Development of a new risk score for hospital-associated venous thromboembolism in critically-ill children not undergoing cardiothoracic surgery

Uncovering Risk Factors and Outcomes of Pulmonary Embolism in a Nationwide Cohort of Hospitalized Children

PURPOSE

The incidence of pulmonary embolism (PE) in hospitalized children has increased in recent years. This study sought to characterize factors and outcomes associated with PE using a national pediatric cohort.

METHODS

The Nationwide Readmissions Database was queried (2016-2018) for patients (<18 years) with a diagnosis of PE. Index and prior hospitalizations (PHs) within 1 year were analyzed. A binary logistic regression utilizing 37 covariates (demographics, procedures, comorbidities, etc.) was constructed to examine a primary outcome of in-hospital mortality.

RESULTS

3440 patients were identified (57% female) with the majority >12 years old (77%). One-third had a known deep vein thrombosis (69% lower and 31% upper extremity). Nineteen percent underwent central venous catheter (CVC) placement. Twenty-one percent had a PH within 1 year. Nine percent underwent an operation with the majority being cardiothoracic (5%). Overall mortality was 5%. Neurocranial surgery, cardiothoracic surgery, and CVC placement were associated with the highest odds of inpatient mortality after logistic regression.

CONCLUSION

Pediatric patients with PE have a high rate of PHs, CVC placement, and inpatient operations, which may be associated with higher mortality. This information can be utilized to improve screening measures and clinical suspicion for PE in hospitalized children.

Hospital-Acquired Venous Thromboembolism and Invasive Mechanical Ventilation: A Report From the Children's Hospital Acquired Thrombosis Consortium

OBJECTIVES

To determine if the duration of invasive mechanical ventilation (IMV) was associated with hospital-acquired venous thromboembolism (HA-VTE) among critically ill children.

DESIGN

A multicenter, matched case-control study as a secondary analysis of Children's Hospital Acquired Thrombosis (CHAT) Consortium registry.

SETTING

PICUs within U.S. CHAT Consortium participating centers.

PATIENTS

Children younger than 21 years old admitted to a PICU receiving IMV for greater than or equal to 1 day duration from January 2012 to March 2022 were included for study. Cases with HA-VTE were matched 1:2 to controls without HA-VTE by patient age groups: younger than 1, 1-12, and older than 12 years.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The primary outcome was IMV duration in days. Descriptive data included demographics, anthropometrics, HA-VTE characteristics (i.e., type, location, and timing), central venous catheterization data, thromboprophylaxis practices, and Braden Q mobility scores. Descriptive, comparative, and associative (multivariate conditional logistic regression for HA-VTE) statistics were employed. A total of 152 cases were matched to 304 controls. Cases with HA-VTE were diagnosed at a median of 7 days (interquartile range [IQR], 3-16 d) after IMV. The HA-VTE were limb deep venous thromboses in 130 of 152 (85.5%) and frequently central venous catheterization-related (111/152, 73%). Cases with HA-VTE experienced a longer length of stay (median, 34 d [IQR, 18-62 d] vs. 11.5 d [IQR, 6-21 d]; p < 0.001) and IMV duration (median, 7 d [IQR, 4-15 d] vs. 4 d [IQR, 1-7 d]; p < 0.001) as compared with controls. In a multivariate logistic model, greater IMV duration (adjusted odds ratio, 1.09; 95% CI, 1.01-1.17; p = 0.023) was independently associated with HA-VTE.

CONCLUSIONS

Among critically ill children undergoing IMV, HA-VTE was associated with greater IMV duration. If prospectively validated, IMV duration should be included as part of prothrombotic risk stratification and future pediatric thromboprophylaxis trials.

Hospital-acquired venous thromboembolism during invasive mechanical ventilation in children: a single-center, retrospective cohort study

BACKGROUND

Invasive mechanical ventilation (IMV) has been independently associated with hospital-acquired venous thromboembolism (HA-VTE) among critically ill children, including extremity deep venous thrombosis and pulmonary embolism.

OBJECTIVES

We aimed to characterize the frequency and timing of HA-VTE following IMV exposure.

METHODS

This was a single-center, retrospective cohort study including children aged <18 years, hospitalized in a pediatric intensive care unit, undergoing mechanical ventilation for >24 hours from October 2020 through April 2022. Encounters with an existing tracheostomy or receiving treatment for HA-VTE prior to endotracheal intubation were excluded. The primary outcomes characterized clinically-relevant HA-VTE, including timing after intubation, location, and the presence of known hypercoagulability risk factors. Secondary outcomes were IMV exposure magnitude, defined by IMV duration and ventilator parameters (ie, volumetric, barometric, and oxygenation indices).

RESULTS

Of 170 consecutive, eligible encounters, 18 (10.6%) experienced HA-VTE at a median of 4 days (IQR, 1.4-6.4) following endotracheal intubation. Those with HA-VTE had an increased frequency of a prior venous thromboembolism (27.8% vs 8.6%, P = .027). No differences in frequency of other HA-VTE risk factors (ie, acute immobility, hematologic malignancy, sepsis, and COVID-19-related illness), presence of a concurrent central venous catheter, or the magnitude of IMV exposure were noted.

CONCLUSION

Children undergoing IMV experience HA-VTE at markedly higher rates than previously estimated in the general pediatric intensive care unit population after endotracheal intubation. While prospective validation is needed, these findings are an important step toward informing the development of risk-stratified thromboprophylaxis trials in critically ill children.

Model-Guided Decision-Making for Thromboprophylaxis and Hospital-Acquired Thromboembolic Events Among Hospitalized Children and Adolescents: The CLOT Randomized Clinical Trial

Importance

Rates of hospital-acquired venous thromboembolism (HA-VTE) are increasing among pediatric patients. Identifying at-risk patients for whom prophylactic interventions should be considered remains challenging.

Objective

To determine whether use of a previously validated HA-VTE prognostic model, together with pediatric hematologist review, could reduce pediatric inpatient rates of HA-VTE.

Design, Setting, and Participants

This pragmatic randomized clinical trial was performed from November 2, 2020, through January 31, 2022, at a single-center academic children's hospital (Monroe Carell Jr Children's Hospital at Vanderbilt). All pediatric hospital admissions (aged <22 years) under inpatient status were included and randomized.

Intervention

All patients had an HA-VTE probability automatically calculated daily, which was visible to the hematology research team for patients in the intervention group. Patients with an elevated risk (predicted probability ≥2.5%) underwent additional medical record review by the research team to determine eligibility for thromboprophylaxis.

Main Outcomes and Measures

The primary outcome was rate of HA-VTE. Secondary outcomes included rates of prophylactic anticoagulation and anticoagulation-associated bleeding events.

Results

A total of 17 427 hospitalizations met eligibility criteria, were randomized, and were included in the primary analysis: patients had a median (IQR) age of 1.7 (0 to 11.1) years; there were 9143 (52.5%) female patients and 8284 (47.5%) male patients, and there were 445 (2.6%) Asian patients, 2739 (15.9%) Black patients, and 11 752 (67.4%) White patients. The 2 groups were evenly balanced in number (8717 in the intervention group and 8710 in the control group) and patient characteristics. A total of 58 patients (0.7%) in the control group and 77 (0.9%) in the intervention group developed HA-VTE (risk difference: 2.2 per 1000 patients; 95% CI, -0.4 to 4.8 per 1000 patients; P = .10). Recommendations to initiate thromboprophylaxis were accepted by primary clinical teams 25.8% of the time (74 of 287 hospitalizations). Minor bleeding events were rare among patients who received anticoagulation (3 of 74 [4.1%]), and no major bleeding events were observed during the study period. Among patients randomized to the control group, the model exhibited high discrimination accuracy (C statistic, 0.799, 95% CI, 0.725 to 0.856).

Conclusions and Relevance

In this randomized clinical trial of the use of a HA-VTE prognostic model to reduce pediatric inpatient rates of HA-VTE, despite the use of an accurate and validated prognostic model for HA-VTE, there was substantial reluctance by primary clinical teams to initiate thromboprophylaxis as recommended. In this context, rates of HA-VTE between the control and intervention groups were not different. Future research is needed to identify improved strategies for prevention of HA-VTE and to overcome clinician concerns regarding thromboprophylaxis.

Trial Registration

ClinicalTrials.gov Identifier: NCT04574895.

Mechanical Ventilation and Hospital-Acquired Venous Thromboembolism Among Critically Ill Children

OBJECTIVES

To estimate the occurrence of, and evaluate associations between, hospital-acquired venous thromboembolism (HA-VTE) and invasive mechanical ventilation (MV) among children hospitalized in the PICU.

METHODS

We performed a multicenter, retrospective cohort study comparing HA-VTE frequencies among subjects <18 years of age hospitalized in the PICU from January 2018 through December 2019 among 47 participating centers, via the Pediatric Health Information Systems registry. We excluded perinatal encounters, those with VTE present at admission, and those with observational status. The primary outcome was the proportion of HA-VTE events before hospital discharge, including extremity deep venous thrombosis, pulmonary embolism, and organ-specific deep venous thrombosis. The HA-VTE frequencies were compared using χ2 tests. The association between HA-VTE and MV was investigated via multivariable logistic regression, adjusting for previously described VTE risk factors.

RESULTS

Of the 205 231 PICU encounters identified for study, 70 829 (34.5%) underwent MV. The occurrence of HA-VTE was 2.2% and was greater among children who received, versus did not receive, MV (4.4% versus 1.1%, P < .001). Multivariable logistic regression revealed significant association between MV and HA-VTE (odds ratio 2.51, 95% confidence interval 2.33-2.69; P < .001).

CONCLUSIONS

In this multicenter, retrospective, registry-based cohort study, HA-VTE were diagnosed in 2.2% of critically-ill children, and after adjustment for central venous catheterization, MV independently increased the risk of HA-VTE 2.5-fold. These findings warrant prospective validation to inform the design of future risk-stratified clinical trials of thromboprophylaxis in critically-ill children.

Use of a real-time risk-prediction model to identify pediatric patients at risk for thromboembolic events: study protocol for the Children's Likelihood Of Thrombosis (CLOT) trial

BACKGROUND

Pediatric patients have increasing rates of hospital-associated venous thromboembolism (HA-VTE), and while several risk-prediction models have been developed, few are designed to assess all general pediatric patients, and none has been shown to improve patient outcomes when implemented in routine clinical care.

METHODS

The Children's Likelihood Of Thrombosis (CLOT) trial is an ongoing pragmatic randomized trial being conducted starting November 2, 2020, in the inpatient units at Monroe Carell Jr. Children's Hospital at Vanderbilt in Nashville, TN, USA. All admitted patients who are 21 years of age and younger are automatically enrolled in the trial and randomly assigned to receive either the current standard-of-care anticoagulation practice or the study intervention. Patients randomized to the intervention arm are assigned an HA-VTE risk probability that is calculated from a validated VTE risk-prediction model; the model is updated daily with the most recent clinical information. Patients in the intervention arm with elevated risk (predicted probability of HA-VTE ≥ 0.025) have an additional review of their clinical course by a team of dedicated hematologists, who make recommendations including pharmacologic prophylaxis with anticoagulation, if appropriate. The anticipated enrollment is approximately 15,000 patients. The primary outcome is the occurrence of HA-VTE. Secondary outcomes include initiation of anticoagulation, reasons for not initiating anticoagulation among patients for whom it was recommended, and adverse bleeding events. Subgroup analyses will be conducted among patients with elevated HA-VTE risk.

DISCUSSION

This ongoing pragmatic randomized trial will provide a prospective assessment of a pediatric risk-prediction tool used to identify hospitalized patients at elevated risk of developing HA-VTE.  TRIAL REGISTRATION: ClinicalTrials.gov NCT04574895. Registered on September 28, 2020. Date of first patient enrollment: November 2, 2020.

Enoxaparin Thromboprophylaxis in Children Hospitalized for COVID-19: A Phase 2 Trial

BACKGROUND

Evidence regarding the safety and efficacy of anticoagulant thromboprophylaxis among pediatric patients hospitalized for coronavirus disease 2019 (COVID-19) is limited. We sought to evaluate safety, dose-finding, and preliminary efficacy of twice-daily enoxaparin as primary thromboprophylaxis among children hospitalized for symptomatic COVID-19, including primary respiratory infection and multisystem inflammatory syndrome in children (MISC).

METHODS

We performed a phase 2, multicenter, prospective, open-label, single-arm clinical trial of twice-daily enoxaparin (initial dose: 0.5mg/kg per dose; max: 60mg; target anti-Xa activity: 0.20-0.49IU/mL) as primary thromboprophylaxis for children <18 years of age hospitalized for symptomatic COVID-19. Study endpoints included: cumulative incidence of International Society of Thrombosis and Haemostasis-defined clinically relevant bleeding; enoxaparin dose-requirements; and cumulative incidence of venous thromboembolism within 30-days of hospital discharge. Descriptive statistics summarized endpoint estimates that were further evaluated by participant age (±12 years) and clinical presentation.

RESULTS

Forty children were enrolled and 38 met analyses criteria. None experienced clinically relevant bleeding. Median (interquartile range) dose to achieve target anti-Xa levels was 0.5 mg/kg (0.48-0.54). Dose-requirement did not differ by age (0.5 [0.46-0.52] mg/kg for age ≥12 years versus 0.52 [0.49-0.55] mg/kg for age <12 years, P = .51) but was greater for participants with MISC (0.52 [0.5-0.61] mg/kg) as compared with primary COVID-19 (0.48 [0.39-0.51] mg/kg, P = .010). Two children (5.3%) developed central-venous catheter-related venous thromboembolism. No serious adverse events were related to trial intervention.

CONCLUSIONS

Among children hospitalized for COVID-19, thromboprophylaxis with twice-daily enoxaparin appears safe and warrants further investigation to assess efficacy.

Prophylaxis of Venous Thromboembolism in Children: A Systematic Review

Venous thromboembolism (VTE) in children is a rare but serious event. Current guidance on pharmacological thromboprophylaxis in children is mostly based on adult studies and expert opinions. The aim of this systematic review was to examine under which conditions children (age ≤ 18 years) would benefit from pharmacological thromboprophylaxis with low molecular weight heparin or unfractionated heparin. Eligible studies included children, who did not receive pharmacological thromboprophylaxis as comparator, and VTE events were radiologically verified. MEDLINE and Embase were searched up to October 3, 2021. Ten studies were included presenting data for 976 children receiving pharmacological thromboprophylaxis. We divided the studies into three categories based on the population studied: children in the intensive care unit (n = 2), children with fractures and/or undergoing surgery (n = 5), and children with systemic disease (n = 3). A lower incidence of VTE was found when pharmacological thromboprophylaxis was used compared with no prophylaxis in children in intensive care unit with central venous catheter and mechanical ventilation (7/27 vs. 13/24), children in the intensive care unit admitted after trauma with a very high risk of VTE based on several risk factors (0/21 vs. 13/96), and children with acute lymphoblastic leukemia treated with L-asparaginase concomitant with steroid and presence of central venous catheter (0/82 vs. 8/121). Pharmacological thromboprophylaxis was not associated with an increased bleeding risk. In conclusion, pharmacological thromboprophylaxis in children is sparsely investigated. Only children with several risk factors for VTE are likely to benefit from pharmacological thromboprophylaxis.

A New Risk Assessment Model for Hospital-Acquired Venous Thromboembolism in Critically Ill Children: A Report From the Children's Hospital-Acquired Thrombosis Consortium

OBJECTIVES

To create a risk model for hospital-acquired venous thromboembolism in critically ill children upon admission to an ICU.

DESIGN

Case-control study.

SETTING

ICUs from eight children's hospitals throughout the United States.

SUBJECTS

Critically ill children with hospital-acquired venous thromboembolism (cases) 0-21 years old and similar children without hospital-acquired venous thromboembolism (controls) from January 2012 to December 2016. Children with a recent cardiac surgery, asymptomatic venous thromboembolism, or a venous thromboembolism diagnosed before ICU admission were excluded.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The multi-institutional Children's Hospital-Acquired Thrombosis registry was used to identify cases and controls. Multivariable logistic regression was used to determine the association between hospital-acquired venous thromboembolism and putative risk factors present at or within 24 hours of ICU admission to develop the final model. A total of 548 hospital-acquired venous thromboembolism cases (median age, 0.8 yr; interquartile range, 0.1-10.2) and 187 controls (median age, 2.4 yr; interquartile range, 0.2-8.3) were analyzed. In the multivariable model, recent central venous catheter placement (odds ratio, 4.4; 95% CI, 2.7-7.1), immobility (odds ratio 3.6, 95% CI, 2.1-6.2), congenital heart disease (odds ratio 2.9, 95% CI, 1.7-4.7), length of hospital stay prior to ICU admission greater than or equal to 3 days (odds ratio, 2.5; 95% CI, 1.1-5.6), and history of autoimmune/inflammatory condition or current infection (odds ratio, 2.1; 95% CI, 1.2-3.4) were each independently associated with hospital-acquired venous thromboembolism. The risk model had an area under the receiver operating characteristic curve of 0.79 (95% CI, 0.73-0.84).

CONCLUSIONS

Using the multicenter Children's Hospital-Acquired Thrombosis registry, we identified five independent risk factors for hospital-acquired venous thromboembolism in critically ill children, deriving a new hospital-acquired venous thromboembolism risk assessment model. A prospective validation study is underway to define a high-risk group for risk-stratified interventional trials investigating the efficacy and safety of prophylactic anticoagulation in critically ill children.

Implementation of automatic data extraction from an enterprise database warehouse (EDW) for validating pediatric VTE decision rule: a prospective observational study in a critical care population

Multiple clinical risk prediction tools for hospital acquired venous thromboembolism (HA-VTE) have been developed. The objectives of this study were to develop and assess the feasibility of data extraction from Electronic Medical Records (EMR) from an enterprise database warehouse (EDW) and to test the validity of a previously developed Pediatric Clot Decision Rule (PCDR). This single-center prospective observational cohort study was conducted between March 2016 and March 2017 and included eligible patients admitted to the intensive care units. Risk score was calculated using the PCDR tool. Sensitivity, specificity, positive and negative predicted value (PPV and NPV) were calculated based on a cut-point of 3. A total of 2822 children were eligible for analysis and 5.1% (95% CI 4.2-6.2) children had a PCDR score of 3. Children with PCDR score of ≥ 3 had a 3 times higher odd of developing VTE compared to those with scores < 3 (OR 3.1; 95% CI 1.93-4.80; p < 0.001). The model performance showed that at the cutoff point of ≥ 3, both the specificity and sensitivity of the PCDR in predicting VTE was 69% and NPV of 98%. We successfully demonstrated using our EDW to populate a research database using an automatic data import. A PCDR score of ≥ 3 was associated with VTE. Collaboration through large registries will be useful in informing practices and guidelines for rare disorders such as pediatric VTE.

Risk factors determining central venous access device-associated deep vein thrombosis resolution in children: a retrospective study

The risk factors associated with the probability of central venous access device (CVAD)-associated deep vein thrombosis (DVT) resolution have been hardly evaluated in children. Current guidelines suggest anticoagulation for a maximum of 3 months in patients with provoked DVT if the provoking factor is resolved. To know if the thrombus will resolve after anticoagulant therapy will help to choose whether to initiate and/or continue this treatment or not. We did a retrospective study of 85 pediatric patients (45 girls, 40 boys) with CVAD-associated DVT to examine the risk factors associated with lack of thrombus resolution in the first 6 months after diagnosis. Sixty-two children had their thrombosis resolved after a median of 50 days (p25-p75 25-97) since diagnosis. In multivariate analysis, variables significantly associated with no resolution were total occlusion (OR 12.50, 95% CI 2.99-52.14, p=.001), location in upper extremity, head, and neck veins (OR 17.70, 95% CI 1.64-191.43, p=.018); collateral circulation in the first 45 days after diagnosis (OR 33.55, 95% CI 2.42-464.71, p=.009); and having between 0 and 3 prothrombotic risk factors at diagnosis (OR 6.20, 95% CI 1.21-31.75, p=.029).Conclusion: CVAD-associated DVT resolution in children in the first 6 months since diagnosis was significantly lower if the thrombosis was occlusive, if it was located in the upper extremity, head, and neck veins; if collateral circulation was seen on ultrasound in the first 45 days; and/or when the patient showed less prothrombotic risk factors at diagnosis. What is Known: • The risk factors associated with central venous access device-associated deep vein thrombosis resolution have been hardly evaluated in children. • Current guidelines suggest anticoagulation for a maximum of 3 months in provoked vein thrombosis if the provoking factor is resolved. What is New: • Thrombus resolution was lower if it was occlusive, located in the upper extremity veins, if collateral circulation was seen, and with less prothrombotic risk factors at diagnosis. • To know if the thrombus will resolve after anticoagulation will help to choose whether to initiate and/or continue it or not.

A Real-time Risk-Prediction Model for Pediatric Venous Thromboembolic Events

BACKGROUND

Hospital-associated venous thromboembolism (HA-VTE) is an increasing cause of morbidity in pediatric populations, yet identification of high-risk patients remains challenging. General pediatric models have been derived from case-control studies, but few have been validated. We developed and validated a predictive model for pediatric HA-VTE using a large, retrospective cohort.

METHODS

The derivation cohort included 111 352 admissions to Monroe Carell Jr. Children's Hospital at Vanderbilt. Potential variables were identified a priori, and corresponding data were extracted. Logistic regression was used to estimate the association of potential risk factors with development of HA-VTE. Variable inclusion in the model was based on univariate analysis, availability in routine medical records, and clinician expertise. The model was validated by using a separate cohort with 44 138 admissions.

RESULTS

A total of 815 encounters were identified with HA-VTE in the derivation cohort. Variables strongly associated with HA-VTE include history of thrombosis (odds ratio [OR] 8.7; 95% confidence interval [CI] 6.6-11.3; P < .01), presence of a central line (OR 4.9; 95% CI 4.0-5.8; P < .01), and patients with cardiology conditions (OR 4.0; 95% CI 3.3-4.8; P < .01). Eleven variables were included, which yielded excellent discriminatory ability in both the derivation cohort (concordance statistic = 0.908) and the validation cohort (concordance statistic = 0.904).

CONCLUSIONS

We created and validated a risk-prediction model that identifies pediatric patients at risk for HA-VTE development. We anticipate early identification of high-risk patients will increase prophylactic interventions and decrease the incidence of pediatric HA-VTE.

Venous Thromboembolism among Critically Ill Children: A Narrative Review

Venous thromboembolism (VTE) is a leading cause of morbidity and mortality among hospitalized patients, including children. In recent years, it has become clear that hospitalization and critical illness bestow an increased VTE risk in pediatrics and relate to mortality and life-limiting comorbidities. For critically ill children, reported rates of VTE vary by study sampling techniques, presence of inherited or acquired thrombophilia, acute and chronic immobility, underlying illness prompting hospitalization, and clinical factors related to illness severity such as central venous catheterization, length of stay, mechanical ventilation, and patient age. Accordingly, critically ill children with new signs of venous congestion, acute inflammation, or unexplained acute organ dysfunction should be routinely evaluated for VTE. This narrative review summarizes recent and historical literature regarding risk factors, prevention, presentation, treatment, and outcomes of VTE in critically ill children. In addition, we identify knowledge gaps and priorities for future collaborative research on this vital condition. Special attention is given to the clinical trial opportunities, challenges, and ongoing efforts in thromboprophylaxis in critically ill children, including those hospitalized for disease related to novel coronavirus (COVID-19) and multisystem inflammatory disease in children.

Venous Thromboembolism among Noncritically Ill Hospitalized Children: Key Considerations for the Pediatric Hospital Medicine Specialist

Venous thromboembolism (VTE) is a leading cause of morbidity and preventable harm among noncritically ill hospitalized children. Several clinical factors relevant to the noncritically ill hospitalized child significantly increase the risk of VTE including the presence of central venous catheters, systemic inflammation, and prolonged immobilization. Although risk mitigation strategies have been described, the diagnosis, treatment, and prevention of VTE require standardization of institutional practices combined with multidisciplinary collaboration among pediatric hospitalists, hematologists, and other care providers. In this narrative review, we summarize the epidemiology of VTE, risk models identifying high-risk conditions associated with VTE, and prevention and treatment strategies. We further describe successful quality improvement efforts implementing institutional VTE risk stratification and thromboprophylaxis procedures. Finally, we highlight unique challenges facing pediatric hospital medicine specialists in the era of the COVID-19 pandemic, including caring for adults admitted to pediatric hospital units, and describe future research opportunities for VTE in the noncritically ill hospitalized child.

Thrombosis in infants in the neonatal intensive care unit: Analysis of a large national database

BACKGROUND

Thrombosis in the neonatal population is rare, but increasing. Its incidence and management are not well understood.

OBJECTIVES

To investigate the incidence, associated factors, and management of thrombosis in the neonatal intensive care unit (NICU) population.

PATIENTS/METHODS

We performed a retrospective cohort study of infants admitted to a Pediatrix Medical Group-affiliated NICU from 1997 through 2015. We determined the prevalence of venous and arterial thrombosis, and assessed demographic characteristics and known risk factors. Categorical variables were compared with the Pearson χ2 test and continuous variables with Wilcoxon rank-sum tests. Stepwise logistic regression was used to identify associated factors. The primary outcome was incidence of thrombosis. Secondary analyses investigated correlations between clinical and demographic characteristics and thrombosis.

RESULTS

Among 1 158 755 infants, we identified 2367 (0.20%) diagnosed with thrombosis. In a multivariable regression analysis, prematurity, male sex, congenital heart disease, sepsis, ventilator support, vasopressor receipt, central venous catheter, invasive procedures, and receipt of erythropoietin were associated with increased risk of thrombosis, while Black race and Hispanic ethnicity were associated with reduced risk. The majority of infants diagnosed with thrombosis (73%) received no anticoagulation, but anticoagulant use in infants with thrombosis was higher than those without (27% versus 0.2%, P < .001). Thrombosis in infants was associated with higher mortality (11% versus 2%, P < .001) and longer hospital stays (57 days, [interquartile range (IQR) 28--100] versus 10 days, [IQR 6--22], P < .001).

CONCLUSIONS

In the largest national study to date, we found that thrombosis in NICU patients is associated with prematurity, low birth weight, sepsis, and invasive procedures.

Development of a Risk Model for Pediatric Hospital-Acquired Thrombosis: A Report from the Children's Hospital-Acquired Thrombosis Consortium

OBJECTIVE

To identify pertinent clinical variables discernible on the day of hospital admission that can be used to assess risk for hospital-acquired venous thromboembolism (HA-VTE) in children.

STUDY DESIGN

The Children's Hospital-Acquired Thrombosis Registry is a multi-institutional registry for all hospitalized participants aged 0-21 years diagnosed with a HA-VTE and non-VTE controls. A risk assessment model (RAM) for the development of HA-VTE using demographic and clinical VTE risk factors present at hospital admission was derived using weighted logistic regression and the least absolute shrinkage and selection (Lasso) procedure. The models were internally validated using 5-fold cross-validation. Discrimination and calibration were assessed using area under the receiver operating characteristic curve and Hosmer-Lemeshow goodness of fit, respectively.

RESULTS

Clinical data from 728 cases with HA-VTE and 839 non-VTE controls, admitted between January 2012 and December 2016, were abstracted. Statistically significant RAM elements included age <1 year and 10-22 years, cancer, congenital heart disease, other high-risk conditions (inflammatory/autoimmune disease, blood-related disorder, protein-losing state, total parental nutrition dependence, thrombophilia/personal history of VTE), recent hospitalization, immobility, platelet count >350 K/μL, central venous catheter, recent surgery, steroids, and mechanical ventilation. The area under the receiver operating characteristic curve was 0.78 (95% CI 0.76-0.80).

CONCLUSIONS

Once externally validated, this RAM will identify those who are at low-risk as well as the greatest-risk groups of hospitalized children for investigation of prophylactic strategies in future clinical trials.

Hospital-Associated Venous Thromboembolism in a Pediatric Cardiac ICU: A Multivariable Predictive Algorithm to Identify Children at High Risk

OBJECTIVES

Critically ill children with cardiac disease are at significant risk for hospital-associated venous thromboembolism, which is associated with increased morbidity, hospital length of stay, and cost. Currently, there are no widely accepted guidelines for prevention of hospital-associated venous thromboembolism in pediatrics. We aimed to develop a predictive algorithm for identifying critically ill children with cardiac disease who are at increased risk for hospital-associated venous thromboembolism as a first step to reducing hospital-associated venous thromboembolism in this population.

DESIGN

This is a prospective observational single-center study.

SETTING

Tertiary care referral children's hospital cardiac ICU.

PATIENTS

Children less than or equal to18 years old admitted to the cardiac ICU who developed a hospital-associated venous thromboembolism from December 2013 to June 2017 were included. Odds ratios and 95% CIs are reported for multivariable predictors.

MEASUREMENTS AND MAIN RESULTS

A total of 2,204 separate cardiac ICU encounters were evaluated with 56 hospital-associated venous thromboembolisms identified in 52 unique patients, yielding an overall prevalence of 25 hospital-associated venous thromboembolism per 1,000 cardiac ICU encounters. We were able to create a predictive algorithm with good internal validity that performs well at predicting hospital-associated venous thromboembolism. The presence of a central venous catheter (odds ratio, 4.76; 95% CI, 2.0-11.1), sepsis (odds ratio, 3.5; 95% CI, 1.5-8.0), single ventricle disease (odds ratio, 2.2; 95% CI, 1.2-3.9), and extracorporeal membrane oxygenation support (odds ratio, 2.7; 95% CI, 1.2-5.7) were independent risk factors for hospital-associated venous thromboembolism. Encounters with hospital-associated venous thromboembolism were associated with a higher rate of stroke (17% vs 1.2%; p < 0.001).

CONCLUSIONS

We developed a multivariable predictive algorithm to help identify children who may be at high risk of hospital-associated venous thromboembolism in the pediatric cardiac ICU.

Comparative validation study of risk assessment models for pediatric hospital-acquired venous thromboembolism

BACKGROUND

Risk assessment models (RAMs) have been developed to identify children at high risk of hospital-acquired venous thromboembolism (HA-VTE). None have been externally validated nor compared.

OBJECTIVES

The objective was to compare performance of these RAMs by externally validating them using the Children's Hospital-Acquired Thrombosis (CHAT) Registry, ie, a multicenter database of children with radiographic-confirmed HA-VTE and corresponding controls.

PATIENTS/METHODS

Risk assessment models were included if the full logistic regression equation was available and all RAM variables were collected in the CHAT Registry. A random sample of 200 cases and 200 controls was selected. The performance of the RAMs was assessed for discrimination using area under the receiver operating characteristic curves (AUROC), and calibration using plots, slopes, and intercepts, and the Hosmer-Lemeshow test.

RESULTS

Three RAMs were included. Each had excellent discrimination with AUROC ≥ 0.85. However, calibration was generally poor, with calibration slopes significantly different from 1 (0.71, P < .001; 1.44, P = .002; 0.68, P < .001), intercepts significantly different from 0 (-1.64, P < .001; -0.62, P < .001; 0.78, P < .001), and Hosmer-Lemeshow test P < .001 for each. Exceptions included the Arlikar et al and Atchison et al RAMs for pediatric HA-VTE in non-intensive care unit (ICU) patients and ICU patients, respectively, despite derivation from ICU and non-ICU patients, respectively. In these subpopulations, both showed excellent discrimination and good calibration.

CONCLUSION

Given the lack of adequate calibration for evaluated RAMs, further investigation and refinement of RAMs for pediatric HA-VTE is needed prior to application of a RAM in a clinical setting or risk-stratified clinical trial of primary thromboprophylaxis against HA-VTE in children.

Thrombotic risk in children undergoing orthopedic surgery

Children are physiologically protected against venous thromboembolism (VTE). Specific triggering events or contributing factors have been identified in the majority of reported cases, which differs from the adult pathology where 50% of the thromboses are considered "idiopathic". This is a rare disease in children with an estimated frequency of less than 1/1000. The risk is highest in neonates, then decreases and increases again around 13 years to reach the same level as adults at 16 years. The risk of VTE is clearly higher in certain situations: significant trauma, prolonged immobilization, central venous catheter, stay in intensive care unit, inherited thrombophilia, cancer, obesity, oral contraceptives, etc. Thromboprophylaxis should not be used systematically, even in adolescents. Proper hydration and early mobilization form the basis of mechanical thromboprophylaxis. A prescription is only given after careful analysis of the child's risk factors and the orthopedic context. Thrombotic risk assessment scores - which are based on expert opinion and large VTE registers but have not been evaluated in clinical studies - are currently the most reliable method to evaluate the thrombotic risk in children and to prescribe thromboprophylaxis. Low-molecular weight heparin are the most commonly used thromboprophylaxis agents in children, with good tolerance and efficacy.

Association of perioperative red blood cell transfusion with postoperative venous thromboembolism in pediatric patients: A propensity score matched analysis

OBJECTIVE

To examine the association between perioperative red blood cell (RBC) transfusion and postoperative venous thromboembolism (VTE) in pediatric surgical patients.

METHODS

Retrospective cohort study using the National Surgical Quality Improvement Project Pediatric, a validated registry of 118 United States children's hospitals. Patients under 19 years of age undergoing a surgical procedure between 2012 and 2017 were included, with the main exposure being RBC transfusion in the perioperative period (48 hours prior to operation to 72 hours after operation). The primary 30-day outcome of interest was a postoperative VTE requiring therapy. Risk-adjusted odds ratios (aOR) were calculated using multiple logistic regression. Subgroup analyses were performed across multiple surgical specialties. Sensitivity analyses were performed after (a) imputation for missing variables and (b) propensity score matching.

RESULTS

During the study years, 482 867 pediatric patients (56.7% male; median age, 6 years [interquartile range, 1-12 years]) underwent an operation. Of these, 30 879 (6.4%) received at least one perioperative RBC transfusion. Postoperative VTE requiring therapy occurred in 618 patients (0.13%). After adjustment for multiple risk factors, perioperative RBC transfusion was associated with an increased risk of VTE (aOR 2.4; 95% CI, 1.9-3.0). The increased VTE risk persisted after imputation of missing demographic and clinical data as well as after 1:1 propensity score matching (29 811 matched pairs, aOR 2.2; 95% CI, 1.7-2.8).

CONCLUSIONS

Perioperative RBC transfusion is associated with an increased, albeit still very low, risk of postoperative VTE in pediatric patients. Patients receiving blood in the perioperative period may benefit from additional monitoring or VTE prophylaxis.

Promising biomarkers for the prediction of catheter-related venous thromboembolism in hospitalized children: An exploratory study

BACKGROUND

Pediatric venous thromboembolism (VTE) has increased over the past 10 years, with central venous catheters (CVC) being the strongest risk factor. Current tools are not sufficient to predict VTE risk. The utility of biomarkers in predicting CVC-related VTE has been minimally explored. Our objective is to determine the utility of microparticles (MPs), factor VIII (FVIII) activity, and thrombin generation (TG) in prospectively predicting VTE occurrence in hospitalized children with CVCs.

PROCEDURE

In this nested case-control pilot study, consecutive hospitalized children needing CVC placement (1 month to 21 years) were enrolled. Venous samples were collected prior to or within 24 h of CVC placement. MPs were measured using factor Xa initiated clot-based assay. FVIII was measured using a one-stage clot-based assay. TG was measured using calibrated automated thrombogram.

RESULTS

There were three CVC-related VTE events (7%) in our cohort of 42 subjects. Xa clotting time (XaCT) ratio was lower (0.68 ± 0.07 vs 0.95 ± 0.21, P = .4), while FVIII (461 ± 120 vs 267 ± 130, P = .02), peak thrombin (418 ± 89 vs 211 ± 101, P = .001), endogenous thrombin potential (ETP) (1828 ± 485 vs 1282 ± 394, P = .03), and velocity index (VI) (182 ± 28 vs 75 ± 53, P = .001) were higher in subjects with CVC-related VTE compared to those without CVC-related VTE. Sensitivity/specificity analysis revealed optimal cutoff values for XaCT ratio (0.75), FVIII (370), ETP (1680), peak (315), and VI (130), with receiver operating characteristic area under the curve values >0.9.

CONCLUSION

MPs, FVIII, and TG can potentially predict pediatric CVC-related VTE in a prospective fashion. Stratification according to VTE risk may aid in guiding preventative efforts in future studies.

Central venous lines in critically ill children: Thrombosis but not infection is site dependent

BACKGROUND

Central venous catheters (CVC) are vital to the management of critically ill children. Despite efforts to minimize complications, central line associated bloodstream infection (CLABSI) and venous thromboembolisms (VTE) still occur.

METHODS

We performed a retrospective review of a prospectively collected database for children admitted to the pediatric intensive care unit (PICU) between November 2013 and December 2016.

RESULTS

In total, 2714 CVC were in place, 979 of which were percutaneous CVC. During the study period, 21 CLABSI (1.6/1000 line days) were identified, of which, nearly half (n = 9, 42.9%) were associated with percutaneous CVC (2.6/1000 line days). Poisson regression analysis did not identify a single risk factor for CLABSI when adjusting for line type, anatomic location and laterality of placement, geographic location of placement, length of PICU admission, presence of gastrostomy tube, concurrent mechanical ventilation, age, weight, and height. Forty clinically significant VTE (2.9/1000 line days) were identified, with percutaneous CVC having the highest incidence (7.5/1000 line days, p < 0.001). Of percutaneous CVC, clinically significant VTE were more often associated with femoral vein cannulation (14.8/1000 line days) compared to internal jugular and subclavian vein (2.5 and 2.4/1000 line days, respectively, p < 0.001).

CONCLUSION

This data suggests that the femoral site may be an important risk factor that should be considered in prevention strategies for catheter-associated VTE in children.

LEVEL OF EVIDENCE

III.

Venous thromboembolism following inpatient pediatric surgery: Analysis of 153,220 patients

PURPOSE

To evaluate venous thromboembolism (VTE) rates and risk factors following inpatient pediatric surgery.

METHODS

153,220 inpatient pediatric surgical patients were selected from the 2012-2015 NSQIP-P database. Demographic and perioperative variables were documented. Primary outcome was VTE requiring treatment within 30 postoperative days. Secondary outcomes included length of stay (LOS) and 30-day mortality. Prediction models were generated using logistic regression. Mortality and time to VTE were assessed using Kaplan-Meier survival analysis.

RESULTS

305 patients (0.20%) developed 296 venous thromboses and 12 pulmonary emboli (3 cooccurrences). Median time to VTE was 9 days. Most VTEs (81%) occurred predischarge. Subspecialties with highest VTE rates were cardiothoracic (0.72%) and general surgery (0.28%). No differences were seen for elective vs. urgent/emergent procedures (p = 0.106). All-cause mortality VTE patients was 1.2% vs. 0.2% in patients without VTE (p < 0.001). After stratifying by American Society of Anesthesiologists (ASA) class, no mortality differences remained when ASA < 3. Preoperative, postoperative, and total LOSs were longer for patients with VTE (p < 0.001 for each). ASA ≥ 3, preoperative sepsis, ventilator dependence, enteral/parenteral feeding, steroid use, preoperative blood transfusion, gastrointestinal disease, hematologic disorders, operative time, and age were independent predictors (C-statistic = 0.83).

CONCLUSIONS

Pediatric postsurgical patients have unique risk factors for developing VTE.

LEVEL OF EVIDENCE

Level II.

Thrombosis in Children: Approach to Anatomic Risks, Thrombophilia, Prevention, and Treatment

Pediatric venous thromboembolism (VTE) is increasing in incidence but minimal data exist for best practices regarding therapy, use of thrombophilia testing, and management of long-term complications. Classification schema use anatomic location and presence of clinical or thrombophilic inciting factors. There are a small number of risk-assessment and risk-modeling systems for incident VTE, but all suffer from low numbers, single-institution design, and lack of prospective validation. Acute treatment is limited to heparin products and thrombolysis may be indicated in specific situations. In addition, chronic postthrombotic comorbidities are expected to increase in incidence and lack evidence-based treatment paradigms.

C-Reactive Protein Predicts Risk of Venous Thromboembolism in Pediatric Musculoskeletal Infection

BACKGROUND

The rate of venous thromboembolism in children with musculoskeletal infections (MSKIs) is markedly elevated compared with hospitalized children in general. Predictive biomarkers to identify high-risk patients are needed to prevent the significant morbidity and rare mortality associated with thrombotic complications. We hypothesize that overactivation of the acute phase response is associated with the development of pathologic thrombi and we aim to determine whether elevations in C-reactive protein (CRP) are associated with increased rates of thrombosis in pediatric patients with MSKI.

METHODS

A retrospective cohort study measuring CRP in pediatric MSKI patients with or without thrombotic complications.

RESULTS

The magnitude and duration of elevation in CRP values correlated with the severity of infection and the development of pathologic thrombosis. In multivariable logistic regression, every 20 mg/L increase in peak CRP was associated with a 29% increased risk of thrombosis (P<0.001). Peak and total CRP were strong predictors of thrombosis with area under the receiver-operator curves of 0.90 and 0.92, respectively.

CONCLUSIONS

Future prospective studies are warranted to further define the discriminatory power of CRP in predicting infection-provoked thrombosis. Pharmacologic prophylaxis and increased surveillance should be strongly considered in patients with MSKI, particularly those with disseminated disease and marked elevation of CRP.

LEVEL OF EVIDENCE

Level III.

Risk factors for venous thromboembolic events in pediatric surgical patients: Defining indications for prophylaxis

BACKGROUND

Venous thromboembolism (VTE) in pediatric surgical patients is a rare event. The risk factors for VTE in pediatric general surgery patients undergoing abdominopelvic procedures are unknown.

STUDY DESIGN

The American College of Surgeon's National Surgical Quality Improvement Program-Pediatric (NSQIP-P) database (2012-2015) was queried for patients with VTE after abdominopelvic general surgery procedures. Patient and operative variables were assessed to identify risk factors associated with VTE and develop a pediatric risk score.

RESULTS

From 2012-2015, 68 of 34,813 (0.20%) patients who underwent abdominopelvic general surgery procedures were diagnosed with VTE. On multivariate analysis, there was no increased risk of VTE based on concomitant malignancy, chemotherapy, inflammatory bowel disease, or laparoscopic surgical approach, while a higher rate of VTE was identified among female patients. The odds of experiencing VTE were increased on stepwise regression for patients older than 15 years and those with preexisting renal failure or a diagnosis of septic shock, patients with American Society of Anesthesia (ASA) classification ≥ 2, and for anesthesia time longer than 2 h. The combination of age > 15 years, ASA classification ≥ 2, anesthesia time > 2 h, renal failure, and septic shock was included in a model for predicting risk of VTE (AUC = 0.907, sensitivity 84.4%, specificity 88.2%).

CONCLUSION

VTE is rare in pediatric patients, but prediction modeling may help identify those patients at heightened risk. Additional studies are needed to validate the factors identified in this study in a risk assessment model as well as to assess the efficacy and cost-effectiveness of prophylaxis methods.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Catheter-Related Venous Thrombosis in Hospitalized Pediatric Patients with Inflammatory Bowel Disease: Incidence, Characteristics, and Role of Anticoagulant Thromboprophylaxis with Enoxaparin

OBJECTIVE

To describe the incidence and characteristics of central venous catheter (CVC)-related thrombosis in hospitalized pediatric patients with active inflammatory bowel disease (IBD) and report the potential usefulness of anticoagulant thromboprophylaxis (AT).

STUDY DESIGN

We conducted a retrospective study of patients who were admitted to our children's hospital in the last 2 years with active IBD and required a CVC and identified all patients with an objectively confirmed symptomatic CVC-related thrombosis. To assess the usefulness of a recently implemented institutional AT protocol, we compared the frequency of CVC-related thrombosis, nadir hemoglobin, and red blood cell transfusion requirements in patients who received AT with those who did not during the study period.

RESULTS

A total of 40 patients with IBD who required 47 consecutive hospitalizations were included. AT was administered during 24 of 47 hospitalizations (51%). Patients who received AT were similar to those who did not receive AT with regard to demographics, IBD phenotypes, extent of colonic involvement, and thrombotic risk factors. CVC-related thrombosis occurred in 5 of 23 hospitalizations (22%) in which AT was withheld compared with 0 of 24 hospitalizations (0%) in which patients received AT (P = .02). The red blood cell transfusion requirements and nadir hemoglobin were not significantly different between the 2 groups.

CONCLUSIONS

We observed a high incidence of CVC-related thrombosis in hospitalized children with IBD. Administration of AT in our population was associated with significant reduction in CVC-related thrombosis without evidence of increased bleeding.

Pediatric issues in thrombosis and hemostasis: The how and why of venous thromboembolism risk stratification in hospitalized children

Multiple observational studies have identified risk factors for venous thromboembolism (VTE) in hospitalized children, but very few interventional studies have assessed the safety and efficacy of thromboprophylaxis in this population. In recent years, however, evidence in pediatric VTE risk stratification has grown considerably. This has led to the conception of a pediatric subpopulation-specific risk-based paradigm for mechanical and pharmacological thromboprophylaxis in hospitalized children. More research is required to validate and further refine pediatric subpopulation-specific risk models and to subsequently investigate risk-stratified thromboprophylaxis strategies for hospitalized children.

Risk factors for hospital-associated venous thromboembolism in critically ill children following cardiothoracic surgery or therapeutic cardiac catheterisation

BACKGROUND

Paediatric hospital-associated venous thromboembolism is a leading quality and safety concern at children's hospitals.

OBJECTIVE

The aim of this study was to determine risk factors for hospital-associated venous thromboembolism in critically ill children following cardiothoracic surgery or therapeutic cardiac catheterisation.

METHODS

We conducted a retrospective, case-control study of children admitted to the cardiovascular intensive care unit at Johns Hopkins All Children's Hospital (St. Petersburg, Florida, United States of America) from 2006 to 2013. Hospital-associated venous thromboembolism cases were identified based on ICD-9 discharge codes and validated using radiological record review. We randomly selected two contemporaneous cardiovascular intensive care unit controls without hospital-associated venous thromboembolism for each hospital-associated venous thromboembolism case, and limited the study population to patients who had undergone cardiothoracic surgery or therapeutic cardiac catheterisation. Odds ratios and 95% confidence intervals for associations between putative risk factors and hospital-associated venous thromboembolism were determined using univariate and multivariate logistic regression.

RESULTS

Among 2718 admissions to the cardiovascular intensive care unit during the study period, 65 met the criteria for hospital-associated venous thromboembolism (occurrence rate, 2%). Restriction to cases and controls having undergone the procedures of interest yielded a final study population of 57 hospital-associated venous thromboembolism cases and 76 controls. In a multiple logistic regression model, major infection (odds ratio=5.77, 95% confidence interval=1.06-31.4), age ⩽1 year (odds ratio=6.75, 95% confidence interval=1.13-160), and central venous catheterisation (odds ratio=7.36, 95% confidence interval=1.13-47.8) were found to be statistically significant independent risk factors for hospital-associated venous thromboembolism in these children. Patients with all three factors had a markedly increased post-test probability of having hospital-associated venous thromboembolism.

CONCLUSION

Major infection, infancy, and central venous catheterisation are independent risk factors for hospital-associated venous thromboembolism in critically ill children following cardiothoracic surgery or cardiac catheter-based intervention, which, in combination, define a high-risk group for hospital-associated venous thromboembolism.

Anticoagulant prophylaxis and therapy in children: current challenges and emerging issues

This review is aimed at describing the unique challenges of anticoagulant prophylaxis and treatment in children, and highlighting areas for research for improving clinical outcomes of children with thromboembolic disease. The evidence presented demonstrates the challenges of advancing the evidence base informing optimal management of thromboembolic disease in children. Recent observational studies have identified risk factors for venous thromboembolism in children, but there are few interventional studies assessing the benefit-risk balance of using thromboprophylaxis in risk-stratified clinical subgroups. A risk level-based framework is proposed for administering mechanical and pharmacological thromboprophylaxis. More research is required to refine the assignment of risk levels. The anticoagulants currently used predominantly in children are unfractionated heparin, low molecular weight heparin, and vitamin K antagonists. There is a paucity of robust evidence on the age-specific pharmacology of these agents, and their efficacy and safety for prevention and treatment of thrombosis in children. The available literature is heterogeneous, reflecting age-specific differences, and the various clinical settings for anticoagulation in children. Monitoring assays and target ranges are not well established. Nevertheless, weight-based dosing appears to achieve acceptable outcomes in most indications. Given the limitations of the classical anticoagulants for children, there is great interest in the direct oral anticoagulants (DOACs), whose properties appear to be particularly suitable for children. All DOACs currently approved for adults have Pediatric Investigation Plans ongoing or planned. These are generating age-specific formulations and systematic dosing information. The ongoing pediatric studies still have to establish whether DOACs have a positive benefit-risk balance in the various pediatric indications and age groups.

Advances in predicting venous thromboembolism risk in children

Paediatric venous thromboembolism (VTE) is a rare disorder but a rising incidence has been observed in recent years, due to improved VTE diagnosis and increased use of central venous catheters in the treatment of severe diseases. Risk assessment strategies are well established for adult patients, however, similar guidelines for paediatric patients are largely lacking. Several risk prediction tools have been reported in recent literature, which make use of established risk factors to assess VTE risk in paediatric subgroups, such as hospitalised children, cancer-diagnosed children and paediatric trauma patients. Although these models suffer several limitations regarding their study size and heterogeneous selection of predictor variables, they offer potential for improving the thromboprophylaxis management in these children. Here, we give an overview on recently reported risk prediction models for paediatric VTE.

Identification of a "VTE-rich" population in pediatrics - Critically ill children with central venous catheters

BACKGROUND

The incidence of venous thromboembolism (VTE) is rising among inpatients in US hospitals, especially among kids with central venous catheters (CVCs) in the pediatric intensive care unit (PICU).

OBJECTIVES

To identify a sub-group of "VTE-rich" population among PICU children, and to assess the effect of VTE on morbidity and mortality.

METHODS

Data was extracted from a multicenter Virtual PICU Database, or VPS, for children with a CVC and presence of a VTE. The primary outcome variable was all cause mortality and secondary outcome measure was prolonged mechanical ventilation. Primary diagnoses and Pediatric risk of mortality 2 (PIM 2) score were also recorded.

RESULTS

The database identified 158,299 PICU patients who had a CVC. A total of 1602 patients had VTE (103 per 10,000 PICU patients). Multivariate analysis showed increased risk of VTE in patients who were <1year old (OR 1.48; 1.30-1.68), mechanically ventilated (OR 2.48; 2.07-2.98), had either a diagnostic (OR 2.32; 1.94-2.78) or therapeutic cardiac catheterization (OR 2.06; 1.66-2.55), PICC (OR 3.91; 3.50-4.37), and percutaneous CVC (OR 3.99; 3.48-4.61). Primary diagnoses associated with VTE were endocrinologic, immunologic, and gastrointestinal disorders. PICU patients with CVC and VTE had increased odds of mortality (OR 1.71; 1.47-2.00) after adjusting for factors associated with mortality, and fewer Ventilator Free Days (VFD) than patients without VTE.

CONCLUSIONS

Critically ill children with CVC have a significant risk of developing VTE. Identification of the above "VTE-rich" population may aid in design of clinical trials aimed at prevention of VTE among hospitalized PICU children.

Venous thromboembolism in children with cystic fibrosis: Retrospective incidence and intrapopulation risk factors

INTRODUCTION

Pediatric venous thromboembolism (VTE) is a rare but serious medical condition. Cystic fibrosis (CF) is a risk for recurrent pediatric VTE and has potential thrombophilic tendency. However, much remains unknown, including incidence and intrapopulation risk factors.

METHODS

A retrospective cohort of pediatric CF patients followed at Children's Hospital Colorado from January 1st 2003 through May 20th 2016 was examined. Cases were identified by informatics and validated manually. Data on CF severity, co-morbidities and treatment, central venous catheter (CVC) use, and thrombophilia were obtained from an institutional CF database and chart review.

RESULTS

Nineteen VTE occurred in 458 participants followed for 3595 person-years, yielding an incidence rate of 53 VTE per 10,000 children with CF. VTE cases had additional co-morbidities including CF-related diabetes (p=0.002) and sinus disease (p=0.04), more total admissions (p<0.001), admit days (p<0.001), positive respiratory cultures (p<0.001), pseudomonas infections (p<0.001), steroid courses (p=0.001), and total CVC days (PICC p=0.03, port p=0.007). On univariate analysis, older age (RR 1.162, p=0.007), sinus disease (RR 2.62, p=0.05), longer hospital stay (RR 1.03, p<0.001), higher ESR (RR 1.02, p=0.03) and CRP (RR 1.07, p=0.007), and an absence of systemic steroids (RR 0.19, p=0.004) increased the risk of VTE.

CONCLUSIONS

In this cohort, children with CF had a higher incidence of VTE when compared to the previously reported incidence in the overall pediatric population at Children's Hospital Colorado. Overall, those with VTE had a greater disease burden and older age, sinus disease, longer hospitalization and increased inflammation were VTE risk factors.

Pediatric Hospital Acquired Venous Thromboembolism

Pediatric hospital acquired venous thromboembolism (HA-VTE) is an increasing problem with an estimated increase from 5.3 events per 10,000 pediatric hospital admissions in the early 1990s to a current estimate of 30-58 events per 10,000 pediatric hospital admissions. Pediatric HA-VTE is associated with significant morbidity and mortality. The etiology is multifactorial but central venous catheters remain the predominant risk factor. Additional HA-VTE risk factors include both acquired (recent surgery, immobility, inflammation, and critical illness) and inherited risk factors. Questions remain regarding the most effective method to assess for HA-VTE risk in hospitalized pediatric patients and what preventative strategies should be implemented. While several risk-assessment models have been published in pediatric patients, these studies have limited power due to small sample size and require prospective validation. Potential thromboprophylactic measures include mechanical and pharmacologic methods both of which have associated harms, the most significant of which is bleeding from anticoagulation. Standard anticoagulation options in pediatric patients currently include unfractionated heparin, low molecular weight heparin, or warfarin all of which pose a monitoring burden. Ongoing pediatric studies with direct oral anticoagulants could potentially revolutionize the prevention and treatment of pediatric thrombosis with the possibility of a convenient route of administration and no requirement for monitoring. Further studies assessing clinical outcomes of venous thromboembolism (VTE) prevention strategies are critical to evaluate the effectiveness and harm of prophylactic interventions in children. Despite HA-VTE prevention efforts, thrombotic events can still occur, and it is important that clinicians have a high clinical suspicion to ensure prompt diagnosis and treatment to prevent further associated harms.

Venous Thromboembolism in Critical Illness and Trauma: Pediatric Perspectives

Critically ill children and those sustaining severe traumatic injuries are at higher risk for developing venous thromboembolism (VTE) than other hospitalized children. Multiple factors including the need for central venous catheters, immobility, surgical procedures, malignancy, and dysregulated inflammatory state confer this increased risk. As well as being at higher risk of VTE, this population is frequently at an increased risk of bleeding, making the decision of prophylactic anticoagulation even more nuanced. The use of pharmacologic and mechanical prophylaxis remains variable in this high-risk cohort. VTE pharmacologic prophylaxis is an accepted practice in adult trauma and intensive care to prevent VTE development and associated morbidity, but it is not standardized in critically ill or injured children. Given the lack of pediatric specific guidelines, prevention strategies are variably extrapolated from the successful use of mechanical and pharmacologic prophylaxis in adults, despite the differences in developmental hemostasis and thrombosis risk between children and adults. Whether the burden of VTE can be reduced in the pediatric critically ill or injured population is not known given the lack of robust data. There are no trials in children showing efficacy of mechanical compression devices or prophylactic anticoagulation in reducing the rate of VTE. Risk stratification using clinical factors has been shown to identify those at highest risk for VTE and allows targeted prophylaxis. It remains unproven if such a strategy will mitigate the risk of VTE and its potential sequelae.

Epidemiology and Risk Assessment of Pediatric Venous Thromboembolism

The incidence of diagnosed venous thromboembolism (VTE) has been increasing concurrent with advances in technology and medical care that enhance our ability to treat pediatric patients with critical illness or complex multiorgan system dysfunction. Although the overall incidence of VTE is estimated at 0.07-0.49 per 10,000 children, higher rates are observed in specific populations including hospitalized children, those with central venous catheters (CVCs) or patients convalescing from a major surgery. While the absolute number of pediatric VTE events may seem trivial compared to adults, the increasing incidence, associated with increased mortality and morbidity, the availability of novel therapies, and the impact on the cost of care have made investigation of VTE risk factors and prevention strategies a high priority. Many putative risk factors for pediatric VTE have been reported, primarily from single-institution, retrospective studies which lack appropriate methods for verifying independent risk factors. In addition, some risk factors have inconsistent definitions, which vex meta-analyses. CVCs are the most prevalent risk factors but have not consistently been assigned the highest level of risk as defined by odds ratios from retrospective, case-control studies. Few risk-assessment models for hospital-acquired pediatric VTE have been published. Some models focus exclusively on hospitalized pediatric patients, while others target specific populations such as patients with cancer or severe trauma. Multicenter, prospective studies are needed to identify and confirm risk factors in order to create a pediatric risk-assessment tool and optimize preventive measures and reduce unintended harm.

Venous thromboembolism occurring during adolescence

OBJECTIVE

Risk assessment for venous thromboembolism (VTE) and thromboprophylaxis in those with risk factors is established in adult practice. Evidence to support efficacy and safety of this approach in adolescents is lacking. We aimed to describe thrombotic risk factors and to determine the proportion of potentially preventable events in a retrospective cohort study of adolescents with VTE.

DESIGN, SETTING AND PATIENTS

Data were collected between 2008 and 2014 from eight tertiary UK centres. Qualifying events were radiologically confirmed VTE in subjects aged 12-17 years. Central venous line-related upper venous system events were excluded.

RESULTS

76 cases were identified, 41 males, median age 15 years. Frequent risk factors were: reduced mobility, 45%; thrombophilia, 24%; malignancy, 20%; surgery, 18%; combined oral contraceptive pill, 12%; congenital venous anomaly, 5%. 28 (37%) had no significant underlying diagnosis and no provoking event/hospitalisation, presenting as outpatients with VTE which was considered 'unpreventable'. Of 48 where there had been opportunity for risk assessment, chemical thromboprophylaxis was not indicated in 26 and was contraindicated in 8. 14/76 (18%) had an indication to consider thromboprophylaxis and no contraindication. Of these, four had cerebral palsy, five malignancy and two inflammatory bowel disease. All had reduced mobility with recent surgery in eight. Four received chemical thromboprophylaxis prior to presentation.

CONCLUSIONS

Among a cohort of adolescents with VTE, a small proportion (13%) had an indication to consider chemical thromboprophylaxis but did not receive it. VTE risk assessment and prevention should focus on adolescents with immobility or surgery, particularly in those with malignancy.