Antithrombotic therapy in neonates and children: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

Beta (β)-antithrombin activity in children and adults: implications for heparin therapy in infants and children

BACKGROUND

Antithrombin, a hemostatic protein and naturally occurring anticoagulant, is a major thrombin inhibitor. The capacity of antithrombin to inhibit thrombin is known to increase a 1000-fold whilst in the presence of unfractionated heparin. β-antithrombin is an isoform of antithrombin with a high affinity for unfractionated heparin. This study aimed to determine the differences in the anticoagulant activity of the β-antithrombin isoform in children compared with adults.

METHODS

Plasma samples were obtained from 105 healthy individuals from the following age groups: neonates (day 1 and day 3), 28 days to 1 year, 1-5 years, 6-10 years, 11-16 years and adults. The method utilized to measure the activity of β-antithrombin in plasma is a modified version of the total antithrombin assay routinely used in diagnostic laboratories. The modified version of this assay allows for the specific quantification of the β-antithrombin glycoform anticoagulant activity alone, as the β-antithrombin molecule is activated under a high salt concentration, which in turn does not allow activation of other antithrombin isoforms.

CONCLUSIONS

This study demonstrated that there are no age-specific differences in the activity of β-antithrombin. However, considering that the total AT activity is significantly reduced in neonates, our results suggest that in this population β-antithrombin activity is a major contributor to the overall activity of AT.

[Deep venous thrombosis complications during infections in pediatric patients: analysis of a series of 24 cases]

Venous thromboembolism disease (VTE) is rare in children (5.3 of 10,000 hospitalized children). However, morbidity and mortality are high, especially when the child is already suffering from severe sepsis. We report an analytical study of 24 cases of deep venous thrombosis occurring in children during infection, recorded at the Montpellier University Hospital between 1999 and 2009. Many parameters were studied in each population (age, sex, familial and personal history of thrombosis, history of thrombophilia, the presence of a venous catheter, a causative organism, time to onset of thrombus, topography of lesions, acquired abnormalities of hemostasis, and thrombosis prophylaxis). The children were aged from 1 day of life to 16 years. Thromboses occurred in two clinical contexts: "contact" thrombosis (which appeared near the infection) and disseminated thrombosis. This is an early complication because in most of the cases, it appeared in the first 10 days of sepsis. Infection and coagulation appear to be closely related and the states of latent or decompensated disseminated intravascular coagulation are common. Nevertheless, it is not possible to predict the occurence of a thrombotic event. The presence of risk factors (venous catheters, acquired thrombophilia, or constitutional thrombophilia) may increase the thrombogenic potential of the infection. VTE should always be suspected and sought in case of an unfavorable clinical course, and routine prophylaxis of thrombosis during sepsis should be discussed.

A multinational study of thromboprophylaxis practice in critically ill children

OBJECTIVES

Although critically ill children are at increased risk for developing deep venous thrombosis, there are few pediatric studies establishing the prevalence of thrombosis or the efficacy of thromboprophylaxis. We tested the hypothesis that thromboprophylaxis is infrequently used in critically ill children even for those in whom it is indicated.

DESIGN

Prospective multinational cross-sectional study over four study dates in 2012.

SETTING

Fifty-nine PICUs in Australia, Canada, New Zealand, Portugal, Singapore, Spain, and the United States.

PATIENTS

All patients less than 18 years old in the PICU during the study dates and times were included in the study, unless the patients were 1) boarding in the unit waiting for a bed outside the PICU or 2) receiving therapeutic anticoagulation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 2,484 children in the study, 2,159 (86.9%) had greater than or equal to 1 risk factor for thrombosis. Only 308 children (12.4%) were receiving pharmacologic thromboprophylaxis (e.g., aspirin, low-molecular-weight heparin, or unfractionated heparin). Of 430 children indicated to receive pharmacologic thromboprophylaxis based on consensus recommendations, only 149 (34.7%) were receiving it. Mechanical thromboprophylaxis was used in 156 of 655 children (23.8%) 8 years old or older, the youngest age for that device. Using nonlinear mixed effects model, presence of cyanotic congenital heart disease (odds ratio, 7.35; p < 0.001) and spinal cord injury (odds ratio, 8.85; p = 0.008) strongly predicted the use of pharmacologic and mechanical thromboprophylaxis, respectively.

CONCLUSIONS

Thromboprophylaxis is infrequently used in critically ill children. This is true even for children at high risk of thrombosis where consensus guidelines recommend pharmacologic thromboprophylaxis.

Pharmacokinetics and pharmacodynamics of anticoagulants in paediatric patients

Given the rising incidence of thrombotic complications in paediatric patients, understanding of the pharmacologic behaviour of anticoagulant drugs in children has gained importance. Significant developmental differences between children and adults in the haemostatic system and pharmacologic parameters for individual drugs highlight potentially unique aspects of anticoagulant pharmacology in this special and vulnerable population. This review focuses on pharmacologic information relevant to the dosing of unfractionated heparin, low molecular weight heparin, warfarin, bivalirudin, argatroban and fondaparinux in paediatric patients. The bulk of clinical experience with paediatric anticoagulation rests with the first three of these agents, each of which requires higher bodyweight-based dosing for the youngest patients, compared with adults, in order to achieve comparable pharmacodynamic effects, likely related to an inverse correlation between age and bodyweight-normalized clearance of these drugs. Whether extrapolation of therapeutic ranges targeted for adult patients prescribed these agents is valid for children, however, is unknown and a high priority for future research. Novel oral anticoagulants, such as dabigatran, rivaroxaban and apixaban, hold promise for future use in paediatrics but require further pharmacologic study in infants, children and adolescents.

Endovascular venous thrombolysis in children younger than 24 months

PURPOSE

To evaluate the technical feasibility and safety of percutaneous endovascular thrombolysis for extremity deep venous thrombosis (DVT) in children < 24 months old.

MATERIALS AND METHODS

A retrospective chart review of a clinical and imaging database was performed for pediatric patients who underwent endovascular therapy for DVT between January 2010 and July 2013. Indications, techniques, technical and clinical success, and complications were reviewed. Techniques for thrombolysis included catheter-directed therapy (CDT) using alteplase infusion via a multi-side hole catheter, mechanical thrombectomy, and angioplasty. Short-term outcomes were assessed using surgical and imaging follow-up examinations for patency of the targeted vessel. Patients included 11 children (mean age, 9 mo; range, 3 wk-23 mo) who consecutively underwent endovascular thrombolysis for upper extremity (n = 6) or lower extremity (n = 5) DVT. The most common indication was preservation of venous access for future cardiac surgery or medical therapy.

RESULTS

The most common risk factor was the presence of a central venous catheter (10 of 11 patients). All patients with upper extremity DVT had congenital heart disease. CDT and angioplasty were performed in all patients. Venous patency was established in all patients. A grade III (95%-100%) thrombolysis response was achieved in seven patients, and a grade II (50%-95%) thrombolysis response was achieved in four patients. A major complication of pulmonary embolism occurred in one patient with upper extremity thrombolysis and was managed by intravenous systemic alteplase and heparin. No recurrence of thrombosis was found on average follow-up of 11.8 months (range, 1-41 mo).

CONCLUSIONS

Percutaneous endovascular thrombolysis for extremity DVT is safe and technically feasible in children < 24 months old.

[Thromboprophylaxis in critically ill children in Spain and Portugal]

INTRODUCTION

Although critically ill children may be at risk from developing deep venous thrombosis (DVT), data on its incidence and effectiveness of thromboprophylaxis are lacking.

OBJECTIVE

To describe the use of thromboprophylaxis in critically ill children in Spain and Portugal, and to compare the results with international data.

MATERIAL AND METHODS

Secondary analysis of the multinational study PROTRACT, carried out in 59 PICUs from 7 developed countries (4 from Portugal and 6 in Spain). Data were collected from patients less than 18 years old, who did not receive therapeutic thromboprophylaxis.

RESULTS

A total of 308 patients in Spanish and Portuguese (Iberian) PICUS were compared with 2176 admitted to international PICUs. Risk factors such as femoral vein (P=.01), jugular vein central catheter (P<.001), cancer (P=.03), and sepsis (P<.001), were more frequent in Iberian PICUs. The percentage of patients with pharmacological thromboprophylaxis was similar in both groups (15.3% vs. 12.0%). Low molecular weight heparin was used more frequently in Iberian patients (P<.001). In treated children, prior history of thrombosis (P=.02), femoral vein catheter (P<.001), cancer (P=.02) and cranial trauma or craniectomy (P=.006), were more frequent in Iberian PICUs. Mechanical thromboprophylaxis was used in only 6.8% of candidates in Iberian PICUs, compared with 23.8% in the international PICUs (P<.001).

CONCLUSIONS

Despite the presence of risk factors for DVT in many patients, thromboprophylaxis is rarely prescribed, with low molecular weight heparin being the most used drug. Passive thromboprophylaxis use is anecdotal. There should be a consensus on guidelines of thromboprophylaxis in critically ill children.

Risk factors for hospital-sssociated venous thromboembolism in the neonatal intensive care unit

OBJECTIVE

To determine hospital-associated venous thromboembolism (HA-VTE) risk factors in critically ill neonates.

METHODS

We conducted a case-control study in the neonatal intensive care unit (NICU) of All Children's Hospital Johns Hopkins Medicine (St. Petersburg, FL), from January 1, 2006 - April 10, 2013. We identified HA-VTE cases using electronic health record. Four NICU controls were randomly selected for each HA-VTE case. Associations between putative risk factors and HA-VTE were estimated using odds ratios (ORs) and ninety-five percent confidence intervals (95%CIs) from univariate and multivariate regression analyses.

RESULTS

Twenty-three HA-VTE cases and 92 controls were included. The annual HA-VTE incidence was approximately 1.4 HA-VTE cases per 1,000 NICU admissions. In univariate analyses, mechanical ventilation (OR=7.27, 95%CI=2.02-26.17, P=0.002), central venous catheter (CVC; OR=52.95, 95%CI=6.80-412.71, P<0.001), infection (OR=7.24, 95%CI=2.66-19.72, P<0.001), major surgery (OR=5.60, 95%CI=1.82-17.22, P=0.003) and length of stay ≥15days (OR=6.67, 95%CI=1.85-23.99, P=0.004) were associated with HA-VTE. Only CVC (OR=29.04, 95%CI=3.18-265.26, P=0.003) remained an independent risk factor in the multivariate analysis. Based on this result, the estimated risk of HA-VTE in NICU patients with a CVC was 0.9%.

CONCLUSION

This study identifies CVC as an independent risk factor for HA-VTE in critically ill neonates. However, the level of risk associated with CVC is below the conventional threshold for primary anticoagulation thromboprophylaxis. Larger studies are needed to substantiate these findings and identify novel putative risk factors to further distinguish NICU patients at highest HA-VTE risk.

Heparin-induced hyperkalemia in an extremely-low-birth-weight infant: a case report

Heparin may cause hyperkalemia by blocking aldosterone biosynthesis in the adrenal gland. Dizygotic twin sisters were born by Cesarean section at 25 weeks' gestation. The younger sister developed acute hyperkalemia (7.4 mEq/L) at 10 days of age. At the time of the development of the hyperkalemia, there were no signs of systemic infection, cardiac or renal failure, adrenal insufficiency, or sudden anemia. She was receiving no medication other than heparin to maintain the vascular catheter. Heparin was changed to dalteparin at 12 days of age. The plasma potassium level normalized after 14 days of age. After this change, the urinary potassium concentration and the aldosterone and plasma renin activity increased. The urinary aldosterone levels before and after the changes were 31 and 183 pg/μg creatinine, respectively. When heparin-induced hyperkalemia is suspected, stopping the heparin administration facilitates diagnosis and treatment; if anticoagulant therapy is required; one treatment option is changing from unfractionated heparin to low-molecular-weight heparin.

Pediatric otogenic sigmoid sinus thrombosis: 12-Year experience

OBJECTIVES

Otogenic sigmoid sinus thrombosis is a rare complication of acute otitis media. Treatment remains controversial particularly regarding extent of surgical intervention. The aim of the study was to review the 12-year experience of a major medical center with the treatment of sigmoid sinus thrombosis in children.

METHODS

Retrospective case series identified by database review in a tertiary university-affiliated pediatric medical center. Twenty-four children aged 7-155 months were treated for sigmoid sinus thrombosis from 2000 through 2011.

RESULTS

The transverse sinus was also involved in 10 patients, and the jugular vein, in 4. Acute otitis media with mastoiditis was the causative factor in all cases. Subperiosteal abscess was diagnosed in 21 patients, 11 with epidural involvement. Treatment in all cases consisted of broad-spectrum antibiotics and ventilation tube insertion. Twenty-one children (87.5%) underwent mastoidectomy with removal of bone covering the sigmoid sinus to drain pus and remove granulations from the epidural cavity, without aspiration or sinus drainage. Twenty-two patients received low-molecular-weight heparin for 3-6 months postoperatively. Children infected with Fusobacterium necrophorum had a longer and more severe course with coexisting osteomyelitis. There were no neurologic sequelae or hematologic complications. Follow-up imaging, performed in 15 children, revealed partial or full recanalization in 87%.

CONCLUSIONS

Relatively conservative surgical intervention appears to yield good results in children with sigmoid sinus thrombosis consequent to acute otitis media. Anticoagulants are safe if correctly administered and may prevent extension of the thrombus.

Blood glucose as a marker of venous thromboembolism in critically ill children

BACKGROUND

The ability to predict the development of venous thromboembolism is highly desirable.

OBJECTIVE

We aim to determine the association between hyperglycemia and venous thromboembolism in non-diabetic critically ill children.

PATIENTS/METHODS

We conducted a retrospective cohort study that included children in the pediatric intensive care unit on a vasopressor or mechanical ventilator and without history of diabetes mellitus or prior diagnosis of thrombosis. Based on maximum blood glucose > 150 mg dL(-1) while admitted to the unit, children were categorized as hyperglycemic or non-hyperglycemic. The primary outcome was development of venous thromboembolism while admitted to the unit. We determined the association between hyperglycemia and venous thromboembolism using logistic regression models adjusting for selected subject characteristics.

RESULTS

Of the 789 subjects analyzed, 34 subjects developed venous thromboembolism (incidence, 4.3%; 95% confidence interval, 3-6%). Venous thromboembolism was more likely to develop in hyperglycemic subjects compared with non-hyperglycemic subjects. A total of 31 subjects (6.2%; 95% confidence interval, 4.2-8.7%) developed venous thromboembolism after becoming hyperglycemic compared with three non-hyperglycemic subjects with venous thromboembolism (1%; 95% confidence interval, 0.2-3%). When adjusted for age, diagnosis, presence of central venous catheter, prophylactic antithrombotic use and severity of illness, the odds ratio of venous thromboembolism with hyperglycemia was 4.1 (95% confidence interval, 1.2-14.1). For every 10 mg dL(-1) increase in maximum blood glucose, the adjusted odds ratio of venous thromboembolism was 1.04 (95% confidence interval, 1.01-1.06).

CONCLUSION

Hyperglycemia is associated with venous thromboembolism in critically ill non-diabetic children. Maximum blood glucose is a potential predictor of venous thromboembolism in this population.

Retrospective evaluation of antithrombin III supplementation in neonates and infants receiving enoxaparin for treatment of thrombosis

BACKGROUND

Thromboembolic events are occurring at increasing rates in neonates and infants. At Children's Mercy Hospitals and Clinics, antithrombin III (AT3) concentrates are often used in combination with enoxaparin to supplement physiologically low AT3 levels. Theoretically, AT3 enhances the anticoagulant activity of enoxaparin and results in decreased time to therapeutic anti-Xa levels. No data exist on use of AT3 for this indication.

PROCEDURE

This retrospective study compared time to therapeutic anti-Xa levels in patients <1 year of age receiving enoxaparin with AT3 (Group 1) and without AT3 (Group 2) for treatment of thrombosis. Primary objective was to compare time to therapeutic anti-Xa levels (0.5-1 U/ml) between groups. Secondary objectives included comparison of the initial and therapeutic dose of enoxaparin, enoxaparin dose changes, AT3 supplementation, and level monitoring. Bleeding events and cost were also evaluated. Statistical tests included Schuirmann's two one-sided tests for equivalence and general linear models/logistic regression for independent effects of age, critical illness, and timing of AT3.

RESULTS

Mean time to therapeutic anti-Xa levels were not equivalent between Groups 1 and 2 (80.7 vs. 65.2 hours; P = 0.28). Initial enoxaparin dose and number of dose changes were equivalent. Group 1 required higher doses of enoxaparin to achieve therapeutic anti-Xa levels. Age, critical illness, and timing of AT3 had no effect on time to therapeutic anti-Xa levels. Bleeding events were not equivalent between Groups 1 and 2 (14.3% vs. 3.9%; P = 0.55).

CONCLUSION

Supplementation with AT3 did not decrease time to therapeutic anti-Xa levels, added significant cost, and was associated with increased bleeding events.

Venous thromboembolism in pediatric nephrotic syndrome

Childhood nephrotic syndrome (NS) is one of the most common pediatric kidney diseases, with an incidence of 2-7 per 100,000. Venous thromboembolism (VTE) is associated with significant morbidity and mortality, and occurs in ∼3 % of children with NS, though incidence approaches 25 % in high-risk groups. VTE etiology is multifactorial, with disease-associated coagulopathy thought to be a significant contributor. Other risks include age, disease severity, and treatment-related hazards, such as the presence of central venous catheters. Non-pharmacologic preventive measures such as ambulation and compression stockings are recommended for patients with identified VTE risks. Central venous catheters should be avoided whenever possible. Symptoms of VTE include venous catheter dysfunction, unilateral extremity symptoms, respiratory compromise, flank pain, and gross hematuria. When VTE is suspected, confirmatory imaging studies should be obtained, followed by appropriate laboratory evaluation and treatment. Therapeutic goals include limiting thrombus growth, extension, and embolization by early institution of anticoagulant therapy. Anticoagulation is recommended for a minimum of 3 months, but should be continued until NS remission is achieved. Further studies are necessary to identify VTE-risk biomarkers and optimal therapeutic regimens. Observational cohort studies are needed to identify VTE-risk groups who may benefit from thromboprophylaxis and to define disease-specific treatment algorithms.

Venous thromboembolism in critically ill children

PURPOSE OF REVIEW

To review the current literature on venous thromboembolism (VTE) in critically ill children.

RECENT FINDINGS

There is an increasing concern for VTE and its complications in critically ill children. Critically ill children are at increased risk of thromboembolism because of the treatment that they are receiving and their underlying condition. A complex relationship exists between thrombosis and infection. A thrombus is a nidus for infection, while infection increases the risk of thrombosis. Pediatric-specific guidelines for the prevention and treatment of thromboembolism are lacking. Current guidelines are based on the data from adults. Novel anticoagulants are now available for use in adults. Studies are ongoing to determine their safety in children. Risk assessment tools have recently been developed to determine the risk of thromboembolism in critically ill children. Certain molecules are associated with thromboembolism in adults.

SUMMARY

Pediatric critical care practitioners should be cognizant of the importance of VTE in critically ill children to allow early identification and treatment. Adequately powered clinical trials are critically needed to generate evidence that will guide the treatment and prevention of thromboembolism in critically ill children. Risk assessment tools that incorporate biomarkers may improve our ability to predict the occurrence of thromboembolism in critically ill children.

VKORC1 and CYP2C9 genotypes are predictors of warfarin-related outcomes in children

BACKGROUND

Despite substantial evidence supporting a pharmacogenetic approach to warfarin therapy in adults, evidence on the importance of genetics in warfarin therapy in children is limited, particularly for clinical outcomes. We assessed the contribution of CYP2C9/VKORC1/CYP4F2 genotypes and variation in other genes involved in vitamin K and coagulation pathways to warfarin dose and related clinical outcomes in children.

PROCEDURE

Clinical and genetic data for 93 children (age ≤ 18 years) who received warfarin therapy were obtained. DNA was genotyped for 93 selected single nucleotide polymorphisms using a custom assay.

RESULTS

With a median age of 4.8 years, our cohort included more young children than most previous studies. Overall, 76.3% of dose variability was explained by weight, indication, VKORC1-1639G/A and CYP2C9 *2/*3, with genotypes accounting for 21.1% of variability. There was a strong correlation (R(2) = 0.68; P < 0.001) between actual and predicted warfarin dose using a pediatric genotype-based dosing model. VKORC1 genotype had a significant impact on time to therapeutic international normalized ratio (INR) (P = 0.047) and time to over-anticoagulation (INR > 4; P = 0.024) during the initiation of therapy. CYP2C9*3 carriers were also at increased risk of major bleeding while receiving warfarin (adjusted OR = 11.28). An additional variant in CYP2C9 (rs7089580) was significantly associated with warfarin dose (P = 0.020) in a multivariate clinical and genetic model.

CONCLUSIONS

This study confirms the importance of VKORC1/CYP2C9 genotypes for warfarin dosing in a young pediatric cohort and demonstrates an impact of genetic factors on clinical outcomes in children. Furthermore, we identified an additional variant in CYP2C9 of potential relevance for warfarin dosing in children.

Emergent thrombectomy in a neonate with an upper extremity arterial thrombus

Case This case report is of a 39 (4/7)weeks infant who presented at the time of birth with an immobile, cyanotic right upper extremity consistent with ischemia but without evidence of gangrene. Doppler examination identified pulses in the axillary but not the brachial or radial arteries. Extremity arterial ultrasound confirmed the diagnosis of an arterial thrombosis extending from the right axillary artery to the brachial artery bifurcation. An emergent balloon thrombectomy was performed successfully with immediate return of blood flow. Intraoperative ultrasound demonstrated patent axillary and brachial arteries with forward flow. A retroperitoneal ultrasound and limited hypercoagulable workup failed to identify a source of the arterial thrombus. The infant had normal return of function without residual limb effects. Conclusion Emergent balloon thrombectomy should be heavily considered in neonates with an extremity arterial thrombosis of undeterminable duration both for limb salvage, preserve function, and to prevent long-term growth discordance.

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.

Mechanical embolectomy for ischemic stroke in a pediatric ventricular assist device patient

The reported incidence of cerebral embolic or hemorrhagic complications related to mechanical circulatory support in children is high, even while subjects are managed with aggressive antithrombotic therapy. The safety and utility of endovascular treatment for stroke in the pediatric VAD population has not been established in the published literature. We describe a nine-yr-old patient on BiVAD support who experienced threatened AIS on two separate occasions. He was treated successfully via mechanical embolectomy on both occasions and survived to transplantation with minimal neurologic deficits.

Impact of decreased heparin dose for flush-lock of implanted venous access ports in pediatric oncology patients

BACKGROUND

Faced with a lack of evidence, institutions often develop local protocols for use of heparin to flush-lock venous access ports. Our objective was to evaluate catheter-related complications in patients after introduction of a lower-concentration heparin flush protocol.

PROCEDURE

Patients with implanted vascular access devices followed by a Pediatric Oncology service were exposed to a practice change in which heparin dose for flush-lock was decreased from 5 ml of 100 units/ml to 5 ml of 10 units/ml. Outcome measures included port malfunctions leading to use of intra-port tissue plasminogen activator (tPA), and positive blood cultures.

RESULTS

Rates of tPA usage were statistically similar before and after the practice change (0.82 compared to 0.59 per 100 line days absolute change -0.23, 95% CI -0.66, 0.20). Positive blood culture rates were also statistically similar before and after the practice change.

CONCLUSIONS

Children with implanted ports had similar complication rates and care safety measures whether their ports were flushed with 10 units/ml of heparin or 100 units/ml. Standardizing flush-locks to lower doses of heparin may be a promising approach to maintaining port patency without compromising patient safety.

Neonatal stroke: a review of the current evidence on epidemiology, pathogenesis, diagnostics and therapeutic options

Neonatal stroke, including perinatal arterial ischaemic stroke and cerebral sinovenous thrombosis, remains a serious problem in the neonate. This article reviews the current evidence on epidemiology, pathogenesis, diagnostics and therapeutic options.

CONCLUSION

Although our understanding of the underlying mechanisms and possible risk factors has improved, little progress has been made towards therapeutic options. Considering the high incidence of neurological sequelae, the need for therapeutic options is high and should be the focus of future research.

Pediatric arterial ischemic stroke

PURPOSE OF REVIEW

This article aims to provide a broad overview of pediatric arterial ischemic stroke, from recognition and diagnosis to the short-term and long-term management based on current available literature.

RECENT FINDINGS

Arterial ischemic stroke in children represents a significant disorder with a concerning high rate of adverse outcomes, including potentially preventable recurrent stroke. Although awareness of pediatric stroke is increasing, diagnosis is still commonly delayed or missed altogether, particularly in younger children. Current vascular imaging techniques have limitations in accurate diagnosis of arteriopathies that are now recognized as an important cause of childhood stroke. Significant variability exists in treatment of pediatric stroke. Management is based on published consensus guidelines; however, individual children require an individualized approach.

SUMMARY

As pediatric stroke specialists become increasingly available, the collaboration of such experts on individual management is crucial. Definitive evidence-based treatment for pediatric stroke awaits the development of randomized controlled trials.

Intra-abdominal venous thrombosis after colectomy in pediatric patients with chronic ulcerative colitis: incidence, treatment, and outcomes

PURPOSE

Children with chronic ulcerative colitis (CUC) are at increased risk for venous thromboembolism, especially after colectomy procedures. We aim to review our patients with CUC who underwent a colectomy and suffered intra-abdominal thrombosis; moreover we wanted to define thrombotic incidence and outcomes

METHODS

In this is IRB approved retrospective study, we reviewed our patients who underwent colectomy for CUC from January 1999 to December 2011 for development of intra-abdominal thrombosis.

RESULTS

Of 366 patients with CUC who underwent colectomy, 15 (4%) were diagnosed with a venous thromboembolism. All patients presented with acute abdominal pain. The locations of thrombus formation varied: 13 (87%) developed thrombi in the portal vein, 4 (27%) in the splenic vein, 2 (13%) in the superior mesenteric vein, 1 (7%) in the hepatic vein, and 1 (7%) in the hepatic artery. The mean number of post-operative days at diagnosis of thrombus was 38.7 days (range 3-180 days). Fourteen patients (93%) underwent anticoagulation for treatment. The mean number of days of anticoagulant therapy until documented resolution of thrombus on imaging was 96.3 days (range 14-364 days). All thrombi resolved with therapy. There was no mortality during follow-up.

CONCLUSIONS

Four percent of our pediatric patients with chronic ulcerative colitis who underwent colectomy developed symptomatic intra-abdominal venous thromboembolism. 3 to 6 months of anticoagulant therapy is adequate treatment in almost all patients. Practitioners should have a high index of suspicion for intra-abdominal venous thrombus when these patients complain of abdominal pain postoperatively. Based on our experience, prophylactic anticoagulation should be strongly considered peri-operatively in this population.

Left ventricular thrombus formation after repair of anomalous left coronary artery from the pulmonary artery

Although thrombus formation following myocardial infarction in adults is well known, intracardiac thrombosis in children is uncommon. We report the case of a large left ventricular thrombus in an infant with ischemic cardiomyopathy secondary to anomalous origin of the left coronary artery from the pulmonary artery. Given its mobility and protrusion across the aortic valve, the patient underwent urgent thrombus removal through a transaortic approach. There were no embolic or neurologic complications. This case highlights that thrombectomy may be performed safely and successfully in critically ill pediatric patients.

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.

Thrombophilia testing in children: a 7 year experience

BACKGROUND

Incidence of venous thromboembolism (VTE) in children is reported to be increasing. We examined thrombophilia testing results in children with VTE that presented in inpatient and outpatient settings to explore patterns of thrombophilia testing.

PATIENTS/METHODS

Children, ages 0-20 years with VTE seen at our institution from Jan 2005 to Apr 2012 were studied retrospectively. All patients with VTE confirmed by imaging were eligible and the presence of significant risk factors was evaluated. Thrombophilia was diagnosed if >1 tests confirmed: persistently low protein C (PC), protein S (PS), and antithrombin (AT) following VTE resolution, persistent antiphospholipid antibodies (APA) positivity >12 weeks from first test, factor V Leiden (FVL) and prothrombin mutation (PTm) hetero- or homozygosity, elevated plasminogen activator inhibitor (PAI-1) levels with 4G/5G or 4G/4G polymorphisms, methylene tetrahydrofolate reductase (MTHFR) polymorphisms with elevated fasting homocysteine levels.

RESULTS

Three hundred ninety-two patients met inclusion criteria. At least one test was ordered in 157/239 inpatients. All 153 outpatients had >1 test ordered. Thrombophilia rate differences between inpatients and outpatients did not reach statistical significance except for PC deficiency, which was significantly higher in outpatients. Of inpatients, central venous line (CVL) was significantly associated with not having tests done (P < 0.0022).

CONCLUSIONS

This study of pediatric VTE demonstrated a low thrombophilia rate in both inpatient and outpatient populations. The role of testing in other pediatric patients should be further explored.

Consensus statements on the risk, prevention, and treatment of venous thromboembolism in inflammatory bowel disease: Canadian Association of Gastroenterology

BACKGROUND & AIMS

Guidelines for the management of venous thromboembolism (VTE) from the American College of Chest Physicians do not address patients with inflammatory bowel disease (IBD), a group with a high risk of both VTE and gastrointestinal bleeding. We present recommendations for the prevention and treatment of VTE in patients with IBD.

METHODS

A systematic literature search was performed to identify studies on VTE in IBD. The quality of evidence and strength of recommendations were rated according to the Grading of Recommendation Assessment, Development, and Evaluation (GRADE) approach. Statements were developed through an iterative online platform, then finalized and voted on by a working group of adult and pediatric gastroenterologists and thrombosis specialists.

RESULTS

IBD patients have an approximately 3-fold higher risk of VTE compared with individuals without IBD, and disease flares further increase this risk. Anticoagulant thromboprophylaxis is recommended for IBD patients who are hospitalized with IBD flares without active bleeding and is suggested when bleeding is nonsevere. Anticoagulant thromboprophylaxis is suggested during moderate-severe IBD flares in outpatients with a history of VTE provoked by an IBD flare or an unprovoked VTE, but not otherwise. The recommended duration of anticoagulation after a first VTE is based on the presence of provoking factors. Specific suggestions are made for the prevention and treatment of VTE in pediatric and pregnant IBD patients.

CONCLUSIONS

Using the American College of Chest Physicians' guidelines as a foundation, we have integrated evidence from IBD studies to develop specific recommendations for the management of VTE in this high-risk population.

Commentary on 'Interventions for restoring patency of central venous catheter lumens'

This is a commentary on a Cochrane review, published in this issue of EBCH, first published as: van Miert C, Hill R, Jones L. Interventions for restoring patency of occluded central venous catheter lumens. Cochrane Database of Systematic Reviews 2012, Issue 4. Art. No.: CD007119. DoI: 10.1002/14651858.CD007119.pub2. Further information for this Cochrane review is available in this issue of EBCH in the accompanying Summary article.

Hospital-associated venous thromboembolism in children: incidence and clinical characteristics

OBJECTIVE

To determine incidence and clinical characteristics of hospital-associated venous thromboembolism (VTE) in pediatric patients.

STUDY DESIGN

A retrospective analysis of patients with hospital-associated VTE at the Johns Hopkins Hospital from 1994 to 2009 was performed. Clinical characteristics of patients aged 21 years and younger who developed VTE symptoms after 2 days of hospitalization or <90 days after hospital discharge were examined. International Classification of Diseases, Ninth Revision codes were used to categorize patients with complex chronic medical conditions and trauma.

RESULTS

There were 270 episodes of hospital-associated VTE in 90,485 admissions (rate 30 per 10,000 admissions). Young adults (18-21 years) and adolescents (14-17 years) had significantly increased rates of VTE compared with children (2-9 years) (incidence rate ratio [IRR] 7.7, 95% CI 5.1-12.0; IRR 4.3, 95% CI 2.7-6.8, respectively). A central venous catheter (CVC) was present in 50% of patients, and a surgical procedure was performed in 45% of patients before VTE diagnosis. For patients without a CVC, trauma was the most common admitting diagnosis. CVC-related VTE was diagnosed most frequently in infants (<1 year old) and in patients with malignancy. Renal and cardiac diseases were associated with the highest rates of VTE (51 and 48 per 10,000, respectively). Rates were significantly higher among those with ≥ 4 medical conditions compared with those with 1 medical condition (IRR 4.0, 95% CI 1.4-8.9).

CONCLUSION

Older age and multiple medical conditions were associated with increased rates of hospital-associated VTE. These data can contribute to the design of future clinical trials to prevent hospital-associated VTE in high-risk children.

IV enoxaparin in pediatric and cardiac ICU patients

OBJECTIVES

To report our experience with the use of IV enoxaparin in neonatal and pediatric patients in the ICU.

DESIGN

We performed a case control from January 1, 2009, to June 30, 2012, comparing patients that received IV enoxaparin to controls that received subcutaneous enoxaparin. Cases were matched to controls in a 1:2 manner. IV enoxaparin doses were infused over 30 minutes and anti-Factor Xa levels were drawn 4 hours after the start of the IV infusion or 4 hours after a subcutaneous dose.

SETTING

The pediatric and cardiac ICUs of a tertiary/quaternary, free-standing, academic children's hospital.

PATIENTS

Forty-five neonatal and pediatric patients receiving prophylactic or therapeutic enoxaparin.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Fifteen cases and 30 controls were included. Of 15 patients, 13 received IV enoxaparin for treatment and two received IV enoxaparin for prophylaxis as compared with 25 of 30 controls receiving subcutaneous enoxaparin for treatment and five receiving subcutaneous enoxaparin for prophylaxis. The ages for the cases ranged from 21 days to 16 years with a median weight of 5 kg, and the ages for controls ranged from 10 days to 23 years with a median weight of 31 kg. The median duration of IV therapy was 11 days (range, 1-120 d) and the median duration for subcutaneous therapy was 15 days (range, 3-85 d). The mean initial IV dose was 1.14 ± 0.38 mg/kg/dose q12h, and the mean initial subcutaneous dose was 0.85 ± 0.2 mg/kg/dose subcutaneous q12h (p = 0.003). The mean therapeutic IV dose was 1.31 ± 0.52 mg/kg/dose q12h, and the mean therapeutic subcutaneous dose was 0.9 ± 0.3 mg/kg/dose q12h (p = 0.016). There were no adverse events reported related to bleeding, thrombosis, or hypersensitivity in any of the cases or controls evaluated.

CONCLUSION

The pharmacodynamics of a 30-minute IV enoxaparin infusion was found to produce therapeutic 4 hour anti-Factor Xa levels similar to subcutaneous doses. Although this was a small study, there were no adverse events, suggesting the safety profile of IV enoxaparin may be similar to subcutaneous dosing with the added benefit of less pain associated with IV dosing. These findings suggest that IV enoxaparin may be a viable option for anticoagulating critically ill children and its use warrants further study.

Acute ischemic stroke in a 12-year-old successfully treated with mechanical thrombectomy

We report the case of a healthy 12-year-old girl with an acute ischemic stroke successfully treated with mechanical thrombectomy. The child was referred to our hospital 6 hours after sudden onset of severe headache and left hemiparesis. Cerebral angiography findings were consistent with right distal internal carotid artery occlusion in addition to ipsilateral middle cerebral artery occlusion. Subsequent mechanical thrombectomy with Solitaire AB device resulted in complete vessel recanalization. The patient experienced progressive neurologic improvement with good clinical recovery at the 3-month follow-up. To our knowledge, only 3 cases of primary mechanical thrombectomy in children have been previously reported in the literature. Safety and efficacy data for endovascular therapies in pediatric acute ischemic stroke are lacking. We propose mechanical thrombectomy as an option in children with significant neurologic deficits and proven arterial occlusion, especially when the therapeutic window for intravenous thrombolysis has been exceeded.

Approach to acute ischemic stroke in childhood

OPINION STATEMENT

Acute ischemic stroke in childhood is a medical emergency. Prompt recognition and intervention is necessary to rescue potentially viable brain tissue, prevent complications, and minimize the risk of recurrent stroke. Conditions that could result in recurrent stroke such as cardiac thrombus or cervical artery dissection need to be identified and treated promptly. Although the care of childhood stroke is based largely on extrapolation from adults, an organized approach to the care of these children is critical to optimize outcome.

Prevention and treatment of intraluminal catheter thrombosis in children hospitalised in a paediatric intensive care unit

AIM

The aim of the study was to develop and implement a protocol for the prevention and treatment of catheter related intraluminal thrombosis in a paediatric intensive care unit

METHODS

A computerised search was carried out on MEDLINE, through PubMed, using the medical subject heading 'central venous catheter', 'central venous access device', 'central venous line' associated with 'occlusion', 'obstruction', 'catheter-related thrombosis', 'critically ill patients' and 'thrombolytic therapy'. References of reviewed articles were also searched for relevant titles as well as non-randomised controlled trials and series of cases when no information of higher level of evidence was available.

RESULTS

With the information gathered, a protocol for the prevention and treatment of catheter related intraluminal thrombosis was elaborated and those recommendations that best suit our environment were included. They were agreed upon by a broad panel of professionals working in the Pediatric Intensive Care Unit and the Pharmacy Department.

CONCLUSIONS

Due to the variety of options available for the pharmacotherapeutic management of intraluminal catheter thrombosis, one measure to improve the quality of the therapy and to diminish the variability in the prescription could be the implementation of a protocol as described in this paper.

Survey results: characterization of direct thrombin inhibitor use in pediatric patients

OBJECTIVES

The objective of this multicenter survey is to characterize the use of direct thrombin inhibitors (DTIs) in the pediatric population. The results of this survey may be used to design a prospective multicenter study with the ultimate goal of developing a dosing/titration recommendation for the use of DTIs in the pediatric population.

METHODS

This is a multicenter, descriptive study to survey hospitals around the country regarding the use of DTIs (argatroban, bivalirudin, and lepirudin) in the pediatic population. Institutional review board approval was obtained. The survey consisted of 42 questions and was designed utilizing Survey Monkey. The survey was emailed to members of the Pediatric Pharmacy Advocacy Group. Listserv members who responded to the survey within 4 weeks of when the survey was emailed were included in the study. Descriptive statistics were performed utilizing Microsoft Excel 2007.

RESULTS

Responses were obtained from 56 institutions from 29 states in the United States. Multiple agents are available on formulary with argatroban being the most common (~80%). The large majority of institutions (41.1%) utilize DTIs 2 to 4 times a year with an additional 33.9% utilizing them less than twice a year. There is no consistent approach to dosing and titration amongst pediatric institutions.

CONCLUSIONS

There are a wide variety of methods used by pediatric institutions with regard to dosing and titration of DTIs. Recently published prospective studies and package insert updates should help guide practitioners toward a more consistent approach to dosing of these high-risk medications.

Coagulation and the surgical neonate

Both coagulopathy and abnormal thrombosis can complicate the anesthetic and surgical management of neonatal patients; however, the patterns of bleeding and thrombosis in neonates differ from those in adults or older children. Severe coagulopathic bleeding most commonly occurs during heart surgery and almost certainly contributes to morbidity and mortality in this population. Such severe bleeding is rare during other surgery; the exception is babies presenting to the operating room with established coagulopathy secondary to severe sepsis. Alternatively, pathological thrombosis will mainly occur in association with indwelling vascular access devices or surgically created vascular shunts. There are important differences between the coagulation system in neonates and older patients. The implication of this is that therapies established in other patient groups will not be optimal for neonates without adaptation. While evidence from high-quality clinical trials is rarely available, an understanding of how coagulation in neonates differs can help to guide practice. This review will discuss important differences between the coagulation system of neonates and older patients and how these relate to newer models of coagulation. The emphasis will be on issues likely to impact on perioperative care. In particular, the management of severe bleeding, the manipulation of coagulation during heart surgery, and the management of coagulopathy in septic neonates will be discussed in detail.

Gradenigo's syndrome: is fusobacterium different? Two cases and review of the literature

Gradenigo's syndrome is a rare but life threatening complication of acute otitis media (AOM), which includes a classic triad of otitis media, deep facial pain and ipsilateral abducens nerve paralysis. The incidence of Fusobacterium necrophorum infections has increased in recent years. We describe two cases of Gradenigo's syndrome caused by F. necrophorum. Additional four cases were identified in a review of the literature. Gradenigo's syndrome as well as other neurologic complications should be considered in cases of complicated acute otitis media. F. necrophorum should be empirically treated while awaiting culture results.

Venous thromboembolism in children with cancer - a population-based cohort study

Introduction

Cancer is a known risk factor for venous thromboembolism (VTE) in adults, but population-based data in children are scarce.

Materials and methods

We conducted a cohort study utilising linkage of the Clinical Practice Research Database (primary care), Hospital Episodes Statistics (secondary care), UK Cancer Registry data and Office for National Statistics cause of death data. From these databases, we selected 498 children with cancer diagnosed between 1997 and 2006 and 20,810 controls without cancer. We calculated VTE incidence rates in children with cancer vs. controls, and hazard ratios (HRs) using Cox regression.

Results

We identified four VTE events in children with cancer compared with four events in the larger control population corresponding to absolute risks of 1.52 and 0.06 per 1000 person-years respectively. The four children with VTE and cancer were diagnosed with hematological, bone or non-specified cancer. Childhood cancer was hence associated with a highly increased risk of VTE (HR adjusted for age and sex: 28.3; 95%CI = 7.0-114.5).

Conclusions

Children with cancer are at increased relative risk of VTE compared to those without cancer. Physicians could consider thromboprophylaxis in children with cancer to reduce their excess risk of VTE however the absolute risk is extremely small and the benefit gained therefore would need to be balanced against the risk invoked of implementing such a strategy.

Novelty & Impact Statements

While there is a reasonable level of knowledge about the risk of VTE in adult populations, it is not well known whether this risk is reflected in paediatric patients. We found a substantial increase in risk of VTE in children with cancer compared to a child population without cancer. While this finding is important, the absolute risk of VTE is still low and must be balanced with the risks of anticoagulation.

Pediatric thrombophilia

Pediatric thrombosis and thrombophilia are increasingly recognized and studied. In this article, both the inherited and acquired factors for the development of thrombosis in neonates and children are categorized using the elements of Virchow's triad: stasis, hypercoagulable state, and vascular injury. The indications and rationale for performing thrombophilia testing are described. Also included are discussions on who, how, when, and why to test. Finally, recommendations for the use of contraceptives for adolescent females with a family history of thrombosis are outlined.

Antithrombotic therapies: anticoagulation and thrombolysis

Pediatric deep vein thrombosis is an increasingly recognized phenomenon, especially with advances in treatment and supportive care of critically ill children and with better diagnostic capabilities. High-quality evidence and uniform management guidelines for antithrombotic treatment, particularly thrombolytic therapy, remain limited. Optimal dosing, intensity and duration strategies for anticoagulation as well as thrombolytic regimens that maximize efficacy and safety need to be determined through well-designed clinical trials using use of a risk-stratified approach.

Anticoagulant treatment with rivaroxaban in severe protein S deficiency

We report a case of a 6-year-old girl with severe protein S deficiency due to a homozygous mutation and recurrent episodes of skin necrosis. She developed purpura fulminans at birth and a catheter-related venous thrombosis complicated by massive pulmonary embolism at the sixth day of life. Long-term oral anticoagulant therapy with a vitamin K-antagonist was started with a therapeutic range of the international normalized ratio of prothrombin time between 2.0 and 3.0. Unfortunately, this common range was not sufficient because recurrent episodes of warfarin-induced skin necrosis developed if the international normalized ratio was <4.0. Vitamin K antagonists decrease plasma level of vitamin K-dependent coagulation proteins, including the natural anticoagulant protein C. In our patient, the hypercoagulable state due to warfarin-induced reduction of protein C, other than severe protein S deficiency, outweighed the anticoagulant efficacy of the inhibition of procoagulant factors II, VII, IX, and X. The switch of anticoagulant therapy from warfarin to rivaroxaban, a direct inhibitor of activated factor X that does not inhibit other vitamin K-dependent proteins, resulted in the disappearance of skin necrosis at 1 year of follow-up. Rivaroxaban may be considered as a valid anticoagulant alternative in patients with severe inherited protein S deficiency and warfarin-induced skin necrosis.

Pathology consultation on anticoagulation monitoring: factor X-related assays

OBJECTIVES

To review various anticoagulation therapies and related laboratory monitoring issues, with a focus on factor X-related chromogenic assays.

METHODS

A case-based approach is used to review pertinent published literatures and product inserts of anticoagulation drugs and to look back on clinical use of factor X-related chromogenic assays.

RESULTS

The number of anticoagulants available to clinicians has increased greatly in the past decade. Whether and how these anticoagulants should be monitored are areas of uncertainty for clinicians, which can lead to misuse of laboratory assays and suboptimal patient management. Factor X-related assays are of particular concern because of the similar and often confusing test names. Based on a common clinical case scenario and literature review regarding anticoagulant monitoring, an up-to-date discussion and review of the various factor X-related assays are provided, focusing on the differences in test designs and clinical utilities between the chromogenic anti-Xa and chromogenic factor X activity assays.

CONCLUSIONS

Anticoagulation therapy and related laboratory monitoring are rapidly evolving areas of clinical practices. A good knowledge of relevant laboratory assays and their clinical applications is necessary to help optimize patient care.