Low-molecular-weight heparin therapy in children

The safety and efficacy of use of low-molecular-weight heparin in pediatric neurosurgical patients

OBJECT

Low-molecular-weight heparins (LMWHs), mainly enoxaparin, offer several advantages over standard anticoagulation therapies such as unfractionated heparin and warfarin, including predictable pharmacokinetics, minimal monitoring, and subcutaneous administration. The purpose of this study was to determine the safety and efficacy of LMWHs in pediatric neurosurgical patients.

METHODS

A retrospective study was performed with patients 18 years old or younger who were admitted to the Pediatric Neurosurgery Service at Texas Children's Hospital and treated with LMWH for either therapeutic or prophylactic purposes between March 1, 2011, and December 30, 2013. Demographic and clinical features and outcomes were recorded.

RESULTS

LMWH was administered for treatment of venous thromboembolic events (VTEs) in 17 children and for prophylaxis in 24 children. Clinical resolution of VTEs occurred in 100% (17 of 17) of patients receiving therapeutic doses of LMWH. No patient receiving prophylactic doses of LMWH developed a new VTE. Major or minor bleeding complications occurred in 18% (3 of 17 children) and 4% (1 of 24 children) of those receiving therapeutic and prophylactic doses, respectively. All 4 patients who experienced hemorrhagic complications had other bleeding risk factors-i.e., coagulopathies and antiplatelet medications.

CONCLUSIONS

LMWH seems to be safe and efficacious for both management and prophylaxis of VTEs in pediatric neurosurgery. However, pediatric practitioners should be aware of higher risk for bleeding complications with increasing doses of LMWH, especially in patients with preexisting bleeding disorders or concurrent use of antiplatelet agents.

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.

Stability and sterility of diluted enoxaparin under three different storage conditions

AIM

This study assessed whether enoxaparin sodium diluted to a concentration of 20 mg/mL for clinical use with 0.9% sodium chloride remained stable and sterile for up to 43 days under three different storage conditions.

METHODS

Enoxaparin dilutions in polypropylene syringes were stored under three different controlled conditions of temperature and light: (i) room temperature (22-26°C) under natural light; (ii) room temperature (22-26°C) in the dark; and (iii) controlled refrigeration (2-8°C) in the dark. A weekly assay of anti-Xa and anti-IIa activity was undertaken to determine if the diluted enoxaparin preparations retained anticoagulant activity, thus remaining suitable for clinical application.

RESULTS

Our findings indicate that diluted enoxaparin, when stored under the tested varied conditions of light and temperature, retained greater than or equal to 90% of baseline anticoagulant activity for anti-Xa and anti-IIa effect for up to 43 days.

CONCLUSIONS

The study results are significant for families, in that they suggest that at least a month's supply of enoxaparin could be dispensed at a time, reducing the frequency of patients/families returning for supply and providing a more convenient service for paediatric patients.

Submucosal hematoma presenting as small bowel obturator obstruction in a patient on low-molecular-weight heparin

Recent studies have shown the efficacy of low-molecular-weight heparin (LMWH) in the treatment of venous thromboembolic disease in children. Compared to unfractionated heparin and coumadin, LMWH has more predictable pharmacokinetics and a reported lower incidence of osteoporosis and heparin-induced thrombocytopenia in children. The overall incidence of severe hemorrhage on LMWH in children is low. To date, there is a single report of a small bowel obstruction in a child secondary to a hematoma while on LMWH. We report the second case of a child, on enoxaparin (Lovenox) therapy, who underwent bowel resection secondary to a completely obstructing small bowel wall hematoma.

Perioperative thromboprophylaxis in children: development of a guideline for management

BACKGROUND

Venous thromboembolic (VTE) events can occur in children at the time of surgery where a patient has associated prothrombotic risk factors. There is currently little advice available to anesthetists on how to assess the risks and provide prophylaxis.

AIM/OBJECTIVE

To increase awareness of thrombosis in the perioperative pediatric patient, and to give some guidance when considering prophylaxis in this group.

METHOD/RESULTS

A guideline outlining risk factors for venous thromboembolism in patients presenting for surgery was written as a flowchart. Recommendations for low risk patients was early mobilization and good hydration; for moderate risk patients having major general surgery to include physical prophylaxis where size permits, i.e. elastic stockings and compression devices; for high-risk patients undergoing major orthopaedic or general surgery to also receive prophylactic low molecular weight heparin enoxaparin 0.5 mg x kg(-1) b.d.

CONCLUSION

Children with multiple risk factors for VTE should be considered for prophylactic measures when presenting for prolonged major surgery.

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.

Venous thromboembolism prevention in the acutely ill medical patient: a review of the literature and focus on special patient populations

Although venous thromboembolism (VTE) is a major public health problem, until recently, our understanding of the risk of VTE in hospitalized acutely ill medical patients has been incomplete. Fortunately, over the past 5 years, there has been an increasing body of literature that highlights the risk of VTE in the nonsurgical patient, identifies unique patient-risk factors, and defines adequate preventative measures. This review highlights the current literature with regard to epidemiology of VTE in hospitalized medical patients and the risk-stratification of these patients and deals with optimal preventative regimens and prevention strategies in special patient groups.

Ischemic stroke in children treated for acute lymphoblastic leukemia: a retrospective study

The clinical and diagnostic findings and the factors influencing the neurologic and radiologic outcome of symptomatic ischemic stroke were evaluated in a group of 2,318 children with acute lymphoblastic leukemia (ALL) treated according to the AIEOP (Italian Association of Pediatric Hematology and Oncology) study protocols. In this multicentric retrospective study, a questionnaire was sent to each of the 43 AIEOP centers participating in the study. The questionnaire was designed to obtain information on the number, type, and time of occurrence of ischemic strokes, biologic and immunologic features of each case, as well as clinical data of the recruited patients. A prevalence of 0.47% was found. All ischemic strokes were sinovenous thrombosis (SVT). The most common neurologic presentations were diffuse neurologic signs and seizures. MRI with or without venography revealed SVT in 100% of cases; superficial SVT was diagnosed in the majority of cases. Antithrombotic drugs, in particular unfractioned heparin and low-molecular-weight heparin, were administered without bleeding complications. This series shows an excellent long-term neurologic outcome in children with SVT. However, a complete radiologic resolution was found in only 54% of cases; the involvement of deep cerebral venous sinuses was associated with an unfavorable imaging outcome.

Diagnosis and treatment of heparin-induced thrombocytopenia in neonates and children

Heparin-induced thrombocytopenia (HIT), a well-known side effect of heparin therapy, occurs with an incidence of 1-2% in certain pediatric patient groups. In affected children, HIT markedly increases the risk of venous and arterial thromboembolism. The use of alternative anticoagulation with danaparoid, lepirudin and argatroban in adults and children has demonstrated to be safe and could reduce morbidity and mortality also in affected pediatric patients. Thus, in children and neonates, an early diagnosis and accurate management is crucial to avoid the deleterious consequences of HIT. This review article will focus on the presentation of HIT in neonates and children. It reviews the pathophysiology of HIT and it summarizes epidemiological data. Finally important diagnostic and therapeutic issues are discussed.

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.

Thrombotic complications of central venous catheters in children

Use of central venous catheters has become standard in the treatment of many chronic conditions during childhood and for the acute treatment of critically ill infants and children. However, these catheters can be associated with numerous complications, including thrombosis at the tip or in the lumen causing difficulty with its overall function. Even more concerning is the occlusion of large veins into which the catheter is placed, which could predispose patients to pulmonary embolism or postthrombotic syndrome. Recent research has focused on identifying risk factors for catheter-related thrombosis in children and determining methods for diagnosing deep venous thrombosis associated with a catheter in the upper extremities. Evidence now exists that as many as 50% of children with catheters develop deep venous thrombosis; however, most events are clinically silent. Few clinical trials have studied prevention of catheter-related thrombosis in pediatric patients. Data regarding incidence, treatment, and long-term outcome of catheter-related thrombosis in children are limited. Although central venous catheters are extremely important in the supportive care of sick children, concerns remain about their immediate and long-term safety.

Use of low molecular mass heparin (enoxaparin) in newborn infants: a prospective cohort study of 62 patients

OBJECTIVE

To detail low molecular mass heparin (enoxaparin) use in the first few months of life.

DESIGN

Prospective, consecutive cohort of unselected newborn infants.

METHODS

Newborn infants were divided into groups by gestational age, underlying condition, hepatic and renal function, thrombocytopenia, and prothrombin time (PT/INR). Groups were analysed with respect to many aspects of enoxaparin treatment using multivariate methods.

RESULTS

Sixty two newborn infants received enoxaparin representing 5.39 treatment years. Thromboembolic events (TEs) occurred predominantly in the lower and upper venous system in the presence of indwelling catheters (69%). Preterm infants required longer than full term infants to achieve an anti-(factor Xa) level in the target range (six versus two days). Preterm infants required higher doses of enoxaparin than full term infants to maintain anti-(factor Xa) levels in the target range (2.1 v 1.7 mg/kg/12 h). Infants with congenital heart disease (CHD) required less enoxaparin than those without CHD to maintain an anti-(factor Xa) level in the target range (1.7 v 2.1 mg/kg/12 h). Impaired renal and liver function influenced the number of dose changes needed (three versus one a month). Complete or partial resolution of TE was accomplished in 59% of newborn infants. Four infants developed major bleeds (1.2% per patient year). Recurrent TE and clot extension occurred in three infants (0.9% per patient year).

CONCLUSIONS

Preterm infants are more difficult to treat with enoxaparin than full term infants. Enoxaparin appears to be an alternative to treatment with standard heparin or no treatment.

Pediatric thrombosis

Although thrombosis is less frequent in children than in adults, it represents a significant source of morbidity and mortality. Multiple factors. both genetic and acquired. contribute to the development of thrombosis in chiidren. Thrombosis in a child warrants investigation of potential underlying prothrombotic conditions. The risk of thrombosis in children with heterozygous deficiencies is not clearly defined, but it appears that children who are heterozygous for more than one risk factor or who have a combination of inherited and acquired defects are at higher risk for thrombosis. Treatment of thrombosis primarily involves a rapidly acting anticoaguiant such as heparin or LMWH to prevent extension, and long-term anticoagulation with warfarin may be instituted to prevent recurrence. Thrombolytic therapy with recombinant tissue plasminogen activator also appears to be safe and effective in children. Prospective and multicenter studies are still needed to clarify the contribution of specific prothrombotic disorders to childhood TE so that evidence-based treatment recommendations can be made.