confirmation of the diagnosis, the physician will request the appropriate tests and will choose the best treatment on the basis of the guidelines and recommendations. Moreover, the paediatrician will have the information he or she needs to identify which children are at highest risk of acute thrombotic events and relevant long-term sequelae and, therefore, to decide on the appropriate prophylactic or pharmacologic strategy. Lastly, we would like to provide the paediatrician with information on future drugs with regard to the treatment and prophylaxis of thrombosis.

Heparin-Induced Thrombocytopenia Screening and Management in Pediatric Patients

The diagnosis and management of heparin-induced thrombocytopenia (HIT) in pediatric patients poses significant challenges. The cardinal findings in HIT, thrombocytopenia and thrombosis with heparin exposure, are seen commonly in critically ill children, but are most often secondary to etiologies other than HIT. However, without prompt diagnosis, discontinuation of heparin, and treatment with an alternative anticoagulant such as a direct thrombin inhibitor (DTI), HIT can result in life- and limb-threatening thrombotic complications. Conversely, DTIs are associated with higher bleeding risks than heparin in adults and their anticoagulant effects are not rapidly reversible; furthermore, the experience with their use in pediatrics is limited. Whereas immunoassays are widely available to aid in diagnosis, they carry a significant false positive rate. Age-dependent differences in the coagulation and immune system may potentially affect manifestations of HIT in children, but have not been extensively examined. In this chapter, diagnostic approaches and management strategies based on a synthesis of the available pediatric studies and adult literature on HIT are discussed.

Old and new antithrombotic drugs in neonates and infants

Thromboembolic complications are becoming more frequent in children and the use of anticoagulation has increased considerably. The most widely used agents in children, heparin, low molecular weight heparin, and warfarin all have limitations which are exaggerated in children. This has led to the study of newer agents with improved pharmacologic properties such as bivalirudin, argatroban, and fondaparinux. Clinical trials are under way to assess several new oral anticoagulants that are in late phase studies or already licensed in adults. Based on the completed studies in children, several recommendations for the use of currently available agents (bivalirudin, argatroban, and fondaparinux) are suggested for clinical use today. Additional studies need to be conducted for the these agents, so that their use may be expanded in selected indications. New regulatory requirements are leading to a number of studies in the newer anticoagulants that are yet to be licensed in adults for treatment of venous thromboembolism. Pediatric thrombosis is entering a fruitful era of research in anticoagulation management, which is sure to lead to significant changes in how children are treated in the next 10 years.

Direct thrombin and factor Xa inhibitors in children: a quest for new anticoagulants for children

Venous thrombosis and pulmonary embolism rarely occur in children but are associated with significant morbidity and mortality. Venous thromboembolism (VTE) mostly affects children with severe underlying conditions and multiple risk factors. Newborns and adolescents are at the highest risk. Standard and low molecular weight heparins and vitamin K antagonists are routinely used for the prevention and treatment of VTE. The new anticoagulants, both parenteral such as argatroban, bivalirudin and fondaparinux and oral such as dabigatran and rivaroxaban, have favourable pharmacological properties, all are approved for clinical use in adults and are currently being investigated in children. Argatroban is the only new anticoagulant licensed for use in children so far. The role of these new anticoagulants as alternative anticoagulants for children remains to be defined. This review focuses on the characteristics of VTE in children and reviews current knowledge on the use of the new thrombin and factor Xa inhibitors in this population.

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.