Dosing and monitoring of enoxaparin (Low molecular weight heparin) therapy in children

Enoxaparin treatment dosing for venous thromboembolism in pediatric patients with obesity

BACKGROUND

The optimal enoxaparin dosing for treatment of venous thromboembolism (VTE) in pediatric patients with obesity remains uncertain. We described the mean enoxaparin dose required to attain anti-factor Xa (anti-Xa) levels of 0.5-1 unit/mL in pediatric patients with obesity.

METHODS

Pediatric patients with obesity (body mass index [BMI] ≥95th percentile) who received treatment dose of enoxaparin from 2013 to 2022 and had at least one appropriately timed anti-Xa level were retrospectively evaluated. Daily enoxaparin dose required to achieve an anti-Xa level of 0.5-1 unit/mL was reviewed and compared by the severity of obesity. The correlation coefficients between enoxaparin dose requirement and BMI, BMI percentile, and weight were measured by Spearman's rank correlation coefficient.

RESULTS

Pediatric patients with obesity (n = 89) required a mean enoxaparin dose of 0.8 ± 0.18 mg/kg twice daily to attain a therapeutic anti-Xa level. Children with BMI 95th-99th percentile and weight ≤100 kg achieved the target level on a significantly higher weight-based enoxaparin dose compared to BMI greater than 99th percentile (0.95 ± 0.15 vs. 0.75 ± 0.15 mg/kg twice daily; p < .001) and weight greater than 100 kg (0.95 ± 0.14 vs. 0.7 ± 0.12 mg/kg twice daily; p < .001). BMI, BMI percentile, and weight showed a moderate to strong negative correlation with enoxaparin dose requirement.

CONCLUSIONS

Pediatric patients with obesity required a lower weight-based dose of enoxaparin to achieve a therapeutic anti-Xa than the recommended starting dose of 1 mg/kg twice daily for treatment of VTE. Among obesity indices, weight showed the strongest negative correlation with total daily enoxaparin requirement.

Characterizing Enoxaparin's Population Pharmacokinetics to Guide Dose Individualization in the Pediatric Population

BACKGROUND AND OBJECTIVE

Pediatric dosing of enoxaparin was derived based on extrapolation of the adult therapeutic range to children. However, a large fraction of children do not achieve therapeutic anticoagulation with initial dosing. We aim to use real-world anti-Xa data obtained from children receiving enoxaparin per standard of care to characterize the population pharmacokinetics (PopPK).Author names: Please confirm if the author names are presented accurately and in the correct sequence (given name, middle name/initial, family name). Also, kindly confirm the details in the metadata are correct.The author names are accurately presented and the metadata are correct.  METHODS: A PopPK analysis was performed using NONMEM, and a stepwise covariate modeling approach was applied for the covariate selection. The final PopPK model, developed with data from 1293 patients ranging in age from 1 day to 18 years, was used to simulate enoxaparin subcutaneous dosing for prophylaxis and treatment based on total body weight (0-18 years, TBW) or fat-free mass (2-18 years, FFM). Simulated exposures in children with obesity (body mass index percentile ≥95th percentile) were compared with those without obesity.

RESULTS

A linear, one-compartment PopPK model that included allometric scaling using TBW (<2 years) or FFM (≥2 years) characterized the enoxaparin pharmacokinetic data. In addition, serum creatinine was identified as a significant covariate influencing clearance. Simulations indicated that in patients aged <2 years, the recommended 1.5 mg/kg TBW-based dosing achieves therapeutic simulated concentrations. In pediatric patients aged ≥2 years, the recommended 1.0 mg/kg dose resulted in exposures more comparable in children with and without obesity when FFM weight-based dosing was applied.

CONCLUSION

Using real-world data and PopPK modeling, enoxaparin's pharmacokinetics were characterized in pediatric patients. Using FFM and twice-daily dosing might reduce the risk of overdosing, especially in children with obesity.

Anticoagulation in Pediatric Patients

The use of antithrombotic agents is increasing in infants, children and adolescents. The more recent routine inclusion of children in FDA-monitored clinical trials has propelled the rapid accumulation of safety and efficacy data on these agents in pediatric patients. Antithrombotic agents in current use include indirect or antithrombin-dependent anticoagulants, intravenous direct thrombin inhibitors, direct oral anticoagulants (DOACs) targeting thrombin or factor Xa, antiplatelet agents and thrombolytic therapies. Each class of antithrombotic agent has distinct mechanisms of action, clearance routes, half-lives, safety and dosing. Anticoagulant efficacy is dependent upon the specific clinical indication and stability of the pediatric patient. Duration of anticoagulant course is also dependent upon the clinical indication as well as rate of thrombus resolution. This manuscript reviews the mechanism of action, route of administration, route of clearance and plasma half-life for the antithrombotic agents in current use in children. Use of anticoagulation in the context of thrombolytic therapy is discussed.

Efficacy, Safety, and Pain Level of Subcutaneous Catheter Use for Administration of Granulocyte Colony-Stimulating Factor (G-CSF) in Children With Cancer: A Randomized Pilot Study

Background: The aim of this study was to explore the efficacy, safety, and pain level of granulocyte colony-stimulating factor (G-CSF) administration via a subcutaneous catheter compared with direct injection in children with cancer. Method: This was a pilot randomized controlled trial of standard G-CSF administration versus subcutaneous catheter administration. Children 2-15 years of age who were beginning G-CSF after their first chemotherapy cycle and anticipated to receive G-CSF following the next three cycles of chemotherapy were eligible. Efficacy, safety, and pain were as outcomes of the study. Results: Twenty-nine children with cancer (median age 12 years) were enrolled in the study (16 children in the subcutaneous catheter group and 13 children in the direct injection group). During Cycle 2, the median number of days to reach absolute neutrophil count (ANC) ≥ 500/mm3 was greater among those in the subcutaneous catheter group (12 vs. 10; p  =  .02). In Cycle 3, however, the subcutaneous catheter group received fewer doses of G-CSF (8 vs. 12; p  =  .004). No complications related to subcutaneous catheter use were observed. No differences in the visual analog scale pain score were observed between groups in Cycles 1 to 3; however, in Cycle 4, children in the subcutaneous catheter group had lower median pain scores than those in the direct subcutaneous injection group (Mdn  =  0, [IQR]  =  0-2 vs. Mdn  =  1, IQR  =  0-6; p < 0.01). Conclusion: Results demonstrated administering G-CSF via a subcutaneous catheter enables ANC to recover with no pain or complications associated with its use. Thus, oncology teams may consider this administration method to be used in children with cancer.

Post-operative Anticoagulation Strategy Following Comprehensive Stage 2 Procedure for Single Ventricle Physiology

Thrombosis, especially thrombosis of the pulmonary artery, is a large contributor to morbidity and mortality following comprehensive stage 2 procedure for single ventricle cardiac physiology. A peri-operative management protocol was implemented at our institution in March 2010. It includes 6 weeks of therapeutic anticoagulation post-operatively to mitigate the thrombotic risks in this patient population. This is a retrospective study of hospitalized children who received post-operative anticoagulation following a comprehensive stage 2 procedure for single ventricle cardiac physiology at a free-standing children's hospital. The primary objectives are to describe our institution's anticoagulation strategy and report on the number of thromboses and major bleeding episodes in the 6 weeks post-operatively. Secondary objectives include the dose of enoxaparin required to obtain a therapeutic low-molecular weight anti-factor-Xa (AFXaLMWH) level, and the number of patients outside of the therapeutic range. A total of 71 infants were included in the final analysis. Four patients experienced a thrombosis episode and three patients experienced clinically significant bleeding. The mean dose of enoxaparin required to obtain a therapeutic AFXaLMWH level between 0.5-1 unit/mL was 1.23 mg/kg SQ every 12 h and 37% of patients achieved goal AFXaLMWH levels with the initial starting dose of enoxaparin 1 mg/kg SQ every 12 h. We describe a 9-year experience of anticoagulation after single ventricle palliation. Anticoagulation with therapeutic AFXaLMWH goals of 0.5-1 unit/mL may reduce the rates of clinically significant thrombosis post-operatively in this population and appears safe without increase in significant bleeding episodes when compared to a historical cohort. Further studies comparing this population to those who do not receive post-operative anticoagulation are warranted.

How to use low-molecular-weight heparin to treat neonatal thrombosis in clinical practice

Among children, neonates have the highest incidence of thrombosis due to risk factors such as catheter instrumentation, an evolving coagulation system and congenital heart disease. Low-molecular-weight heparins (LMWHs) are the most commonly used anticoagulants in neonates. Published guidelines delineate dosing and monitoring protocols for LMWH therapy in newborns. However, challenging clinical situations frequently present that warrant healthcare providers to think critically beyond the range of guidelines, and judiciously resolve specific problems. This review describes the use of LMWH in the neonatal population, including practical aspects such as route and site of administration, preparation from concentrated formulations and methods to minimize pain of subcutaneous injection. It is followed by a discussion on dosing, monitoring and outcomes of LMWH therapy in neonates. The risk of recurrence of thrombosis in neonates after LMWH therapy is approximately 3% based on a pooled analysis of studies reporting this outcome over the last 24 years. The article concludes with an overview of the side-effects of LMWH, including the risk of bleeding which is around 4% based on pooled analyses of more than 30 studies.

Enoxaparin Dose Requirements to Achieve Therapeutic Low-molecular-weight Heparin Anti-factor Xa Levels in Infants and Young Children

INTRODUCTION

Enoxaparin is commonly used to treat pediatric thrombosis. Several small retrospective studies have suggested that infants and young children require higher enoxaparin doses to achieve therapeutic anti-factor Xa levels compared with adults.

MATERIALS AND METHODS

This is a retrospective study of hospitalized children who received enoxaparin for the treatment of thrombosis at a free-standing children's hospital. The primary objective was to ascertain the enoxaparin dose required to achieve an anti-factor Xa level of 0.5 to 1.0 U/mL among 4 age groups in a large cohort of infants and young children between 60 days and 5 years of age.

RESULTS

A total of 176 infants and children were evaluated. The majority of patients were less than 1 year of age (n=104). An inverse relationship between enoxaparin dose needed to achieve therapeutic anti-factor Xa levels and patient age was noted, particularly in the first year of life. Patients who were 60 days to less than 7 months at the time of enoxaparin initiation (n=73) required the highest mean dose among the age groups at 1.73 mg/kg subcutaneously every 12 hours (P<0.0001).

CONCLUSION

Infants and young children require higher doses of enoxaparin to achieve therapeutic anti-factor Xa levels compared with adults.

The Trilogy of SARS-CoV-2 in Pediatrics (Part 3): Thrombosis, Anticoagulant, and Antiplatelet Considerations

The hypercoagulable state induced by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) affects all patients regardless of age. The incidence of venous thromboembolism in pediatric patients with SARS-CoV-2-related illnesses is not well established. Although deep vein thrombosis is rare in children in the absence of risk factors, coagulopathy and the development of thromboses have been described in pediatric patients with acute COVID-19 and multisystem inflammatory syndrome. This comprehensive review provides a detailed overview of SARS-CoV-2-associated coagulopathy as well as strategies for optimizing the evaluation, management, and prevention of thrombosis in pediatric patients.

Enoxaparin Reduces Catheter Associated Venous Thrombosis Following Infant Cardiac Surgery

BACKGROUND

Central venous catheter (CVC) related venous thrombosis (VT) following pediatric cardiac surgery increases the morbidity and mortality. Although VT prevention using low dose anticoagulation has proven ineffective, anticoagulation using high dose enoxaparin to achieve a therapeutic anti-xa level has not been studied. We hypothesized that high dose enoxaparin would reduce VT after pediatric cardiac surgery.

METHODS

Enoxaparin was administered to infants < 150 days when post-operative CVC duration was anticipated to extend beyond 5 days. The primary outcome was the rate of VT, re-exploration for bleeding, and post-operative red blood cell (RBC) transfusions per 1,000 CVC days.

RESULTS

From 2012-2019, 157 infants were treated with enoxaparin. Infants were divided into two groups: 1) SubTherapeutic (SubTher) (N = 51) - therapeutic anti-xa level (0.5-1.0 IU/mL) was not achieved, 2) Therapeutic (Ther) (N = 106) - therapeutic anti-xa level was achieved. Baseline demographics demonstrated a lower age at operation within the Ther group. The SubTher group had a higher VT rate/1,000 CVC days (8.2) compared to the Ther group (2.6; p=0.005). Re-exploration for bleeding was similar between groups. The number of post-operative RBC transfusions/1,000 CVC days was significantly greater in the SubTher group (109.4 vs. 81.6; p=0.008). Multivariate analysis demonstrated that higher median anti-xa levels reduced the risk of VT (OR 0.02, CI: 0.001, 0.63; p = 0.02).

CONCLUSIONS

This data suggests that enoxaparin treatment resulting in a therapeutic anti-xa level reduces post-operative CVC associated VT without increasing bleeding complications.

Diagnosis and Management of Pediatric Venous Thromboembolism: New Therapies on the Horizon

ABSTRACT

The incidence of venous thromboembolism (VTE) is increasing in pediatric patients. Prompt recognition and evaluation of VTE in young patients could prevent significant morbidity or mortality. In contrast to VTE in adults, current treatment guidelines are largely based on expert opinion as limited randomized controlled trial data exist about the appropriate management in pediatric patients with traditional anticoagulants. However, recently approved direct-acting oral anticoagulants in adults are also being investigated in pediatric VTE and these data could inform future evidence-based treatment principles. Thus, healthcare providers must be well informed about the management of pediatric VTE and the data from these trials to date. This continuing medical education article will provide a summary of management of pediatric VTE with particular emphasis on emerging direct-acting oral anticoagulants.

Low-molecular-weight heparin versus unfractionated heparin in pediatric traumatic brain injury

OBJECTIVE

The incidence of venous thromboembolism (VTE) in patients with traumatic brain injury (TBI) has increased significantly. The Eastern Association for the Surgery of Trauma recommends using low-molecular-weight heparin (LMWH) over unfractionated heparin (UH) in pediatric patients requiring VTE prophylaxis, although this strategy is unsupported by the literature. In this study, the authors compare the outcomes of pediatric TBI patients receiving LMWH versus UH.

METHODS

The authors performed a 4-year (2014-2017) analysis of the pediatric American College of Surgeons Trauma Quality Improvement Program. All trauma patients (age ≤ 18 years) with TBI requiring thromboprophylaxis with UH or LMWH were potentially eligible for inclusion. Patients who had been transferred, had died in the emergency department, or had penetrating trauma were excluded. Patients were stratified into either the LMWH or the UH group on the basis of the prophylaxis they had received. Patients were matched on the basis of demographics, injury characteristics, vital signs, and transfusion requirements using propensity score matching (PSM). The study endpoints were VTE, death, and craniotomy after initiation of prophylaxis. Univariate analysis was performed after PSM to compare outcomes.

RESULTS

A total of 2479 patients met the inclusion criteria (mean age 15.5 ± 3.7 years and 32.0% female), of which 1570 (63.3%) had received LMWH and 909 (36.7%) had received UH. Before PSM, patients receiving UH were younger, had a lower Glasgow Coma Scale score, and had a higher Injury Severity Score. Patients treated in pediatric hospitals were more likely to receive UH (12.9% vs 9.0%, p < 0.001) than patients treated in adult hospitals. Matched patients receiving UH had a higher incidence of VTE (5.1% vs 2.9%, p = 0.03).

CONCLUSIONS

LMWH prophylaxis in pediatric TBI appears to be more effective than UH in preventing VTE. Large, multicenter prospective studies are warranted to confirm the superiority of LMWH over UH in pediatric patients with TBI. Moreover, outcomes of VTE prophylaxis in the very young remain understudied; therefore, dedicated studies to evaluate this population are needed.

Secondary Anticoagulation Prophylaxis for Catheter-Related Thrombosis in Pediatric Intestinal Failure: Comparison of Short- Vs Long-Term Treatment Protocols

INTRODUCTION

Catheter-related thrombosis (CRT) is a devastating complication of central venous catheters in children with intestinal failure (IF), but the optimal preventive therapy of CRT is unknown. This study assessed the efficacy and safety of 2 protocols of secondary anticoagulation prophylaxis with low-molecular-weight heparin (LMWH).

METHODS

This is a comparative cohort study of children from 2 IF programs who received secondary anticoagulation prophylaxis with LMWH for CRT. The short-term protocol group (N = 13) received therapeutic dosing until thrombus resolution or ≤3 months. In the long-term protocol group (N = 26), prophylactic dosing continued until line removal. Patients underwent routine annual vascular ultrasound and were followed for ≥1 year. The primary outcome was development of secondary thrombosis; post hoc analysis assessed rates of secondary thrombosis at 12 months.

RESULTS

Patient demographics were similar between groups. Secondary thrombosis occurred in 8 of 13 (62%) patients in the short-term group and in 9 of 26 (35%) in the long-term protocol group (P = .019) in a median time of 144.5 and 689 days, respectively (P = .01). Secondary thrombosis within 12 months occurred in 7 of 13 (54%, short term) and 2 of 26 (8%, long term) patients (P = .001). Secondary thrombosis was associated with catheter replacements (23.5 vs 5.5 catheters per 1000 catheter days; P = .016) and longer daily parenteral nutrition (PN) infusion (24 vs 15.25 hours; P = .044). Compliance was good (>80% of doses) in 92% of patients.

CONCLUSIONS

Long-term secondary anticoagulation prophylaxis with LMWH reduces the incidence of secondary thrombosis and should be considered in children with CRT that require PN for prolonged periods of time.

Challenges and Opportunities in the Pharmacological Treatment of Acute Venous Thromboembolism in Children

Venous thromboembolism (VTE) is an important but historically under-recognized problem in pediatrics, with an incidence concentrated in hospitalized children. A number of specific VTE diseases with discrete triggers have been described, but the most common pediatric trigger is the presence of central venous access devices. VTE diseases, though heterogenous in etiology, are linked by the common therapeutic strategies shared by their management. Historically, the most commonly used drug therapies have been unfractionated heparin, low-molecular-weight heparins, and vitamin K antagonists, based on extrapolation from adult data rather than any specific pediatric trials. Although these widely used drugs appear safe and effective in expert hands, the historical lack of pediatric data is problematic in view of the recognized significant differences between children and adults with regards to hemostatic physiology, VTE etiology, and drug pharmacokinetics. The increasing adult usage of novel VTE pharmacotherapies such as direct oral anticoagulants (DOACs) has led to considerable interest in exploring the pediatric applications of these newer drugs. This review summarizes the advantages and disadvantages of existing VTE pharmacotherapies and outlines emerging novel pediatric VTE therapies, particularly DOACs, within the context of the current pediatric trial landscape.

Age-specific differences in the in vitro anticoagulant effect of Bivalirudin in healthy neonates and children compared to adults

Bivalirudin is a reversible direct thrombin inhibitor that inhibits both bound and free thrombin and binds to the active (catalytic) and fibrinogen-binding sites of thrombin, with high affinity and specificity. Off-label use of bivalirudin in the paediatric population has increased, as an alternative to heparin, particularly in the setting of anticoagulation for patients undergoing coronary bypass surgery (CPB), extracorporeal life support (ECLS) and those on ventricular assist devices (VAD). This study aimed to determine the age-specific in vitro effect of bivalirudin in children compared to adults. Age-specific pools (neonates, ≤2 years, >2 to 5 years, 6 to 10 years, 11 to 17 years and Adults) were prepared using platelet poor plasma samples from 20 individuals per age group. Pooled plasma was spiked with increasing concentrations of Bivalirudin (from 0 g/mL to 10μg/mL), and thrombin inhibition was measured using standard coagulation assays. There was a significantly increased response to bivalirudin across all paediatric age groups as compared to adults. The age-specific difference in response to bivalirudin was specifically evident in neonates, where the potential to generate thrombin was decreased 2-fold compared to adults (p < 0.001). Our findings support the concept of age-specific pharmaco-dynamic responses to Bivalirudin and support the need for further ex vivo studies in hospitalised children to determine accurate clinical dosing recommendations.

Intravenous Enoxaparin in Pediatric Burn Patients: A Case Series

Patients with acute burns experience a hypercoagulable state that may necessitate the use of anticoagulants to prevent the complications of venous thromboembolism (VTE). Enoxaparin is a low molecular weight heparin that is commonly used for this purpose; however, the traditional SC route of administration poses potential limitations in the pediatric burn population. These include pain upon injection, increased anxiety, erroneous absorption and distribution, and difficulty in finding an administration site when burns encompass a large percentage of body surface area. As a result, the IV route of administration may be preferable in these patients. To date, a limited number of studies in critically ill pediatric patients have been performed. In this report, we present a case series of 3 pediatric burn patients who initially received SC enoxaparin and were transitioned to IV enoxaparin for VTE prophylaxis. The patients were 2, 8, and 10 years old. Burn involvement ranged from 8% to 75% total body surface area, and all patients had central line access. Adequate prophylactic low molecular weight heparin anti-Xa peak concentrations (0.1-0.3 international units/mL) were achieved with IV doses ranging from 0.35 to 0.5 mg/kg administered every 12 hours. No adverse effects, major bleeding events, or treatment failures occurred.

Retrospective comparison of two enoxaparin dosing and monitoring protocols at a pediatric hospital

PURPOSE

The study analyzes the effectiveness and safety of a higher than standard enoxaparin dosing protocol implemented for pediatric patients requiring initiation of therapeutic anticoagulation.

METHODS

A retrospective review of 2 enoxaparin dosing and monitoring protocols was performed. The standard protocol used 1.5 mg/kg/dose (in patients <3 months of age) and 1 mg/kg/dose (in patients ≥3 months of age) with anti-Xa monitoring following the first dose. The high-dose protocol was implemented at 1.7 mg/kg/dose (in patients <3 months of age), 1.5 mg/kg/dose (in patients 3 through 11 months of age), 1.2 mg/kg/dose (in patients 1 through 4 years of age), and 1.1 mg/kg/dose (in patients 5 through 17 years of age), with anti-Xa monitoring after the second dose. Primary outcomes were number of dosing changes prior to and time to first target anti-Xa level. Secondary outcomes included percentage of patients with anti-Xa levels above target level.

RESULTS

The median number of dose changes required to achieve a target anti-Xa level was 1 (interquartile range [IQR], 0-1.5) and 0 (IQR, 0-1) for the standard-dose (n = 87) and high-dose groups (n = 132) (p = 0.17), respectively. The median number of dose adjustments to achieve target anti-Xa levels in the 3 through 11 months of age subgroup declined from 2 (IQR, 1-3.25) to 0 (IQR, 0-1) in the standard- versus high-dose groups, respectively (p < 0.01). No difference was seen in other age subgroups. Patients with above-target levels did not differ statistically between groups.

CONCLUSION

Initiating enoxaparin at higher doses in pediatric patients may result in fewer dosing changes than standard dosing. Benefit was demonstrated for the 3-11 months of age high-dose subgroup. Across all groups, the high-dose strategy was safe and did not result in a statistically significant increase in above-target levels.

A Critical Evaluation of Enoxaparin Dose Adjustment Guidelines in Children

OBJECTIVES

The purposes of this study are to perform a large-scale evaluation of the standardized dosage adjustment nomogram recommended by the American College of Chest Physicians (CHEST) for the management of enoxaparin in hospitalized pediatric patients and to determine the necessity of routine and repeated anti-factor Xa (anti-Xa) levels.

METHODS

A retrospective cohort study was designed, and charts were reviewed in a single tertiary care institution for all patients who received enoxaparin between October 1, 2010, through September 30, 2016. Patients were included if they were receiving treatment doses of enoxaparin according to the pediatric CHEST guidelines, had a subtherapeutic or supratherapeutic anti-Xa level drawn at 3.5 to 6 hours after a dose, had a dose changed in an attempt to attain a therapeutic anti-Xa level, and had a second anti-Xa level drawn 3.5 to 6 hours after the dose change. Descriptive statistical methods were used to characterize the ability of dose adjustment via a nomogram to attain an anti-Xa of 0.5 to 1 unit/mL.

RESULTS

A total of 467 patients were identified who received the appropriate initial dose and dosage adjustment and whose levels were drawn according to the CHEST guidelines. In patients who had an initial anti-Xa level of <0.35 units/mL and received the nomogram recommended dose increase of 25% ± 5%, 28 out of 96 patients (29.2%) reached therapeutic levels. Of 197 patients who had an initial anti-Xa level between 0.35 and 0.49 units/mL and who received the nomogram recommended dose increase of 10% ± 5%, 116 (58.9%) reached therapeutic levels. Of 50 patients with an initial anti-Xa level between 1.1 and 1.5 units/mL and who received the nomogram dose decrease of 20% ± 5%, 31 (62%) reached therapeutic levels.

CONCLUSIONS

The current dosage adjustment nomogram recommended by the CHEST guidelines does not reliably lead to therapeutic anti-Xa levels when used to adjust enoxaparin doses in pediatric patients.

Analysis of Patient Characteristics and Risk Factors for Thrombosis After Surgery for Congenital Heart Disease

OBJECTIVES

Thrombosis is a cause of morbidity in 4-15% of children who undergo pediatric cardiac surgery. Data on how to prevent this complication are sorely needed. We aimed to identify risk factors for thrombosis following pediatric cardiac surgery and determine if use of low molecular weight heparin prophylaxis is associated with a reduction in thrombosis risk.

DESIGN

Retrospective cohort study.

SETTING

Tertiary pediatric cardiovascular ICU.

PATIENTS

Patients who underwent cardiac surgery between June 2014 and December 2015.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Data from patients with venous or arterial thrombosis confirmed by radiologic studies were matched two-to-one to controls based on age, Society of Thoracic Surgeons-European Association for Cardio-Thoracic Surgery mortality category, and gender. Thrombosis was detected in 33 patients (6.2%): 25 patients (76%) had venous thromboses, five patients (15%) had arterial thromboses, and three patients (9%) had both. Median time to thrombosis detection was 13 days (25-75%; 7-31 d). On multivariate analysis, which included adjustment for postoperative disease severity, fresh frozen plasma exposure was independently associated with thrombosis (odds ratio, 3.7; 95% CI, 1.4-9.4). Twenty-eight patients (85%) had central venous catheter-related thromboses. Low molecular weight heparin prophylaxis use in this subset of patients was not statistically different from controls (50% vs 45%, respectively; p = 0.47). On multivariable analysis, fresh frozen plasma exposure was also independently associated with central venous catheter-related thrombosis (odds ratio, 3.6; 95% CI, 1.2-10.6).

CONCLUSIONS

The occurrence of thrombosis after pediatric cardiac surgery at our institution was 6.2%, similar to what has been reported in other studies, despite frequent use of low molecular weight heparin. Further study is needed to determine the role of low molecular weight heparin for thromboprophylaxis and the relationship between fresh frozen plasma and thrombosis risk in children who undergo cardiac surgery.

Management of thrombosis in children and neonates: practical use of anticoagulants in children

Venous thrombosis (VTE) in children and neonates presents numerous management challenges. Although increasing in frequency, VTE in children and neonates is still uncommon compared with adults. The epidemiology of VTE is vastly different in neonates vs children vs adolescents vs adults. In reality, pediatric thrombosis should be viewed as a multitude of rare diseases (eg, renal vein thrombosis, spontaneous thrombosis, catheter-related thrombosis, cerebral sinovenous thrombosis), all requiring different approaches to diagnosis and with different short- and long-term consequences, but linked by the use of common therapeutic agents. Further, children have fundamentally different physiology in terms of blood flow, developmental hemostasis, and, likely, endothelial function. The American Society of Hematology 2017 Guidelines for Management of Venous Thromboembolism: Treatment of Pediatric VTE provides up-to-date evidence-based guidelines related to treatment. Therefore, this article will focus on the practical use of therapeutic agents in the management of pediatric VTE, especially unfractionated heparin, low-molecular-weight heparin, and oral vitamin K antagonists, as the most common anticoagulants used in children. Direct oral anticoagulants (DOACs) remain in clinical trials in children and should not be used outside of formal trials for the foreseeable future.

Pharmacokinetics of Enoxaparin After Renal Transplantation in Pediatric Patients

Enoxaparin is commonly used in the prevention of renal allograft vascular thrombosis but off-label in children, and no consensus exists regarding the optimal dosing and dose adjustment. In this retrospective study, 444 anti-Xa levels were obtained from 30 pediatric renal transplant recipients in order to investigate enoxaparin population pharmacokinetics. The main results were (1) 25% of children achieved the target anti-Xa activity 36 hours after initiation of treatment, (2) anti-Xa time courses were best described by a 1-compartment open model with first-order absorption, (3) body weight but not renal function was the sole covariate influencing clearance and volume of distribution, and (4) large between-subject and between-occasion variabilities in anti-Xa activity were observed. However, creatinine-based estimated glomerular filtration rate in the first post-renal transplantation hours may not reliably reflect the actual renal function of the children. Based on the final population model, a Bayesian-based program was developed in order to estimate the individual pharmacokinetic parameters on a single anti-Xa measurement, allowing determination of the next enoxaparin dose that will quickly achieve an appropriate anti-Xa activity (targeting 0.3-0.5 IU/mL) and anticoagulation. Finally, these results should help standardize practices that remain to date largely heterogeneous in pediatric intensive care units.

Prevention of perioperative venous thromboembolism in pediatric patients: Guidelines from the Association of Paediatric Anaesthetists of Great Britain and Ireland (APAGBI)

The Association of Paediatric Anaesthetists of Great Britain and Ireland (APAGBI) Guidelines Working Group on Thromboprophylaxis in Children has reviewed the literature and where possible provided advice on the care of children in the perioperative period. Areas reviewed include the incidence of perioperative venous thromboembolism (VTE), risk factors, evidence for mechanical and chemical prophylaxis, and complications. Safe practice of regional anesthesia with anticoagulant prophylaxis is detailed. In summary, there are few areas of strong evidence. Routine prophylaxis cannot be recommended for young children. Postpubertal adolescents (approximately 13 years and over) are at a slightly increased risk of VTE and should be assessed for prophylaxis and may warrant intervention if other risk factors are present. However, the incidence of VTE is significantly lower than in the adult population. This special interest review presents a summary and discussion of the key recommendations, a decision-making algorithm and a risk assessment chart. For the full guideline, go to www.apagbi.org.uk/publications/apa-guidelines.

The catastrophic antiphospholipid syndrome in children

PURPOSE OF REVIEW

To review the difficult syndrome of catastrophic antiphospholipid syndrome, emphasizing new developments in the diagnosis, pathogenesis and treatment.

RECENT FINDINGS

Few recent publications directly address pediatric catastrophic antiphospholipid syndrome (CAPS). Most articles are case reports or are data from adult and pediatric registries. The major factors contributing to most pediatric catastrophic antiphospholipid syndrome include infection and the presence of antiphospholipid antibodies, but complement activation also is important in creating diffuse thrombosis in the microcirculation. Treatment of the acute emergency requires anticoagulation, suppression of the hyperinflammatory state and elimination of the triggering infection. Inhibition of complement activation appears to improve outcome in limited studies, and suppression of antiphospholipid antibody formation may be important in long-term management.

SUMMARY

CAPS, an antibody-mediated diffuse thrombotic disease of microvasculature, is rare in childhood but has high mortality (33-50%). It requires prompt recognition and aggressive multimodality treatment, including anticoagulation, anti-inflammatory therapy and elimination of inciting infection and pathogenic autoantibodies.

Population pharmacokinetics of enoxaparin in early stage of paediatric liver transplantation

AIMS

Preventing post-liver transplantation (LT) hepatic artery and portal vein thrombosis includes enoxaparin administration. Enoxaparin pharmacokinetics (PK) has not been investigated in children following LT. We described an enoxaparin PK model in 22 children the first week following LT.

METHODS

Anti-Xa activity time-courses were analysed using a nonlinear mixed effects approach with Monolix version 2016R.

RESULTS

Anti-Xa activity time-courses were well described by a one-compartment model with first order absorption and elimination. Bodyweight prior to surgery (BW_PREOP ) and the related postoperative variation (BW(t)) were the main covariates explaining CL and V between subject variabilities. Parameter estimates were CL_i  = CL_TYP * (BW_PREOP /70)^3/4 ; V_i  = V_TYP * (BW(t)/70)¹ ; where typical clearance (CL_TYP ) and typical volume of distribution (V_TYP ) were 1.23 l h^-1 and 14.6 l, respectively. Standard dosing regimens of 50 IU kg^-1  12 h^-1 were insufficient to reach the target range of anti-Xa activity of 0.2-0.4 IU ml^-1 . Specifically, seven children (32%) never attained the target range during the whole period of treatment and all children were at least once underdosed. According to the final results, we simulated individualized dosing regimens within 4 h following the first administration. More than 100 IU kg^-1  12 h^-1 are suggested to reach the target range of anti-Xa activity of 0.2-0.4 IU ml^-1 from the first day.

CONCLUSION

Thanks to this model, the initial and maintenance doses could be assessed to rapidly achieve the target range. Higher doses per kg, especially in the youngest children, are suggested.

Anticoagulant prophylaxis and therapy in children: current challenges and emerging issues

This review is aimed at describing the unique challenges of anticoagulant prophylaxis and treatment in children, and highlighting areas for research for improving clinical outcomes of children with thromboembolic disease. The evidence presented demonstrates the challenges of advancing the evidence base informing optimal management of thromboembolic disease in children. Recent observational studies have identified risk factors for venous thromboembolism in children, but there are few interventional studies assessing the benefit-risk balance of using thromboprophylaxis in risk-stratified clinical subgroups. A risk level-based framework is proposed for administering mechanical and pharmacological thromboprophylaxis. More research is required to refine the assignment of risk levels. The anticoagulants currently used predominantly in children are unfractionated heparin, low molecular weight heparin, and vitamin K antagonists. There is a paucity of robust evidence on the age-specific pharmacology of these agents, and their efficacy and safety for prevention and treatment of thrombosis in children. The available literature is heterogeneous, reflecting age-specific differences, and the various clinical settings for anticoagulation in children. Monitoring assays and target ranges are not well established. Nevertheless, weight-based dosing appears to achieve acceptable outcomes in most indications. Given the limitations of the classical anticoagulants for children, there is great interest in the direct oral anticoagulants (DOACs), whose properties appear to be particularly suitable for children. All DOACs currently approved for adults have Pediatric Investigation Plans ongoing or planned. These are generating age-specific formulations and systematic dosing information. The ongoing pediatric studies still have to establish whether DOACs have a positive benefit-risk balance in the various pediatric indications and age groups.

Evaluation of the age-dependent dosing recommendations for the administration of daily tinzaparin in children with thrombosis

Essentials The once-daily dosing of tinzaparin provides an advantage over other low molecular weight heparins. The recommended age-dependent doses of tinzaparin in children have not previously been validated. Once-daily administration of tinzaparin is a safe and effective treatment of childhood thrombosis. Recommended doses are appropriate but monitoring may be required due to inter-individual variation.

SUMMARY

Background The recommended starting doses of tinzaparin for the treatment of thrombosis in children have not previously been validated. There are few data to support the efficacy and safety of once-daily tinzaparin dosing in children with thrombosis. Objectives To investigate the use of tinzaparin for the treatment of childhood thrombosis, and to evaluate the age-dependent dosing recommendations and define outcomes in terms of efficacy and safety. Methods This was a retrospective cohort study of children aged 0 to < 16 years treated for thrombosis at a large teaching hospital in the UK between 2008 and 2015. Medical records were reviewed to evaluate tinzaparin dosing, anti-activated factor X (FXa) levels, and patient outcomes. Results Seventy-nine children were identified as having received tinzaparin. Dosing information was available for 57. Younger children required higher doses to reach a therapeutic level. The therapeutic dose requirement varied within age groups, supporting the use of anti-FXa monitoring. Over a median follow-up of 35 months, there were 13 (16%) bleeding episodes (two major; seven clinically relevant but non-major; and four minor). There were two (3%) recurrent episodes of thrombosis. Children were treated for a median duration of 3 months, and the majority (86%) remained on tinzaparin for the duration of their anticoagulant therapy. Conclusion Once-daily tinzaparin is a safe and effective treatment for childhood thrombosis, with rates of recurrence and bleeding similar to those for other anticoagulants used in children. The recommended starting doses are appropriate, but anti-FXa monitoring may be required, owing to interindividual variability in the therapeutic dose requirement.

Six Weeks Versus 3 Months of Anticoagulant Treatment for Pediatric Central Venous Catheter-related Venous Thromboembolism

OBJECTIVE

Central venous catheters (CVCs) are the single most important predisposing factor for the development of pediatric venous thromboembolism (VTE). Treatment recommendations suggest anticoagulation for the duration of 6 weeks to 3 months. This project investigated clinical outcomes associated with 6 weeks compared with 3 months of enoxaparin therapy following diagnosis of a CVC-related VTE.

METHODS

This retrospective cohort study enrolled patients aged 18 years and below treated with enoxaparin with/without unfractionated heparin for a radiologically confirmed CVC-related VTE. Patients were identified using the pharmacy database, radiologic imaging, and medical records. Patients were divided into 2 groups based on the duration of anticoagulation (6+1 or 12±2 wk) and data were analyzed using descriptive statistics.

RESULTS

Seventy-four patients were included. Higher rates of complete thrombosis resolution were observed in children treated for 6 weeks at treatment cessation (39.4%) and long-term follow-up (61.5%), compared with 3 months (11.8% and 9.0%, respectively).

CONCLUSIONS

Six weeks of treatment for CVC-related VTE may provide noninferior clinical outcomes compared with 3 months of anticoagulation. An international randomized-controlled trial (Kids-DOTT) is underway to explore the optimal duration of anticoagulation for acute-provoked VTE in children. This manuscript highlights that data from such studies is urgently needed.

IV Versus Subcutaneous Enoxaparin in Critically Ill Infants and Children: Comparison of Dosing, Anticoagulation Quality, Efficacy, and Safety Outcomes

OBJECTIVE

Subcutaneous enoxaparin is the mainstay anticoagulant in critically ill pediatric patients although it poses several challenges in this patient population. Enoxaparin infused IV over 30 minutes represents an attractive alternative, but there is limited experience with this route of administration in children. In this study, we assess dosing, anticoagulation quality, safety, and clinical efficacy of IV enoxaparin compared to subcutaneous enoxaparin in critically ill infants and children.

DESIGN

Retrospective single-center study comparing dosing, anticoagulation quality, safety, and clinical efficacy of two different routes of enoxaparin administration (IV vs subcutaneous) in critically ill infants and children. Key outcome measures included dose needed to achieve target antifactor Xa levels, time required to achieve target antifactor Xa levels, proportion of patients achieving target anticoagulation levels on initial dosing, number of dose adjustments, duration spent in the target antifactor Xa range, anticoagulation-related bleeding complications, anticoagulation failure, and radiologic response to anticoagulation.

SETTING

Tertiary care pediatric hospital.

PATIENTS

All children admitted to the cardiac ICU, PICU, or neonatal ICU who were prescribed enoxaparin between January 2014 and March 2016 were studied.

INTERVENTIONS

One hundred ten patients were identified who had received IV or subcutaneous enoxaparin and had at least one postadministration peak antifactor Xa level documented.

MEASUREMENTS AND MAIN RESULTS

Of the 139 courses of enoxaparin administered, 96 were therapeutic dose courses (40 IV and 56 subcutaneous) and 43 were prophylactic dose courses (20 IV and 23 subcutaneous). Dosing, anticoagulation quality measurements, safety, and clinical efficacy were not significantly different between the two groups.

CONCLUSIONS

Our study suggests that anticoagulation with IV enoxaparin infused over 30 minutes is a safe and an equally effective alternative to subcutaneous enoxaparin in critically ill infants and children.

Stability and Sterility of Enoxaparin 8 mg/mL Subcutaneous Injectable Solution

BACKGROUND: Enoxaparin is often diluted to accurately deliver doses to neonatal and infant patients. Current recommendations for dilutions may not be adequate for the smallest patients. METHODS: Review of dosing at our institution occurred, and an 8 mg/mL concentration of enoxaparin was chosen. A concentration of 8 mg/mL was compounded by diluting 0.4 mL of enoxaparin (100 mg/mL) into 4.6 mL of sterile water for injection into an empty sterile vial. Four syringes of the 8 mg/mL concentration were prepared by 5 technicians (20 total syringes). Stability and sterility testing occurred a 0, 7, 14, and 30 days. One-way repeated-measures analysis of variance was used to detect significant differences in Anti-Factor Xa concentrations at the testing time points. RESULTS: The dilution of enoxaparin was sterile at 30 days but exhibited significant degradation at the 30-day point (p < 0.05). CONCLUSION: A dilution of enoxaparin 8 mg/mL is stable and sterile for 14 days refrigerated but is not stable at 30 days.

Improving evidence on anticoagulant therapies for venous thromboembolism in children: key challenges and opportunities

Venous thromboembolism (VTE) is increasingly diagnosed in pediatric patients, and anticoagulant use in this population has become common, despite the absence of US Food and Drug Administration (FDA) approval for this indication. Guidelines for the use of anticoagulants in pediatrics are largely extrapolated from large randomized controlled trials (RCTs) in adults, smaller dose-finding and observational studies in children, and expert opinion. The recently FDA-approved direct oral anticoagulants (DOACs), such as dabigatran, rivaroxaban, apixaban, and edoxaban, provide potential advantages over oral vitamin K antagonists and subcutaneous low-molecular-weight heparins (LMWHs). However, key questions arise regarding their potential off-label clinical application in pediatric thromboembolic disease. In this Perspective, we provide background on the use of LMWHs such as enoxaparin as the mainstay of treatment of pediatric provoked VTE; identify key questions and challenges with regard to DOAC trials and future DOAC therapy in pediatric VTE; and discuss applicable lessons learned from the recent pilot/feasibility phase of a large multicenter RCT of anticoagulant duration in pediatric VTE. The challenges and lessons learned present opportunities to improve evidence for anticoagulant therapies in pediatric VTE through future clinical trials.

Feasibility and safety of enoxaparin whole milligram dosing in premature and term neonates

OBJECTIVE

The objective of our study was to determine the feasibility and safety of enoxaparin whole milligram dosing in premature and term neonates, and to assess response to treatment.

STUDY DESIGN

Retrospective study of neonates with thrombosis treated between January 2008 and December 2014.

RESULT

Nineteen premature and 21 term neonates were treated with whole milligram doses of enoxaparin. The mean starting and therapeutic enoxaparin doses were 1.72±0.17 and 1.86±0.17 mg kg(-1), respectively. Twenty-five (64%) reached therapeutic antifactor Xa (anti-Xa) levels with the starting dose, whereas 14 (36%) required dose adjustments. One neonate reached a supratherapeutic anti-Xa level (>1.0 IU ml(-1)) in the loading phase. No bleeding episodes occurred. The mean treatment duration was 12 weeks. Among 34 (85%) evaluable patients, 23 (68%) had a complete response, 9 (26%) partial and 2 (6%) had a stable thrombotic state.

CONCLUSION

Whole milligram dosing of enoxaparin for thrombosis is feasible, safe and effective in premature and term neonates.

[Heparin for clearance of peripherally inserted central venous catheter in newborns: an in vitro study]

Objective:

To compare the efficacy of two concentrations of heparin to clear the lumen of in vitro clotted neonatal peripherally inserted central catheters (PICCs).

Methods:

This is an in vitro, experimental quantitative study of 76 neonatal 2.0-Fr PICCs coagulated in vitro. The catheters were divided into two groups of 38 PICCs each. In both groups an infusion of low molecular weight heparin was administered with a dose of 25IU/mL for Group 1 and 50IU/mL for Group 2. The negative pressure technique was applied to the catheters of both groups at 5, 15 and 30min and at 4h to test their permeability. Kaplan-Meier survival analysis was used to verify the outcome of the groups according to time intervals.

Results:

The comparison between both groups in the first 5min showed that more catheters from Group 2 were cleared compared to Group 1 (57.9 vs. 21.1%, respectively). Kaplan-Meier survival analysis showed that less time was needed to clear catheters treated with 50IU/mL of heparin (p<0.001).

Conclusions:

The use of low molecular weight heparin at a concentration of 50IU/mL was more effective in restoring the permeability of neonatal PICCs occluded in vitro by a clot, and the use of this concentration is within the safety margin indicated by scientific literature.

A retrospective analysis of outcomes of dalteparin use in pediatric patients: a single institution experience

BACKGROUND

Dalteparin is a commonly used low molecular weight heparin (LMWH) with extensive safety data in adults. With distinct advantages of once daily dosing and relative safety in renal impairment, it has been used off-label in pediatric practice; however, age-based dosing guidelines, safety and efficacy data in children are evolving.

OBJECTIVES

To report our institutional experience with the use of dalteparin in the treatment and prophylaxis of venous thromboembolism (VTE) in pediatric patients.

PATIENTS/METHODS

Retrospective chart review of all children (0-18years) that received dalteparin from December 1, 2000 through December 31, 2011. Doses per unit body weight per day (units/kg/day) were calculated for age-based group comparisons.

RESULTS

Of 166 patients identified, 116 (70%) received prophylactic doses while 50 (30%) received therapeutic doses of dalteparin. Infants (<1year) required significantly higher weight-based dosing to achieve therapeutic anti-Xa levels compared to children (1-10years) or adolescents (>10-18years) (mean dose units/kg/day; 396.6 versus 236.7 and 178.8 respectively, p<0.0001). Overall response rate, including complete and partial thrombus resolution, was 83%. Bleeding complications were minor and the rates were similar in therapeutic and prophylaxis patients. No significant differences in dosing or bleeding events were noted based on obesity or malignancy.

CONCLUSIONS

In our experience, dalteparin is effective for prophylaxis and therapy of VTE in pediatric patients. Dosing should be customized in an age-based manner with close monitoring of anti-Xa activity in order to achieve optimal levels, prevent bleeding complications, and to allow full benefit of prevention or therapy of thrombotic complications.

A practical approach to the use of low molecular weight heparins in VTE treatment and prophylaxis in children and newborns

Low-molecular weight heparins are currently the most commonly used anticoagulants in children and newborns. However, since thrombotic complications rarely occur outside large children's hospitals, physicians often encounter some practical problems in managing these treatments when a pediatric thrombosis specialist is not available. The drug of choice is enoxaparin, due to its favorable FXa/FIIa ratio and the availability of pharmacokinetic and pharmacodynamic data. The treatment of acute thrombosis should be started with two daily injections but when compliance is an issue, a single daily administration schedule could be chosen for secondary prophylaxis ensuring careful measurement of the post 24-hour anti-FXa activity. Furthermore, a subcutaneous device may be a useful tool and a topical dermal anesthetic could be effective in controlling pain without affecting anti-FXa levels. In neonate and toddlers, where mini doses are frequently needed, the dead space of syringes and needles could represent an issue and therefore the use of insulin syringes without dead space is advisable, while a dilution of the drug is useful with other syringes. This article derives from a nonsystematic review of the available literature, with special attention to recent international guidelines and expert recommendations, combined to authors' clinical practice in large tertiary pediatric hospitals and will provide concise and practical information for the use of low-molecular weight heparin in childhood and infancy in a sort of "answering frequently asked questions."

Evaluation of Enoxaparin Dosing and Monitoring in Pediatric Patients at Children's Teaching Hospital

OBJECTIVES

The primary objective of this study was to evaluate whether empirical enoxaparin doses according to Chest guidelines resulted in therapeutic antifactor Xa concentrations in pediatric patients. Secondary objectives were to determine the median enoxaparin dose that resulted in therapeutic anticoagulation, the median time to therapeutic concentrations, and the percentage of patients who experienced major bleeding.

METHODS

Patients in a tertiary medical center who were <18 years of age and received treatment doses of enoxaparin between July 2007 and June 2010 were included. Patients with <2 antifactor Xa concentrations or with only supratherapeutic concentrations and doses that were higher than recommended by the guidelines were excluded. Subgroup analysis was conducted by dividing children into 4 age groups: <2 months of age, 2 months to <1 year of age, 1 year to <3 years of age, and 3 to 17 years of age.

RESULTS

Thirty-two patients were included in the study. Thirty-seven percent of the patients achieved a therapeutic drug level with empirical dosing. The therapeutic dose ranged from 1 to 1.9 mg/kg in patients <1 year old, and 0.6 to 1.5 mg/kg in those =1 year of age. Comparison of the median therapeutic doses for patients 2 months to <1 year to that for patients =1 year old using the Mann-Whitney U test showed the median doses to be significantly difierent between the 2 groups (p=0.01). The antifactor Xa level became therapeutic on day 5 (median). There were no major bleeding events.

CONCLUSION

Less than 40% of patients were therapeutic with empirical dosing, which supports findings from other studies that suggest a need for modification of empirical treatment dosing of enoxaparin in children.

Anticoagulant therapy in pediatrics

Thromboembolic episodes are disorders encountered in both children and adults, but relatively more common in adults. However, the occurrence of venous thromboembolism and use of anticoagulants in pediatrics are increasing. Unfractionated Heparin (UH) is used as a treatment and prevention of thrombosis in adults and critically ill children. Heparin utilization in pediatric is limited by many factors and the most important ones are Heparin Induced Thrombocytopenia (HIT) and anaphylaxis. However, Low Molecular Weight Heparin (LMWH) appears to be an effective and safe alternative treatment. Hence, it is preferred over than UH due to favorable pharmacokinetic and side effect profile. Direct Thrombin Inhibitors (DTI) is a promising class over the other anticoagulants since it offers potential advantages. The aim of this review is to discuss the differences between adult and pediatric thromboembolism and to review the current anticoagulants in terms of pharmacological action, doses, drug reactions, pharmacokinetics, interactions, and parameters. This review also highlights the differences between old and new anticoagulant therapy in pediatrics.

Pharmacokinetics and pharmacodynamics of anticoagulants in paediatric patients

Given the rising incidence of thrombotic complications in paediatric patients, understanding of the pharmacologic behaviour of anticoagulant drugs in children has gained importance. Significant developmental differences between children and adults in the haemostatic system and pharmacologic parameters for individual drugs highlight potentially unique aspects of anticoagulant pharmacology in this special and vulnerable population. This review focuses on pharmacologic information relevant to the dosing of unfractionated heparin, low molecular weight heparin, warfarin, bivalirudin, argatroban and fondaparinux in paediatric patients. The bulk of clinical experience with paediatric anticoagulation rests with the first three of these agents, each of which requires higher bodyweight-based dosing for the youngest patients, compared with adults, in order to achieve comparable pharmacodynamic effects, likely related to an inverse correlation between age and bodyweight-normalized clearance of these drugs. Whether extrapolation of therapeutic ranges targeted for adult patients prescribed these agents is valid for children, however, is unknown and a high priority for future research. Novel oral anticoagulants, such as dabigatran, rivaroxaban and apixaban, hold promise for future use in paediatrics but require further pharmacologic study in infants, children and adolescents.

Dosing and monitoring of enoxaparin therapy in children: experience in a tertiary care hospital

Pediatric deep vein thrombosis (DVT) is an emerging problem in tertiary care hospitals, recent reviews shows a rate of 40.2/10,000 admissions. Experts affirm that enoxaparin has become in the drug of choice for DVT therapy. Despite this, there is a little information regarding the optimal dose schedule for enoxaparin therapy in children and the therapeutic guidelines for enoxaparin use in children are extrapolated from adult guidelines. Monitoring by antifactor Xa (anti-Xa) measurement and target concentrations between 0.5-1 U/ml at 4-6 h postdose are recommended. This study was designed to analyse our experience in paediatric-specific dosage requirements for enoxaparin therapy. A retrospective study was performed with patients less than 16 years old, who were treated with enoxaparin for DVT and monitored by anti-Xa concentration, between January 2005 and March 2012. Demographic and clinical characteristics and outcomes were obtained. Fourteen patients were analyzed: boy/girl ratio, 8/4; median age, 3.5 months. Cerebral venous sinus thrombosis was the most common indication for therapy. All patients presented thrombosis risks factors. Dose increases were necessary only in patients less than 6 years old. Target anti-Xa concentrations were achieved in 12 (85%) patients. Children younger than 1 year required a higher dose of enoxaparin/kg (1.5-2.7 mg/kg per 12 h). Complete resolutions of DVT were registered in all cases. The mean number of dose increases was three and a median of 11 days to achieve target anti-Xa concentration. This study indicates that an initial higher enoxaparin dose may be necessary in neonates and infants, but other factors must be considered to improve management.

Evaluation of the use of low-molecular-weight heparin in neonates: a retrospective, single-center study

Controversies exist over the currently recommended guidelines for the use of low-molecular-weight heparin (LMWH) in neonates. We retrospectively studied 30 neonates treated with LMWH and found a poor therapeutic response to recommended doses as measured by anti-Xa levels. Sixty percent of the study participants required their doses to be increased because of subtherapeutic anti-Xa levels during the initial course of their treatment. The mean starting enoxaparin dose was 1.53 ± 0.38 mg/kg. The mean enoxaparin dose, once therapeutic anti-Xa levels had been achieved, was 1.86 ± 0.50 mg/kg. Preterm and term infants required doses of 2.06 ± 0.61 mg/kg and 1.67 ± 0.26 mg/kg, respectively, to achieve therapeutic anti-Xa levels. In summary, our results suggest that higher initial doses are required to achieve therapeutic anticoagulation in neonates.