Guidelines for antithrombotic therapy in pediatric patients

Pediatric Orthopaedic Venous Thromboembolism: A Systematic Review Investigating Incidence, Risk Factors, and Outcome

Background

There is growing evidence of increased venous thromboembolism (VTE) incidence in children with trauma or infection. The purpose of this study was to conduct a systematic review of existing literature related to VTE in the pediatric orthopaedic population, to estimate the overall incidence of VTE and identify risk factors associated with this condition.

Methods

A systematic review of the available literature was performed to identify articles that described VTE in pediatric orthopaedic surgery or admission. Literature queries were performed to identify articles published from 1980 to 2021 that included patients ≤21 years of age. A stepwise search strategy of 5 electronic databases yielded 1,426 articles, which were filtered by 2 reviewers to identify 30 articles for full-text review. The primary aim was to determine the rate of VTE, and the secondary aim was to identify risk factors for VTE. The pooled incidence of VTE was estimated and reported in cases per 10,000. Studies were stratified by study size, by trauma versus elective surgery, and by orthopaedic subspecialty.

Results

The 30 articles reported 3,113 VTE events in 2,467,764 pediatric patients (including those with non-orthopaedic conditions), for a pooled VTE incidence of 20 events (95% confidence interval [CI] = 10.8 to 37.2) per 10,000. Four of the studies were excluded for incomplete data or high heterogeneity. The remaining 26 studies had 850,268 orthopaedic patients with 1,108 cases of VTE, for a pooled VTE incidence of 16.6 events (95% CI = 9.1 to 30.5) per 10,000. Studies with <10,000 patients and those involving a diagnosis of trauma had the highest VTE incidence when stratification was performed. The most frequently analyzed risk factors in 15 available studies included age, sex, obesity/body mass index, type of surgery, and use of a central venous catheter.

Conclusions

This systematic review indicated that the risk of VTE associated with pediatric orthopaedic surgery or admission remains low, at <17 events per 10,000 cases. However, orthopaedic surgeons should be aware of the most common risk factors associated with pediatric orthopaedic VTE and should pay special attention to traumatic etiologies, as these yielded the highest incidence.

Levels of Evidence

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Systemic Catheter-Related Venous Thromboembolism in Children: Data From the Italian Registry of Pediatric Thrombosis

BACKGROUND

Central venous catheters (CVCs) represent one of the main risk factors for venous thrombotic events (VTEs) in children.

METHODS

We studied the Italian Registry of Pediatric Thrombosis (RITI) with regard to systemic radiologically confirmed CVC-related VTEs (CVC-VTEs) occurred during 6.5 years in children aged 29 days to 18 years.

RESULTS

A total of 78 CVC-VTEs were included, which occurred in 76 patients (40/76, 53% males). CVC-VTEs comprised 67 non-cardiac VTEs (86%) and 11 intracardiac thrombotic events (ICTEs) (14%); the median age at onset was 19 and 17 months, respectively. The most frequent reason for CVC insertion was supportive therapy. The catheters were placed percutaneously in 85% of cases (56/66) and surgically in the remaining 15% (10/66). Peripherally inserted central catheters (PICCs) were used in 47% (31/66) cases, partially implanted catheters in 42% (28/66), non-implantable catheters in 7% (5/66), and totally implanted catheters (Port) in 2% (1/66). CVC-VTEs were symptomatic in 77% of cases (60/78), while in the remaining 23%, they were incidentally detected on the imaging performed for the underlying condition. The median time between CVC insertion and the onset of symptoms was 10 days in non-cardiac VTEs and 39 days in ICTEs. Doppler ultrasound was the diagnostic technique most frequently used. The venous compartment most frequently affected was the veins of the lower extremities (52%, 43/73). Anti-thrombotic treatment was administered in 96% of CVC-VTEs (75/78). About 2.6% (2/76) of patients experienced a second thrombotic event. At discharge, post-thrombotic syndrome was reported in 13.5% (5/37) events with available data, CVC replacement in 10.8% (4/47), and ischemic necrosis with toe finger amputation in 2.7% (1/37). Three patients died due to an underlying condition; no CVC-VTE-related deaths were reported.

CONCLUSIONS

We have carried out a registry-based study on CVC-VTEs in the children in Italy, providing the data that may help improve the detection and management of this CVC-related complication.

Venous Thromboembolism Risk and Thromboprophylaxis in Pediatric Neurosurgery and Spinal Injury: Current Trends and Literature Review

Although the entities of venous thromboembolism (VTE), deep venous thrombosis, pulmonary embolus, and thromboprophylaxis in adult patients undergoing brain tumor and spine surgery, traumatic brain injury and elective neurosurgical procedures are widely elucidated, the same is not valid when pediatric patients are under consideration. An attempt to review the peculiarities of these patients through a comprehensive bibliographic review is undertaken. We performed a narrative summary of the relevant literature dedicated to pediatric patients, centered on traumatic brain injury, the general incidence of thromboembolic disease in this patient population, the role of low molecular weight heparin (LMWH) in the treatment and prophylaxis of VTE, and its role in elective neurosurgical procedures, including spinal operations. Additionally, the risk of deep venous thrombosis in elective neurosurgical procedures is reviewed. Due to inherent limitations of the current studies, particularly a restricted number of patients, our data are underpowered to give a definitive protocol and guidelines for all the affected patients. Our current conclusions, based only on pediatric patients, argue that there is limited risk of VTE in pediatric patients suffering from brain tumors and that the possibility of VTE is very low in children undergoing elective neurosurgical procedures. There is no consensus regarding the exact incidence of VTE in traumatic brain injury patients. LMWH seems to be a safe and effective choice for the "at risk" pediatric patient population defined as being older than 15 years, venous catheterization, nonaccidental trauma, increased length of hospital stays, orthopaedic (including spinal) surgery, and cranial surgery.

Low-molecular-weight heparin administered by subcutaneous catheter is a safe and effective anti-coagulation regimen in selected inpatient infants and children with complex congenital heart disease

BACKGROUND/HYPOTHESIS

Disadvantages of intravenous therapeutic unfractionated heparin, the first-line anti-coagulant agent in children with complex congenital heart disease, include unpredictable pharmacokinetics requiring frequent phlebotomies and the need for continuous intravenous access.

OBJECTIVE

To compare efficacy and safety of low-molecular-weight heparin administered by a subcutaneous indwelling catheter with intravenous unfractionated heparin.

MATERIALS AND METHODS

Clinical data from 31 inpatients prospectively enrolled to receive subcutaneous low-molecular-weight heparin were compared with those from a historical group of 44 inpatients receiving intravenous unfractionated heparin. Investigation of parents' satisfaction by telephone survey.

RESULTS

The percentage of anti-factor Xa levels outside therapeutic range was lower in the subcutaneous low-molecular-weight heparin group compared with the percentage of activated partial thromboplastin times outside therapeutic range in the intravenous unfractionated heparin group (40% versus 90%, p < 0.001). Neither group had a major complication. Transient local reactions occurred in 19% of patients of the subcutaneous low-molecular-weight heparin group. The number of needle punctures and that of placement of indwelling catheters were significantly lower in the subcutaneous low-molecular-weight heparin compared with the intravenous unfractionated heparin group (p < 0.001). In total, 84.2% of parents in the subcutaneous low-molecular-weight heparin group reported a positive experience when asked about comparison with prior intravenous unfractionated heparin treatment.

CONCLUSION

Subcutaneous low-molecular-weight heparin offers a safe anti-coagulation regimen for children with complex congenital heart disease providing more efficient therapeutic anti-coagulation and a reduction in needle punctures, thus causing less pain and anxiety in this children.

Health-related quality of life correlates with time in therapeutic range in children on anticoagulants with International Normalised Ratio self-monitoring

BACKGROUND

Managing oral anticoagulant therapy with vitamin K antagonists remains challenging in paediatric medicine.

AIMS

This study aimed to assess the correlation between time in therapeutic range and quality of life in children participating in a non-selective International Normalised Ratio self-monitoring and vitamin K antagonist education programme.

METHODS

Children aged from 2 to 18 years and receiving vitamin K antagonist therapy were eligible for this prospective multicentre study. Clinical and demographic data were collected. Health-related quality of life was assessed using the PedsQL™ 4.0 questionnaire. Correlations between quality of life scores and time in therapeutic range were measured.

RESULTS

A total of 121 children were included in the study (mean age 9.6±4.9 years). Cardiac conditions were the predominant indication for vitamin K antagonists. The mean time in therapeutic range was 0.78±0.15 overall, and 0.76±0.24 over the 3-month period before quality of life assessment. The mean total quality of life score was 76.2±18 in self reports, 71.4±22 in mother reports and 73.5±19 in father reports. The time in therapeutic range correlated with the total quality of life scores in self reports (r=0.22; P=0.04), mother reports (r=0.23; P=0.02) and father reports (r=0.28; P=0.02). The time in therapeutic range predominantly correlated with school functioning in self reports (r=0.38; P=0.002) and mother reports (r=0.40; P<0.001), and with physical functioning in father reports (r=0.28; P=0.03).

CONCLUSIONS

Time in therapeutic range correlated with quality of life in children participating in a non-selective International Normalised Ratio self-monitoring and vitamin K antagonist education programme. Regular assessment of quality of life in patient education programmes contributes towards understanding the concerns and needs of patients.

Incidence of Pediatric Venous Thromboembolism After Elective Spine and Lower-Extremity Surgery in Children With Neuromuscular Complex Chronic Conditions: Do we Need Prophylaxis?

BACKGROUND

The incidence of venous thromboembolism (VTE) after elective surgery in children with mobility impairments, including those with a neuromuscular complex chronic condition (NCCC), is unknown. Therefore, our objectives were to assess the incidence of VTE after elective spine and lower-extremity surgery in children with NCCC.

METHODS

A retrospective analysis of children with NCCC undergoing elective lower-extremity and/or spinal surgeries from 2005 to 2009 included in the Pediatric Health Information Systems Plus (PHIS+) database. VTE during hospitalization for surgery was assessed through abstraction and review of ultrasound (U/S) and computed tomography results by 2 independent reviewers. VTEs related to pre-existing central venous catheters were excluded.

RESULTS

There were 4,583 children with NCCC who underwent orthopaedic surgery during the study period at 6 centers. Most were male (56.3%), non-Hispanic whites (72.7%), and had private insurance (52.2%). The most common NCCC diagnoses were cerebral palsy (46.7%), brain and spinal cord malformations (31.1%), and central nervous system degenerative conditions (14.5%). Forty children (0.9%) underwent U/S to assess VTE. Eighteen children (0.4%) underwent computed tomography to assess VTE. Four children (with cerebral palsy) had a positive U/S for a lower-extremity VTE (10-18 y of age), yet 2 had their VTE before surgery. Therefore, the adjusted VTE rate for children with NCCC undergoing orthopaedic lower-extremity or spine surgery was 4 per 10,000 (2 cases per 4583 surgeries). Each of the 2 cases had a known coagulation disorder preoperatively. Only 10% of the cohort used compression devices, 3% enoxaparin, and 1.6% aspirin for prophylaxis.

CONCLUSION

The rate of non-central-venous-catheter-related VTE associated with orthopaedic surgery in children with NCCC is very low and lower than rates reported in healthy children.

SIGNIFICANCE

To our knowledge, this is the first multi-institutional study reporting the incidence of VTE in children with NCCCs undergoing elective hip and spine surgery. These data support no additional prophylaxis is required in children with NCCC undergoing elective hip and spine surgery unless other known risk factors are also present.

Development of a perioperative venous thromboembolism prophylaxis algorithm for pediatric orthopedic surgical patients

Venous thromboembolism (VTE) has been recognized as a rare but potentially serious complication in pediatric orthopedic patients. However, standardized guidelines for screening and management of at-risk patients do not exist. The aim of the study was to develop a VTE prophylaxis screening tool for postoperative orthopedic patients after conducting an institutional needs assessment survey. A needs assessment survey was conducted after institutional ethics board approval. Development of perioperative VTE prophylaxis algorithm for pediatric orthopedic surgical patients was planned after thorough literature review, consultation with national and international experts as well as using a modified nominal and consensus development conference (serial meetings) method for reaching a consensus. NAS as well as discussion with stakeholders indicated support for development of perioperative VTE prophylaxis algorithm for orthopedic patients. Using above methods, a VTE prophylaxis algorithm was developed and implemented at IWK Health Center. The present study involved development of a perioperative VTE prophylaxis algorithm for pediatric orthopedic surgical patients that could be easily and rapidly administered as a point of care assessment tool.

Management of Extremity Venous Thrombosis in Neonates and Infants: An Experience From a Resource Challenged Setting

We aimed to evaluate the outcome of different treatment modalities for extremity venous thrombosis (VT) in neonates and infants, highlighting the current debate on their best tool of management. This retrospective study took place over a 9-year period from January 2009 to December 2017. All treated patients were referred to the vascular and pediatric surgery departments from the neonatal intensive care unit. All patients underwent a thorough history-taking as well as general clinical and local examination of the affected limb. Patients were divided into 2 groups: group I included those who underwent a conservative treated with the sole administration of unfractionated heparin (UFH), whereas group II included those who were treated with UFH plus warfarin. Sixty-three patients were included in this study. They were 36 males and 27 females. Their age ranged from 3 to 302 days. Forty-one (65%) patients had VT in the upper limb, whereas the remaining 22 (35%) had lower extremity VT. The success rate of the nonsurgical treatment was accomplished in 81% of patients. The remaining 19% underwent limb severing, due to established gangrene. The Kaplan-Meier survival method revealed a highly significant increase in both mean and median survival times in those groups treated with heparin and warfarin compared to heparin-only group ( P < .001). Nonoperative treatment with anticoagulation or observation (ie, wait-and-see policy) alone may be an easily applicable, effective, and a safe modality for management of VT in neonates and infants, especially in developing countries with poor or highly challenged resource settings.

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

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

Association of outcomes and anti-Xa levels in the treatment of pediatric venous thromboembolism

BACKGROUND

There are few data in the pediatric population evaluating the relationship between measured anti-Xa levels during enoxaparin therapy and thrombotic outcomes.

OBJECTIVE

To determine whether there is a difference in outcomes in children who receive enoxaparin with mean anti-Xa levels between 0.45 and 0.79 unit/ml (low therapeutic range) versus between 0.80 and 1.05 unit/ml (high therapeutic range) throughout their course of their treatment.

METHODS

We retrospectively identified subjects with uncomplicated venous thromboembolism treated with enoxaparin.

RESULTS

Of 69 patients with any response to therapy, 48 (70%) had mean anti-Xa levels in the low therapeutic range and 21 (30%) had mean anti-Xa levels in the high therapeutic range. Of 20 patients with no documented response to therapy, 13 (65%) had mean anti-Xa levels in the low therapeutic range and 7 (35%) had mean anti-Xa levels in the high therapeutic range. Forty-eight (79%) of the 61 patients with low-range mean anti-Xa level had any response to therapy. Twenty-one (75%) of the 28 patients with high-range mean anti-Xa level had any response to therapy. Chi-square test (P = 0.080) and logistic regression (OR = 1.23, P = 0.70) demonstrated no significant association between mean anti-Xa range (lower vs. upper) and therapy response.

CONCLUSIONS

There was no statistically significant difference between low-range versus high-range mean anti-Xa levels and thrombus resolution. Empiric clinical practices of targeting anti-Xa levels in the higher therapeutic range to achieve better outcomes may not be warranted.

Risk of deep venous thrombosis in elective neurosurgical procedures: a prospective, Doppler ultrasound-based study in children 12 years of age or younger

OBJECTIVE The risk of venous thromboembolism (VTE) from deep venous thrombosis (DVT) is significant in neurosurgical patients. VTE is considered a leading cause of preventable hospital deaths and preventing DVT is a closely monitored quality metric, often tied to accreditation, hospital ratings, and reimbursement. Adult protocols include prophylaxis with anticoagulant medications. Children's hospitals may adopt adult protocols, although the incidence of DVT and the risk or efficacy of treatment is not well defined. The incidence of DVT in children is likely less than in adults, although there is very little prospectively collected information. Most consider the risk of DVT to be extremely low in children 12 years of age or younger. However, this consideration is based on tradition and retrospective reviews of trauma databases. In this study, the authors prospectively evaluated pediatric patients undergoing a variety of elective neurosurgical procedures and performed Doppler ultrasound studies before and after surgery. METHODS A total of 100 patients were prospectively enrolled in this study. All of the patients were between the ages of 1 month and 12 years and were undergoing elective neurosurgical procedures. The 91 patients who completed the protocol received a bilateral lower-extremity Doppler ultrasound examination within 48 hours prior to surgery. Patients did not receive either medical or mechanical DVT prophylaxis during or after surgery. The ultrasound examination was repeated within 72 hours after surgery. An independent, board-certified radiologist evaluated all sonograms. We prospectively collected data, including potential risk factors, details of surgery, and details of the clinical course. All patients were followed clinically for at least 1 year. RESULTS There was no clinical or ultrasound evidence of DVT or VTE in any of the 91 patients. There was no clinical evidence of VTE in the 9 patients who did not complete the protocol. CONCLUSIONS In this prospective study, no DVTs were found in 91 patients evaluated by ultrasound and 9 patients followed clinically. While the study is underpowered to give a definitive incidence, the data suggest that the risk of DVT and VTE is very low in children undergoing elective neurosurgical procedures. Prophylactic protocols designed for adults may not apply to pediatric patients. Clinical trial registration no.: NCT02037607 (clinicaltrials.gov).

Efficacy of Urokinase and Alteplase to Reopen Occluded Central Venous Catheters in Children

Objective:

To compare the efficacy of alteplase with that of urokinase (UK) in restoring the patency of occluded central venous catheters in children.

Study Design:

Retrospective case–control study at Hôpital Ste-Justine, a pediatric teaching hospital.

Results:

87 UK and 46 alteplase prescriptions were studied. Alteplase was effective in 93.2% of cases of occluded central venous catheters and UK in 54.5% of cases (p < 0.001).

Conclusions:

Alteplase was clearly superior to UK for restoring the patency of occluded central venous catheters in children. The study is limited by its retrospective design.

Initial Experience with Tissue Plasminogen Activator in Two Pediatric Oncology Patients

With the more frequent use of central venous catheters in children for therapeutic interventions such as the administration of chemotherapy and total parenteral nutrition, there has been an increased recognition of thrombotic complications including thrombotic occlusion, deep venous thrombosis, and superior vena cava syndrome. In the symptomatic child, treatment may be warranted to prevent the sequelae of venous thrombosis including embolic phenomena, secondary bacterial infection, as well as post-thrombotic changes in an extremity. One option for treatment is the use of a thrombolytic agent such as tissue plasminogen activator (TPA). The authors present two children who developed thrombotic complications of central venous devices. TPA successfully resolved the clot and reversed the clinical signs and symptoms of venous obstruction. The literature concerning the use of TPA in pediatric patients, its application in such situations, adverse affects, and dosing regimens are presented.

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

OBJECT

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Pulmonary embolism in the pediatric emergency department: a case demonstrating the application of point-of-care cardiac ultrasound in a pediatric patient with pulmonary embolism

Although pulmonary embolism in children is rare, it is important for the pediatric emergency medicine provider to be aware of its presentation and emergent management. We present a case of bilateral pulmonary embolisms in an adolescent patient to illustrate the benefits from the timely diagnosis of right ventricular dysfunction by point-of-care echocardiography performed by emergency medicine physicians. Ultrasonographic techniques and the emergent management of pulmonary embolism are reviewed.

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.

Current and future antithrombotic agents in children

Thromboembolic complications are increasing in children, and the use of anticoagulation has seen a dramatic increase despite the lack of randomized clinical trials. The most widely used agents in children are heparin and warfarin, however these agents have limitations that are exaggerated in children. This has led to the use of newer agents with improved pharmacologic properties such as low-molecular-weight heparin, however, the use of novel agents such as direct thrombin inhibitors has been limited to case reports. These agents, however, have potential advantages over heparin, low-molecular-weight heparin and warfarin. Current clinical trials are in progress to define the proper dose of two such agents--argatroban (Argatroban, GlaxoSmithKline) and bivalirudin (Angiomax, The Medicines Company). The selective Factor Xa inhibitor fondaparinux (Arixtra, Sanofi-Synthelabo) has not been used in children; however, there are situations in which this agent may be advantageous. This review will discuss the currently available agents, with an emphasis on those that are novel and their potential uses in children.

Clot dissolution: a novel treatment of midgut volvulus

Midgut volvulus due to malrotation may result in loss of the small bowel. Until now, after derotation of the volvulus, pediatric surgeons do not deal with the mesenteric thrombosis, which causes continuing ischemia of the intestine. On occasion, a "second look" laparotomy is performed in the hope that some improvement in blood supply to the intestine has occurred. We describe a new combined treatment to restore intestinal perfusion based on digital massage of the superior mesenteric vessels after derotation and systemic infusion of tissue-type plasminogen activator. This new therapy has been successful in 2 neonates with severe intestinal ischemia due to volvulus.

Spinal cord injuries in children and adolescents

This chapter provides an overview of spinal cord injuries (SCI) in children and adolescents, including epidemiology, medical and musculoskeletal complications, rehabilitation and psychosocial aspects. Males are more commonly affected than females during adolescence; however, as the age at injury decreases, the preponderance of males becomes less marked, and by 3 years of age the number of females with SCIs equals that of males. The neurologic level and degree of completeness varies with age; among children injured prior to 12 years of age approximately two-thirds are paraplegic and approximately two-thirds have complete lesions. Among adolescents, approximately 50% have paraplegia and 55% have complete lesions. Management of pediatric-onset SCI should be family centered and developmentally based, responsive to the dynamic changes that occur during growth and development. Distinctive anatomical and physiological features of children and adolescents, along with growth and development, are responsible for unique manifestations and complications of pediatric SCI. SCI without radiological abnormalities (SCIWORA), birth injuries, lap-belt injuries, upper cervical injuries, and the delayed onset of neurological deficits are relatively unique to pediatric SCI. Children who sustain their SCI before puberty experience a higher incidence of musculoskeletal complications, such as scoliosis and hip dislocation.

Pre-clinical Implants of the Levitronix PediVAS® Pediatric Ventricular Assist Device - Strategy for Regulatory Approval

The PediVAS blood pump is a magnetically levitated centrifugal pump designed for pediatric bridge-to-decision or bridge-to-recovery in pediatric patients from 3-20kg in weight. In preparation for submission of an investigational device exemption (IDE) application, we completed a final six-animal series of pre-clinical studies. The studies were conducted under controlled conditions as prescribed by the recently released FDA guidance document for animal studies for cardiovascular devices. Three 30-day chronic left ventricular support studies were completed in a juvenile lamb model to demonstrate the safety and hemocompatibility of the PediVAS pump. Three additional 8-hour acute biventricular support studies were performed to demonstrate the feasibility of this approach from a hemodynamic and systems standpoint. It is estimated that 50% of pediatric patients who require left ventricular support also require right ventricular support. All studies were successfully completed without complications, device malfunctions, or adverse events. End-organ function was normal for the chronic studies. We noted small surface lesions on one kidney from each chronic study as well as the presence of ring thrombus on connectors, as expected for these types of studies in animal models. The strategy and challenges imposed by performing a controlled cardiovascular device study in a juvenile lamb model are discussed. We believe that these successful implants demonstrate safety and performance for the PediVAS device for support of an IDE application to initiate human clinical trials and provide a roadmap for other researchers.

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.

Management of childhood onset nephrotic syndrome

The therapeutic approach to childhood nephrotic syndrome is based on a series of studies that began with an international collaborative effort sponsored by the International Study of Kidney Disease in Children in 1967. The characteristics of children presenting with nephrotic syndrome have changed over recent decades with greater frequency of the challenging condition focal segmental glomerulosclerosis and a greater prevalence of obesity and diabetes mellitus, which may be resistant to glucocorticoids in the former and exacerbated by long-term glucocorticoid therapy in the latter 2 conditions. The Children's Nephrotic Syndrome Consensus Conference was formed to systematically review the published literature and generate a children's primary nephrotic syndrome guideline for use in educational, therapeutic, and research venues.

Prospective, randomized trial of two different modalities of flushing central venous catheters in pediatric patients with cancer

PURPOSE

There are limited prospective data on whether the method of flushing affects the complication rate of tunnelled central venous catheters (CVCs).

PATIENTS AND METHODS

During a 25-month period, 203 pediatric patients who had newly placed Broviac-Hickman CVCs were randomly assigned to standard flushing with heparin solution or to experimental flushing with normal saline via a positive-pressure cap.

RESULTS

Two hundred twenty-one complications were recorded among 75,249 CVC-days (2.94 per 1,000 CVC-days). A higher incidence of CVC occlusion (83 v 41 episodes; P = .0002) and bacteremia (24 v 9; P = .01) were found in the experimental arm. The cumulative probability of developing at least one CVC complication was higher in the experimental arm than in the standard arm (65.1% [95% CI, 55% to 75%] v 43.8% [95% CI, 34% to 54%], respectively; P = .01). No difference was found in either the cause or the frequency of premature removal of CVCs between the two study arms. After a median follow-up of 360 days (range, 4 to 1,073), CVC survival was similar: 77% (95% CI, 66% to 84%) for the experimental arm and 69% (95% CI, 53% to 80%) for the standard arm (P = .7). The factors associated with the occurrence of CVC complication were a diagnosis of leukemia/lymphoma, double-lumen CVC, and experimental flushing. The only factor significantly associated with premature removal of a CVC was a diagnosis of leukemia/lymphoma (hazard rate, 2.3; 95% CI, 1.1 to 4.7).

CONCLUSION

An increased complication rate was found with normal saline flushing, but additional investigation is warranted to clarify whether it is related to saline use or to once-a-week flushing.

Peculiaridades da terapia trombolítica na síndrome nefrótica pediátrica: monitorização do fator anti-Xa

OBJETIVO: Descrever a importância do tromboembolismo pulmonar (TEP) na síndrome nefrótica pediátrica e o uso da heparina de baixo peso molecular como opção terapêutica segura e eficaz. DESCRIÇÃO DO CASO: Menino de 5,7 anos com síndrome nefrótica córtico-resistente e glomérulo-esclerose segmentar e focal foi internado devido à diarréia, distúrbios eletrolíticos e anasarca. No 11º dia de internação, evoluiu com desconforto respiratório súbito, cuja investigação mostrou área de alta probabilidade de TEP na cintilografia pulmonar ventilação/perfusão e obstrução em veia jugular interna esquerda ao ultra-som doppler. Iniciado suporte ventilatório com nebulização de oxigênio e anticoagulação com enoxaparina (2mg/kg/dia). Após seis dias, evoluiu com sintomas neurológicos compatíveis com episódio isquêmico transitório, sem alteração na tomografia computadorizada de crânio. A monitorização do fator anti-Xa no soro demonstrou nível subterapêutico e a dose de enoxaparina foi ajustada para 3mg/kg/dia. O edema e os sintomas pulmonares melhoraram e o paciente recebeu alta hospitalar após 33 dias. COMENTÁRIOS: Embora o TEP seja raro em crianças, a síndrome nefrótica é uma condição pró-trombótica que favorece a complicação. A heparina de baixo peso molecular pode ser considerada no tratamento e na profilaxia secundária do TEP, sendo importante monitorizar o nível sérico do fator anti-Xa para ajustar sua dose e promover tratamento seguro e eficaz.

The influence of age on in vitro plasmin generation in the presence of fibrin monomer

BACKGROUND AND OBJECTIVES

The components of the fibrinolytic system interact to generate plasmin from its zymogen form, plasminogen. At birth, all the components of the fibrinolytic system are present but with differing plasma concentrations. The present study was undertaken to explore the effect of physiological, age-dependent factors of the fibrinolytic system during childhood on the capacity to generate plasmin.

DESIGN AND METHODS

Total plasmin generation was measured in venous plasma from umbilical cords and adults, on plastic and cell surfaces, in the presence of fibrin monomer, Desafib. Plasminogen, its inhibitors alpha2-antiplasmin and plasminogen activator inhibitor type 1, and plasmin-alpha2-antiplasmin complex in the time samples were assayed by enzyme-linked immunosorbent assay. The effect of addition of plasminogen on the plasmin generation in cord plasma and the effect of lipoprotein on adult and cord plasmin generation were measured.

RESULTS

On the surface of human umbilical vein endothelial cells, onset of plasmin generation was earlier (40 min) compared to plastic (60 min) but total plasmin generation was similar on both surfaces. The addition of plasminogen to cord plasma increased plasmin generation. Supplementation of lipoprotein in adult plasma had an inhibitory effect, but there was no significant effect in cord plasma.

INTERPRETATIONS AND CONCLUSIONS

Plasmin generation is reduced in newborn compared to adult plasma. Decreased plasmin generation in cord plasma is likely due to decreased plasminogen concentration. The antifibrinolytic effect of lipoprotein is more pronounced in adults as compared to newborns due to the presence of higher plasminogen concentration.

Parental narratives of quality of life in children with leukemia as associated with the placement of a central venous catheter

Thirty mothers of children with leukemia were interviewed about the child's and family's daily routines using a version of the Ecocultural Family Interview. Parental narratives were analyzed qualitatively and quantitatively. Four broad dimensions, encompassing 23 subthemes, were identified: child coping (alpha=0.88), child quality of life (alpha=0.72), parental coping (alpha=0.72), and parental trust in the medical care (alpha=0.73). Two objective variables were drawn from the medical charts (time from the diagnosis, time from central venous catheter [CVC] placement). Regression analyses showed that the number of days from the CVC placement (beta=0.46) and child coping (beta=0.44) significantly predicted children's quality of life, which in turn predicted parental trust in the medical care (beta=0.31). The methodological implications of our narrative approach are discussed.

Interaction of antibiotics and warfarin in pediatric cardiology patients

Antibiotics are known to alter the anticoagulation induced by warfarin in adults, but little is known about this interaction in children. In a retrospective review of patients under the age of 21 years, we found that antibiotic therapy (89 courses of antibiotics in 23 patients) was associated with an increase in the mean international normalized ratio (INR) from 2.7 to 3.6. The change in INR correlated inversely with patient age. These data suggest that more intensive monitoring of the INR after starting antibiotics may help to mitigate excessive anticoagulation in children receiving warfarin.

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

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

Central venous catheter use in the pediatric patient: mechanical and infectious complications

OBJECTIVE

Following the introduction and widespread use of central venous catheters (CVCs) in adults, these devices are being used with increasing frequency in the pediatric population. This review will focus on differences between adults and children regarding CVC use and its potential complications. Both mechanical and infectious complications will be discussed.

DATA SOURCES

Systematic review of the literature.

CONCLUSIONS

CVC-related complications in pediatric patients are closely linked to age, body size, and age-related immune status. In older children, many complications are similar to those encountered in adult patients. Because of ongoing growth and body changes, a cutoff point beyond which children can be regarded as "young adults" is difficult to define; many of our recommendations are therefore age-related. More frequently than in adults, an implanted port may be the first choice in pediatric patients when long indwelling times are expected. The optimal site of insertion also depends on factors such as the patients' age as well as the need for sedation and analgesia during the insertion procedure. In contrast to guidelines in adult patients, we recommend that a radiograph always be made following CVC insertion to check the position of the catheter. Regarding prevention of infectious complications, we recommend full sterile barrier precautions during CVC insertion and strict protocols for catheter care. CVCs should be removed as soon as possible when they are no longer needed, but there is no place for elective CVC replacement on a routine basis. New developments such as the use of impregnated catheters might help reduce infection rates; however, additional research will be required to provide more evidence of benefit in the pediatric population.

Thrombosis during infancy and childhood: what we know and what we do not know

Despite underlying illnesses, children have a greater chance to survive and are expected to live 6 to 8 decades following an episode of venous or arterial thrombosis. The disproportionate benefits of preventing thrombosis and its sequelae in pediatric patients are evident. Therefore, it is necessary to develop appropriate strategies for diagnosis and management of thromboembolic events in children and to understand their acute and long-term effects. There still are many unanswered questions and clinical trials are being designed to help study these important issues.

Analysis of pediatric thrombotic patients in Turkey

This study analyzes the data of thrombotic children who were followed up in different pediatric referral centers of Turkey, to obtain more general data on the diagnosis, risk factors, management, and outcome of thrombosis in Turkish children. A simple two-page questionnaire was distributed among contact people from each center to standardize data collection. Thirteen pediatric referral centers responded to the invitation and the total number of cases was 271. All children were diagnosed with thromboembolic disease between January 1995 and October 2001. Median age at time of first thrombotic event was 7.0 years. Of the children 4% of the cases were neonates, 12% were infants less than 1 year old, and 17% were adolescents. Thromboembolic event was mostly located in the cerebral vascular system (32%), deep venous system of the limbs, femoral and iliac veins (24%), portal veins (10%), and intracardiac region (9%). Acquired risk factors were present in 86% of the children. Infection was the most common underlying risk factor. Inherited risk factors were present in 30% of the children. FVL was the most common inherited risk factor. Acquired and inherited risk factors were present simultaneously in 19% of the patients. Eleven children had a history of familial thrombosis. Due to the local treatment preferences, the treatment of the children varied greatly. Outcome of the 142 patients (52%) was reported: 88 (62%) patients had complete resolution, 47 (33%) had complications, 12 (9%) had recurrent thrombosis, and 34 (24%) died. Three children (2.1%) died as a direct consequence of their thromboembolic disease. The significant morbidity and mortality found in this study supports the need for multicentric prospective clinical trials to obtain more generalizable data on management and outcome of thrombosis in Turkish children.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Central venous catheter-related thrombosis presenting as superior vena cava syndrome in a haemophilic patient with inhibitors

We report the case of a 10.5-year-old boy with severe haemophilia A (SHA) and inhibitors who presented with superior vena cava (SVC) obstruction while on immune tolerance induction (ITI) with daily recombinant factor VIII (rFVIII) and factor eight bypassing activity (FEIBA) (75 U kg(-1)) twice a week. The boy had a right-sided implanted central venous catheter. Imaging revealed a large occlusive thrombus in the SVC with all upper venous system drainage occurring through the azygos and collateral veins. Despite initial success with local thrombolytic therapy using recombinant tissue plasminogen activator, the thrombus persisted. Mechanical thrombolysis and angioplasty resulted in the successful removal of the thrombus and resolution of the SVC syndrome. Unfractionated heparin was used to prevent thrombus reformation/propagation. A work-up did not reveal any underlying genetic prothrombotic risk factors. The occurrence of such a profoundly symptomatic thromboembolism (TE) in a boy with SHA with inhibitors is unusual. A combination of risk factors, including the ongoing infusion of high doses of FVIII in the context of a disappearance of inhibitors together with the infusion of clotting factors known to be potentially thrombogenic, may place haemophilic patients on ITI (immune tolerance induction) at risk for this rare, life-threatening complication. The appropriate management of TEs in such a setting is unknown.

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

OBJECTIVE

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

DESIGN

Prospective, consecutive cohort of unselected newborn infants.

METHODS

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

RESULTS

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

CONCLUSIONS

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

Nephrotic syndrome in childhood

Childhood nephrotic syndromes are most commonly caused by one of two idiopathic diseases: minimal-change nephrotic syndrome (MCNS) and focal segmental glomerulosclerosis (FSGS). A third distinct type, membranous nephropathy, is rare in children. Other causes of isolated nephrotic syndrome can be subdivided into two major categories: rare genetic disorders, and secondary diseases associated with drugs, infections, or neoplasia. The cause of idiopathic nephrotic syndrome remains unknown, but evidence suggests it may be a primary T-cell disorder that leads to glomerular podocyte dysfunction. Genetic studies in children with familial nephrotic syndrome have identified mutations in genes that encode important podocyte proteins. Patients with idiopathic nephrotic syndrome are initially treated with corticosteroids. Steroid-responsiveness is of greater prognostic use than renal histology. Several second-line drugs, including alkylating agents, ciclosporin, and levamisole, may be effective for complicated and steroid-unresponsive MCNS and FSGS patients. Nephrotic syndrome is associated with several medical complications, the most severe and potentially fatal being bacterial infections and thromboembolism. Idiopathic nephrotic syndrome is a chronic relapsing disease for most steroid-responsive patients, whereas most children with refractory FSGS ultimately develop end-stage renal disease. Research is being done to further elucidate the disorder's molecular pathogenesis, identify new prognostic indicators, and to develop better approaches to treatment.

Pediatric thrombosis

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

Recombinant plasminogen activator therapy for cerebral vein thrombosis in a child carrier of prothrombin gene mutation

Venous thrombosis of transverse and sigmoid sinuses was diagnosed in a 3-year-old child who is a carrier of the G20210A prothrombin gene mutation. Recombinant tissue plasminogen activator (rt-PA) treatment was started 9 days following the onset of neurologic signs. Nine days of rt-PA therapy completely dissolved the thrombus. This case provides further evidence that rt-PA is useful and safe in children with thrombosis.

Use of tissue plasminogen activator (rt-PA) in young children with cancer and dysfunctional central venous catheters

PURPOSE

To determine the efficacy and safety of low, nonescalating dose tissue plasminogen activator (rt-PA) in restoring the patency of occluded central venous access devices (CVCs) in children with cancer who weigh less than 30 kg.

PATIENTS AND METHODS

A single-center review of the use of rt-PA (0.5 mg indwelling for 30 minutes in the CVC) was conducted in 42 cancer patients with large bore central venous access devices implanted over a 2-year period. All patients weighed less than 30 kg. None had been previously treated with a thrombolytic agent. The efficacy for restoring function to CVCs was measured and correlated with patient age, weight and CVC lumen size. Propensity to rethrombose following an initial occlusion and treatment was also determined.

RESULTS

Of 235 doses of rt-PA administered in a 2-year period, 55 doses administered to 42 patients met the eligibility criteria as outlined. Twenty-nine patients (69%) had function restored with a single dose; 8 patients (19%) required 2 doses, and 5 patients (12%) failed 2 doses; for an overall success rate of 88%. No significant adverse events occurred. Of the 37 cleared CVCs, 14 (38%) reoccluded within 1 month. A higher proportion of patients initially treated with one rt-PA (71%) experienced another CVC dysfunction within 1 month, compared with 29% CVC dysfunction in those requiring >1 dose.

CONCLUSIONS

This article describes the use of rt-PA (0.5 mg, without dose escalation) to lyse CVC-associated thrombi specifically in small children with cancer, a patient population in which it is particularly desirable to minimize the degree of fibrinolysis. One dose of 0.5 mg rt-PA, with an additional dose if necessary, is as safe and effective as previously reported escalating dose regimens for CVC clot lysis. There is no statistically significant correlation of treatment failure with patient age, weight, or catheter lumen size, and no significant propensity for rapid rethrombosis following a single dysfunction and treatment. Patients initially treated with a single dose of rt-PA appear to have more subsequent dysfunctions in the month after treatment, an observation that warrants further study.

Neonatal sinovenous thrombosis associated with homozygous thermolabile methylenetetrahydrofolate reductase in both mother and infant

The C677T mutation in 5,10-methylenetetrahydrofolate reductase (MTHFR) predicts substitution of valine for alanine at residue 223 (A223V). This thermolabile form of MTHFR has 50% reduced activity, has been associated with hyperhomocystinemia, and is a described risk factor for thrombosis in adults.(1-3) In addition, it has been associated with birth defects in the infants of affected mothers and with recurrent fetal losses.(4-6) We report the occurrence of sinovenous thrombosis in a newborn infant who presented with seizures. Both infant and mother were subsequently identified as having homozygous C677T alleles for MTHFR.

Catheter-related deep venous thrombosis in children with hemophilia

Central venous catheters (CVCs) are a common adjunct to hemophilia therapy, but the risk of CVC-related deep venous thrombosis (DVT) in hemophiliacs is not well defined. In a previous study, 13 patients with CVCs had no radiographic evidence of DVT. However, recent abstracts and case studies demonstrate that DVT does occur. Therefore, this study sought to determine the frequency of DVT in children with hemophilia and long-term CVCs and to correlate venographic findings with clinical features. All hemophilia patients with tunneled subclavian CVCs in place for 12 months or more were candidates for evaluation. Patients were examined for physical signs of DVT and questioned about catheter dysfunction. Contrast venograms were obtained to identify DVT. Fifteen boys with severe hemophilia were evaluated, including 9 from the initially studied group of 13. Eight patients had evidence of DVT, 5 of whom previously had normal venograms. Five of 15 patients had clinical problems related to the CVC, all of whom had DVT. Four of 15 patients had suggestive physical signs; 3 had DVT. The mean duration of catheter placement for all patients was 57.5 months (range, 12-102 months). For patients with DVT, the mean duration was 66.6 +/- 7.5 months, compared to 49.5 +/- 7.2 months for patients without DVT (P =.06). No patient whose CVC was in place fewer than 48 months had an abnormal venogram. Many hemophilia patients with CVCs develop DVT of the upper venous system, and the risk increases with duration of catheter placement.