Use of enoxaparin in a preterm infant

Questions around a case of in utero thrombosis in a premature child, concerning the management of anticoagulant treatments

We report the case of a preterm infant presenting a thrombosis, discovered on ultrasound at 22 weeks of gestational age and confirmed at birth following additional examinations. We describe the anticoagulant treatment of this patient by intravenous enoxaparin, tinzaparin and rivaroxaban, from questioning to practice.

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.

Effect of Plasmapheresis on the Anti-Factor Xa Activity of Enoxaparin in an Obese Adolescent Patient

To our knowledge, the effect of plasmapheresis on the anti-factor Xa activity of enoxaparin has never been reported. We describe a 13-year-old, obese (92-kg) girl who was treated with enoxaparin for a pulmonary embolism while receiving plasmapheresis for suspected autoimmune encephalitis and who experienced clinically significant reductions in anti-factor Xa activity after plasmapheresis. She received five courses of plasmapheresis, with the final two administered during treatment with enoxaparin. Her anti-factor Xa concentrations were highly variable, and we hypothesized that plasmapheresis was affecting these levels. To test this hypothesis, anti-factor Xa concentrations were measured before and immediately after the patient's last plasmapheresis treatment, and then again 2 days after plasmapheresis. The rate of anti-factor Xa activity decline was 0.28 IU/mL/hour with plasmapheresis and only 0.088 IU/mL/hour on the day without plasmapheresis, representing a greater than 3-fold difference. The changes in anti-factor Xa activity due to plasmapheresis altered the final enoxaparin dosage required to remain in the therapeutic range of 0.5-1 IU/mL (0.98 mg/kg/dose while receiving plasmapheresis vs 0.69 mg/kg/dose without plasmapheresis). Our patient's data suggest that plasmapheresis can significantly alter enoxaparin's anticoagulant effect as measured by anti-factor Xa concentrations, which could cause a decreased anticoagulant effect during plasmapheresis and an increased risk of bleeding on plasmapheresis discontinuation. If concurrent enoxaparin-based anticoagulation and plasmapheresis are necessary, close monitoring of anti-factor Xa levels is advisable. Dose escalations and reductions of enoxaparin may be necessary when initiating and discontinuing plasmapheresis, respectively.

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.

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.

Anticoagulation in neonates and children: Pitfalls and dilemmas

Anticoagulation in children is problematic for many reasons, related to the patient population as well as the anticoagulant drugs themselves. This paper describes the multitude of reasons why providing anticoagulation therapy in children is different from anticoagulation therapy in adults, and hence why dedicated paediatric anticoagulant services are the ideal structure to provide this service. The paper then describes the three most common anticoagulants used in children, and details specifically what is and is not known about them in the paediatric population. Finally the paper addresses the issue of how best to introduce newer anticoagulant drugs into the paediatric population. There remains much research to be done in this field, in the meantime clinicians need to carefully consider the evidence available to them and manage each individual patient accordingly.

Antithrombotic therapy in neonates and children: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition)

This chapter about antithrombotic therapy in neonates and children is part of the Antithrombotic and Thrombolytic Therapy: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Grade 1 recommendations are strong and indicate that the benefits do, or do not, outweigh risks, burden, and costs, and Grade 2 suggests that individual patient values may lead to different choices (for a full understanding of the grading, see Guyatt et al in this supplement, pages 123S-131S). In this chapter, many recommendations are based on extrapolation of adult data, and the reader is referred to the appropriate chapters relating to guidelines for adult populations. Within this chapter, the majority of recommendations are separate for neonates and children, reflecting the significant differences in epidemiology of thrombosis and safety and efficacy of therapy in these two populations. Among the key recommendations in this chapter are the following: In children with first episode of venous thromboembolism (VTE), we recommend anticoagulant therapy with either unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH) [Grade 1B]. Dosing of IV UFH should prolong the activated partial thromboplastin time (aPTT) to a range that corresponds to an anti-factor Xa assay (anti-FXa) level of 0.35 to 0.7 U/mL, whereas LMWH should achieve an anti-FXa level of 0.5 to 1.0 U/mL 4 h after an injection for twice-daily dosing. In neonates with first VTE, we suggest either anticoagulation or supportive care with radiologic monitoring and subsequent anticoagulation if extension of the thrombosis occurs during supportive care (Grade 2C). We recommend against the use of routine systemic thromboprophylaxis for children with central venous lines (Grade 1B). For children with cerebral sinovenous thrombosis (CSVT) without significant intracranial hemorrhage (ICH), we recommend anticoagulation initially with UFH, or LMWH and subsequently with LMWH or vitamin K antagonists (VKAs) for a minimum of 3 months (Grade 1B). For children with non-sickle-cell disease-related acute arterial ischemic stroke (AIS), we recommend UFH or LMWH or aspirin (1 to 5 mg/kg/d) as initial therapy until dissection and embolic causes have been excluded (Grade 1B). For neonates with a first AIS, in the absence of a documented ongoing cardioembolic source, we recommend against anticoagulation or aspirin therapy (Grade 1B).

Nadroparin therapy in pediatric patients with venous thromboembolic disease

Low-molecular-weight heparins are increasingly used for treatment of pediatric venous thromboembolic disease (VTE). Pediatric data about therapeutic doses of nadroparin are not available. To evaluate pharmacodynamics and safety of therapeutic doses of nadroparin, consecutive patients (age 0 to 18 y) with objectively diagnosed VTE and treated with nadroparin were included in this single center study over a 12-year period. All patients started with 85.5 IU/kg of nadroparin twice daily. The target therapeutic range (TTR) was set at 0.5 to 1.0 anti-Xa IU/mL 4 hours postdose. Safety end points were major bleeding and therapy-related death. A total of 84 patients were enrolled, of whom 8 patients did not undergo measurement of anti-Xa levels. Fifty-four (71%) of 76 patients achieved TTR. The maintenance dose (mean+/-SE) was 448+/-42 IU/kg/d in neonates (<2 mo, n=6), 253+/-22 IU/kg/d in infants (2 mo to 1 y, n=10), 214+/-8 IU/kg/d in children (2 to 11 y, n=13), and 183+/-5 IU/kg/d in adolescents (12 to 18 y, n=25). Neonates required significantly more dose adjustments and time to achieve TTR than adolescents. No major bleeding or therapy-related death occurred. In summary, an age-dependent response to nadroparin exists in pediatric patients. Nadroparin therapy seems to be safe for treatment of pediatric VTE.

Outcome of cardiac thrombi in infants

Use of central lines in the neonatal intensive care unit (NICU) has led to the formation of intracardiac thrombi. A paucity of data exists on the management of neonatal cardiac thrombi, with the few reported cases focusing on outcomes following thrombolytic therapy. This study was undertaken to evaluate the outcome of cardiac thrombi in neonates who do not receive thrombolytic therapy. Nineteen patients younger than 3 months of age diagnosed with cardiac thrombi were included. All 19 patients had a central line. Management consisted of a combination of antibiotics and low-molecular-weight heparin (n = 16) or surgical removal (n = 2). In one case, no treatment was instituted. One patient was lost to follow-up after partial resolution of the thrombus. Complete thrombus resolution occurred in 18 patients, 9 with negative blood cultures and 9 with positive blood cultures. It took longer for resolution of thrombi associated with positive blood cultures than for sterile thrombi. No patient had evidence of thrombus embolization. From these data we concluded that the natural history of cardiac thrombi is resolution. Infected thrombi require more prolonged therapy. Surgery is seldom required and thrombolytics are not usually necessary for clot resolution.

An assessment of published pediatric dosage guidelines for enoxaparin: a retrospective review

OBJECTIVE

To evaluate the ability of published dosage guidelines for enoxaparin to achieve therapeutic anticoagulation and to determine whether the routine monitoring of anti-Xa levels is still necessary at a tertiary care pediatric institution.

METHODS

Consecutive charts and laboratory records were reviewed for all patients receiving treatment doses of enoxaparin for thrombosis in the authors institution over a 4-year period (1998-2002).

RESULTS

Sixty-six percent (25/38) of the anti-Xa levels were within the recommended therapeutic range (0.5-1.0 [+/- 10%] U/mL) after two doses. The success rates of achieving therapeutic levels were 1/6, 2/3, 6/9, 10/11, and 6/9, for patients 2 months or younger, more than 2 months to 1 year, more than 1 year to 6 years, more than 6 years to 12 years, and more than 12 years of age, respectively. Patients with cardiac or renal disease were more likely to achieve high anti-Xa levels. Thirty-seven percent of patients reported adverse effects. The most common effects were injection site-related bruising and minor bleeding. One patient experienced a major bleed that was not life-threatening.

CONCLUSIONS

Most patients achieved therapeutic anticoagulation when dosed according to the published guidelines. Children with cardiac conditions or renal insufficiency or those younger than 2 months were more likely to require dosage adjustments to achieve the therapeutic range. Routine monitoring of anti-Xa levels is still necessary in these patient populations, particularly when the early establishment of therapeutic anticoagulation may be critical. Enoxaparin appears to be well tolerated in the authors' patient population.

Management of preterm infants with intracardiac thrombi: use of thrombolytic agents

Improvement in neonatal care has led to improvements in survival and patient outcome in preterm infants; however, this improved survival has been associated with the development of secondary complications, such as catheter-associated intravascular and intracardiac thrombus formation with a non-negligible morbidity and mortality. The sick preterm infant is at high risk of catheter-related thrombus formation because of the combination of a high prothrombotic activity, low levels of natural anticoagulants, and various imbalances in the fibrinolytic systems. Based on clinical experience in adults and children, and several neonatal case reports demonstrating the efficacy and tolerability of specific thrombolytic treatment, this approach should be recommended as a first choice treatment in the premature infant with intracardiac or intravascular thrombosis. The thrombolytic agents of choice are urokinase or tissue plasminogen activator (tPA); however, none of them have proven to be superior to the other in terms of efficacy or tolerability, either in adult patients or premature infants. In the past, it has been suggested that newborn infants may require higher doses of thrombolytic agents than adults for effective systemic thrombolysis; however, based on more recent in vitro studies, it seems unlikely that this is true. Nevertheless, systemic (high dose) fibrinolysis is of concern as premature neonates present an increased risk of cerebral haemorrhage during the first weeks of life; therefore, low dose treatment has been proposed with, if possible, direct infusion of the fibrinolytic agent into, or close to, the thrombus. This approach has proven to be efficient and well tolerated in several small case series of newborn and preterm infants. Recommended doses are 1000 to 3000 U/kg/h for urokinase or 0.01 to 0.05 mg/kg/h for tPA. A systemic proteolytic state will not be induced by this low dose; however, specific monitoring of fibrinogen plasma levels has to be recommended. Fibrinogen levels should remain above 100 mg/dL during low dose treatment. Lower levels of fibrinogen will indicate the presence of an unwanted systemic fibrinolytic state. After successful thrombolysis, a follow-up treatment, preferentially with low-molecular-weight heparin for neonates at adjusted doses, should be instituted for at least 6 weeks in the absence of any persisting thrombophilic factor. A longer course (3 to 6 months) of anticoagulation therapy is recommended when thrombophilic factors (i.e. hereditary thrombophilia or central venous catheter still in place) are present. Furthermore, it is recommended that any neonate with thrombosis should be evaluated for hereditary thrombophilia later in life.