Anticoagulation in neonates and children: Pitfalls and dilemmas

Neonatal respiratory and cardiac ECMO in Europe

Neonatal extracorporeal membrane oxygenation (ECMO) is a life-saving procedure for critically ill neonates suffering from a potentially reversible disease, causing severe cardiac and/or respiratory failure and refractory to maximal conventional management. Since the 1970s, technology, management, and clinical applications of neonatal ECMO have changed. Pulmonary diseases still represent the principal neonatal diagnosis, with an overall 74% survival rate, and up to one-third of cases are due to congenital diaphragmatic hernia. The overall survival rate in cardiac ECMO is lower, with congenital heart defect representing the main indication. This review provides an overview of the available evidence in the field of neonatal ECMO. We will address the changing epidemiology, basic principles, technologic advances in circuitry, and monitoring, and deliver a current multidisciplinary management framework, focusing on ECMO applications, complications, and long-term morbidities. Lastly, areas for further research will be highlighted.Conclusions: ECMO is a life support with a potential impact on long-term patients' outcomes. In the next years, advances in knowledge, technology, and expertise may push neonatal ECMO boundaries towards more premature and increasingly complex infants, with the final aim to reduce the burden of ECMO-related complications and improve overall patients' outcomes. What is Known: • ECMO is a life-saving option in newborns with refractory respiratory and/or cardiac failure. • The multidisciplinary ECMO management is challenging and may expose neonates to complications with an impact on long-term outcomes. What is New: • Advances in technology and biomaterials will improve neonatal ECMO management and, eventually, the long-term outcome of these complex patients. • Experimental models of artificial placenta and womb technology are under investigation and may provide clinical translation and future research opportunities.

The use of extracorporeal membrane oxygenation in children with acute fulminant myocarditis

Acute fulminant myocarditis (AFM) occurs as an inflammatory response to an initial myocardial insult. Its rapid and deadly progression calls for prompt diagnosis with aggressive treatment measures. The demonstration of its excellent recovery potential has led to increasing use of mechanical circulatory support, especially extracorporeal membrane oxygenation (ECMO). Arrhythmias, organ failure, elevated cardiac biomarkers, and decreased ventricular function at presentation predict requirement for ECMO. In these patients, ECMO should be considered earlier as the clinical course of AFM can be unpredictable and can lead to rapid haemodynamic collapse. Key uncertainties that clinicians face when managing children with AFM such as timing of initiation of ECMO and left ventricular decompression need further investigation.

Participant-reported Warfarin Adherence in Community-based Pediatric Patients

Warfarin is the most commonly prescribed anticoagulant for children in the outpatient setting in Australia. Pediatric patients likely have different challenges to warfarin adherence compared with their adult counterparts; however, little is known about warfarin adherence among this population. This study aimed to understand warfarin adherence among community-based pediatric patients by using an online survey design. The survey instrument incorporated parent or patient self-reported warfarin doses missed in the preceding month, a validated warfarin adherence assessment tool, the 13-item Self-Efficacy for Appropriate Medication use Scale (SEAMS-13), and an open-ended question asking about the challenges of warfarin adherence. The indication of warfarin administration and patient's time in therapeutic range were obtained from medical records. The study recruited outpatients managed by a tertiary pediatric hospital who had previously consented to participate in warfarin research. In total, 53 families were contacted with 43 responses (81% response rate) and 41 completed surveys. The median age of the children from participating families was 10.6 years (range, 4.1 to 18.9 y). The majority of these children (n=42) used warfarin prophylactically and only 1 child used it to treat deep venous thrombosis. The time in therapeutic range achievement of this cohort was 64.4% (95% confidence interval, 58.7-70.2). The mean SEAMS-13 score was 33.5 (95% confidence interval, 31.75-35.37) and the total missed doses was 2.5%. Participants also identified barriers and enablers of warfarin adherence. This study was the first of its kind and thus it provides baseline data for future research. The warfarin adherence of this cohort was likely optimized because of frequent clinical contact and access to self-testing. Future studies are required to examine the different approaches aiming to improve the anticoagulant adherence after the emergence of direct oral anticoagulants with a wider therapeutic index and minimal monitoring that could contribute to less clinical contact.

Anticoagulation during ECMO in neonatal and paediatric patients

Extracorporeal Membrane Oxygenation (ECMO) is a form of Extracorporeal Life Support (ECLS) which is used frequently in the paediatric and neonatal setting to support either the pulmonary, or both the pulmonary and cardiac systems. Management of ECMO requires the use of systemic anticoagulation to prevent patient and circuit based thrombosis, which in turn increases the risk of haemorrhage. A number of coagulation tests, laboratory and point of care based, are used to monitor anticoagulation, however the evidence for correlation of the test results with level of anticoagulant and clinical outcomes in children remains poor.

Age dependency for coagulation parameters in paediatric populations

Understanding of developmental haemostasis is critical to ensure optimal prevention, diagnosis, and treatment of haemorrhagic and thrombotic diseases in children. As coagulation test results are known to be dependent on the reagents/analysers used, it is recommended for each laboratory to define the age-dependent reference ranges by using its own technical condition. That study was carried out in seven centers to establish age-specific reference ranges using the same reagents and analyser. Plasma samples were obtained from 1437 paediatric patients from the following age groups: 15 days-4 weeks (n=36), 1–5 months (n=320), 6–12 months (n=176), 1–5 years (n=507), 6–10 years (n=132) and 11–17 years (n=262). Indication of coagulation testing was pre-operative screening for non-acute diseases in most cases. PT values were similar in the different age groups to those in adults, whereas longer aPTTs were demonstrated in the younger children. Plasma levels of all clotting factors, except for FV, were significantly decreased (p<0.0001) in the youngest children, adult values being usually reached before the end of the first year. The same applied to antithrombin, protein C/S, and plasminogen. In contrast, FVIII and VWF levels were elevated in the youngest children and returned to adult values within six months. The same applied to D-dimer levels, which were found elevated, particularly until six months of life, until puberty. These data suggest that most coagulation test results are highly dependent on age, mainly during the first year of life, and that age-specific reference ranges must be used to ensure proper evaluation of coagulation in children.

Impact of thrombelastography in paediatric intensive care

We assessed the clinical impact of thrombelastography (TEG®) results (TEG® 5000, Haemonetics Corporation, Braintree, MA, USA) by measuring their ability to cause changes in a theoretical treatment plan and contribute to the understanding of haemostasis. We prospectively included paediatric intensive care unit (PICU) patients who had standard tests of haemostasis and TEG ordered and had an arterial catheter or extracorporeal access port in situ. Blood for standard tests and TEG was taken simultaneously. Independent of patient care, general patient information and results of standard laboratory tests were presented to five clinicians who were asked to document their theoretical treatment plan. Clinicians were then shown TEG results and asked if they caused a change in their plan, if they confirmed initial standard laboratory test results, if they enabled a better understanding of haemostasis and if they provided additional information. Inter-rater agreement between the clinicians was determined. Forty-two TEG results were obtained from 34 patients. Overall, the inclusion of TEG results led to a change in treatment plan in 97 of 207 occasions (47%), confirmed standard laboratory test results in 177 of 204 occasions (87%), enabled a better understanding of haemostasis in 140 of 204 occasions (69%) and provided additional information in 131 of 204 occasions (64%). Variation existed between clinicians, seemingly due to individual differences, with poor inter-rater agreement. We conclude that TEG results led to changes in treatment plans almost half the time, confirmed findings of standard tests and provided a better understanding of haemostasis, but randomised controlled trials are required to determine the role and influence of TEG results on patient outcome.

Safe Use of Low-Molecular-weight Heparin in Pediatric Acute Lymphoblastic Leukemia and Lymphoma Around Lumbar Punctures

Children with acute lymphoblastic leukemia or lymphoma (ALL) undergo multiple lumbar punctures (LPs) and frequently require low-molecular-weight heparin (LMWH) for thromboembolic complications. We evaluated if withholding LMWH 24 hours before and after LPs prevented bleeding complications. Children (n=133) with ALL from who were: (1) treated at St. Jude Children's Research Hospital, (2) received LMWH (2×/day of ~1 mg/kg) between January 2004 until December 2012, and (3) underwent a LP were analyzed. Spinal hematoma was defined as a clinical suspicion leading to diagnostic imaging. Traumatic LP was defined as ≥10 red blood cells per microliter of cerebrospinal fluid. In 1708 LPs, no hematomas occurred. For each child treated with LMWH, the probability of experiencing a spinal hematoma during the entire ALL treatment course was 0% (95% confidence interval [CI], 0.0%-2.7%), and in each LP, assuming no intrapatient correlation, the probability of spinal hematoma was 0% (95% CI, 0.0%-0.2%). Traumatic LPs were more common when performed when children were not receiving LMWH therapy (odds ratio [OR], 1.5; 95% CI, 1.1-2.2) which may be explained by clinician optimization of known risk factors for traumatic cerebrospinal fluid before the procedures. Withholding LMWH for 24 hours before and after LPs in children being treated for ALL is safe.

Effect of CYP2C9, VKORC1, and CYP4F2 polymorphisms on warfarin maintenance dose in children aged less than 18 years: a protocol for systematic review and meta-analysis

BACKGROUND

Despite its shortcomings, warfarin is still the most commonly prescribed anticoagulant to prevent thromboembolism in children. In adults, numerous studies confirmed the robust relationship between warfarin maintenance doses and single nucleotide polymorphisms of cytochrome P450 2C9 (CYP2C9), vitamin K epoxide reductase (VKORC1), and cytochrome P450 4F2 (CYP4F2). However, their effect in children still remains to be determined. The primary objective of the present systematic review and meta-analysis is to assess the effect of genotypes of CYP2C9, VKORC1, and CYP4F2 on warfarin maintenance dose in children.

METHODS/DESIGN

A comprehensive literature review search using the OVID platform will be conducted by a specialized librarian, without language restrictions (i.e., MEDLINE/EMBASE/Cochrane Central Register of Controlled Trials), and all abstracts will be reviewed by two authors. Data abstraction from each eligible study will be extracted individually by two authors (MT and TK), and disagreements will be resolved through discussion with a third person (SI). Critical appraisal of the included analysis of the primary objective will follow the Newcastle-Ottawa Scale, in addition to the Strengthening the Reporting of Genetic Association study (STREGA) statement, and data reporting will follow the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. For the meta-analysis, the presence vs. absence of each genetic polymorphism will be pursued, respectively, using a random effect model with effect size expressed as a mean difference plus 95 % confidence interval.

DISCUSSION

Our study will provide a comprehensive systematic review and meta-analysis on the potential effects of CYP2C9, VKORC1, or CYP4F2 on the warfarin maintenance dose in children, exploring the feasibility of the development of pharmacogenetic-guided warfarin dosing algorithm for children on oral vitamin K antagonists.

SYSTEMATIC REVIEW REGISTRATION

The review has been registered with PROSPERO (registration number CRD42015016172 ).

Pharmacogenetics-based warfarin dosing in children

Clinical factors, demographic variables and variations in two genes, CYP2C9 and VKORC1, have been shown to contribute to the variability in warfarin dose requirements among adult patients. Less is known about their relative importance for dose variability in children. A few small studies have been reported, but the results have been conflicting, especially regarding the impact of genotypes. In this article, we critically review published pharmacogenetic-based prediction models for warfarin dosing in children, and present results from a head-to-head comparison of predictive performance in a distinct cohort of warfarin-treated children. Finally we discuss what properties a prediction model should have, and what knowledge gaps need to be filled, to improve warfarin therapy in children of all ages.

[Evaluation of an educational program for oral anticoagulation in children with the INR home-monitoring CoaguChek XS(®)]

OBJECTIVE

To assesses the results of our education program relative to anticoagulation therapy and self-monitoring of INR.

MATERIALS AND METHODS

All children treated with oral anticoagulation therapy and followed using INR self-monitoring in Tours and Nantes, France, were included. A questionnaire on the treatment and its management was sent to the patients and their family. We analyzed the quality of anticoagulation using the proportion of INR within the target range.

RESULTS

Thirty-three children were included, with a mean age of 10.9years. Thirty-one questionnaires could be analyzed. Insufficient knowledge on the treatment objective and risks, the INR target range, and the interpretation of the INR was observed. We found 65.8% of INRs within the target range. The proportion of INRs within the target range was better with the INR self-testing than with the laboratory test (69.7% vs. 49.1%, P=0.003). There was no major complication observed during the study period. A moderate correlation (K=0.57) was noted between the INRs measured with the point-of-care monitor and the laboratory test on the same day.

CONCLUSION

However, home-monitoring of oral anticoagulation therapy increases the quality of anticoagulation. Both education and the training program need improvement in order to provide patients and their families with better knowledge on anticoagulation therapy.

Clinically significant thrombosis in pediatric heart transplant recipients during their waiting period

Thrombosis is a serious complication of heart failure for which available data on pediatric patients are scarce. This report describes the frequency and risk factors of clinically significant thrombosis (CST) for children awaiting transplantation. A retrospective study analyzed a cohort of heart recipients with CST, defined by the presence of intracardiac thrombus by imaging, explant pathology, or symptomatic clinical event. Among the 123 patients in the study, 56 % were male and 44 % had congenital heart disease. The median age at transplantation was 6.6 years (range 0-30 years). The prevalence of CST was 12.2 % (15/123), and its incidence was 32.7 events per 100 patient-years. The thromboembolic event frequencies were 2.4 % and 6.5 events per 100 patient-years. The median interval from listing to CST was eight days (range 0-113 days). The median wait-list duration was 31 days (range 8-169 days) in the CST group versus 51 days (range 0-1,743 days) in the non-CST group. Inpatient status was statistically associated with CST (14 of 15 subjects were inpatients, p = 0.03). Inotropic support (p = 0.068) and United Network for Organ Sharing (UNOS) status 1 (p = 0.061) approached significance. Clinically significant thrombosis was common in this end-stage heart failure population. Until randomized clinical trial data are available, it may be reasonable to consider anticoagulation for children admitted with decompensated heart failure and listed as UNOS status 1.

Warfarin dose prediction in children using pharmacometric bridging--comparison with published pharmacogenetic dosing algorithms

Purpose

Numerous studies have investigated causes of warfarin dose variability in adults, whereas studies in children are limited both in numbers and size. Mechanism-based population modelling provides an opportunity to condense and propagate prior knowledge from one population to another. The main objectives with this study were to evaluate the predictive performance of a theoretically bridged adult warfarin model in children, and to compare accuracy in dose prediction relative to published warfarin algorithms for children.

Method

An adult population pharmacokinetic/pharmacodynamic (PK/PD) model for warfarin, with CYP2C9 and VKORC1 genotype, age and target international normalized ratio (INR) as dose predictors, was bridged to children using allometric scaling methods. Its predictive properties were evaluated in an external data set of children 0–18 years old, including comparison of dose prediction accuracy with three pharmacogenetics-based algorithms for children.

Results

Overall, the bridged model predicted INR response well in 64 warfarin-treated Swedish children (median age 4.3 years), but with a tendency to overpredict INR in children ≤2 years old. The bridged model predicted 20 of 49 children (41 %) within ± 20 % of actual maintenance dose (median age 7.2 years). In comparison, the published dosing algorithms predicted 33–41 % of the children within ±20 % of actual dose. Dose optimization with the bridged model based on up to three individual INR observations increased the proportion within ±20 % of actual dose to 70 %.

Conclusion

A mechanism-based population model developed on adult data provides a promising first step towards more individualized warfarin therapy in children.

Electronic supplementary material

The online version of this article (doi:10.1007/s00228-012-1466-4) contains supplementary material, which is available to authorized users.

The impact of quality and duration of enoxaparin therapy on recurrent venous thrombosis in children

BACKGROUND

Venous thromboembolism (VTE) and recurrent venous thromboembolism (rVTE) are rare, but significant problems in pediatrics. Current recommendations for anticoagulant therapy arise from adult literature, and there is little data on clinical outcomes following therapeutic low-molecular-weight heparin in children.

METHOD

All patients <19 years of age that were diagnosed with a VTE or right atrial thrombus via standard imaging methods at St. Jude Children's Research Hospital were retrospectively identified from January 2004 through August 2008. Demographic characteristics, coexisting clinic conditions, description of anticoagulant therapy, and record of rVTE were chronicled following a comprehensive chart review. Descriptive statistics of clinical characteristics and anticoagulation are presented.

RESULTS

Venous thrombosis was identified in 149 children with 21% (31/149) developing a rVTE. Coexisting clinical conditions were identified in 93% of children at initial diagnosis with 48% (71/149) of patients having a coexisting malignancy. Seventy-seven percent (114/149) of children received anticoagulant therapy with UFH (10/114) or enoxaparin (104/114). Neither duration of enoxaparin therapy (>6, 3-6, <3 months) (P = 0.61), nor quality of therapy (≥75% of time on anticoagulation spent with an anti-FXa of 0.5-1.0 U/ml) (P = 1.0) were found to be protective against rVTE.

CONCLUSION

Anticoagulation with enoxaparin based on adult literature may be suboptimal in preventing rVTE in pediatric populations. Future prospective randomized controlled trials in pediatrics using clinical outcomes with anticoagulant therapy are urgently needed.

The Switch Back Ross Operation: Report of Two Cases With Good Medium-to-Long-Term Follow-Up

Submitted July 20, 2011; Accepted October 6, 2011. Neoaortic root dilatation and neoaortic valve regurgitation following the arterial switch operation for transposition of the great arteries may ultimately require neoaortic root and/or neoaortic valve surgery. The ideal surgical approach to these lesions remains debatable. Hazekamp et al, in 1997, introduced the replacement of the neoaortic root by the neopulmonary autograft and named this procedure the switch back Ross operation. We report two patients who were successfully treated at our institution with the switch back Ross operation, with good results at, respectively, four- and five-year follow-up.

Vitamin K antagonists in children with heart disease: height and VKORC1 genotype are the main determinants of the warfarin dose requirement

Managing vitamin K antagonist (VKA) therapy is challenging in children because of a narrow therapeutic range and wide inter- and intra-individual variability in dose response. Only a few small studies have investigated the effect of nongenetic and genetic factors on the dose response to VKAs in children. In a cohort study including 118 children (median age 9 years; range, 3 months-18 years) mostly with cardiac disease, we evaluated by multivariate analysis the relative contribution of nongenetic factors and VKORC1/CYP2C9/CYP4F2 genotypes on warfarin (n = 83) or fluindione (n = 35) maintenance dose and the influence of these factors on the time spent within/above/below the range. The results showed that height, target international normalized ratio and VKORC1 and CYP2C9 genotypes were the main determinants of warfarin dose requirement, accounting for 48.1%, 4.4%, 18.2%, and 2.0% of variability, respectively, and explaining 69.7% of the variability. Our model predicted the warfarin dose within 7 mg/wk in 86.7% of patients. None of the covariates was associated with the time spent above or below the international normalized ratio range. Whether this model predicts accurately the effective maintenance dose is currently being investigated.