Vascular anomaly cases for the pediatric hematologist oncologists-An interdisciplinary review

Vascular anomalies (VAs) are classified as tumors or malformations depending on their clinical characteristics, pathological diagnosis, and genomic information. Diagnosis can be challenging because of the heterogeneity of clinical presentation; thus, the best diagnosis and care are provided by an interdisciplinary team of specialists. Over the past 10 years, an increasing number of pediatric hematologist/oncologists are caring for patients with VAs secondary to new medical therapy options and clinical trials. This paper focuses on complicated VA issues often seen by the pediatric hematologist/oncologist. The paper reviews clinical pearls on diagnosis, histology, radiology, and treatment options.

Rationale and design of a phase III safety trial of idarucizumab in children receiving dabigatran etexilate for venous thromboembolism

BACKGROUND

The incidence of venous thromboembolism (VTE) in children has been increasing. Anticoagulants are the mainstay of treatment but are associated with bleeding events that may be life-threatening. Idarucizumab is a fragment antigen-binding (fab) that provides immediate, complete, and sustained reversal of dabigatran's anticoagulant effects in adults.

OBJECTIVE AND METHODS

This phase III, open-label, single-arm, multicenter, multinational trial will assess the safety of idarucizumab in children participating in two ongoing trials investigating dabigatran etexilate. Eligible patients will be children with VTE (aged 0-≤18 years; n = ~5) with life-threatening or uncontrolled bleeding (group A), and children who require emergency surgery/urgent procedures for a condition other than bleeding (group B). Patients will receive idarucizumab up to 5 g as two consecutive intravenous infusions over 5-10 minutes each, as two 10-15-minute drips or as two bolus injections (15 minutes apart) and will be monitored for 30 days. The primary endpoint will be the safety of idarucizumab assessed by the occurrence of drug-related adverse events (including immune reactions) and all-cause mortality. Secondary endpoints will be the reversal of dabigatran anticoagulant effects assessed by changes in diluted thrombin time and ecarin clotting time, time to achieve complete reversal and the duration of the reversal and bleeding severity (group A). The formation of antidrug antibodies at 30 days post-dose and cessation of bleeding will also be assessed.

CONCLUSION

This study will report the safety of idarucizumab in children with VTE who require rapid reversal of the anticoagulant effects of dabigatran. Clinical trial registration: NCT02815670.

Variants in chondroitin sulfate metabolism genes in thrombotic storm

INTRODUCTION

Thrombotic storm (TS) presents as a severe, acute thrombotic phenotype, characterized by multiple clotting events and frequently affecting younger adults. Understanding the extensive hypercoagulation of an extreme phenotype as TS will also provide insight into the pathogenesis of a wider spectrum of thrombotic disorders.

MATERIAL AND METHODS

We completed whole exome sequencing on 26 TS patients, including 1 multiplex family, 13 trios and 12 isolated TS patients. We examined both dominant and recessive inheritance models for known thrombotic factors as well as performed a genome-wide screen. Identified genes of interest in the family and trios were screened in the remaining TS patients. Variants were filtered on frequency (<5% in 1000 genomes), conservation and function in gene and were annotated for effect on protein and overall functionality.

RESULTS

We observed an accumulation of variants in genes linked to chondroitin sulfate (CS), but not heparan sulfate metabolism. Sixteen conserved, rare missense and nonsense variants in genes involved in CS metabolism (CHPF, CHPF2, CHST3, CHST12, CHST15, SLC26A2, PAPSS2, STAB2) were identified in over one-third of the TS patients. In contrast, we identified only seven variants in known thrombosis genes (including FV Leiden).

CONCLUSIONS

As CS has multiple functions in the glycocalyx protecting the endothelial cells, reduced availability of CS could diminish the normal control mechanisms for blood coagulation, making these CS metabolism genes strong potential risk factors for TS. Overall, no single gene was identified with strong evidence for TS causality; however, our data suggest TS is mediated by an accumulation of rare pro-thrombotic risk factors.

Incidence of infective endocarditis and its thromboembolic complications in a pediatric population over 30years

BACKGROUND

Pediatric infective endocarditis (IE) has been associated with high morbidity and mortality, mostly related to thromboembolic complications (TEC). The objective of our study was to describe the experience in children with IE and to review the changes over a thirty-year period, regarding origin of IE, incidence of vegetations, TEC and their respective morbidity and mortality rates.

METHODS

A retrospective chart review of children aged 0-18years with IE defined by the Duke Criteria and admitted to The Hospital for Sick Children, was conducted. Data were divided into three periods (P); P1 (1979-1988); P2 (1989-1998); and P3 (1999-2008).

RESULTS

The study included 113 patients, median age 7yrs.; females: 46 (41%), congenital heart defects 95 (84%), comparable in all periods. Overall, cardiac vegetations were found in 68/113 patients (60%); large vegetations (≥1cm) in 32 patients (28%). Fourty-five (45/133 [40%]) TEC were documented, 22 patients (20%) developed cerebrovascular events (CVE) and 23 patients (20%) had non-CVE. Patients diagnosed during P3 were older, had more vegetations (p<0.05), and a higher incidence of community acquired-IE (p<0.05). Overall, mortality was 15%, comparable in all periods. Significant risk factors for mortality were vegetations (HR 6.44; 95% CI: 2.07-20.01, p=0.002) and heart failure (HR 28.39; 95% CI: 10.49-76.85, p<0.001).

CONCLUSIONS

Over the study period, we report a growing incidence of community acquired pediatric IE in older children accompanied by an increasing rate of TEC. Heart failure and vegetations were associated with an increased mortality. These preliminary data need to be confirmed by prospective data.

Evaluation of the need for chest X-rays in the management of asymptomatic, intraluminal vascular access device occlusion in childhood cancer

BACKGROUND

Venous access device (VAD) occlusion from intraluminal thrombus is a common complication during childhood cancer treatment. Current practice at many institutions is to assess VAD position with a chest X-ray (CXR) prior to intraluminal administration of tissue plasminogen activator (tPA). We aimed to determine the utility of this practice.

PROCEDURE

A retrospective chart review of children with newly diagnosed cancer with a VAD, treated at The Hospital for Sick Children between 2010 and 2011, was performed. Episodes of line occlusion were identified both by reviewing patient CXRs for indication and identifying tPA doses dispensed. These episodes were reviewed to determine whether CXR findings resulted in management other than tPA. Cases in which the X-ray resulted in a change in management were further reviewed to determine whether administration of tPA could have resulted in potential patient harm.

RESULTS

A total of 330 patients with newly diagnosed cancer with VADs were identified. Eighty-five (25.8%) patients experienced 123 episodes of VAD occlusion. VAD occlusions occurred more frequently in patients with tunneled external central venous lines (16/39, 41.5%) and peripherally inserted central catheters (PICC) (27/73, 37.0%) versus PORT (42/216, 19.4%; P = 0.001). There were nine (8.1%) episodes of VAD occlusion evaluated with a CXR in which the findings led to a change in management other than administering tPA. In each case, multiple specialists independently concluded that administration of tPA would have been unlikely to cause patient harm.

CONCLUSION

Routine CXRs prior to the administration of tPA for asymptomatic VAD occlusion can safely be omitted.

Comparing the burden of illness of haemophilia between resource-constrained and unconstrained countries: the São Paulo-Toronto Hemophilia Study

INTRODUCTION

Although the regular replacement of clotting factor concentrates (prophylaxis) has been well established as the standard of care for severe haemophilia, the high cost of factor concentrates has limited access to prophylaxis in countries with under-developed or developing economies.

AIMS

We studied the health gap that could be addressed by providing unlimited access to clotting factor concentrates with implementation of long-term prophylaxis initiated from an early age in life.

METHODS

We performed a cross-sectional study of a random, representative sample of boys with moderate and severe haemophilia at three haemophilia treatment centres in Sao Paulo, Brazil, and one centre in Toronto, Canada.

RESULTS

Canadian subjects were more often treated with prophylaxis, and began treatment at an earlier age. Fewer Canadian subjects had bleeds within the preceding 6 months (19 vs. 34, P = 0.003). Canadian subjects had lower (better) Pettersson radiographic scores (1.5 vs. 6.0, P = 0.0016), lower (better) Hemophilia Joint Health Scores (5.5 vs. 10.5, P = 0.0038), higher (better) Activity Scale for Kids scores (96.6 vs. 92.0, P = 0.033), more time spent in vigorous activity, and higher (better) social participation scores.

CONCLUSIONS

Our findings suggest that increasing access to clotting factor concentrates for young boys with severe haemophilia is a global imperative.

Risk Factors, Prophylaxis, and Treatment of Venous Thromboembolism in Congenital Heart Disease Patients

Congenital heart disease (CHD) is a common condition in the pediatric population, affecting up to 1% of all live births (i.e., around 40,000 newborns/year in the United States). Although CHD does have a wide range of severity, by the age of 5 years approximately 80% of patients will require at least one surgical intervention to achieve a complete/palliative cardiac repair. Today, in light of their much-improved surgical survival, the care of these patients focuses on morbidity prevention and/or treatment. One such morbidity has been the increased frequency of thrombotic occlusions [e.g., cardioembolic arterial ischemic strokes; arterial, cardiac, and/or newly created shunt thrombosis; venous thromboembolism (VTE)]. Patients with CHD are at high risk of developing thrombosis due to the disruption of blood flow, CHD-related coagulopathy, inflammation, and/or platelet activation secondary to extracorporeal circulation support required during open-heart surgery or as a bridge to recovery, which can increase thrombus formation. In this article, we will discuss how the coagulation system is altered in patients with CHD in regard to the patient's anatomy, procedures they undergo to correct their congenital heart defect, and other risk factors that may increase their thrombotic risk, focusing on VTE. We will also discuss the most recently published reports pertaining to guidelines on prophylaxis and treatment of VTE in this population. Finally, we will briefly address the long-term VTE outcomes for patients with CHD.

Development of CAPTSureTM - a new index for the assessment of pediatric postthrombotic syndrome

Essentials We developed a discriminative and evaluative index for pediatric postthrombotic syndrome (PTS). A Delphi-survey was used for item reduction and multi-criteria decision analysis for item weighting. The new index assesses limb PTS based on the relative severity of each sign and symptom. Higher scores related to higher odds of parental dissatisfaction with their child's condition.

SUMMARY

Background Postthrombotic syndrome (PTS) is a complication of deep vein thrombosis defined by the presence of characteristic signs and symptoms. We developed a discriminative and evaluative index for the assessment of upper extremity (UE) and lower extremity (LE) pediatric PTS. Methods The items to be included in the index were voted for by 26 pediatric thrombosis experts invited to participate in a Delphi survey. Subsequent item weighting was based on item importance elicited by the use of multicriteria decision analysis (MCDA); 122 healthcare providers and patients/parents were invited to participate in item weighting. The implications of the overall scores were explored by comparison with PTS diagnosis (independently assessed by two clinical experts) and parental satisfaction/dissatisfaction with their child's current condition. Results Items voted for inclusion by at least 70% of the Delphi survey respondents (81% response rate) were pain, paresthesia, swelling, heaviness, endurance, collateral circulation and arm circumference difference for the UE, and pain, paresthesia, swelling, heaviness, tightness, tired limb, redness/purple or blotchy skin, endurance, ulcers and thigh/calf circumference difference for the LE. Items were then weighted by the use of MCDA (82% response rate). The index had excellent discrimination for patients with/without PTS. For every 10-point increase in index scores (with higher scores being indicative of worse PTS), the odds of parental dissatisfaction increased by 75% and 92% in the UE and LE, respectively. Conclusion We report the development of the CAPTSure™ (index for the Clinical Assessment of Postthrombotic Syndrome in children), which reflects collective judgement of the severity of pediatric PTS. We also provide information on the meaning of the scores.

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

BACKGROUND

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

METHODS/DESIGN

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

DISCUSSION

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

SYSTEMATIC REVIEW REGISTRATION

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

Timing of low bone mineral density and predictors of bone mineral density trajectory in children on long-term warfarin: a longitudinal study

We studied bone mineral density (BMD) of children exposed to long-term warfarin. BMD Z-scores ≤ -2.0 were estimated to occur in less than one fifth of the patients after 10 years of warfarin exposure, and BMI and growth hormone deficiency predicted BMD changes over time. These predictors can help identify high-risk patients.

INTRODUCTION

Children with chronic diseases are at increased risk of developing thrombosis, which may require long-term warfarin therapy. Warfarin could further jeopardize the bone health of a population already at risk for bone fragility. Our objective was to investigate the occurrence and timing of low bone mineral density (BMD) and the predictors that influence BMD trajectory in children receiving warfarin for >1 year.

METHODS

We analyzed the results of an institutional protocol that includes dual-energy X-ray absorptiometry, with or without spinal X-rays and laboratory biomarkers, as required.

RESULTS

Low BMD (age, sex, race, and height-for-age-Z-score adjusted BMD Z-score ≤ -2.0) was detected in 13 % (9/70) of the patients at some point during their follow-up; these patients were more likely to have complex underlying medical conditions and low body mass index (BMI) percentile. BMD Z-scores remained within normal range in 87 % of children. Survival analysis showed that the estimated 10-year abnormal BMD-free rate for the entire group was 81 % (95 % confidence interval [CI] 69 to 93 %). Trajectory analysis revealed that BMI percentiles at baseline and growth hormone deficiency (GHD) were associated with lower BMD Z-scores at the first assessment, whereas baseline BMI percentile was the only predictor of BMD Z-score over time.

CONCLUSIONS

Our findings identified BMI and GHD as risk factors influencing BMD in children exposed to long-term warfarin, creating an opportunity for early detection and intervention in these patients.

Management and Outcomes of Patients with Occlusive Thrombosis after Pediatric Cardiac Surgery

OBJECTIVES

To evaluate management and outcomes of thrombosis after pediatric cardiac surgery and stratify thrombi according to risk of short- and long-term complications to better guide therapeutic choices.

STUDY DESIGN

Retrospective review was performed of 513 thrombi (400 occlusive) diagnosed after 213 pediatric cardiac operations. Long-term outcomes over time were assessed with the use of parametric hazard regression models.

RESULTS

Serious complications and/or high-intensity treatment occurred with 17%-24% of thrombi depending on location, most commonly in thrombi affecting the cardiac and cerebral circulation. Bleeding complications affected 13% of patients; associated factors included thrombolytics (OR 8.7, P < .001), greater daily dose of unfractionated heparin (OR 1.25 per 5 U/kg/day, P = .03), and extracorporeal support (OR 4.5, P = .007). Radiologic thrombus persistence was identified in 30% ± 3% at 12 months; associated factors included extracorporeal support (hazard ratio [HR] 1.9, P = .003), venous (HR 1.7, P = .003), and occlusive thrombi at presentation (HR 1.8, P = .001); greater oxygen saturation before surgery (HR 1.13/10%, P = .05) and thrombi in femoral veins (HR 1.9, P = .001) were associated with increased hazard of resolution. Freedom from postthrombotic syndrome was 83% ± 4% at 6 years, greater number of persistent vessel segment occlusions (HR 1.8/vessel, P = .001) and greater fibrinogen at diagnosis (HR 1.1 per g/L, P = .02) were associated with increased hazard.

CONCLUSIONS

Thrombosis outcomes after pediatric cardiac surgery remain suboptimal. Given that more intensive treatment would likely increase the risk of bleeding, the focus should be on both thrombosis-prevention strategies, as well as in tailoring therapy according to a thrombosis outcome risk stratification approach.

Severe Cerebral Vasospasm and Childhood Arterial Ischemic Stroke After Intrathecal Cytarabine

We report on 2 patients who developed widespread cerebral vasospasm and arterial ischemic strokes (AIS) after application of intrathecal (IT) cytarabine. In a 3-year-old child with acute lymphoblastic leukemia (ALL), left leg weakness, hyperreflexia, and clonus were noted 4 days after her first dose of IT cytarabine during the induction phase of her chemotherapy. Cerebral MRI revealed multiple acute cerebral ischemic infarcts and widespread cerebral vasospasm. A 5-year-old girl complained of right arm and leg pain and began limping 11 days after IT cytarabine. Symptoms progressed to right dense hemiplegia, left gaze deviation, headache, and speech arrest. MRI revealed 2 large cortical areas of diffusion restriction in the right frontal and left parietal lobes. Cerebral magnetic resonance angiography (MRA) showed irregular narrowing affecting much of the intracranial arterial circulation. Although the first child fully recovered from her neurologic symptoms, the second patient had persistent hemiplegia on follow-up. Including this report, there are now 4 pediatric ALL cases of severe cerebral vasospasm and AIS in the context of IT cytarabine administration, strongly suggesting a true association. Differential diagnosis and management issues are discussed. Along with the more widespread use of MRI and MRA, the true frequency of this severe adverse effect will become clearer in future. For any child with neurologic symptoms within hours or days of receiving IT cytarabine, a low threshold for cerebral imaging with MRI and MRA is recommended.

Childhood physical activity body contact risk: feasibility of a novel technique for objective measurements of impact speed, frequency, and intentionality

INTRODUCTION

Children at risk for bleeding injuries are restricted from body contact during physical activity but current recommendations are based on expert opinion.

AIM

Evaluate high-speed digital video recording as an objective measure of body contact risk during physical activity.

METHODS

Observational study of physical activities among healthy children, grouped according to participation in teams (vs. individual) and on their perceived risk of injury (high/low). High speed digital video recordings documented the collision target (floor/ground/ice, people, wall, equipment), estimated speed, and impact rates for team and individual activities, with and without expected body contact.

RESULTS

Among 348 participating children (3-16 years, 51% female), 32% to 78% experienced at least one contact. Impact type varied significantly (chi-square, p < 0.001) by activity category. Unstructured and Team high risk activity impacts were primarily with the floor/ground, whereas Individual low risk activities were characterized by equipment impacts. Impact speeds were typically 1.0 to 2.1 m s(-1) . Higher impact speeds occurred during instructional classes (2.1 m s(-1) ), unstructured free swim (1.9 m s(-1) ) and ball hockey (1.7 m s(-1) ). Impact rates were higher during Team high risk and Team low risk sports (3.0 and 1.8 impacts per minute, respectively) compared to Individual (high or low risk) or Unstructured activities (0.2-0.3 impacts per minute).

CONCLUSIONS

High speed video recordings of childhood physical activity are a feasible method for characterizing the frequency, type, direction and speed of impacts. Quantifying the impacts that occur during childhood physical activity could inform the guidelines for physical activity participation among children with identified bleeding risks.

A critical review of scoring options for clinical measurement tools

BACKGROUND

The aim of this paper is twofold: (1) to describe the fundamental differences between formative and reflective measurement models, and (2) to review the options proposed in the literature to obtain overall instrument summary scores, with a particular focus on formative models.

METHODS

An extensive literature search was conducted using the following databases: MEDLINE, EMBASE, PsycINFO, CINAHL and ABI/INFORM, using "formative" and "reflective" as text words; relevant articles' reference lists were hand searched.

RESULTS

Reflective models are most frequently scored by means of simple summation, which is consistent with the theory underlying these models. However, our review suggests that formative models might be better summarized using weighted combinations of indicators, since each indicator captures unique features of the underlying construct. For this purpose, indicator weights have been obtained using choice-based, statistical, researcher-based, and combined approaches.

CONCLUSION

Whereas simple summation is a theoretically justified scoring system for reflective measurement models, formative measures likely benefit from the use of weighted scores that preserve the contribution of each of the aspects of the construct.

Normal values for segmental bioimpedance spectroscopy in pediatric patients

INTRODUCTION

Localized limb edema is a clinically relevant sign in diseases such as post-thrombotic syndrome and lymphedema. Quantitative evaluation of localized edema in children is mainly done by measuring the absolute difference in limb circumference, which includes fat and fat-free mass. Bioimpedance spectroscopy (BIS) provides information on the fluid volume of a body segment. Our objective was to determine normal ranges for segmental (arm and leg) BIS measurements in healthy children. Additionally, we determined the normal ranges for the difference in arm and ankle circumference and explored the influence of handedness and the correlation between techniques.

METHODS

Healthy children aged 1-18 years were recruited. The ratio of extracellular fluid content between contralateral limbs (estimated as the inter-arm and inter-leg extracellular impedance ratio), and the ratio of extracellular to intracellular fluid content for each limb (estimated as the intracellular to extracellular impedance ratio) were determined with a bioimpedance spectrometer. Arm and ankle circumference was determined with a Gulick II tape.

RESULTS

We recruited 223 healthy children (48 infants, 54 preschoolers, 66 school-aged children, and 55 teenagers). Normal values for arm and leg BIS measurements, and for the difference in arm and ankle circumference were estimated for each age category. No influence of handedness was found. We found a statistically significant correlation between extracellular impedance ratio and circumference difference for arms among teenagers.

CONCLUSION

We determined normal BIS ranges for arms and legs and for the difference in circumference between arms and between ankles in children. There was no statistically significant correlation between extracellular impedance ratio and difference in circumference, except in the case of arms in adolescents. This may indicate that limb circumference measures quantities other than fluid, challenging the adequacy of this technique to determine the presence of localized edema in most age groups.

Do children without a known bleeding tendency undergoing PICC placement require coagulation laboratory testing?

BACKGROUND

Obtaining basic hemostatic laboratory investigations prior to peripherally inserted central catheter (PICC) insertion remains controversial, even if the procedure is converted to a tunneled central venous line (CVL) placement.

OBJECTIVE

To determine the value of pre-procedural blood screening (hemoglobin level, platelet count, aPTT/INR) in hospitalized children without a known bleeding diathesis.

MATERIALS AND METHODS

This retrospective review included pediatric patients undergoing PICC insertion who had both laboratory screening and post-PICC hemoglobin level. Two cohorts (A: 0-3 months; B: >3 months-18 years) were analyzed for procedural major/minor bleeding.

RESULTS

Of 1,441 consecutive children identified during a 3-year period, 832 patients (226 in cohort A, 606 in cohort B) fulfilled the inclusion criteria. Overall, 36% (300/832) of the patients had at least one abnormal laboratory result. Only 0.2% (3/1,441) of patients required conversion to a central venous line. In cohort A no major bleeding occurred; the minor bleeding frequency was 30% (68/226). Neither abnormal laboratory results nor correction of abnormal laboratory results was associated with minor bleeding complications. The positive and negative predictive values (PPV/NPV) of having abnormal laboratory screening were 0.22 and 0.68, respectively. In cohort B the major bleeding frequency was 1% (6/606) but no patient required any blood transfusion; minor bleeding occurred in 29% (174/606). Neither abnormal laboratory results nor correction of abnormal laboratory results was associated with minor bleeding complications. The PPV and NPV of abnormal laboratory screening results were 0.24 and 0.72, respectively.

CONCLUSION

Pre-procedural blood screening did not predict bleeding in hospitalized children without a known bleeding diathesis undergoing PICC insertion. The rarity of major bleeding complications and need for conversion to a central venous line did not support a need for laboratory screening.

Assessment of the outcomes associated with periprocedural anticoagulation management in children with acute lymphoblastic leukemia

OBJECTIVE

To report the outcomes of an institutional protocol for periprocedural anticoagulant (AC) management in children with acute lymphoblastic leukemia (ALL).

STUDY DESIGN

Children being treated for ALL who received full-dose (therapeutic) anticoagulation before undergoing at least 1 lumbar puncture (LP) were included in this retrospective cohort study. The main outcome was the risk of traumatic LP; exploratory analysis included the risks of symptomatic spinal hematoma and progression/recurrence of the thrombotic event. Analyses were conducted using logistic regression analysis with a generalized estimating equation approach.

RESULTS

Twenty-two children with ALL receiving an AC underwent a total of 396 LPs. Although traumatic LP was associated with full-dose AC therapy in univariable analysis, a multiple logistic regression model controlling for other risk factors for traumatic LP showed that AC therapy was not significantly associated with the risk of traumatic LP when the ACs were held as per the institutional protocol. No patient developed symptomatic spinal hematoma. Exploratory analysis revealed that AC dose, a likely marker of thrombus burden, was significantly associated with progression/recurrence of the thrombotic event in univariable analysis.

CONCLUSION

In our cohort, recent AC therapy was not statistically associated with an increased risk of bleeding after LP when following a specific protocol for periprocedural AC management. The risk associated with the progression/recurrence of thromboembolic events requires further evaluation.

Low molecular weight heparin for prevention of central venous catheterization-related thrombosis in children

BACKGROUND

The prevalence of children diagnosed with deep vein thrombosis or pulmonary embolism has been increasing in the last decade. The most common thrombosis risk factor in neonates, infants and children is the placement of a central venous catheter (CVC). To date, it is unknown if the practice of anticoagulation prophylaxis with low molecular weight heparin (LMWH) decreases CVC-related thrombosis in children.

OBJECTIVES

The primary objective of this review was to determine the effect of LMWH prophylaxis on reducing the incidence of CVC-related thrombosis in children.Secondary objectives were to determine the effect of LMWH on occlusion of CVCs, number of days of CVC patency, episodes of catheter-related sepsis, side effects of LMWH (allergic reactions, major and minor bleeding complications, abnormal coagulation profile, osteoporosis) and mortality during therapy.

SEARCH METHODS

The Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched the Specialised Register (last searched June 2013), CENTRAL (2013, Issue 5) and clinical trial databases. The authors searched MEDLINE and EMBASE (July 2013). Bibliographies of identified articles were searched. There were no language restrictions.

SELECTION CRITERIA

Randomised and quasi-randomised trials comparing LMWH prophylaxis to standard care given to prevent CVC-related thrombotic events in children were included. We selected studies conducted in children aged 0 to 18 years.

DATA COLLECTION AND ANALYSIS

Two review authors independently identified eligible studies, which were assessed for study quality including bias, and extracted unadjusted data where available. In the data analysis step, all outcomes were analysed as binary or dichotomous outcomes. The effects of interventions were summarised with risk ratios (RR) and their respective 95% confidence intervals (CI).

MAIN RESULTS

One of 17 studies retrieved for full-text assessment for eligibility was included in the final analysis. This study included a total of 186 participants and investigated the effect of LMWH to prevent CVC-related thrombosis compared to standard care. The risk of bias of the study was assessed to be low, except for the unclear risk of selection bias (allocation concealment not reported) and detection bias since it was an open-label study. Nonetheless, outcome adjudication was blinded. However, overall the quality of the evidence was low due to the fact that the study was underpowered. The CIs for the risk of CVC-related thrombosis (symptomatic and asymptomatic events) were compatible with benefits of either LMWH (reviparin) or the control (RR for symptomatic thrombosis 1.03, 95% CI 0.21 to 4.93; RR for asymptomatic thrombosis 1.17, 95% CI 0.45 to 3.08). Similarly, only one patient in the standard care group suffered a major bleeding event, while minor bleeding was found in 53.3% of patients in the reviparin arm and in 44.7% of patients in the standard care arm (major bleeding RR 0.34, 95% CI 0.01 to 8.26; minor bleeding RR 1.20, 95% CI 0.91 to 1.58). Lastly, there were two deaths within the study and neither were the result of a venous thrombotic event (VTE), occurring in the standard care arm. No additional adverse effects were reported. Other pre-specified outcomes for this review were not reported.

AUTHORS' CONCLUSIONS

A single study reported imprecise effects for the risk of CVC-related thrombosis in children on a CVC anticoagulant prophylaxis regimen. The quality of the evidence was low due to the fact that the included study was clearly underpowered, hampering any conclusions in regards to the efficacy of LMWH prophylaxis to prevent CVC-related thrombi in children. Further prospective randomised studies are highly encouraged.

Different unfractionated heparin doses for preventing arterial thrombosis in children undergoing cardiac catheterization

BACKGROUND

The role of cardiac catheterization in pediatrics has progressed significantly over the last two decades, evolving from a primary diagnostic tool to a primary treatment modality in children with congenital heart disease. Vascular complications, particularly arterial thrombosis, are among the most common unwanted post-cardiac catheterization events. In 1974, unfractionated heparin proved to be superior to placebo in decreasing the incidence of arterial thrombosis in pediatric patients. However, the optimal dose of unfractionated heparin to be utilized in this setting remains a matter of controversy.

OBJECTIVES

To evaluate the use of low-dose (< 100 units/kg) versus high-dose (≥ 100 units/kg) unfractionated heparin administered as an intravenous bolus at the time of initiation of cardiac catheterization (that is, immediately after arterial puncture), with or without subsequent heparin maintenance doses, for the prevention of post-procedural arterial thrombosis in children.

SEARCH METHODS

The Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched the Specialised Register (last searched November 2013) and CENTRAL (2013, Issue 10). The authors searched MEDLINE, EMBASE, and the Virtual Health Library. Clinical trials databases and sources of grey literature were searched. No language restrictions were applied.

SELECTION CRITERIA

Randomized or quasi-randomized trials that compared low dose to high dose unfractionated heparin administered prior to cardiac catheterization were included. We selected studies conducted in children aged 0 to 18 years.

DATA COLLECTION AND ANALYSIS

The first screening of potentially eligible studies was conducted by one of the authors (MLA). The second screening, quality assessment and data extraction were independently conducted by two authors (MLA, LRB). Outcomes (thrombotic events, bleeding complications, other complications) were treated as dichotomous variables. The effect measures used were risk ratio (RR), risk difference (RD) and number needed to treat (NNT), with 95% confidence intervals (CI).

MAIN RESULTS

Two studies with a total of 492 participants were eligible for inclusion. Risk of bias was low for all domains in one of the studies and unclear for the other. One of the trials was stopped early. The quality of evidence for our key outcomes was moderate. The CI for the risk of arterial thrombotic events was compatible with benefits of either high or low unfractionated heparin dose regimens (RR low-dose versus high-dose 1.06, 95% CI 0.58 to 1.92). Only one of the studies reported the frequency of bleeding events for the cohort of patients and found no statistically significant difference in the incidence of major and minor bleeding events between arms (RR low-dose versus high-dose 1.38, 95% CI 0.46 to 4.13 for minor bleeding; RR low-dose versus high-dose 2.96, 95% CI 0.12 to 71.34 for major bleeding events). This study also reported on the incidence of deep vein thrombosis when comparing the high versus low dose of heparin and reported a non-significant difference (RR low-dose versus high-dose 0.34, 95% CI 0.01 to 8.28). The other study lacked information about bleeding. Side effects of heparin other than bleeding complications were not reported in either of the studies.

AUTHORS' CONCLUSIONS

Due to the limitations of the current evidence, small number of included studies, and lack of details reported in one study, we are unable to determine the effects of different dosing regimens of unfractionated heparin for the prevention of vascular thrombosis during cardiac catheterization in children. A further adequately powered, randomized clinical trial is needed.

Clinical causes and treatment of the thrombotic storm

Thrombotic storm represents an extreme prothrombotic phenotype, characterized by multiple thrombotic events affecting diverse vascular beds occurring over a brief period of time. Thrombotic events involve venous and arterial circulation, including unusual locations, such as cerebral sinus venous thrombosis, intra-abdominal thromboembolic occlusions and microvascular events. Some patients will have antiphospholipid antibodies, but a significant number have no identifiable hypercoagulable state. The mainstay of treatment consists of anticoagulant therapy, although some patients appear to benefit from the addition of immunomodulatory therapies. Other disorders that share this thrombotic storm phenotype include catastrophic antiphospholipid syndrome, spontaneous heparin-induced thrombocytopenia and similar aggressive clinical disorders. Ongoing studies are focused on identifying underlying genetic factors that may predispose patients to develop this extreme clinical phenotype.

Systematic review on heparin-induced thrombocytopenia in children: a call to action

BACKGROUND

Heparin-induced thrombocytopenia (HIT) has increasingly been reported in children as an indication for use of new alternative anticoagulant drugs (NAADs).

OBJECTIVES

To systematically review the literature regarding: (i) the incidence and prevalence of seroconversion and HIT and (ii) the clinical/laboratory findings and management of HIT in children.

DESIGN/METHODS

MEDLINE and EMBASE databases were searched for studies that reported pediatric cases of HIT. Methodological reliability assessment of studies was performed with the Loney scale.

RESULTS

The incidence of seroconversion in neonates ranged between 0% and 1.7%. There were no cases of neonatal HIT in the included cohorts. The incidence range of seroconversion in the non-neonatal population was 1.3-52%. The incidence of HIT in non-neonates after cardiopulmonary bypass was 0.33% (95%CI, < 0.01-2.04). Whereas more than half of pediatric cases labeled as HIT (30/52) did not include pivotal features of this syndrome, 80% of them received NAADs.

CONCLUSION

The incidence of HIT is likely to have been overestimated in children, leading to potential misuse of NAADs in many cases. Clinical findings and laboratory assessment of pediatric cases are poorly described in the literature at present. Thorough laboratory investigation, proper reporting of cases and adequate design of studies are mandatory to elucidate the clinical/laboratory picture of pediatric HIT.

Thrombotic complications and thromboprophylaxis across all three stages of single ventricle heart palliation

OBJECTIVES

To describe the incidence of thrombotic complications across all 3 stages of single ventricle palliation and the association between thromboprophylaxis use and thrombotic risk.

STUDY DESIGN

Two separate cross-sectional studies were performed that included 195 patients born between 2003-2008 and 162 patients who underwent Fontan after 2000.

RESULTS

The incidence of thrombotic complications was 40% and 28% after initial palliation and superior cavopulmonary connection (SCPC), respectively; 5-year freedom from thrombotic complications after Fontan was 79%. Thromboprophylaxis was initiated for 70%, 46%, and 94% of patients after initial palliation, SCPC, and Fontan, respectively. Thromboprophylaxis with enoxaparin (vs no thromboprophylaxis) was associated with a reduction in risk of thrombotic complications after initial palliation (hazard ratio [HR] 0.5, P = .05) and SCPC (HR 0.2, P = .04). Thromboprophylaxis with warfarin was associated with a reduction in thrombotic complications after Fontan (HR 0.27, P = .05 vs acetylsalicylic acid; HR 0.18, P = .02 vs no thromboprophylaxis). Thrombotic complications were associated with increased mortality after initial palliation (HR 5.5, P < .001) and SCPC (HR 12.5, P < .001). Three patients experienced major bleeding complications without permanent sequelae (2 enoxaparin, 1 warfarin).

CONCLUSIONS

Given the negative impact of thrombotic complications on survival, the low risk of serious bleeding complications, and the association between thromboprophylaxis and lowered thrombotic complication risk across all 3 palliative stages, routine use of thromboprophylaxis from the initial palliation to the early post-Fontan period in this population may be indicated.

Do children with central venous line (CVL) dysfunction have increased risk of symptomatic thromboembolism compared to those without CVL-dysfunction, while on cancer therapy?

Background

Thromboembolism (TE) and infection are two common complications of central venous line (CVL). Thrombotic CVL-dysfunction is a common, yet less studied, complication of CVL. Two retrospective studies have reported significant association of CVL-dysfunction and TE. Recent studies indicate association of CVL-related small clot with infection. Infection is the most common cause of non-cancer related mortality in children with cancer. We and others have shown reduced overall survival (OS) in children with cancer and CVL-dysfunction compared to those without CVL-dysfunction. Despite these observations, to date there are no prospective studies to evaluate the clinical significance of CVL-dysfunction and it’s impact on the development of TE, infection, or outcome of children with cancer.

Study design

This is a prospective, analytical cohort study conducted at five tertiary care pediatric oncology centers in Ontario. Children (≤ 18 years of age) with non-central nervous system cancers and CVL will be eligible for the study. Primary outcome measure is symptomatic TE and secondary outcomes are infection, recurrence of cancer and death due to any cause. Data will be analyzed using regression analyses.

Discussion

The overall objective is to delineate the relationship between CVL-dysfunction, infection and TE. The primary aim is to evaluate the role of CVL-dysfunction as a predictor of symptomatic TE in children with cancer. We hypothesize that children with CVL-dysfunction have activation of the coagulation system resulting in an increased risk of symptomatic TE. The secondary aims are to study the impact of CVL-dysfunction on the rate of infection and the survival [OS and event free survival (EFS)] of children with cancer. We postulate that patients with CVL-dysfunction have an occult CVL-related clot which acts as a microbial focus with resultant increased risk of infection. Further, CVL-dysfunction by itself or in combination with associated complications may cause therapy delays resulting in adverse outcome.

This study will help to identify children at high risk for TE and infection. Based on the study results, we will design randomized controlled trials of prophylactic anticoagulant therapy to reduce the incidence of TE and infection. This in turn will help to improve the outcome in children with cancer.

The role of prothrombotic factors in the ocular manifestations of abusive and non-abusive head trauma: a feasibility study

OBJECTIVES

Retinal hemorrhage is a cardinal manifestation of abusive head injury. Thrombophilia is relatively common in the general population and in adults can be associated with retinal hemorrhage. The specificity of retinal hemorrhage for abusive head trauma in the presence of prothrombotic factors, in particular following non-abusive head trauma, has not been investigated. Our objective was to determine whether the hypothesis that prothrombotic factors affect specificity of retinal hemorrhage to AHT can be tested. This may have important ramifications both for diagnosis and expert witness testimony.

METHODS

To investigate the feasibility of studying this issue, we conducted a prospective cohort study of children with abusive and non-abusive head trauma. Thrombophilia screening and ophthalmic examinations were performed.

RESULTS

Six of 30 admitted children were fully enrolled. Enrollment obstacles included caregiver stress, animosity towards allegations of abuse, child protection services involvement, and research phlebotomy coordination. Prevalence of thrombophilia was high in children with retinal hemorrhage and in 1 case the question of hemorrhage adjudicated as abuse was considered in light of a history of a fall.

CONCLUSION

We estimate that to answer the critical question of retinal hemorrhage specificity for abuse in the presence of thrombophilia will require 53 centers for a 1 year study or 18 centers for a 3-year study. We identify potential obstacles and interventions.

Unfractionated heparin dosing in young infants: clinical outcomes in a cohort monitored with anti-factor Xa levels

BACKGROUND

Unfractionated heparin (UFH) is a widely used anticoagulant. Current American College of Chest Physicians guidelines for infants extrapolated from adults recommend 28 U kg(-1) h(1) of UFH to achieve an anti-factor Xa level of 0.35-0.7 IU mL(-1).

OBJECTIVE

To assess the profile of anti-FXa-based UFH dosing guidelines in infants.

PATIENTS/METHODS

We included all infants aged < 6 months treated with per-protocol intravenous UFH at the Hospital for Sick Children, Toronto, over a 3.5-year period.

RESULTS

Of 100 infants, 11% achieved sustained therapeutic anti-FXa levels with current dose recommendations. Only 15% achieved target anti-FXa levels within 24 h with per-protocol dose escalations. Seventeen per cent of patients never achieved therapeutic anti-FXa levels, despite up to 60 days of therapy and triple the recommended dose. The median dose needed to achieve therapeutic anti-FXa levels in the remaining 83 infants was 33 U kg(-1) h(-1) (interquartile range, 30-36). Two in three infants had decreased thrombus size at completion of therapy and no thrombus progression/recurrence, and 11/100 infants suffered major bleeding. Without exclusion of extracorporeal membrane oxygenation patients, an activated partial thromboplastin time (APTT) of > 180 s was detected as a risk factor for major bleeding.

CONCLUSIONS

UFH monitoring is challenging in infants. Despite their delay in reaching therapeutic anti-FXa levels, infants monitored with the adult-based anti-FXa range have a high thrombus resolution rate, no thrombus progression, but a relatively high bleeding rate. Extreme APTT elevation may contribute to this bleeding risk, particularly in critically ill patients. Current UFH guidelines for young infants may still be inadequate, and laboratory methods with age-appropriate ranges may be required to further improve clinical outcomes within this population.

A reliable and safe method of collecting blood samples from implantable central venous catheters for determination of plasma gentamicin concentrations

STUDY OBJECTIVE

To evaluate the extent of agreement between plasma gentamicin concentrations determined from samples collected by using implantable subcutaneous central venous catheters (ports) with the push-pull method and those collected by finger lancet punctures in children with febrile neutropenia.

DESIGN

Prospective, randomized study.

SETTING

University-affiliated, tertiary care hospital.

PATIENTS

Sixty-two children with cancer who had single- or double-lumen ports and who received gentamicin for treatment of febrile neutropenia between February 2008 and October 2009.

INTERVENTION

One blood sample was collected from the port by using the push-pull method at the same time one blood sample was collected by finger lancet puncture for determination of plasma gentamicin concentrations.

MEASUREMENTS AND MAIN RESULTS

Forty-four pairs of samples were available for assessment of agreement, and 43 were available for pharmacokinetic analysis. Agreement between plasma gentamicin concentrations determined from blood samples from ports and finger lancet punctures was assessed by the intraclass correlation coefficient (ICC), Bland-Altman analysis, and comparison of simulated dosage adjustments. Changes in port patency were monitored for 1 week after port sampling. Differences in simulated dosage adjustments calculated by using either the port or finger lancet puncture samples that differed by greater than 20% were considered clinically significant. Agreement between the 44 finger lancet puncture and port sample pairs was excellent (ICC 0.991, 95% confidence interval 0.984-0.995). Port plasma gentamicin concentrations were 4.7% lower than those concentrations determined in blood from finger lancet punctures. The observed limits of agreement ranged from -20.5% to 11%. Differences in dosage adjustments calculated by using port and finger lancet puncture plasma gentamicin concentrations were not clinically significant in 38 (88%) of 43 cases. No changes in port patency were observed in the week after port sampling.

CONCLUSION

The push-pull method of blood sampling is a reliable and safe option for determining plasma gentamicin concentrations in children with ports.

Pulmonary embolism in children

Pulmonary embolism (PE) has long been described in children. Nevertheless, most of the algorithms applied to patients within this age range, from diagnosis to therapy, have been adapted from adult protocols. This article reviews the progresses that occurred to PE in children placing them in historical perspective with the key events relevant to PE in adults. A brief summary of the initial reports encountered in the pediatric literature followed by key conclusions drawn from national database reports characterizing its epidemiology in children is highlighted. Additionally, a section with the diagnostic tools pertaining to children is included. Closing remarks encompass commentaries related to therapy and outcomes, reflecting on current knowledge gaps related to PE in children.

Longer blood storage is associated with suboptimal outcomes in high-risk pediatric cardiac surgery

BACKGROUND

The negative effects of long-term storage of allogeneic red blood cells (RBCs) on outcomes in adult cardiac surgery have been established, but evidence of a similar effect in pediatric cardiac surgery is limited.

METHODS

The weighted average duration of storage for RBC units used in 1,225 pediatric cardiac operations was determined. Operations were divided into high RBC use (more than 4 units or more than 150 mL/kg) or low RBC use. For both categories, associations between storage duration and surgical outcomes, adjusted for relevant patient characteristics, were evaluated.

RESULTS

High RBC use was associated with higher surgical complexity. Storage duration for patients who received low RBC volumes was not associated with surgical outcomes. For patients with high RBC transfusion volumes, longer storage duration (per day) was associated with higher odds of bleeding complications (odds ratio 1.029, p=0.07), renal insufficiency (odds ratio 1.085, p=0.001), higher inotrope score after surgery (12 to 24 hours +0.08, p=0.002; 24 to 48 hours +0.07, p<0.001), greater chest tube drainage (24 hours +1.5 mL/kg, p<0.001), longer postoperative hospitalization (+0.3 days p=0.02), and increased in-hospital mortality (odds ratio 1.054, p=0.03). Effects of RBC transfusions on postoperative bleeding were greatest for storage duration longer than 14 days.

CONCLUSIONS

The freshest RBC units available should be used for pediatric cardiac operations expected to require more than 4 units or more than 150 mL/kg of allogeneic RBC transfusions, with no units more than 14 days old being transfused whenever possible.

Neonatal renal vein thrombosis

Neonatal renal vein thrombosis (RVT) continues to pose significant challenges for pediatric hematologists and nephrologists. The precise mechanism for the onset and propagation of renal thrombosis within the neonatal population is unclear, but there is suggestion that acquired and/or inherited thrombophilia traits may increase the risk for renal thromboembolic disease during the newborn period. This review summarizes the most recent studies of neonatal RVT, examining its most common features, the prevalence of acquired and inherited prothrombotic risk factors among these patients, and evaluates their short and long term renal and thrombotic outcomes as they may relate to these risk factors. Although there is some consensus regarding the management of neonatal RVT, the most recent antithrombotic therapy guidelines for the management of childhood thrombosis do not provide a risk-based algorithm for the acute management of RVT among newborns with hereditary prothrombotic disorders. Whereas neonatal RVT is not a condition associated with a high mortality rate, it is associated with significant morbidity due to renal impairment. Recent evidence to evaluate the effects of heparin-based anticoagulation and thrombolytic therapy on the long term renal function of these patients has yielded conflicting results. Long term cohort studies and randomized trials may be helpful to clarify the impact of acute versus prolonged antithrombotic therapy for reducing the morbidity that is associated with neonatal RVT.

Risk, clinical features, and outcomes of thrombosis associated with pediatric cardiac surgery

BACKGROUND

Thrombosis, usually considered a serious but rare complication of pediatric cardiac surgery, has not been a major clinical and/or research focus in the past.

METHODS AND RESULTS

We noted 444 thrombi (66% occlusive, 60% symptomatic) in 171 of 1542 surgeries (11%). Factors associated with increased odds of thrombosis were age <31 days (odds ratio [OR], 2.0; P=0.002), baseline oxygen saturation <85% (OR, 2.0; P=0.001), previous thrombosis (OR, 2.6; P=0.001), heart transplantation (OR, 4.1; P<0.001), use of deep hypothermic circulatory arrest (OR, 1.9 P=0.01), longer cumulative time with central lines (OR, 1.2 per 5-day equivalent; P<0.001), and postoperative use of extracorporeal support (OR, 5.2; P<0.001). Serious complications of thrombosis occurred with 64 of 444 thrombi (14%) in 47 of 171 patients (28%), and were associated with thrombus location (intrathoracic, 45%; extrathoracic arterial, 19%; extrathoracic venous, 8%; P<0.001), symptomatic thrombi (OR, 8.0; P=0.02), and partially/fully occluding thrombi (OR, 14.3; P=0.001); indwelling access line in vessel (versus no access line) was associated with lower risk of serious complications (OR, 0.4; P=0.05). Thrombosis was associated with longer intensive care unit (+10.0 days; P<0.001) and hospital stay (+15.2 days; P<0.001); higher odds of cardiac arrest (OR, 4.9; P<0.001), catheter reintervention (OR, 3.3; P=0.002), and reoperation (OR, 2.5; P=0.003); and increased mortality (OR, 5.1; P<0.001). Long-term outcome assessment was possible for 316 thrombi in 129 patients. Of those, 197 (62%) had resolved at the last follow-up. Factors associated with increased odds of thrombus resolution were location (intrathoracic, 75%; extrathoracic arterial, 89%; extrathoracic venous, 60%; P<0.001), nonocclusive thrombi (OR, 2.2; P=0.01), older age at surgery (OR, 1.2 per year; P=0.04), higher white blood cell count (OR, 1.1/10(9) cells per 1 mL; P=0.002), and lower fibrinogen (OR, 1.4/g/L; P=0.02) after surgery.

CONCLUSIONS

Thrombosis affects a high proportion of children undergoing cardiac surgery and is associated with suboptimal outcomes. Increased awareness and effective prevention and detection strategies are needed.

Thrombotic events after pediatric liver transplantation

TE may contribute to morbidity and mortality after LT. The objectives were to determine the incidence of early TE post-pediatric LT and compare differences between children with and without TE. A retrospective review of 88 transplanted children (January 2002-October 2007) was performed to determine the incidence of Doppler-confirmed DVT and ATE in the first month post-LT. Fourteen (16%) patients developed TE: DVT in seven (8%) and ATE in seven (8%) patients. Six of 88 (6.8%) developed symptomatic CVL-related DVT. Median (range) time post-LT to DVT and ATE were 7 (4-18) and 8 (1-31) days, respectively. There was no significant difference in age/body weight at LT between patients with or without DVT and ATE. There was no significant difference between patients with or without HAT in age and weight at LT, cold ischemic time, duration of surgery, hematocrit levels, whole-organ graft type, intraoperative FFP, high-risk CMV status, or early acute cellular rejection. In conclusion, the incidence of early TE post-pediatric LT was 16%, including DVT in 8%. Prospective studies are necessary to evaluate the role of prophylactic anticoagulation and potential modifiable risk factors post-pediatric LT.

Management and monitoring of anticoagulation for children undergoing cardiopulmonary bypass in cardiac surgery

Cardiopulmonary bypass (CPB) creates a pro-coagulant state by causing platelet activation and inflammation leading to thrombin generation and platelet dysfunction. It is associated with severe derangements in normal homeostasis resulting in both thrombotic and hemorrhagic complications. This derangement is greater in children with congenital heart disease than in adults because of the immaturity of the coagulation system, hemodilution of coagulation factors, hyperreactive platelets, and in some patients, physiologic changes associated with cyanosis. During CPB, an appropriate amount of heparin is given with the goal of minimizing the risk of thrombosis and platelet activation and at the same time reducing the risk of bleeding from over anticoagulation. In young children, this balance is more difficult to achieve because of inherent characteristics of the hemostatic system in these patients. Historically, protocols for heparin dosing and monitoring in children have been adapted from adult protocols without re-validation for children. Extreme hemodilution of coagulation factors and platelets in young children affects the accuracy of anticoagulation monitoring in children. The activated clotting time does not correlate with plasma levels of heparin. In addition, recent studies suggest that children need larger doses of heparin than adults, because they have lower antithrombin levels, and they metabolize heparin more rapidly. Preliminary studies demonstrated that the use of individualized heparin and protamine monitoring and management in children is associated with reduced platelet activation and dysfunction and improved clinical outcomes. However, this review article clearly establishes that further studies are necessary to obtain evidence-based protocols for the proper management of anticoagulation of children undergoing cardiopulmonary bypass.

Efficacy of local instillation of recombinant tissue plasminogen activator for restoring occluded central venous catheters in neonates

OBJECTIVE

To evaluate the efficacy of local instillation of tissue plasminogen activator (tPA) for restoring function to occluded central venous catheters (CVCs) in the neonatal population.

STUDY DESIGN

This was a retrospective review of patients admitted to the neonatal intensive care unit during September 2000 to April 2006 who received instillation of tPA for occluded CVCs.

RESULTS

Among 18 infants who received tPA for occluded CVCs, gestational age at birth was 32.5 weeks, birth weight was 1550 g, and gestational age at tPA administration was 39 weeks, with 4 neonates < or =32 weeks' gestational age at tPA administration; age at tPA use was 39 days (medians reported). Ten of 18 (55%) of CVC occlusions were successfully opened after using tPA. No bleeding complications of tPA were noted, including increased or new-onset intraventricular hemorrhage, overt bleeding, or changes in INR or partial thromboplastin time attributed to tPA use. Three patients (16.5%) had bacteremia within 7 days of tPA administration, and no catheter ruptures occurred.

CONCLUSIONS

Local instillation of tPA was successful in restoring function to occluded CVCs in a significant proportion of neonates, although success rates were lower than that reported in populations of older age. Despite the vulnerability of neonates to the potential complications of tPA, no major complications were detected even among premature infants.

Clinical probability score and D-dimer estimation lack utility in the diagnosis of childhood pulmonary embolism

BACKGROUND

Childhood pulmonary embolism (PE) causes significant mortality and evidence suggests that it is under-diagnosed. Clinical probability scores and D-dimer estimation to assess pre-test probability have not been studied in children with suspected PE.

PATIENTS/METHODS

This retrospective cohort study evaluated Wells simplified probability score for PE in 50 children with PE and 25 PE negative control patients, and D-dimer values in 27 PE positive and 12 PE negative children.

RESULTS

PE positive and PE negative groups had similar rates of risk factors for venous thromboembolism (VTE). Wells simplified probability score showed a small difference between PE positive and PE negative children (median score: PE positive, 4.5; PE negative, 4; P = 0.009), children with PE are more likely to obtain a 'PE likely' score (score > 4), P = 0.012. The difference was of slightly greater significance when the Wells score was adjusted to account for pediatric normal ranges for heart rate, P = 0.007, and signs/symptoms of upper limb DVT, P = 0.006. Children with PE were as likely as PE negative patients to have a D-dimer value within the normal range (PE positive, 15%; PE negative, 25%; P = 0.654). A combination of a 'PE unlikely' score and normal D-dimer value occurred in 1/12 (8%) of PE negative children.

CONCLUSIONS

The Wells clinical probability score and D-dimer estimation may lack utility in the determination of pre-test probability of PE in children. Validation of a pediatric clinical probability score, incorporating D-dimer estimation, by prospective study, would be difficult as a result of the rarity of childhood PE.

The use of elastic compression stockings for post-thrombotic syndrome in a child

Post-thrombotic syndrome (PTS) is a potential complication following deep vein thrombosis (DVT) in children. Guidelines for management of PTS in children are non-existent. The absence of guidelines may limit the use of elastic compression stockings (ECS), offered for prevention and treatment of PTS in adults. We report the case of a 6-year-old, who developed PTS following a presumed line-related lower limb DVT, with dramatic improvement in functional status with ECS use. The presented case highlights the subtle nature of symptoms, potential benefits and limitations of ECS use for PTS, and current lack of evidence in children.

A prospective longitudinal multicenter study of coagulation in pediatric patients undergoing allogeneic stem cell transplantation

BACKGROUND

Thrombotic complications occur in adult patients undergoing stem cell transplantation (SCT), especially following high dose chemo-radiotherapy. There is little published information in children on the impact of SCT on coagulation, as well as potential correlations between altered coagulation and SCT-associated thrombosis and organ failure.

PROCEDURE

Forty three pediatric subjects who underwent allogeneic SCT were prospectively evaluated for congenital thrombophilia, anticoagulant levels, coagulation activation, and fibrinolysis at pre-established set points encompassing the period from the 2 to 4 weeks prior to conditioning to 28 days post-transplantation.

RESULTS

A significant decrease of protein C and antithrombin levels was found in 39% and 31% of subjects respectively, between SCT days +6 and +7. A peak in plasminogen activator inhibitor-1 levels in 31% of subjects was noted between days +9 and +10. No subject experienced a thrombotic event or other SCT-related organ failure. Antithrombin deficiency correlated with underlying malignancy, donor HLA-mismatch, and TBI, whereas decreased PC activity demonstrated a trend of association with lack of T-cell depletion and TBI. Prophylactic heparin did not influence the pattern of acquired hemostatic abnormalities observed in this cohort.

CONCLUSIONS

Children undergoing allogeneic SCT develop a state of acquired thrombophilia in the early post-transplantation period. Although no SCT-related thromboembolic events were observed, our results provide new information about the hemostatic changes in children undergoing allogeneic SCT and their potential clinical triggers. The significance of these findings requires further prospective evaluation in a larger cohort of patients.

A comprehensive review of rFVIIa use in a tertiary care pediatric center

BACKGROUND

Recombinant activated factor VII (rFVIIa) is a hemostatic agent developed for the treatment of bleeds in patients with hemophilia and inhibitors. Case reports/series document its growing use in patients without hemophilia. Such reports however do not accurately describe the proportion of rFVIIa used for various indications. We sought to document the complete use of rFVIIa at our institution over a 6-year period (2000-2005).

PROCEDURE

Using a computerized registry documenting all rFVIIa use in our institution a complete list of patients receiving rFVIIa was generated. Clinical data on these patients was obtained through chart review.

RESULTS

111 patients received 7,016,400 microg of rFVIIa over the 6 years: 23 patients had congenital bleeding disorders (10 patients with hemophilia and inhibitors; 7 with congenital FVII deficiency; 6 with platelet function disorders). These 23 patients (21% of all patients receiving rFVIIa) accounted for 79.9% of all rFVIIa used; patients with hemophilia alone accounted for 68.6%. The 88 patients without a congenital bleeding disorder (79% of all patients using rFVIIa) accounted for 20.1% of rFVIIa used. However their annual use of rFVIIa increased 10-fold during the 6 years.

CONCLUSIONS

Patients with hemophilia use massive amounts of rFVIIa repeatedly while patients without hemophilia use rFVIIa infrequently and at smaller doses. The use of rFVIIa in patients without congenital bleeding disorders (all "off-label" use) is rapidly growing in both number of patients and in total use and has likely significant clinical and economic ramifications.

Exercise-induced deep vein thrombosis of the upper extremity. 1. Literature review

Paget-Schroetter syndrome or effort-related upper extremity deep vein thrombosis is a rare condition that usually afflicts young healthy individuals, most commonly males. The cause is multifactorial but almost always involves extrinsic compression of the subclavian vein at the thoracic inlet, causing venous stenosis from repetitive trauma. The diagnosis of this condition may be difficult, and its delay may contribute to potential complications including thrombosis progression, pulmonary embolism, thrombosis recurrence, and post-thrombotic syndrome. Similarly, the best therapeutic option has not been established and in the lack of evidence-based guidelines, treatment may be extremely challenging especially in children, in whom long-term complications can be particularly disabling.