Survey of oral anticoagulant treatment in children

Deep vein thrombosis in children

We describe a rare case of deep vein thrombosis (DVT) in children, highlight the importance of early diagnosis of rare disease with potential complications. In a 5 year old boy presented with persistent leg pain without any obvious cause. Detailed investigation led to diagnosis of DVT. As there are common differential diagnoses for leg pain in children, pediatricians usually have a low index of suspicious of DVT in children. This case highlight that paediatricians must consider DVT in their differential diagnosis when children present with leg pain.

Antithrombotic therapy in neonates and children: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

Neonates and children differ from adults in physiology, pharmacologic responses to drugs, epidemiology, and long-term consequences of thrombosis. This guideline addresses optimal strategies for the management of thrombosis in neonates and children.

METHODS

The methods of this guideline follow those described in the Methodology for the Development of Antithrombotic Therapy and Prevention of Thrombosis Guidelines: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines.

RESULTS

We suggest that where possible, pediatric hematologists with experience in thromboembolism manage pediatric patients with thromboembolism (Grade 2C). When this is not possible, we suggest a combination of a neonatologist/pediatrician and adult hematologist supported by consultation with an experienced pediatric hematologist (Grade 2C). We suggest that therapeutic unfractionated heparin in children is titrated to achieve a target anti-Xa range of 0.35 to 0.7 units/mL or an activated partial thromboplastin time range that correlates to this anti-Xa range or to a protamine titration range of 0.2 to 0.4 units/mL (Grade 2C). For neonates and children receiving either daily or bid therapeutic low-molecular-weight heparin, we suggest that the drug be monitored to a target range of 0.5 to 1.0 units/mL in a sample taken 4 to 6 h after subcutaneous injection or, alternatively, 0.5 to 0.8 units/mL in a sample taken 2 to 6 h after subcutaneous injection (Grade 2C).

CONCLUSIONS

The evidence supporting most recommendations for antithrombotic therapy in neonates and children remains weak. Studies addressing appropriate drug target ranges and monitoring requirements are urgently required in addition to site- and clinical situation-specific thrombosis management strategies.

Oral anticoagulation therapy in children

Treatment of thromboembolic complications in children has been the subject of considerable research in the last decade. Recommendations for oral anticoagulant therapy in children have been extrapolated from adult clinical trials. Coumarin derivatives are the preeminent oral antithrombotic agents used in children. Warfarin, acenocoumarol and phenprocoumon are the vitamin K antagonists used in children with thrombotic complications in different countries according to their experience and familiarity within a country or region. Prospective studies from Canada and Argentina propose guidelines for administering and monitoring warfarin and acenocoumarol therapy in children. These studies highlight the difficulty of their use in pediatric patients. Infants younger than 12 months of age require increased doses to achieve and maintain the therapeutic target INR, adjustments of loading dose to achieve the target INR faster with no overshooting, more frequent INR testing and dose adjustments, and fewer INR in the target range. The current indications for oral anticoagulants in children with thrombotic complications, the side effects of these agents and the reversal of the anticoagulant effect are discussed.

Acenocoumarol therapy in pediatric patients

To determine guidelines for administering and monitoring acenocoumarol therapy in children, 93 patients (median 5.1 years, range: 0.2-18 years) were prospectively evaluated over a 33-month period. The loading doses used were: <1 year, 0.20 mg x kg-1; >1-5 years, 0.09 mg x kg-1; 6-10 years, 0.07 mg x kg-1; 11-18 years, 0.06 mg x kg-1. In this study, the loading dose and the dose to achieve and maintain target therapeutic range (TTR) for acenocoumarol are age-dependent, with infants having the highest and teenagers having the lowest requirements. The use of a different loading dose according to age has allowed most of the children (80%) in all the age groups to achieve TTR in less than 1 week. No patients had serious bleeding or thrombotic complications. We conclude that there is an age-dependent response to acenocoumarol in pediatric patients. The implementation of an age-adjusted loading dose regimen reduces the length of hospitalization required to achieve effective anticoagulant therapy.

Analysis of Warfarin Therapy in Pediatric Patients: A Prospective Cohort Study of 319 Patients

This study details warfarin use in a large pediatric population followed in a central anticoagulation clinic. A prospective, consecutive cohort of nonselected children were studied. Patients were divided into groups by age, target international normalized ratio (INR) range, disease, medications, and vitamin K supplemented enteral nutrition use. Groups were analyzed on multiple aspects of warfarin therapy using multivariate methods. A total of 319 patients received 352 warfarin courses representing 391 treatment years. Age independently influenced all aspects of therapy. When compared with all older children, the ≤1 year of age group required increased warfarin doses, longer overlap with heparin, longer time to achieve target INR ranges, more frequent INR testing and dose adjustments, and fewer INR values in the target range. Although significantly different than children ≤1 year, children 1 to 6 years of age showed the same findings when compared with 7- to 18-year-olds. Fontan patients required 25% decreased dosage as compared with other congenital heart disease patients. Children on corticosteroids had less INRs in the target range and children on phenobarbital/carbamazepine required increased maintenance dosages of warfarin. Also, patients receiving enteral nutrition required increased dosages of warfarin. Serious bleeding occurred in 2 children (0.5% per patient year). Recurrent thromboembolic events (TEs) occurred in 8 children. Two children had recurrences while receiving warfarin (1.3% per patient year). This study outlines the profound effect of age and relative complexity of clinical management of warfarin therapy in children.

Analysis of Warfarin Therapy in Pediatric Patients: A Prospective Cohort Study of 319 Patients

This study details warfarin use in a large pediatric population followed in a central anticoagulation clinic. A prospective, consecutive cohort of nonselected children were studied. Patients were divided into groups by age, target international normalized ratio (INR) range, disease, medications, and vitamin K supplemented enteral nutrition use. Groups were analyzed on multiple aspects of warfarin therapy using multivariate methods. A total of 319 patients received 352 warfarin courses representing 391 treatment years. Age independently influenced all aspects of therapy. When compared with all older children, the ≤1 year of age group required increased warfarin doses, longer overlap with heparin, longer time to achieve target INR ranges, more frequent INR testing and dose adjustments, and fewer INR values in the target range. Although significantly different than children ≤1 year, children 1 to 6 years of age showed the same findings when compared with 7- to 18-year-olds. Fontan patients required 25% decreased dosage as compared with other congenital heart disease patients. Children on corticosteroids had less INRs in the target range and children on phenobarbital/carbamazepine required increased maintenance dosages of warfarin. Also, patients receiving enteral nutrition required increased dosages of warfarin. Serious bleeding occurred in 2 children (0.5% per patient year). Recurrent thromboembolic events (TEs) occurred in 8 children. Two children had recurrences while receiving warfarin (1.3% per patient year). This study outlines the profound effect of age and relative complexity of clinical management of warfarin therapy in children.

Low dose oral anticoagulation therapy in Chinese children with congenital heart disease

OBJECTIVES

This study aims to evaluate the efficacy of a low dose warfarin regimen for Chinese children requiring anticoagulation therapy and its safety when monitored on an outpatient basis. Current recommendations are based on extrapolations from the adult experience and a high target international normalised ratio (INR) is adopted amongst the Western countries.

METHODOLOGY

This is a 10-year retrospective study from January 1986 to June 1996. Effectiveness of warfarin therapy was monitored by the prothrombin time, standardised and expressed as the INR. A target INR of 1.5-2.5 was adopted for children with cardiac diseases requiring anticoagulation therapy for primary and secondary prophylaxis against thromboembolism. From the clinical records, demographic data, induction warfarin dosage, changes of dosages and related events on follow-up, frequency of outpatient visits, complications and serial INR results were reviewed.

RESULTS

Thirty-five patients (23 boys, 12 girls) were included with a mean age at initiation of warfarin therapy of 8.4+/-5.8 years. Amongst these, 66% (n = 23) were after isolated valvar replacement, 28% (n = 10) after Fontan operation with or without valvar replacement and 6% (n = 2) after deep vein thrombosis. Regression estimate of the induction dose was 0.05-0.13 mg x kg(-1) in order to achieve the target INR range after 2 days of warfarin therapy. The daily maintenance warfarin dose was correlated with the bodyweight [dose (mg x day(-1))= 0.04 x bodyweight (kg) + 0.87, r = 0.63, P<0.0001]. Young children required significantly higher daily warfarin maintenance dose when adjusted for bodyweight [dose (mg x kg day(-1)) = antilog(10)¿-0.02 x age (years)- 0.80¿, r = -0.74, P<0.0001]. The mean maintenance warfarin dosage was significantly lower in patients after the Fontan operation, with or without valvar replacement, in the absence of apparent liver dysfunction. The total period of followup was 159 patient-years. No serious bleeding complications or embolic phenomena were documented. One patient died of thrombosis of the mitral valve prosthesis. The overall incidence of thrombosis was 0.6 per 100 patient-years.

CONCLUSIONS

A low dose warfarin regimen to maintain a target INR of 1.5-2.5 provides adequate protection in Chinese children against thromboembolism whilst allowing safe outpatient monitoring of the anticoagulation status.

Venous thromboembolic events in pediatric patients. Diagnosis and management

Venous thromboembolism is a rapidly increasing secondary complication in children being treated for serious, life-threatening, primary diseases. Most current management guidelines and recommendations for imaging techniques have been extrapolated from the results of trials in adults. This may be less than optimal for children as there are important differences. The purpose of this article is to summarize the information on venous thromboembolism in children, and offer some guidelines for diagnosis, prophylaxis, and therapeutic intervention based on the best available evidence.

Guidelines for antithrombotic therapy in pediatric patients

Because of the relatively low incidence of TEs in children, the diagnostic and therapeutic approaches used are largely extrapolated from guidelines for adults. Features that differ in children compared with adults include underlying disorders, high incidence of CVL-related DVT in the upper venous system, and response to SH, warfarin, and thrombolytic agents. There is a paucity of information on the risk/benefit ratio of the therapeutic interventions and long-term outcome. Clinical trials are urgently needed to clarify optimal management for pediatric patients with TEs.

Anticoagulation with warfarin in infants and children

OBJECTIVE

To provide a comprehensive review of warfarin use in infants and children, including recommendations for appropriate dosage and monitoring parameters.

DATA SOURCES

A MEDLINE search (1966-1995) was used to identify pertinent English-language articles in the medical literature. The key search term was warfarin. Additional material was obtained from references cited in articles retrieved through MEDLINE.

STUDY SELECTION

All articles involving children younger than 18 years were evaluated. In addition, articles on the pharmacokinetics and pharmacodynamics in adults, adverse effects, and drug interactions were included.

DATA EXTRACTION

Material selected for review included clinical trials, case reports, and surveys of practice.

DATA SYNTHESIS

Warfarin has been used as prophylactic therapy in children with prosthetic cardiac valves as well as for prevention of thromboembolic complications associated with autoimmune disorders and protein C or protein S deficiency. Warfarin also has been used to prevent embolization in children with deep-vein thrombosis or clots in central venous catheters. According to the literature, an initial dosage of 0.1 mg/kg/d should provide anticoagulation without significant adverse effects. As in adults, dosing should be adjusted to achieve a target international normalized ratio (INR). Although the target range in children is not well established, INR values of 1.5-3 are recommended for most patients. Higher values have been used in children with prosthetic cardiac valves and hereditary clotting disorders.

CONCLUSIONS

Due to its infrequent use, there is limited information on the effects of warfarin in children. Basic guidelines for initiating and monitoring warfarin were developed by using data gathered from clinical trials, retrospective reviews, case series, and surveys of practice.

Oral anticoagulation in paediatric patients: dose requirements and complications

The lack of oral anticoagulant guidelines specific to paediatric practice has led to the adoption of adult regimens, often without scientific evidence of efficacy or safety. A two year prospective study of anticoagulant control was carried out in 45 children aged 9 months to 18 years, the majority of whom were receiving primary prophylactic anticoagulation. The main indication was congenital heart disease, either with (n = 8) or without (n = 34) mechanical valve prosthesis. During a follow up period of 602 patient months the average interval between visits was three weeks. Target international normalised ratios (INRs) were achieved on 62% and 39% of visits for children with low target INR (2.0-3.0) and high target INR (3.0-4.0) respectively. However warfarin dose was altered on only 22% of visits. Warfarin doses required to achieve a stable INR of 2.0-3.0 in 33 children were strongly correlated with weight [dose (mg/d) = 0.07 x weight (kg) + 0.54] but independently influenced by age. No thrombotic complications were recorded, and haemorrhagic events were infrequent (2.1% of visits) and, with one exception, minor. Safe outpatient oral anticoagulation is feasible in children, whose warfarin requirements appear moderately predictable and whose control is no more erratic than that of adults.

Indications and drugs for anticoagulation therapy in children

The indications for using anticoagulants in children are reviewed. These include venous thromboembolic disease, thrombosis associated with central venous lines, inherited conditions, arterial thromboembolic disease and umbilical catheterization. The anticoagulants presently available for paediatric use consist of heparin and oral agents including low molecular weight heparin (LMWH). The problems associated with their use in children are examined and potential advantages described. Increasing numbers of children are now requiring anticoagulant therapy and the potential advantages of LMWHs makes it imperative that randomized, controlled trials be carried out in children in prophylactic as well as therapeutic situations.

Systemic thromboembolism leading to myocardial infarction and stroke after fenestrated total cavopulmonary connection

Thromboembolic phenomena involving the caval veins, right atrium, and pulmonary artery are recognised complications after the Fontan operation and other forms of total cavopulmonary connection. A rare case of systemic thromboembolism is reported in a 3 year old girl who had repeated coronary and cerebral thromboembolic events after a fenestrated total cavopulmonary shunt operation. A survey of the 18 paediatric cardiac units in the United Kingdom and Ireland showed a wide discrepancy in anticoagulation policies after Fontan-type operations. Prevention of thrombotic complications by lifelong postoperative anticoagulation may outweigh the risk of haemorrhage.