Brief Communication
Anticoagulation clinics for children achieve improved warfarin management

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Introduction

Oral anticoagulant therapy is difficult to manage in children as the children who require anticoagulation usually have complex underlying health problems, are on multiple medications and are often difficult to venesect. Multiple studies in adults have demonstrated that dedicated anticoagulation clinics (AC) achieve superior results in terms of keeping patients within their specified target therapeutic range (TTR). One of the most important advantages of AC management of warfarinised patients is the provision of regular, consistent education and feedback to the patient by the same staff members [2], [3], [4], [5], [6], [7], [8]. There is only one previous report of a paediatric AC. In 1999, we established a nurse-coordinated paediatric AC with emphasis on parent education, whole tablet dosing and monitoring protocols. This report is the first analysis of this program.

Significant paediatric medical advances in the last decade have seen patients for whom no therapy was known 10 years ago, now receiving life saving care. This reduction in infant and child mortality is not without sequelae, however, and thromboembolic disease is now recognised as a potential adverse event for many children presenting with serious health problems. This increased risk of thromboembolic disease has significantly contributed to the increased use of warfarin in paediatrics, both therapeutically and prophylactically [9].

Despite the advances that have been made in the management of seriously ill children, the delivery of effective warfarin therapy to infants and children remains a challenge. Streif et al, in the largest published cohort of children requiring warfarin therapy, achieved the target therapeutic range (TTR) INR in only 54% of test points. Warfarin use in children has proven to be a greater challenge than warfarin use in adults. Reasons include variable age-related dose response rates, frequent concomitant medications, chronic health conditions and frequent intercurrent illnesses [9], [10], [11], [12], [13], [14]. Lack of control over these confounding factors can contribute to an increase in warfarin related adverse events [15]. Strategies that minimise the impact of these confounding variables are needed to optimise anticoagulant management in infants and children. Such strategies are most likely to be generated through a dedicated paediatric AC.

Section snippets

Methods

In 1999 a dedicated paediatric AC was established at the Royal Children's Hospital, Melbourne, Australia. This clinic comprised Consultant Haematologists and an Anticoagulation Nurse, and incorporated the services of the hospital's Pathology Collection department and Core Laboratory. The Anticoagulation Nurse made all clinical management decisions, supervised by a Consultant Haematologist.

A prospective audit of results for the third year of this program (Dec 2001–Nov 2002) was conducted. All

Results

Ninety-four children received warfarin for a total of 61.8 warfarin years (range: 1 week to 12 months). The children ranged in age from 3 months to 20 years. There were 50 females and 44 males. The majority of patients had an underlying cardiac anomaly, consisting of Fontan patients (n=30), prosthetic valves (n=11), cardiomyopathy (n=11), pulmonary hypertension (n=9) and other forms of congenital heart disease (n=6). Fifteen patients with short gut anomalies received concomitant warfarin

Discussion

This prospective study evaluated the efficacy and safety of a specialised paediatric AC. All patients requiring warfarin over a 12-month period were included in this study, except the child with homozygous protein C deficiency. Primary indications for oral anticoagulant therapy likely reflect institutional specialisation and local medical management strategies. Warfarin use in children is primarily prophylactic, with few children in our series requiring warfarin for the management of confirmed

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      Reasons as to why warfarin therapy does not outperform ASA in this patient population remain speculative and may reflect the multifactorial mechanisms of thrombus formation in Fontan patients, including decreased cardiac output, abnormal venous flow, prosthetic material, blind cavities, lack of atrioventricular synchrony, coagulation defects, and platelet abnormalities [16,18,29–31]. Alternatively, the lack of superiority of prophylactic anticoagulation versus antiplatelet therapy may be due, in part, to difficulties achieving and maintaining therapeutic INR levels [16,18,32,33]. In an exploratory analysis of the pediatric Fontan study, patients on warfarin who often failed to meet targeted INR levels experienced a significantly higher rate of thromboemboli than those who consistently achieved targeted INR levels or received ASA therapy [18].

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