Thrombosis in the pediatric population

Thrombophilia screening revisited: an issue of personalized medicine

Clinical thrombophilia is the consequence of multiple gene and/or environment interactions. Thrombophilia screening requires a targeted patient with specific indication, in which a finding would have implications. Carrying out a thrombophilia examination in the physician's practice is often a cause of uncertainty and concern. The concerns begin in choosing the right patient to be examined, are associated with the time of investigation, with the choice of analysis, the test-material and with the correct interpretation of the results. Difficulties, which can influence the results, can occur with both organization and blood sampling. As common for any analysis, pre-analytical, analytical and post-analytical factors should be considered, as well as the possibility of false positive or false negative results. Finally, recommendation of correct therapeutic and prophylactic measures for the patient and his relatives is an additional focus. In this article we want to provide-on the basis of the evidence and personal experience-the theory of thrombophilia-investigation, the indications for testing, as well as practical recommendations for treatment options.

Easily-handled method to isolate mesenchymal stem cells from coagulated human bone marrow samples

AIM: To establish an easily-handled method to isolate mesenchymal stem cells (MSCs) from coagulated human bone marrow samples.

METHODS: Thrombin was added to aliquots of seven heparinized human bone marrow samples to mimic marrow coagulation. The clots were untreated, treated with urokinase or mechanically cut into pieces before culture for MSCs. The un-coagulated samples and the clots were also stored at 4 °C for 8 or 16 h before the treatment. The numbers of colony-forming unit-fibroblast (CFU-F) in the different samples were determined. The adherent cells from different groups were passaged and their surface profile was analyzed with flow cytometry. Their capacities of in vitro osteogenesis and adipogenesis were observed after the cells were exposed to specific inductive agents.

RESULTS: The average CFU-F number of urokinase-treated samples (16.85 ± 11.77/10⁶) was comparable to that of un-coagulated control samples (20.22 ± 10.65/10⁶, P = 0.293), which was significantly higher than those of mechanically-cut clots (6.5 ± 5.32/10⁶, P < 0.01) and untreated clots (1.95 ± 1.86/10⁶, P < 0.01). The CFU-F numbers decreased after samples were stored, but those of control and urokinase-treated clots remained higher than the other two groups. Consistently, the numbers of the attached cells at passage 0 were higher in control and urokinase-treated clots than those of mechanically-cut clots and untreated clots. The attached cells were fibroblast-like in morphology and homogenously positive for CD44, CD73 and CD90, and negative for CD31 and CD45. Also, they could be induced to differentiate into osteoblasts and adipocytes in vitro.

CONCLUSION: Urokinase pretreatment is an optimal strategy to isolate MSCs from human bone marrow samples that are poorly aspirated and clotted.

Fibromyxoid excrescence of the aortic valve that manifested after catheterisation and required resection

A 2-year-old boy developed fibromyxoid excrescence of the aortic valve 2 years after balloon dilatation for simple coarctation. Transthoracic echocardiography showed a mobile mass on the non-coronary cusp of the aortic valve. Definitive diagnosis was achieved after operative resection. This pathology was attributed to injury during catheter manipulation. Catheterised patients should be followed up carefully to avoid missing morphological changes.

A practical approach to the use of low molecular weight heparins in VTE treatment and prophylaxis in children and newborns

Low-molecular weight heparins are currently the most commonly used anticoagulants in children and newborns. However, since thrombotic complications rarely occur outside large children's hospitals, physicians often encounter some practical problems in managing these treatments when a pediatric thrombosis specialist is not available. The drug of choice is enoxaparin, due to its favorable FXa/FIIa ratio and the availability of pharmacokinetic and pharmacodynamic data. The treatment of acute thrombosis should be started with two daily injections but when compliance is an issue, a single daily administration schedule could be chosen for secondary prophylaxis ensuring careful measurement of the post 24-hour anti-FXa activity. Furthermore, a subcutaneous device may be a useful tool and a topical dermal anesthetic could be effective in controlling pain without affecting anti-FXa levels. In neonate and toddlers, where mini doses are frequently needed, the dead space of syringes and needles could represent an issue and therefore the use of insulin syringes without dead space is advisable, while a dilution of the drug is useful with other syringes. This article derives from a nonsystematic review of the available literature, with special attention to recent international guidelines and expert recommendations, combined to authors' clinical practice in large tertiary pediatric hospitals and will provide concise and practical information for the use of low-molecular weight heparin in childhood and infancy in a sort of "answering frequently asked questions."

Minimizing transfusion requirements for children undergoing craniosynostosis repair: the CHoR protocol

OBJECT

Children with craniosynostosis may require cranial vault remodeling to prevent or relieve elevated intracranial pressure and to correct the underlying craniofacial abnormalities. The procedure is typically associated with significant blood loss and high transfusion rates. The risks associated with transfusions are well documented and include transmission of infectious agents, bacterial contamination, acute hemolytic reactions, transfusion-related lung injury, and transfusion-related immune modulation. This study presents the Children's Hospital of Richmond (CHoR) protocol, which was developed to reduce the rate of blood transfusion in infants undergoing primary craniosynostosis repair.

METHODS

A retrospective chart review of pediatric patients treated between January 2003 and Febuary 2012 was performed. The CHoR protocol was instituted in November 2008, with the following 3 components; 1) the use of preoperative erythropoietin and iron therapy, 2) the use of an intraoperative blood recycling device, and 3) acceptance of a lower level of hemoglobin as a trigger for transfusion (< 7 g/dl). Patients who underwent surgery prior to the protocol implementation served as controls.

RESULTS

A total of 60 children were included in the study, 32 of whom were treated with the CHoR protocol. The control (C) and protocol (P) groups were comparable with respect to patient age (7 vs 8.4 months, p = 0.145). Recombinant erythropoietin effectively raised the mean preoperative hemoglobin level in the P group (12 vs 9.7 g/dl, p < 0.001). Although adoption of more aggressive surgical vault remodeling in 2008 resulted in a higher estimated blood loss (212 vs 114.5 ml, p = 0.004) and length of surgery (4 vs 2.8 hours, p < 0.001), transfusion was performed in significantly fewer cases in the P group (56% vs 96%, p < 0.001). The mean length of stay in the hospital was shorter for the P group (2.6 vs 3.4 days, p < 0.001).

CONCLUSIONS

A protocol that includes preoperative administration of recombinant erythropoietin, intraoperative autologous blood recycling, and accepting a lower transfusion trigger significantly decreased transfusion utilization (p < 0.001). A decreased length of stay (p < 0.001) was seen, although the authors did not investigate whether composite transfusion complication reductions led to better outcomes.

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.

[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.

Recurrent arterial and venous thrombosis in a 16-year-old boy in the course of primary antiphospholipid syndrome despite treatment with low-molecular-weight heparin: a case report

INTRODUCTION

Antiphospholipid syndrome is a multisystem autoimmune disease characterized by arterial and/or venous thrombosis and persistent presence of antiphospholipid antibodies. It can be a primary disease or secondary when associated with other autoimmune diseases.

CASE PRESENTATION

We present a case of a 16-year-old Caucasian boy with a massive arterial and venous thrombosis in his lower limbs as well as in his central nervous system with clinical symptoms such as headaches and chorea. He did not present any clinical or laboratory signs of a systemic inflammatory connective tissue disease, including systemic lupus erythematosus. Based on the clinical picture and results of the diagnostic tests (positive antibodies against β2-glycoprotein and a high titre of anticardiolipin antibodies) we finally diagnosed primary antiphospholipid syndrome. During a 9-month follow up after the acute phase of the disease, he was treated with low-molecular-weight heparin. Neurological symptoms were relieved. Features of recanalization in the vessels of his lower limbs were observed. After a subsequent 6 months, because of the failure of preventive treatment - an incident of thrombosis of the vessels of his testis - treatment was modified and heparin was replaced with warfarin.

CONCLUSION

Although the preventive treatment with warfarin in our patient has continued for 1 year of follow up without new symptoms, further observation is needed.

Protein C deficiency as the major cause of thrombophilias in childhood

Genetic predisposition of thromboembolism depends on the racial background. Factor V Leiden (G1691A) and factor II mutation (G20210A) are the leading causes of inherited thrombophilias in Caucasians, but are not found in Asian ancestries. Protein S (PS), protein C (PC) and antithrombin (AT) activity are reportedly low in 65% of adult Japanese patients with deep vein thrombosis. Approximately half of the patients with each deficiency carry the heterozygous mutation of PS (PROS1; 20%), PC (PROC; 10%), and AT genes (SERPINC1: 5%). Recently, several studies have revealed an outline of inherited thrombophilias in Japanese children. Congenital thrombophilias in 48 patients less than age 20 years consisted of 45% PC deficiency, 15% PS deficiency and 10% AT deficiency, along with other causes. All PS- and AT-deficient patients had a heterozygous mutation of the respective gene. On the other hand, PC-deficient patients were considered to carry the homozygous or compound heterozygous mutation in 50%, the heterozygous mutation in 25%, and unknown causes in the remaining 25% of patients. Half of unrelated patients with homozygous or compound heterozygous PROC mutations carried PC-nagoya (1362delG), while their parents with its heterozygous mutation were asymptomatic. Most of the PC-deficient patients developed intracranial lesion and/or purpura fulminans within 2 weeks after birth. Non-inherited PC deficiency also conveyed thromboembolic events in early infancy. The molecular epidemiology of thrombosis in Asian children would provide a clue to establish the early intervention and optimal anticoagulant therapy in pediatric PC deficiency.

Death after adenotonsillectomy secondary to massive pulmonary embolism

Tonsillectomy is one of the most common surgical procedures performed in the United States. Although relatively safe, there is a small risk of post-operative mortality. The majority of deaths come from airway compromise or hemorrhage. The authors present a case of a 32-month-old child who underwent routine adenotonsillectomy for sleep disordered breathing and chronic pharyngitis who was found unresponsive and pulseless in his bed on the morning of postoperative day 2. The cause of death determined by post mortem autopsy was massive pulmonary embolism (PE). PE is a rare event in children and has never been reported as the cause of death following adenotonsillectomy in a child. This case is reviewed in addition to recent literature regarding obstructive sleep apnea (OSA) as a risk factor for venous thrombosis and PE.

Neonatal and infant pulmonary thromboembolism: a literature review

Pulmonary thromboembolism (PTE) is rare in neonates and infants; however evidence suggests it is underdiagnosed. The primary objective is to conduct a scientific review to determine if the presentation, diagnosis, treatment and outcomes of neonates and infants with PTE are consistent across studies. Secondly, to develop an algorithm to establish the diagnosis and management of the condition based on current information. Two authors searched the literature independently using existing databases and verified that identical articles were assembled. Infants aged less than 1 year with PTE were included and further categorized into neonates 28 days or less and infants 29 days to 1 year or less. Forty-five articles with 157 cases (121 neonates; 36 infants) were identified with PTE. All of the reports were descriptive and neither randomized controlled trials nor prospective or case-control studies were identified. The reports are sub-classified into cases of pulmonary air embolism (PAE) with a higher mortality rate and patients with PTE. Diagnostic and treatment strategies varied widely and were individually case-based, dependent on clinical findings, which influenced patient outcomes. Scientific data to guide an evidence-based, diagnostic and treatment approach to PTE is limited because of the absence of rigorous clinical trials. Large scale, multicenter collaborative studies are required to firmly establish the management of PTE in this population.

Trends in venous thromboembolism-related hospitalizations, 1994-2009

OBJECTIVE

Information on trends in venous thromboembolism (VTE) in US children is scant and inconsistent. We assessed national trends in VTE-associated pediatric hospitalizations.

METHODS

All nonroutine newborn hospitalizations for children 0 to 17 years of age in the 1994-2009 Nationwide Inpatient Samples were included; routine newborn discharges were excluded. VTE diagnoses were identified by using the International Classification of Diseases, Ninth Revision, Clinical Modification codes. Variance weighted least square regression was used to assess trends in patient characteristics and rates of hospitalization per 100000 population <18 years of age. Multivariable logistic regression models were used to estimate the probability of VTE diagnosis over the study period.

RESULTS

The rate of VTE-associated hospitalization increased for all age subgroups (<1, 1-5, 6-11, and 12-17 years), with the largest increase noted among children <1 year of age (from 18.1 per 100000 during 1994 to 49.6 per 100000 during 2009). Compared with 1994-1997, the adjusted odds of hospitalization with a VTE diagnosis were 88% higher during 2006-2009 (adjusted odds ratio: 1.88 [95% confidence interval: 1.64-2.17]). Venous catheter use, mechanical ventilation, malignancy, hospitalization ≥ 5 days, and VTE-related medical conditions were associated with increased likelihood of VTE diagnosis.

CONCLUSIONS

The rate of VTE-associated hospitalization among US children increased from 1994 through 2009. Increases in venous catheter procedures were associated with and may have contributed to the observed trends. The degree to which increased awareness of VTE influenced the temporal differences could not be determined.

Thrombosis risk factor assessment and implications for prevention in critically ill children

OBJECTIVES

To describe nursing compliance with a computer-based pediatric thrombosis risk assessment tool; to generate an estimate of risk factors present in our population; and to explore relationships between risk factors and confirmed thrombotic events.

DESIGN

Institutional review board-approved prospective, observational cohort study.

SETTING

Pediatric intensive care unit within a tertiary care children's hospital.

PATIENTS

All infants and children admitted to the pediatric intensive care unit during a 6-month study period (January 1, 2010-June 30, 2010).

MEASUREMENTS AND MAIN RESULTS

Eight hundred admissions were enrolled, representing 742 patients. Thrombosis risk assessment scores were recorded for 707 admissions (88% of total). Mean age = 6.95 ± 6 yrs, mean weight = 28 ± 23 kg, 45% female. A total of 32 thrombi (14 prehospital and 18 in-hospital) were present in the study group. This translated to an overall occurrence rate of 4.3% (1.9% for prehospital and 2.4% for in-hospital). Logistic regression identified that for every 1-point increase in total thrombosis score, the risk of developing a symptomatic thrombus increased by 1.57-fold (95% confidence interval 0.192-5.5) to 2.12-fold (95% confidence interval 0.175-18.34), for prehospital and in-hospital thrombi, respectively (p < .05). The most important risk factors identified for development of any thrombus were thrombophilia (acquired or inherited) (p < .001), presence of a central catheter (p = .01), and age <1 or >14 yrs (p = .052).

CONCLUSIONS

Incorporation of a scoring system into the bedside nursing assessment flow sheet was successful and identified children at risk for in-hospital thrombosis. The overall score appears to be most indicative of thrombus risk. These data may serve as a platform for future development of routine screening and possible interventional trials in critically ill children.

Pulmonary embolism in children

Unlike in adults, pulmonary embolism (PE) is an infrequent event in children. It has a marked bimodal distribution during the paediatric years, occurring predominantly in neonates and adolescents. The most important predisposing factors to PE in children are the presence of a central venous line (CVL), infection, and congenital heart disease. Clinical signs of PE are non-specific in children or can be masked by underlying conditions. Diagnostic testing is necessary in children, especially with the lack of clinical prediction rules. Recommendations for tests are derived from adult studies with ventilation/perfusion (V/Q) scintigraphy being well established. There exists an increasing role for computerised tomography pulmonary angiography (CTPA) and magnetic resonance pulmonary angiography (MRPA). Thrombotic events in children are initially treated with unfractionated heparin (UFH) or low molecular weight heparin (LMWH). For the extended anticoagulant therapy LMWH or vitamin K antagonists can be used with duration of treatment recommendations extrapolated from adult data. Mortality rates for PE in children are reported to be around 10%, with death usually related to the underlying disease processes. Exact data about recurrence risk in children is unknown. Because of the difference in aetiology, presentation, diagnostic methods and treatment between adults and children further research is necessary to assess the validity of recommendations for children.

Survey of pharmacologic thromboprophylaxis in critically ill children

OBJECTIVE

There is lack of evidence to guide thromboprophylaxis in the pediatric intensive care unit. We aimed to assess current prescribing practice for pharmacologic thromboprophylaxis in critically ill children.

SETTING

Pediatric intensive care units in the United States and Canada with at least ten beds.

DESIGN

Cross-sectional self-administered survey of pediatric intensivists using adolescent, child, and infant scenarios.

PARTICIPANTS

Pediatric intensive care unit clinical directors or section heads.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Physician leaders from 97 of 151 (64.2%) pediatric intensive care units or their designees responded to the survey. In mechanically ventilated children, 42.3% of the respondents would usually or always prescribe thromboprophylaxis for the adolescent but only 1.0% would prescribe it for the child and 1.1% for the infant. Considering all pediatric intensive care unit patients, 3.1%, 32.0%, and 44.2% of respondents would never prescribe thromboprophylaxis for the adolescent, child, and infant scenarios, respectively. These findings were significant (p < .001 for the adolescent vs. child and infant; p = .002 for child vs. infant). Other patient factors that increased the likelihood of prescribing prophylaxis to a critically ill child for all three scenarios were the presence of hypercoagulability, prior deep venous thrombosis, or a cavopulmonary anastomosis. Prophylaxis was less likely to be prescribed to patients with major bleeding or an anticipated invasive intervention. Low-molecular-weight heparin was the most commonly prescribed drug.

CONCLUSIONS

In these scenarios, physician leaders in pediatric intensive care units were more likely to prescribe thromboprophylaxis to adolescents compared with children or infants, but they prescribed it less often in adolescents than is recommended by evidence-based guidelines for adults. The heterogeneity in practice we documented underscores the need for rigorous randomized trials to determine the need for thromboprophylaxis in critically ill adolescents and children.

Mortality-adjusted duration of mechanical ventilation in critically ill children with symptomatic central venous line-related deep venous thrombosis

OBJECTIVE

To determine the association between symptomatic central venous line-related deep venous thrombosis and a mortality-adjusted measure of duration of mechanical ventilation in critically ill children with central venous lines.

DESIGN

Retrospective matched cohort study.

SETTING

Eleven pediatric intensive care units across the United States.

PATIENTS

Twenty-nine index critically ill children with central venous line-related deep vein thrombosis from a previous prospective observational study on symptomatic venous thromboembolism were compared with 116 control children with central venous lines without venous thrombosis. Each index patient was matched to four control patients based on age group, disease category, severity of illness score, and number of days in the intensive care unit before central venous line insertion.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Index patients were appropriately matched to control patients with similar characteristics between the two groups. Index patients had fewer ventilator-free days (ie, days alive and breathing unassisted within 28 days after central venous line insertion) compared with matched control patients (16.8 ± 11.5 days vs. 22.3 ± 4.9 days, p = .040). Index patients also had less intensive care unit-free days (ie, days alive and discharged from the intensive care unit within 28 days after central venous line insertion) (9.8 ± 9.9 days vs. 17.9 ± 5.7 days, p < .001). Durations of mechanical ventilation (17.6 ± 40.6 days vs. 5.2 ± 5.5 days, p = .236) and intensive care unit stay (38.1 ± 61.7 days vs. 11.9 ± 10.9 days, p = .011) were longer in index patients. The mortality rate was statistically similar between the two groups.

CONCLUSIONS

The presence of symptomatic central venous line-related deep vein thrombosis is associated with worse outcomes, particularly fewer ventilator-free days, in critically ill children. The causal relationship that deep venous thrombosis leads to impairment in lung function and delays weaning from mechanical ventilation and discharge from the intensive care unit needs to be proven prospectively. Ventilator-free days is a possible alternative outcome measure for future deep venous thrombosis studies.

Pneumothorax, pneumomediastinum, and pulmonary embolism

This article discusses pneumothorax, pneumomediastinum, and pulmonary embolism in pediatric practice. Although children appear to have better outcomes than adults, the risk factors are substantial. Topics covered include the pathophysiology incidence, presentation, diagnosis, and management of these diseases.