Antithrombotic therapy in children

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.

Intrauterine upper extremity thrombosis successfully treated with recombinant tissue plasminogen activator, enoxaparin and collagenase

Intrauterine ischemia of the limbs is a rare condition involving thrombosis and ischemia of the extremities before birth. The clinical presentation depends on the extremity affected as well as the timing of thrombosis. Very few cases with extremity hypoperfusion and gangrene due to intrauterine thrombosis have been reported in the literature, and therefore there is no consensus on the optimal therapeutic strategy for such cases. Presented here is a case of a newborn with intrauterine brachial arterial thrombosis of the right upper extremity who was successfully treated by a combination of recombinant tissue plasminogen activator, enoxaparin and collagenase application followed by surgery.

Endovascular treatment of near-fatal neonatal superior vena cava syndrome

OBJECTIVE

We describe the endovascular management of an 8-wk-old previously healthy female who developed superior vena cava syndrome secondary to Pseudomonas septic shock and disseminated intravascular coagulation. Doppler ultrasound confirmed near-total thrombotic occlusion of the superior vena cava and right internal jugular vein. She was taken emergently for cardiac catheterization, which confirmed the large superior vena cava thrombus extending into the right internal jugular vein and innominate vein with almost complete occlusion of the innominate vein. The superior vena cava to right atrium gradient was 14 mm Hg with very little antegrade flow into the right atrium, right femoral artery occlusion, and branch pulmonary artery emboli. Intervention involved serial balloon dilation inflations across the superior vena cava and innominate vein with improvement in the superior vena cava to right atrium gradient to 5 mm Hg and significant improvement in left ventricular function. Anticoagulation included heparin infusion for 48 hrs followed by enoxaparin for 1 month, alteplase for 48 hrs, eptifibatide (glycoprotein IIb/IIIa inhibitor) for 9 days followed by aspirin.

DATA SOURCES

Chart review. Case reports are exempt from approval of our Institutional Review Board.

STUDY SELECTION

None.

DATA EXTRACTION

None.

DATA SYNTHESIS

None.

CONCLUSIONS

Daily head ultrasounds were performed without evidence of intracranial hemorrhage. All thromboses resolved within 3 wks. Her organ function recovered and she was discharged to home. The etiology of her colitis is still unknown. At 9-month follow-up, she was doing well with no residual organ dysfunction.

Oral anticoagulants in pediatric cardiac practice: A systematic review of the literature

Recent advances in the pediatric heart surgery, especially the Fontan procedure, has necessitated an increased use of oral anticoagulants in pediatric cardiac patients. Warfarin is the standard agent used for most pediatric indications, though there are very few randomized control studies in children regarding its use. This review summarizes the current indications and evidence base regarding the use of oral anticoagulants in the pediatric age group.

Dosing and monitoring of low-molecular-weight heparin in high-risk pregnancy: single-center experience

STUDY OBJECTIVE

To evaluate dosing requirements and monitoring patterns of low-molecular-weight heparin (LMWH) when used in high-risk pregnancy.

DESIGN

Retrospective, observational, cohort study.

SETTING

University-affiliated medical center.

PATIENTS

Forty-nine women treated with LMWH between 2001 and 2005 for either prophylaxis or treatment of venous thromboembolism during pregnancy and monitored with antifactor Xa activity.

MEASUREMENTS AND MAIN RESULTS

Data were obtained on 53 pregnancies in the 49 women. The primary outcome was change in dosing requirements of LMWH throughout pregnancy as determined by the corresponding antifactor Xa activity peak levels. Mean starting doses of twice-daily enoxaparin and doses most proximate to delivery were 39.2 mg (range 30-60 mg) and 55.0 mg (range 30-100 mg, p=0.06), respectively, for the prophylaxis group and 83.0 mg (range 30-180 mg) and 85.7 mg (range 30-160 mg, p=0.41), respectively, for the therapeutic group. Weight-based mean starting doses and doses most proximate to delivery were 0.46 and 0.62 mg/kg (p=0.03), respectively, for the prophylaxis group and 0.90 and 0.87 mg/kg (p=0.29), respectively, for the therapeutic group. Dose changes were required in 9 (69%) of 13 pregnancies and 21 (55%) of 38 pregnancies (data from two of the 40 pregnancies were excluded-one in a patient receiving dalteparin, and one in a patient with mitral valve replacement who had higher antifactor Xa goals) in the prophylaxis and therapeutic groups, respectively, to achieve target antifactor Xa activity. The weight-based prophylactic dose was consistently 0.6 mg/kg in all three trimesters, achieving a mean ± SD target antifactor Xa activity of 0.39 ± 0.18 units/ml, whereas the therapeutic dose was 0.9 mg/kg to maintain antifactor Xa activity of 0.71 ± 0.22 units/ml.

CONCLUSION

Dose changes for LMWH throughout pregnancy as guided by antifactor Xa activity were common. A significant increase in the LMWH dose requirements in the prophylactic group suggests that more frequent monitoring of antifactor Xa activity may be appropriate in pregnant patients to maintain target anticoagulant levels.

Safety and efficacy of warfarin in paediatric patients with prosthetic cardiac valves: a retrospective audit

INTRODUCTION

Guidelines for warfarin management in children are essentially extrapolated from adult evidence. This study aimed to address that lack of paediatric-specific data regarding warfarin safety and efficacy for this population.

MATERIALS AND METHODS

A retrospective clinical audit was conducted within a cardiac referral centre incorporating a paediatric anticoagulation service. Children (0-16 years) with a prosthetic cardiac valve were included. Warfarin related outcomes were collected between January 1st 2004 and December 31st 2009. Analysis included the percentage of INR tests within, above, or below the target therapeutic range (TTR). Adverse event data was collected regarding major bleeding and thrombotic events.

RESULTS

75 patient years of warfarin therapy were recorded. 44.0% of INR tests were within the TTR. INR tests not within the TTR were twice as likely to be sub-therapeutic. Children with aortic prosthetic valves achieved their TTR less frequently than children with prosthetic mitral or tricuspid valves. There were no thrombotic events and 3 major bleeding events.

CONCLUSIONS

Although less than 50% of INR results were within the TTR, oral anticoagulant management resulted in acceptable safety and efficacy outcomes for this cohort. Further studies are needed to confirm optimal paediatric-specific warfarin management strategies for children with prosthetic heart valves.

Thromboembolism and venous thrombosis of the deep veins in surgical children--an increasing challenge?

Children share many known predisposing risk factors for venous thromboembolism and deep venous thrombosis but appears less common and is probably underestimated. Fatal pulmonary embolism is rare but may also be missed because of low level of clinical awareness. The aim of this study was to investigate children with thromboembolism of deep veins to evaluate risk factors and highlight their danger.

METHODS

This was a retrospective review of all children (<13 years old) diagnosed with a venous thromboembolism (1993-2009). Clinical and radiologic features and any risk factors were documented. Venous thromboembolism was diagnosed on clinical suspicion together with compressive Doppler studies, spiral computed tomography, or magnetic resonance scan.

RESULTS

Eighteen children with a consistent clinical picture were identified (painful unilateral limb swelling). Their mean age was 9.3 years with a male/female ratio of 3.5:1. Predisposing factors were identified in 17 (95%). These included infective conditions (n = 11), previous femoral line (n = 3), trauma (n = 2), and complicated appendicitis (n = 2). Chronic infective and inflammatory conditions included tuberculosis (n = 4), HIV (n = 3), staphylococcal septicemia (n = 2), and Takayasu arteritis (n = 1). Pulmonary embolism occurred in 5 (28%), and 1 presented later with a post-phlebitic leg. Elevated factor VIII was seen in 3.

CONCLUSION

This study identified an association with known risk factors in most children with venous thromboembolism and suggests that those with femoral venous access or ongoing chronic infective states (eg, TB/HIV) are particularly at risk.

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.

Pharmacology in childhood arterial ischemic stroke

In recent years, there has been increasing recognition of the impact of childhood stroke and interest in the role of drugs in the acute, chronic, and prophylactic management of this condition. Most treatment strategies are based on studies in adults with stroke, and the relative infrequency of stroke and the heterogeneity of etiologies in childhood compared with adults present significant challenges in study design for childhood stroke studies. The presence of thrombophilia has been associated with stroke in children, strengthening the concept that antithrombotic, antiplatelet, and even thrombolytic agents have a role in stroke treatment and prevention. There are several potential roles for drugs in the treatment of childhood stroke including hyperacute therapy, antithrombotic medication, antiplatelet medication, and disease-specific medications. Herein, we review the use and rationale of these medications in childhood arterial ischemic stroke.

[Large deep venous thrombosis in childhood--three cases]

Deep venous thrombosis is a rare disease in children under the age of 18, with an estimated incidence of 1/100,000 per year in Hungary. Its typical localization in children is in the extremities, usually occurring in newborns and in teenagers. Both congenital and acquired risk factors can be in the background. Although it is a rarity, we should think of it, because late diagnosis can cause life-threatening conditions like pulmonary embolism or central nervous system thrombosis. Detailed medical history can help the diagnosis. Etiology, possible congenital and acquired risk factors, as well as diagnostic and therapeutic options are discussed through three cases of teenage children. Diagnostic difficulties of deep venous thrombosis in childhood are the following: the occurrence is rarer than in adulthood therefore it is often forgotten as a possible diagnosis, coagulation parameters are age-dependent, and diagnosis with imaging techniques is more difficult.

Population pharmacokinetics of enoxaparin in infants, children and adolescents during secondary thromboembolic prophylaxis: a cohort study

BACKGROUND

Enoxaparin has been extensively studied in adults on its safety and efficacy during prevention of symptomatic thromboembolism when acute anticoagulation or secondary prevention is required as a result of venous thrombosis or stroke. In children, it is still used off-label and little is known about the pharmacokinetics in children.

OBJECTIVES

The aim of the present study was to evaluate whether a once- or twice-daily dosing regimen would be feasible in children to achieve appropriate plasma levels of enoxaparin.

PATIENTS/METHODS

A population pharmacokinetic model was developed using anti-factor (F)Xa activity data from 126 children (median age: 5.9 years) receiving enoxaparin either as a once- or twice-daily dosing regimen.

RESULTS

A two-compartment model was adequate for describing the enoxaparin kinetics. Body weight proved to be the most predictive covariate for clearance and central volume of distribution: clearance 15 mL h⁻¹ kg⁻¹, central volume of distribution 169 mL kg⁻¹, intercompartmental clearance 58 mL h⁻¹, peripheral volume of distribution 10 L and absorption rate 0.414 h⁻¹. Interindividual variability was found to be 54% for clearance and 42% for volume of distribution.

CONCLUSION

The model is capable of describing all age groups and dosing levels of our population and predicts 12 h and 24 h enoxaparin activities sufficiently. According to our results, a once-daily enoxaparin dosing regimen with frequent monitoring is feasible. In 53.2% of the patients the median 24 h trough level was above the desired range of 0.1 IU mL⁻¹ anti-FXa activity for prophylaxis therapy.

Management of acquired bleeding problems in cancer patients

Cancer patients can have acquired bleeding problems for many reasons. In this review, an approach to the evaluation and management of the bleeding patient is discussed. Specific issues including coagulation defects, thrombocytopenia, platelet dysfunction, and bleeding complications of specific hematological malignancies due to anticoagulation, are discussed.

Long-term anticoagulation in Kawasaki disease: Initial use of low molecular weight heparin is a viable option for patients with severe coronary artery abnormalities

Patients with severe coronary artery involvement after Kawasaki disease (KD) require long-term systemic anticoagulation. We sought to compare our experience with thrombotic coronary artery occlusions, safety profile, and degree of coronary artery aneurysm regression in KD patients treated with low molecular weight heparin (LMWH) versus warfarin. Medical records of all KD patients diagnosed between January 1990 and April 2007 were reviewed. Of 1374 KD patients, 38 (3%) received systemic anticoagulation, 25 patients received LMWH from diagnosis onward, 12 of whom were subsequently switched to warfarin, and 13 received warfarin from onset. The frequency of thrombotic coronary artery occlusions was similar between drugs. Severe bleeding was more frequent in patients on warfarin, but minor bleeding was more frequent for patients on LMWH. Patients on warfarin were at greater risk of underanticoagulation or overanticoagulation (defined as achieving an anti-activated factor X level or an international normalized ratio below or above target level) than patients on LMWH (P < 0.05). Maximum coronary artery aneurysm z-scores diminished with time for patients on LMWH (P = 0.03) but not for those on warfarin (P = 0.55). This study suggests that LMWH is a potentially viable alternative for patients, especially young ones, with severe coronary artery involvement after KD.

Observational Cohort Study of Pediatric Inpatients With Central Venous Catheters at “Intermediate Risk” of Thrombosis and Eligible for Anticoagulant Prophylaxis

The risk of deep vein thrombosis (DVT) among hospitalized children is rising.The optimal approach to DVT prophylaxis in children is unclear. This study set out to ascertain the prevalence of DVT among pediatric inpatients who neither have contraindications to nor absolute indications for prophylactic therapy. A prospective surveillance of at-risk children plus a retrospective chart review were conducted. Patients were considered to be at risk after the first 2 days of their admission. Of 1,637patients reviewed, 198 patients met criteria; among these, 84% did not receive prophylaxis. Of 2,354 observed days at risk for nonprophylaxed patients (including days at risk prior to initiating prophylaxis among prophlyaxed patients), there were 9 DVT events, for a rate 3.82/1,000 days observed. A total of 31 patients received prophylaxis. Three of these patients experienced a DVT. One patient had a bleeding event, hematuria. These results describe patients who may be eligible for prophylaxis and should be screened for further risk factors.

Aspects of anticoagulation in children

The number of children receiving anticoagulation is increasing. Thromboembolic events are associated with significant risk of morbidity and mortality although the optimal management of asymptomatic events remains unclear. Specific challenges in paediatrics include the diagnosis of thrombosis, delivery and monitoring of anticoagulation in a wide range of ages from neonates through to adolescents. The development of the haemostatic system as children age results in changing pathophysiology of thrombosis and response to anticoagulation agents. Although registry and observational studies have provided vital information, specific paediatric, prospective anticoagulation studies have been few and limited in design. The result is that much of current practice is extrapolated from adult studies. Traditional anticoagulants have significant limitations. Both heparin and warfarin are in widespread use but many fundamental questions regarding dose, therapeutic range, efficacy and optimum duration have not been fully answered. Alternative agents, such as direct thrombin inhibitors and the selective anti-factor Xa inhibitor fondaparinux, may have advantages for children. Clinical trials in adults and preliminary data in children are promising but caution should be applied until specific paediatric studies have demonstrated safety and efficacy.

Syncope: a rare presentation of massive pulmonary embolism in a previously healthy girl

Pulmonary embolism is a very infrequent event in previously healthy children, particularly in the outpatient scenario. This report involves a 7-year-old girl who presented to the emergency room after syncope. A prompt diagnostic workup showed a massive pulmonary embolism. A timely treatment initiation permitted a good and rapid response. She represented a diagnostic and treatment challenge, mainly because of the atypical presentation and the absence of known risk factors. Finally, a thorough study uncovered a nephrotic-range urine protein loss. At the beginning, the patient did not meet the whole nephrotic syndrome diagnostic requirements. The complete thombophilic study was normal. The clinical presentation, epidemiology, diagnostic tools and the treatment of pulmonary embolism are reviewed. We also discuss a recently described risk factor, present in our patient, as a potential role in the development of pulmonary embolism.

Effects of Age and Weight-Based Dosing of Enoxaparin on Anti-Factor Xa Levels In Pediatric Patients

OBJECTIVE

The objective of this dose range study is to expand on the relationship between age and weight-based doses of enoxaparin and resulting levels of anti-factor Xa (anti-Xa) in pediatric patients. The primary outcome of this study is to determine the average dose of enoxaparin required to produce a therapeutic effect. Secondary outcomes include the number of enoxaparin dose changes required to achieve a therapeutic level of anti-Xa in each age group, the success rates of achieving and maintaining therapeutic anti-Xa levels, and the effect of serum antithrombin concentrations on anti-Xa levels. The study will also determine whether different dispensed concentrations of enoxaparin play a role in achieving therapeutic levels of anti-Xa.

METHODS

Single center, retrospective chart review. Patients were excluded from the study if they were older than 18 years of age, were receiving enoxaparin for prophylactic purposes, had a creatinine clearance &lt; 30 ml/min/1.73m2, and if no anti-factor Xa levels were drawn.

RESULTS

Average enoxaparin doses required for therapeutic levels of anti-factor Xa were 1.8 mg/kg for patients &lt;1 month, 1.64 mg/kg (1 month to 1 year), 1.45 mg/kg (1 to 6 years), and 1.05 mg/kg (&gt;6 years of age). An average of 3.24 dose changes was required for neonates to achieve therapeutic levels anti-factor Xa. The success rates for achieving and maintaining therapeutic levels were both 41%. Patients with low serum antithrombin levels were more likely to have low anti-Xa levels than those with normal or high values, 52% vs 40% vs 18%, respectively. Patients receiving diluted concentrations, 10 or 20 mg/mL, experienced lower anti-Xa levels than patients who received the standard manufactured concentration of 100 mg/mL, 61% vs 33%.

CONCLUSION

Based on this dose-range study, enoxaparin should be initiated at larger doses than recommended by the current guidelines to promptly achieve therapeutic anti-Xa levels. Doses should be divided into three age groups instead of two as currently suggested in the guidelines. To increase the likelihood of achieving therapeutic levels, the commercially available enoxaparin product should not be diluted if possible.

Low-dose systemic thrombolytic therapy for deep vein thrombosis in pediatric patients

Reduction of thrombus size and recanalization of vessels after deep vein thrombosis (DVT) are important goals to prevent recurrent thrombosis and development of postthrombotic syndrome. Thrombolysis is effective but concern for bleeding complications has limited its use in children. We retrospectively analyzed data for children with DVT treated with a low-dose systemic tissue plasminogen activator (tPA) regimen. Twenty-three pediatric patients (12 males and 11 females, median age 12 y) received low-dose systemic tPA, initiated at 0.03 to 0.06 mg/kg/h for a median of 24 hours (range 12 to 48 h). Of the 20 patients imaged within 24 hours of therapy, 6 (30%) showed partial to complete thrombus resolution. Eight patients subsequently received increased tPA at 0.12 mg/kg/h for an additional 24 hours (range 12 to 36 h). Six of these 8 (75%) patients responded to the increased dose. The overall response at the end of thrombolytic therapy was 59% (13/22). Two bleeding complications occurred without serious sequelae. Low-dose tPA administration leads to a substantial response rate although the risk of bleeding remains unclear. A prospective multicenter trial of low-dose thrombolytic therapy in children with acute DVT is warranted.

Defining the role of recombinant activated factor VII in pediatric cardiac surgery: where should we go from here?

OBJECTIVES

Postoperative hemorrhage is a recognized complication of pediatric cardiac surgery. Both the immature coagulation system and increased susceptibility to hemodilution increase the likelihood of pediatric patients developing coagulopathy when compared with adult counterparts. Treatment options remain limited. Recombinant factor VII (rFVIIa) is a hemostatic agent increasingly used to reduce hemorrhage in other surgical settings, the role of which is unclear in this population. This article systematically reviews the published literature on the use of rFVIIa in pediatric cardiac surgery.

DATA SOURCES AND STUDY SELECTION

A systematic literature search identified reports of rFVIIa administration in pediatric patients undergoing cardiac surgery. Where possible, individual patient-specific data were extracted and pooled statistical analysis was performed.

DATA EXTRACTION AND SYNTHESIS

Twenty-nine articles reporting on the administration of rFVIIa to 169 patients were identified. rFVIIa has been administered to patients with predefined congenital abnormalities of hemostasis to arrest hemorrhage refractory to other interventions and prophylactically in the hope of reducing blood loss. Treatment regimens vary widely, in terms of both first and cumulative dose. Data on chest tube blood loss and two markers of coagulation were pooled and analyzed, and significant improvements were demonstrated. Mortality was 4.4% for the entire cohort but 20% of patients on extracorporeal membrane oxygenation suffered significant thromboembolic complications.

CONCLUSIONS

rFVIIa has an increasingly accepted role in the management of patients with congenital coagulopathies undergoing major surgery. However, randomized trials are required to define the role of rFVIIa as an adjunct to control major hemorrhage in the pediatric cardiac surgical population. Any future work must focus not only on benefits but also on patient safety, particularly, risk of morbid thromboembolic complication.

Management of acquired bleeding problems in cancer patients

Cancer patients can have acquired bleeding problems for many reasons. In this review, an approach to the bleeding patient in the Emergency Department is discussed. Specific issue including coagulation defects, thrombocytopenia, platelet dysfunction, bleeding complications of specific hematological malignancies and due to anticoagulation, are discussed.

Cerebral venous thrombosis treated with enoxaparin in an IUGR neonate with DIC

BACKGROUND

The case of a term IUGR newborn who presented a cerebral vein thrombosis diagnosed by routine ultrasound brain scan, and confirmed by magnetic resonance imaging and magnetic resonance venography, is reported. A thrombosis of cortical cerebral veins and intracerebral haemorrhage in the right frontal paramedian region was observed.

METHODS

Treatment with enoxaparin was started at the initial dose of 0.5 mg/kg subcutaneously every 12 h and then at 1.25 mg/kg per 12 h in order to obtain anti-factor Xa levels between 0.5 and 1.0 U/ml. After hospital discharge, enoxaparin was continued for 2 months with a lower dose (1.8 mg/kg/die).

CONCLUSION

Treatment with enoxaparin was effective as demonstrated by a complete "restitutio ad integrum".

Hemostatic changes in vasculitides

The systemic vasculitides are an heterogeneous group of rare diseases characterized by inflammation and fibrinoid necrosis of blood vessel walls. Today it is well known that the inflammatory process characterizing vasculitides activates coagulation factors, inhibits anticoagulant factors, inhibits fibrinolytic processes, increases platelet activity and production and determines endothelial dysfunction. So far the mortality in vasculitides, even if falling, remains substantially high. Patients with vasculitic syndrome are at increased risk of developing atherosclerosis and in these patients prevalence of cardiovascular disease and cardiovascular events is higher than in the general population. Vasculitides can be associated with antiphospholipid syndrome. It is important to establish a strategy of antithrombotic therapy management in vasculitic patients, but this has not yet been clearly achieved.

Blood conservation strategies in pediatric anesthesia

Management of bleeding in the neonate, infant, or child presents its own set of dilemmas and challenges. One of the primary problems is the lack of good scientific evidence regarding the best management strategies for children rather than for adults. The key to success in the predicament is firstly to ensure that the physician has a clear understanding of the underlying normal physiology of the young child's hematologic status. Then by adding knowledge of the abnormal pathology that is being presented, the physician can at least understand what anomalies he or she is facing. Once all the available information concerning the patient's clinical condition and the options available has been well digested, a multidisciplinary approach allows the optimal use of all available resources. Good teamwork, understanding, and communication between all vested parties allows for a synergistic relationship to enhance patient care and give the best available end result.

Anticoagulation: Low-Molecular-Weight Heparins in Renal Impairment and Obesity: Available Evidence and Clinical Practice Recommendations Across Medical and Surgical Settings

Objective

To develop practical recommendations for the use of low-molecular-weight heparins (LMWHs) as prophylaxis and treatment of venous thromboembolism and acute coronary syndromes in patients with impaired renal function or obesity.

Data Sources

Multiple MEDLINE searches were performed (November 2008) to identify studies for inclusion, using a comprehensive list of search terms including, but not limited to, LMWH, enoxaparin, dalteparin, tinzaparin, obesity, weight, renal, kidney, elderly, monitoring, and anti-Xa.

Study Selection And Data Extraction

Only articles published in English that were relevant for this review were included.

Data Synthesis

In the majority of patients, standardized prophylaxis or treatment doses of LMWHs can be used without the need for monitoring and adjusting regimens. For patients with severe renal impairment (estimated creatinine clearance [CrCl] <30 mL/min), doses of some LMWHs should be adjusted or unfractionated heparin should be used instead. CrCl should be estimated using the Cockcroft-Gault method. Differences are noted in the degree of accumulation of various LMWHs in patients with moderate-to-severe renal impairment, and thus, the degree of dose adjustment may differ among the various LMWHs. Increasing the prophylactic doses of LMWH may be appropriate in morbidly obese patients (body mass index ≥40 kg/m2). The use of total body weight is appropriate for therapeutic doses of LMWH in obese patients. Laboratory monitoring of the anticoagulation effect of LMWHs is generally not necessary, but should be considered in patients with morbid obesity (weight >190 kg), those with severe renal impairment, and those with moderate renal impairment with prolonged (>10 days) LMWH use. When anti-Xa activity is monitored, it should be determined using a chromogenic method and a calibration curve based on the LMWH used.

Conclusions

Additional data are needed for specific dose guiding in obese and renally impaired patients, who are often excluded from larger clinical trials. Practice recommendations are made based on available evidence and authors' clinical opinions.

Epidemiology and clinical risk factors predisposing to thromboembolism in children with cancer

PURPOSE

The prevalence and risk factors for thromboembolism (TE) in children with cancer are largely unknown. This retrospective cohort study aims to determine the epidemiology of TE and to identify potential risk factors for TE in children with cancer.

METHODS

We used logistic regression to determine the association of age (<10 years vs. > or =10 years), gender, type of cancer, presence or absence of intra-thoracic disease (mediastinal mass or any primary or metastatic pulmonary disease), type of central venous line (CVL) and CVL-dysfunction (difficulty of blood draw, infusion or documented CVL infection) on the risk of developing TE.

RESULTS

Fifty-seven of 726 patients [7.9%; 95% confidence intervals (CI); 6.0,10.0] developed TE; children with brain tumors (n = 201) had significantly lower prevalence of TE (0.5%; P < 0.001). Older patients had increased risk of developing TE compared to younger patients [Odds ratios (OR) 1.8; 95% CI; 1.0,3.2; P = 0.036]. Children with acute lymphoblastic leukemia (ALL) (OR 4.6; 95% CI; 1.8, 12.3; P = 0.002), lymphoma (OR 3.8; 95% CI; 1.3, 11.1; P = 0.016), and sarcoma (OR 4.3; 95% CI; 1.4, 13.3; P = 0.012) had an increased risk of TE. Subgroup analyses showed that patients with CVL-dysfunction and intra-thoracic disease had a higher prevalence of TE compared to those without CVL-dysfunction (22.8% vs. 8.8%; 95% CI; 4.0, 24.3; P = 0.006) and intra-thoracic disease (18.0% vs. 6.1%; 95% CI; 2.4, 21.4; P = 0.02).

CONCLUSIONS

TE is common in children with cancer. Age and type of cancer are independent risk factors for TE in children with non-CNS cancers. CVL-dysfunction and intra-thoracic disease are significantly associated with the diagnosis of TE.

A retrospective study of the factors associated with hypercoagulability in the pediatric patients at a tertiary care children's hospital

OBJECTIVE

The objective of this study was to determine the risk factors of hypercoagulability in children. We explored the interaction of multiple risk factors with the incidence of thrombosis. Our hypothesis was that as the number of risk factors for thrombosis increased the actual incidence of thrombosis would also increase.

DESIGN

Retrospective review from 2003 through 2006 based on a search using two electronic medical record databases.

SETTING

Pediatric Tertiary Care Children's Hospital.

PATIENTS

Two hundred twenty-six patients were identified and analyzed.

MEASUREMENTS

Search terms included factor V Leiden polymerase chain reaction, prothrombin gene 20210A mutation, methylene tetrahydrofolate reductase mutation, antithrombin III, and protein C and S levels. Clinical data were compiled for regression analysis.

MAIN RESULTS

The presence of one risk factor was not significant. Two risk factors increased the risk of thrombosis (p = 0.005; OR 3.128). Three or more risk factors further increased the risk of thrombosis (p = 0.003; OR 4.861). Older age (>11 yrs) was protective against thrombosis (p = 0.007; OR 0.995), and the presence of a central venous catheter when analyzed against accumulating risk factors showed a higher risk than that found during the regression analysis (p = 0.001; OR 3.638).

CONCLUSIONS

The population at our institution is reflective of the previously reported standards for the genetic predispositions toward thrombosis. Although older age is associated with a lower incidence of thrombosis, the presence of a central venous access device is detrimental. Accumulation of factors results in an increased risk of thrombosis. This article suggests that when inserting a central venous access device, consideration of a hypercoagulation workup should occur. Those with any two or more risk factors, genetic or acquired, and the comorbidity of a CVL may warrant consideration for the institution of anticoagulation with an agent like low molecular weight heparin.

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).

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.

Prevention and management of central venous catheter occlusion and thrombosis in children with cancer

BACKGROUND

The views and clinical practice of children's cancer units were surveyed regarding management of central venous catheter (CVC) occlusion (CVC-occlusion), CVC-related thrombosis (CVC-thrombosis) and thromboembolism (CVC-thromboembolism).

PROCEDURE

A questionnaire was sent to all 22 United Kingdom Children's Cancer Study Group centres, requesting information about their views of the importance of, and their practices regarding, prophylaxis, diagnosis and treatment of CVC-occlusion/thrombosis.

RESULTS

Twenty (91%) centres responded. Eighty percent, 80% and 70%, respectively, stated that CVC-occlusion, CVC-thrombosis and CVC-thromboembolism were clinically important concerns. All centres used heparinised saline flushes as prophylaxis against CVC-occlusion, with little variation (</=30% centres) in frequency, volume and heparin concentration. Symptoms or signs suggesting partial CVC-occlusion, total CVC-occlusion, or CVC-thrombosis/thromboembolism were always investigated in 20%, 55% and 85% of centres, respectively, but with considerable variability in the nature and sequence of investigations performed, which included (depending on the clinical scenario) chest X-ray, contrast linography or venography, ultrasonography, echocardiography and magnetic resonance venography. A fibrinolytic lock was administered before investigation of CVC-occlusion in 75% of centres. Although 45%, 60% and 80%, respectively, always treated partial CVC-occlusion, total CVC-occlusion or CVC-thrombosis/thromboembolism, the type and order of treatments differed greatly between centres, especially for CVC-thrombosis/thromboembolism, in which CVC removal, systemic anticoagulation (heparin or warfarin), local or systemic fibrinolysis, or thrombectomy were performed in at least some centres.

CONCLUSIONS

The clinical practice of UKCCSG centres regarding prevention, investigation and treatment of CVC-occlusion/thrombosis varies greatly. Additional trials should facilitate development of evidence-based guidelines.

Antiphospholipid antibodies in pediatric systemic lupus erythematosus and the antiphospholipid syndrome

The antiphospholipid syndrome (APS) is recognized increasingly as the most common acquired hypercoagulation state of autoimmune etiology and may occur as an isolated clinical entity (primary APS) or in association with an underlying systemic disease, particularly systemic lupus erythematosus (SLE). The major differences between pediatric and adult APS include absence of common acquired risk factors for thrombosis, absence of pregnancy-related morbidity, increased incidence of infection-induced antibodies, differences in cut-off values for determination of aPL and specific factors regarding long-term therapy in children. APS in children has been largely reported in patients with arterial or venous thromboses and less frequently in association with neurological or hematological manifestations. The presence of aPL in pediatric SLE can modify the disease expression and may be an important predictor of the development of irreversible organ damage. Two recently established international registries of neonates and children with APS provide a good opportunity to conduct large, prospective studies on the clinical significance of aPL and long-term outcome of pediatric APS.

Comparison of low-molecular-weight heparin and antithrombin versus antithrombin alone for the prevention of symptomatic venous thromboembolism in children with acute lymphoblastic leukemia

BACKGROUND

Children with acute lymphoblastic leukemia (ALL) have a substantial risk for thromboembolism (TE) that is related to L-asparaginase-induced antithrombin (AT) deficiency and placement of central venous lines. Recent in vitro studies showed that the anticoagulant effects of low-molecular-weight heparin were profoundly affected by endogenous AT levels in children undergoing ALL therapy.

METHODS

A total of 112 consecutively recruited children with newly diagnosed ALL treated according to BFM 95/2000 protocols were enrolled in this trial. This prospective cohort study was carried out to determine the influence of combined low molecular weight heparin-prophylaxis (enoxaparin 1 mg/kg/ per day) and AT supplementation versus AT alone (noncontemporaneous control group) on the incidence of symptomatic TE during a follow-up of 240 days.

RESULTS

To maintain AT plasma levels above 50%, nearly 60% of all children needed at least one, most children two or three AT supplementations during induction therapy. 12.7% of the children that did receive only AT-prophylaxis (n = 71) (95% CI = 6.0-22.7) developed objectively confirmed symptomatic TE, as compared with no TE in children after combined prophylaxis (n = 41) (95% CI = 0.0-8.6, P < 0.05). Thromboses were located in the sinovenous system in the brain (n = 3), the lower deep veins (n = 3), the upper deep veins (n = 2) and in an upper deep vein combined with pulmonary embolism (n = 1).

CONCLUSION

Prophylaxis with enoxaparin was safe and effective in preventing TE. Although our data are encouraging, the in vivo efficacy of combined enoxaparin and AT prophylaxis to prevent symptomatic venous TE in children with ALL should be evaluated in a prospective randomized clinical trial.

Arterial thromboembolic disease: a single-centre case series study

AIM

Paediatric venous thromboembolic disease has been reported with increased frequency during the last decade. In contrast, the pathophysiology of arterial thromboembolic disease in infants and children has not been adequately explored. The aim of this study was to determine the prevalence, aetiology, diagnostic criteria, management and outcome of arterial thromboembolism (TE) in a tertiary paediatric centre.

METHODS

A prospective, single-centre registry was established at an Australian tertiary paediatric centre in order to address the aim of this study.

RESULTS

One-hundred-and-two arterial thrombotic events occurred in 98 patients during 48 months. Infants were most likely to have a lower limb arterial TE (n = 22) whilst children were most likely to have a central nervous system arterial TE (n = 26). Surgery was a frequent predisposing factor in both infants and children. Doppler ultrasonography, computerized tomography and magnetic resonance imaging were the most commonly used diagnostic modalities. Unfractionated heparin was the most frequently used treatment in both age groups. At discharge, 25 infants and twelve children had complete resolution of their arterial TE. Direct thrombosis-related mortality was 4% in infants and 9% in children. Duration of follow-up ranged from 1 to 900 days, with thirteen infants and 32 children never achieving complete resolution. Forty-nine percent of post-discharge survivors had significant long term sequelae directly attributable to their arterial TE.

CONCLUSION

Arterial TE occurred as frequently as venous TE in our tertiary paediatric population. The clinical outcome and long term sequelae of such events are significant.

Thromboembolism in children with sarcoma

BACKGROUND

Thromboembolism (TE) is a common complication and cause of death in adults with cancer. Cancer has been identified as a major risk factor in children with TE. However, the information regarding the epidemiology of TE in children with cancer, especially in association with childhood solid tumors, is scant.

OBJECTIVE

To define the prevalence and epidemiology of TE in children with sarcoma.

PROCEDURE

Hospital records of children </=18 years of age with sarcoma diagnosed and treated at McMaster Children's Hospital during January 1990 to December 2005 were reviewed for demographic details, details of diagnosis and therapy for sarcoma, and details of diagnosis and management of TE. Statistical analysis was performed using Fisher's exact t-test.

RESULTS

Ten of 70 (14.3%; 95% CI; 7.1, 24.7) patients with sarcoma developed symptomatic TE. Patients with CVL-dysfunction (n = 9) were at significantly higher risk for symptomatic TE compared to those without CVL dysfunction (n = 61) (55.5 vs. 8.2%; P = 0.002, 95% CI; 14.2, 80.5). Patients with pulmonary disease (n = 23) had higher prevalence of TE compared to those without pulmonary disease (n = 47) (26 vs.8.5%; P = 0.07, 95% CI; -2.06, 37.2). Older patients, patients with metastatic disease and those with Ewing sarcoma had higher prevalence of TE.

CONCLUSIONS

TE is a significant complication in children with sarcoma. Over 50% of patients with CVL dysfunction had symptomatic TE; such patients may warrant careful evaluation for associated TE. Large prospective studies are needed to define the epidemiology and identify risk factors predisposing to TE in children with sarcoma.

Enoxaparin therapy for arterial thrombosis in infants with congenital heart disease

OBJECTIVE

To investigate efficacy and safety of enoxaparin for catheter-related arterial thrombosis in infants with congenital heart disease.

DESIGN

Prospective observational study.

SETTING

Pediatric Intensive Care and Cardiology Unit at the University Children's Hospital of Zurich.

PATIENTS

A cohort of 32[Symbol: see text]infants aged 0-12[Symbol: see text]months treated with enoxaparin for catheter-related arterial thrombosis from 2002 to 2005.

MEASUREMENTS

Dose requirements of enoxaparin, resolution of thrombosis by Doppler ultrasound, and bleeding complications.

RESULTS

Catheter-related arterial thrombosis was located in the iliac/femoral arteries in 31 (97%) infants and aorta in 1 infant, and was related to indwelling catheters and cardiac catheterization in 17 (53%) and 15 (47%) cases, respectively. Newborns required increased doses of enoxaparin to achieve therapeutic anti-FXa levels (mean 1.62[Symbol: see text]mg/kg per dose) compared with infants aged 2-12 months (mean 1.12 mg/kg per dose; p=0.0002). Complete resolution of arterial thrombosis occurred in 29 (91%) infants at a mean of 23 days after initiation of enoxaparin therapy. Partial or no resolution was observed in 1 (3%) and 2 (6%) infants, respectively, at a mean follow-up time of 4.3 months. Bleeding complications occurred in 1 (3%) infant.

CONCLUSION

Enoxaparin is efficient and safe for infants with congenital heart disease and catheter-related arterial thrombosis, possibly representing a valid alternative to the currently recommended unfractionated heparin.

A randomized controlled trial for maintaining peripheral intravenous lock in children

The most effective and safe method of maintaining peripheral intravenous lock in children is an important clinical question that has been identified by the researchers. The results of recent studies comparing saline versus 10 units/ml of heparin saline flush using a 24-gauge catheter in neonatal and pediatric populations are conflicting and inconclusive. The objectives of this study were to evaluate the effectiveness and safety of three flush solutions: normal saline, 1 unit/ml of heparin saline and 10 units/ml of heparin saline for maintaining peripheral intravenous locks in children, and to establish a research-based practice in the study hospital. In a prospective, randomized controlled, double-blind trial, one hundred and twenty-three subjects ranging in age from 1-10 years with 123 intravenous locks were randomly chosen to receive 1 unit/ml of heparin saline, 10 units/ml of heparin saline and normal saline to evaluate length of catheter use, survival rate and incidence of intravenous complications. The study found no statistically significant differences in length of catheter use, estimated catheter survival and the incidence of intravenous complications among the three groups. The group that received 1 unit/ml of heparin saline demonstrated the highest rate of survival. The mean length of catheter use of the group that received 1 unit/ml of heparin saline (49.8 hours) was 17 hours longer than the group that received normal saline (32.5 hours). There are no significant differences among the three types of flushing solution in terms of the catheter longevity and incidence of intravenous complications.

Oral anticoagulation in a pediatric hospital: impact of a quality improvement initiative on warfarin management strategies

BACKGROUND

There are potential risks associated with the use of warfarin in children, particularly as the dosing requirements may decrease as patients get older.

CONTEXT

Our facility is a 715-bed freestanding pediatric tertiary care center with a large cardiac surgery center. A significant number of patients receive warfarin for treatment or prophylaxis of thromboembolic events while in hospital.

KEY MEASURES FOR IMPROVEMENT

Initial dose of warfarin and time taken to achieve goal therapeutic international normalized ratio (INR).

STRATEGIES FOR CHANGE

The intervention included: (1) revision of hospital drug formulary so that warfarin dosing was in accordance with the most recent guidelines; (2) warfarin administration restricted to one time of the day (12.00 noon); (3) target therapeutic INR level documented with each warfarin order; and (4) pharmacy computer system mandated that the pharmacist confirmed the target INR, documented the most current INR, and compared the dose with the formulary guidelines. If the warfarin dose was not in accordance with the formulary guidelines, the pharmacist contacted the physician and made dosing recommendations according to the guidelines.

EFFECTS OF CHANGE

The number of patients with supratherapeutic INR values during the hospital admission was decreased by more than 50% and goal INR values were documented more frequently in the medical record. There was also an increase in subtherapeutic INR values. The intervention had no effect on the time taken to achieve the goal therapeutic INR.

LESSONS LEARNED

Instituting changes in a number of aspects of anticoagulation management and incorporating an intensive educational effort across a breadth of healthcare providers can improve anticoagulation management with warfarin in challenging patient populations such as children. Similar methods could possibly improve anticoagulation with other agents such as unfractionated heparin or low molecular weight heparin.

Congenital prothrombotic disorders in children with peripheral venous and arterial thromboses

AIMS

To evaluate the prevalence of congenital prothrombotic disorders in children with peripheral venous and arterial thromboses.

METHODS

Deficiencies in antithrombin (AT), proteins C (PC) and S (PS), and increased lipoprotein (a), and the presence of factor V (FV) G1691A, prothrombin G20210A and methylenetetrahydrofolate reductase (MTHFR) mutations were investigated.

RESULTS

Forty-eight patients (mean age, 3.4 years) were investigated. Of these patients, 23 had venous thrombosis, 22 had arterial thrombosis, and 3 had both. No patients had AT, PC or PS deficiency. FV G1691A mutation was present in 2 (7.6%) and 3 (12%) patients with venous and arterial thromboses, respectively. The prothrombin G20210A mutation was present in 1 (4%) patient with arterial thrombosis. Homozygous MTHFR C677T mutation was detected in 4 (18%) and 2 (9%) patients with venous and arterial thromboses, respectively. Increased lipoprotein (a) was present in 2 (10%) and 1 (4.5%) patients with venous and arterial thromboses, respectively. Regarding acquired risk factors, 79% of all thrombotic events were related to catheter usage. An underlying disease was present in 96% of the patients.

CONCLUSIONS

Compared to acquired risk factors, congenital prothrombotic disorders are rarely present in children with peripheral venous and arterial thromboses. These results do not support general screening of children with venous and arterial thromboses for congenital prothrombotic disorders.

Venous thromboembolic disease: a single-centre case series study

AIM

The epidemiology of venous thromboembolism in children has likely changed since first being described a decade ago because of evolving management strategies and a greater awareness of predisposing factors for thrombosis in children. The Royal Children's Hospital commenced a 4-year prospective registry of venous thrombosis in 1999 to determine the current Australian epidemiology of venous thrombosis in infants and children.

METHODS

A prospective, single-centre registry was established to determine the prevalence, aetiology, diagnostic criteria, management and outcome of venous thromboembolism in an Australian tertiary paediatric centre.

RESULTS

The incidence of venous thrombosis was 8.0/10 000 hospital admissions. Fifty-eight per cent of infants and 49% of children were male. Seventy-seven per cent of venous thromboses in infants were associated with central venous cannulation compared with 47% in children. Doppler ultrasonography was the most frequently used diagnostic tool. Treatment strategies varied between age groups. The all-cause mortality rate for infants and children in this study was 8.4% (direct thrombus-related mortality 0%). Fifteen per cent of all patients demonstrated complete resolution of their venous thrombosis at discharge, with 48% demonstrating complete resolution at follow-up assessment. Fifteen per cent of patients experienced significant thrombosis-related morbidity at follow-up assessment.

CONCLUSION

In this single-centre registry, venous thrombosis in infants and children occurred with greater frequency than has previously been reported and its epidemiology varied. Central venous catheterisation continues to be a common precipitant to venous thrombosis. Optimal diagnostic and treatment interventions for venous thromboembolism have not yet been determined for infants and children, despite the significant incidence of long-term sequelae.

Minimizing perioperative blood loss and transfusions in children

PURPOSE

To summarize the physiology and pathophysiology relevant to perioperative blood loss in children. Strategies to reduce blood losses are reviewed.

METHODS

The literature was reviewed using the electronic library PUBMED and the Cochrane Database of Systematic Reviews. Relevant studies published in English or French with an English abstract are included. The following keywords were used: children, blood transfusion, surgical blood loss, erythropoietin, autologous blood, red blood cell saver, normovolemic hemodilution, desmopressin, aminocaproic acid, tranexamic acid, aprotinin, cardiac surgery, liver transplantation and scoliosis surgery.

MAIN FINDINGS

For patients with idiopathic scoliosis, predonation with or without the addition of erythropoietin is a safe and effective way to avoid the use of allogenic blood products. For open heart procedures: whole blood of less than 48 hr is helpful for children of less than two years of age undergoing complex procedures; tranexamic acid may be helpful for cyanotic heart disease and, to a lesser degree, for reoperations; while anti-kallikrein blood levels of aprotinin may both reduce the need for allogenic blood transfusions and improve postoperative oxygenation in infants.

CONCLUSION

Reducing perioperative allogenic blood transfusions is possible in pediatric patients provided that prophylactic measures are adapted to age, disease and type of surgery.

Clinical Measures of Heparin’s Effect and Thrombin Inhibitor Levels in Pediatric Patients with Congenital Heart Disease

In this investigation, we examined the relationship among three thrombin inhibitors, antithrombin III (ATIII), heparin cofactor II (HCII), and alpha-2-macroglobulin (alpha2M), and several clinical tests of heparin's effect in pediatric patients with congenital heart disease undergoing cardiopulmonary bypass. One hundred eighteen children were stratified into six age groups: <1 mo, 1-3 mo, 3-6 mo, 6-12 mo, 12-24 mo, and >10 yr. Baseline ATIII, HCII, and alpha2M values were measured. Baseline celite- and kaolin-activated clotting times (ACT) were also measured and repeated 3 min after a standard heparin dose of 400 U/kg. Differences in ACT values before and after heparin administration and a heparin dose-response relationship were calculated for each patient. Kaolin-activated ACT tests showed less variation after heparin administration than celite-activated tests. In contrast to what has been demonstrated in adults, ATIII showed no positive correlation with the clinical tests of heparin's effect nor did the other thrombin inhibitors. Additionally, patients <1 mo old had unexpectedly low levels of alpha2M accompanying their expected low levels of ATIII and HCII. Our findings raise concerns about the ability of heparin to adequately anticoagulate these neonates during cardiopulmonary bypass and, consequently, challenge the accuracy of ACT prolongation to truly reflect the extent of their anticoagulation.

Stroke following Glenn anastomosis in a child with inherited thrombophilia

The optimal anticoagulation following Fontan operation and its modifications remain controversial and it is even less well defined as regards patients with inherited thrombophilia. We present a case of a child with bidirectional Glenn anastomosis for double inlet left ventricle that suffered a stroke despite aspirin prophylaxis; the patient was combined homozygous for prothrombin G20210A mutation and for methylenetetrahydrofolate reductase C677T mutation as well. The family history was positive for fetal loss and premature cardiovascular disease. Large-scale studies are needed to evaluate whether carriers of thrombophilia mutations need more intense thromboprophylaxis.

Diagnosis and management of heparin-induced thrombocytopenia

PURPOSE

To review recent developments in the pathogenesis, clinical features, laboratory testing and treatment of heparin-induced thrombocytopenia (HIT).

METHODS

Narrative review of the literature, including relevant papers published in English or French.

PRINCIPAL FINDINGS

Although the prevalence of HIT has decreased with the widespread use of low molecular weight heparin in the past ten years, HIT remains a life-threatening prothrombotic state. This immune adverse event due to heparin-dependent antibodies that bind to chemokines (such as platelet factor 4) induces platelet activation and hypercoagulability. Heparin-induced thrombocytopenia can be complicated by thrombosis even after withdrawing heparin, explaining why substituting heparin with an alternative anticoagulant (danaparoid, lepirudin, argatroban) is always necessary. However, management of these alternative treatments is difficult, and in some patients there is the risk of withdrawing heparin without taking the time to diagnose HIT properly on the basis of clinical and laboratory findings (evolution of platelet count, laboratory testing such as antigen assays and platelet activation tests).

CONCLUSIONS

Management of HIT has become easier in recent years with the development of more specific and sensitive laboratory tests and new antithrombotic drugs. However, the diagnosis of HIT is often difficult, and it remains very important to investigate this adverse reaction systematically in every patient treated with heparin who develops thrombocytopenia.

Management of oral anticoagulation in a population of children with cardiac disease using a computerised system to support decision-making

OBJECTIVE

To assess the impact of a computerised system to support decision-making concerning the management of warfarin used in maintenance of anti-coagulation.

DESIGN

Retrospective case series study comparing manual and computerised records of prescribing.

SETTING

A tertiary paediatric cardiology department in a teaching hospital.

PARTICIPANTS

The 26 children receiving warfarin to maintain anticoagulation at the time of introduction of a computerised system to support decision-making.

INTERVENTIONS

A rules-based computerised system to support decisions, based on existing departmental guidelines, for management of anticoagulation using warfarin was introduced to aid prescribing physicians.

MAIN OUTCOMES

We assessed the stability of the International Normalised Ratio, along with the number of checks made of the ratio, and the adjustments of dosage. Dosages, and recheck interval prescriptions, were compared to the guidelines established by our department.

RESULTS

We compared 274 prescriptions made manually, and 608 made using the computerised system to support decision-making, covering periods of 4, and 11, months respectively. The mean proportion of time spent by the patients within their target range for the International ratio was maintained during the period studied, at 76 percent versus 79 percent (p = 0.79). The median number of checks of the ratio made for each patient over a period of 28 days was unchanged, at 1.9 versus 2.1 (p = 0.58). There was a significant change in prescribing practices, which more closely followed the departmental guidelines.

CONCLUSION

The introduction of a computerised system to support decision-making maintained the stability of the International ratio using warfarin, without increasing the number of checks or adjustments of dosages, in a point-of-care service for anticoagulation in children.

Therapeutic approaches and advances in pediatric stroke

Evidence-based therapeutic interventions for pediatric ischemic cerebrovascular disease are beginning to emerge. The primary therapeutic target is usually the pathological prothrombotic disturbance that underlies the majority of pediatric stroke. A battle between anticoagulation and anti-platelet therapies continues to provide controversy and is the inspiration for upcoming randomized trials. Supportive care and neuroprotective strategies are an important consideration in children with stroke. Attempts to determine the safety of acute thrombolytic interventions are also underway. Finally, unique medical and surgical treatments for specific diseases leading to stroke in children continue to evolve. After briefly summarizing the epidemiology, pathophysiology, diagnosis, and outcomes of ischemic strokes in children, treatment approaches and alternatives will be reviewed in detail with emphasis placed on current areas of controversy and future directions for clinical research.