Age-Dependent Heterogeneity in the Efficacy of Prophylaxis With Enoxaparin Against Catheter-Associated Thrombosis in Critically Ill Children: A Post Hoc Analysis of a Bayesian Phase 2b Randomized Clinical Trial

Protocol for the Catheter-Related Early Thromboprophylaxis With Enoxaparin (CRETE) Studies

OBJECTIVES

In post hoc analyses of our previous phase 2b Bayesian randomized clinical trial (RCT), prophylaxis with enoxaparin reduced central venous catheter (CVC)-associated deep venous thrombosis (CADVT) in critically ill older children but not in infants. The goal of the Catheter-Related Early Thromboprophylaxis with Enoxaparin (CRETE) Studies is to investigate this newly identified age-dependent heterogeneity in the efficacy of prophylaxis with enoxaparin against CADVT in critically ill children.

DESIGN

Two parallel, multicenter Bayesian superiority explanatory RCTs, that is, phase 3 for older children and phase 2b for infants, and an exploratory mechanistic nested case-control study (Trial Registration ClinicalTrials.gov NCT04924322, June 7, 2021).

SETTING

At least 15 PICUs across the United States.

PATIENTS

Older children 1-17 years old ( n = 90) and infants older than 36 weeks corrected gestational age younger than 1 year old ( n = 168) admitted to the PICU with an untunneled CVC inserted in the prior 24 hours. Subjects with or at high risk of clinically relevant bleeding will be excluded.

INTERVENTIONS

Prophylactic dose of enoxaparin starting at 0.5 mg/kg then adjusted to anti-Xa range of 0.2-0.5 international units (IU)/mL for older children and therapeutic dose of enoxaparin starting at 1.5 mg/kg then adjusted to anti-Xa range of greater than 0.5-1.0 IU/mL or 0.2-0.5 IU/mL for infants while CVC is in situ.

MEASUREMENTS AND MAIN RESULTS

Randomization is 2:1 to enoxaparin or usual care (no enoxaparin) for older children and 1:1:1 to either of 2 anti-Xa ranges of enoxaparin or usual care for infants. Ultrasonography will be performed after removal of CVC to assess for CADVT. Subjects will be monitored for bleeding. Platelet poor plasma will be analyzed for markers of thrombin generation. Samples from subjects with CADVT will be counter-matched 1:1 to subjects without CADVT from the opposite trial arm. Institutional Review Board approved the "CRETE Studies" on July 1, 2021. Enrollment is ongoing with planned completion in July 2025 for older children and July 2026 for infants.

Invasive Mechanical Ventilation and Risk of Hospital-Acquired Venous Thromboembolism

BACKGROUND

This study sought to estimate the overall cumulative incidence and odds of Hospital-acquired venous thromboembolism (VTE) among critically ill children with and without exposure to invasive ventilation. In doing so, we also aimed to describe the temporal relationship between invasive ventilation and hospital-acquired VTE development.

METHODS

We performed a retrospective cohort study using Virtual Pediatric Systems (VPS) data from 142 North American pediatric ICUs among children < 18 y of age from January 1, 2016-December 31, 2022. After exclusion criteria were applied, cohorts were identified by presence of invasive ventilation exposure. The primary outcome was cumulative incidence of hospital-acquired VTE, defined as limb/neck deep venous thrombosis or pulmonary embolism. Multivariate logistic regression was used to determine whether invasive ventilation was an independent risk factor for hospital-acquired VTE development.

RESULTS

Of 691,118 children studied, 86,922 (12.4%) underwent invasive ventilation. The cumulative incidence of hospital-acquired VTE for those who received invasive ventilation was 1.9% and 0.12% for those who did not (P < .001). The median time to hospital-acquired VTE after endotracheal intubation was 6 (interquartile range 3-14) d. In multivariate models, invasive ventilation exposure and duration were each independently associated with development of hospital-acquired VTE (adjusted odds ratio 1.64 [95% CI 1.42-1.86], P < .001; and adjusted odds ratio 1.03 [95% CI 1.02-1.03], P < .001, respectively).

CONCLUSIONS

In this multi-center retrospective review from the VPS registry, invasive ventilation exposure and duration were independent risk factors for hospital-acquired VTE among critically ill children. Children undergoing invasive ventilation represent an important target population for risk-stratified thromboprophylaxis trials.

Association of an In-Hospital Desirability of Outcomes Ranking Scale With Postdischarge Health-Related Quality of Life: A Secondary Analysis of the Life After Pediatric Sepsis Evaluation

OBJECTIVES

To develop a desirability of outcome ranking (DOOR) scale for use in children with septic shock and determine its correlation with a decrease in 3-month postadmission health-related quality of life (HRQL) or death.

DESIGN

Secondary analysis of the Life After Pediatric Sepsis Evaluation prospective study.

SETTING

Twelve U.S. PICUs, 2013-2017.

PATIENTS

Children (1 mo-18 yr) with septic shock.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We applied a 7-point pediatric critical care (PCC) DOOR scale: 7: death; 6: extracorporeal life support; 5: supported by life-sustaining therapies (continuous renal replacement therapy, vasoactive, or invasive ventilation); 4: hospitalized with or 3: without organ dysfunction; 2: discharged with or 1: without new morbidity to patients by assigning the highest applicable score on specific days post-PICU admission. We analyzed Spearman rank-order correlations (95% CIs) between proximal outcomes (PCC-DOOR scale on days 7, 14, and 21, ventilator-free days, cumulative 28-day Pediatric Logistic Organ Dysfunction-2 (PELOD-2) scores, and PICU-free days) and 3-month decrease in HRQL or death. HRQL was measured by Pediatric Quality of Life Inventory 4.0 or Functional Status II-R for patients with developmental delay. Patients who died were assigned the worst possible HRQL score. PCC-DOOR scores were applied to 385 patients, median age 6 years (interquartile range 2, 13) and 177 (46%) with a complex chronic condition(s). Three-month outcomes were available for 245 patients (64%) and 42 patients (17%) died. PCC-DOOR scale on days 7, 14, and 21 demonstrated fair correlation with the primary outcome (-0.42 [-0.52, -0.31], -0.47 [-0.56, -0.36], and -0.52 [-0.61, -0.42]), similar to the correlations for cumulative 28-day PELOD-2 scores (-0.51 [-0.59, -0.41]), ventilator-free days (0.43 [0.32, 0.53]), and PICU-free days (0.46 [0.35, 0.55]).

CONCLUSIONS

The PCC-DOOR scale is a feasible, practical outcome for pediatric sepsis trials and demonstrates fair correlation with decrease in HRQL or death at 3 months.

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.

Antithrombin activity and central venous catheter-associated thrombosis in critically ill children at high risk of bleeding

BACKGROUND

Normalization of antithrombin activity may prevent catheter-associated thrombosis in critically ill children at high risk of bleeding.

OBJECTIVES

To characterize the temporal pattern of antithrombin activity, assess its association with catheter-associated thrombosis and clinically relevant bleeding, and evaluate its relationship with thrombin generation in these children.

METHODS

In this prospective cohort study, critically ill children <18 years old at high risk of bleeding with central venous catheter were eligible. Antithrombin activity and thrombin generation were measured from platelet-poor plasma and after in vitro antithrombin supplementation. Systematic surveillance ultrasound was performed to diagnose thrombosis. Children were followed for bleeding.

RESULTS

We enrolled 8 infants (median age: 0.2 years, IQR: 0.2, 0.3 years) and 72 older children (median age: 14.3 years, IQR: 9.1, 16.1 years). Mean antithrombin on the day of catheter insertion was 64 IU/dL (SD: 32 IU/dL) in infants and 83 IU/dL (SD: 35 IU/dL) in older children. Antithrombin normalized by the day of catheter removal. Thrombosis developed in 27 children, while 31 children bled. Thrombosis (regression coefficient: 0.008, 95% CI: -0.01, 0.03) and bleeding (regression coefficient: -0.0007, 95% CI: -0.02, 0.02) were not associated with antithrombin. Antithrombin was not correlated with in vivo change in endogenous thrombin potential (correlation coefficient: -0.07, 95% CI: -0.21, 0.08). In vitro supplementation reduced endogenous thrombin potential (correlation coefficient: -0.78; 95% CI: -0.95, -0.23).

CONCLUSION

These findings may not support normalization of antithrombin activity to prevent catheter-associated thrombosis in critically ill children at high risk of bleeding.

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.

Prophylactic Enoxaparin Against Catheter-Associated Thrombosis in Postoperative Cardiac Children: An Interrupted Time Series Analysis

OBJECTIVES

The effectiveness of pharmacologic prophylaxis against catheter-associated thrombosis in children is unclear. We evaluated the compliance and outcomes associated with a prophylactic enoxaparin protocol in postoperative cardiac children.

DESIGN

The protocol was implemented as a quality improvement initiative and then analyzed using interrupted time series method. Data collected from November 2014 to December 2018 were divided into preprotocol (period 1), protocol implementation (period 2), and protocol revision (period 3).

SETTING

A 12-bed academic pediatric cardiac ICU.

PATIENTS

Children less than or equal to 18 years old with congenital heart disease admitted postoperatively with central venous catheter in situ for greater than or equal to 1 day.

INTERVENTIONS

Before 2016, prophylactic enoxaparin was administered according to physician preference. In January 2016, an enoxaparin protocol was implemented with a goal anti-Xa range of 0.25-0.49 international units/mL. Protocol was revised in February 2017 to increase the starting dose by 25% for infants less than 1 year old.

MEASUREMENTS AND MAIN RESULTS

We analyzed 780 hospitalizations from 636 children. Median percentage of catheter-days on prophylactic enoxaparin was 33% (interquartile range [IQR], 23-47%), 42% (IQR, 30-51%), and 38% (IQR, 35-52%) in periods 1-3, respectively. Percentage of catheter-days on enoxaparin showed immediate increase of 90% (95% CI, 17-210%) between periods 1 and 2 and sustained increase of 2% (95% CI, 0.3-4%) between periods 2 and 3. Median rates of thrombosis per 1,000 catheter-days were 5.8 (IQR, 0-9.3), 3.8 (IQR, 0-12), and 0 (IQR, 0-5.3) in periods 1-3, respectively. Rate of thrombosis showed immediate decrease of 67% (95% CI, 12-87%) between periods 1 and 2 and sustained decrease of 11% (95% CI, 2-18%) between periods 1 and 3.

CONCLUSIONS

The temporal association between increase in percentage of catheter-days on enoxaparin and decrease in rate of thrombosis suggests the effectiveness of prophylactic enoxaparin.

Central venous catheter-associated deep vein thrombosis in critically ill pediatric patients: risk factors, prevention, and treatment

PURPOSE OF REVIEW

Central venous catheter (CVC) placement and ICU admission are the two most important risk factors for pediatric deep vein thrombosis. The optimal prevention and treatment strategies for CVC-associated deep vein thrombosis (CADVT) are unclear, but recently, seminal studies have been published. This review aims to summarize the recent literature on CADVT in critically ill children.

RECENT FINDINGS

Recent publications focused on three themes: risk factors, prevention, and treatment of CADVT. Newly identified risk factors for CADVT relate to Virchow's triad of hemostasis, blood vessel injury, and hypercoagulability. New risk prediction models have moderately good accuracy in predicting CADVT. Though previous data on pharmacologic CADVT prophylaxis was equivocal, recent studies indicate that low-molecular-weight heparin may be effective in preventing CADVT, particularly in critically ill children. Finally, new studies suggest that direct oral anticoagulants and shorter treatment times are noninferior to traditional agents and treatment durations in the treatment of CADVT.

SUMMARY

Recent research suggests new ways to accurately identify children at high risk of CADVT, effectively prevent CADVT, and optimize CADVT treatment. Future research should focus on understanding the pathobiology of CADVT formation, prevention, and treatment in critically ill children.

Outcomes of Prophylactic Enoxaparin Against Venous Thromboembolism in Hospitalized Children

OBJECTIVES

To assess the biochemical and clinical outcomes of hospitalized children who received prophylactic enoxaparin.

METHODS

We conducted a retrospective observational study of hospitalized children aged <18 years who received prophylactic enoxaparin against hospital-acquired venous thromboembolism (HA-VTE). Weight-based enoxaparin dosing was administered using a pharmacy-driven protocol, which later included a low molecular weight, anti-Xa level directed-dose adjustment strategy. Primary biochemical and clinical outcomes were achievement of goal anti-Xa range of 0.2 to 0.5 IU/mL and development of HA-VTE, respectively. Secondary clinical outcome was development of clinically relevant bleed.

RESULTS

We analyzed 194 children with 13 (6.7%) infants aged <1 year and 181 (93.3%) older children aged ≥1 year. After the initial dose, only 1 (11.1%) infant, but 62 (57.9%) older children, achieved goal. Median number of anti-Xa levels until goal was 2 (interquartile range: 2-3) in infants and 1 (interquartile range: 1-2) in older children (P = .01). HA-VTE developed in 2 (15.4%) infants and 9 (5.0%) older children. Among children with anti-Xa level, HA-VTE developed less frequently in children who achieved (2.1%) than in those who did not achieve (13.6%) goal (P = .046). A total of 4 (2.1%) older children and no infants developed clinically relevant bleed. Among children with anti-Xa level, frequency of bleeding was comparable between children who did (3.2%) and did not achieve (0%) goal (P >.99).

CONCLUSIONS

Our findings suggest the effectiveness and safety of an anti-Xa level directed strategy of prophylactic enoxaparin. However, this strategy should be investigated in prospective controlled studies.

The Continued Rise of Venous Thromboembolism Across US Children's Hospitals

OBJECTIVES

In 2009, a large multicenter study demonstrated that the rate of pediatric venous thromboembolism (VTE) across US children's hospitals had significantly increased from 2001 to 2007. The objective of this study was to evaluate the rate of pediatric VTE from 2008 to 2019 using similar methodology.

METHODS

A retrospective cohort study using the Pediatric Health Information System (PHIS) database. Subjects from birth to <18 years admitted from 2008 through 2019 who had an ICD-9-CM or ICD-10-CM code for VTE were included. Demographics, underling medical comorbidities and mortality were collected. VTE location and anticoagulation data during admission were extracted.

RESULTS

During the 12-year study period, there were 52 401 hospital admissions among 39 713 pediatric patients with a diagnosis of VTE. The VTE admission rate increased from 46 VTE cases per 10 000 admissions in 2008 to 106 VTE cases per 10 000 admissions in 2019, a 130% increase (P < .0001) in VTE events. The median age at admission was 6.1 years, and almost one-third (31.3%) of patients with VTE were in the adolescent age group (13-17 years). Most patients (78%) had an underlying chronic medical condition.

CONCLUSIONS

The rate of VTE in hospitalized pediatric patients continues to increase from a 70% increase reported from 2001 to 2007 to the 130% increase from 2008 to 2019. These findings support the need for more effective VTE prevention strategies. Clinical trials focused on risk stratification and VTE prevention are needed.

Prevention of recurrent thrombotic events in children with central venous catheter-associated venous thrombosis

Central venous catheters (CVC) are the most significant risk factor for pediatric venous thromboembolism (VTE). After an index CVC-associated VTE (CVC-VTE), the role of secondary prophylaxis for subsequent CVC placement is uncertain. Aims of this single-center retrospective study were to evaluate the efficacy of secondary prophylaxis for patients with a prior CVC-VTE and identify risk factors associated with recurrent VTE in patients less than 19 years with an index CVC-VTE between 2003 and 2013. Data collection included clinical and demographic factors, subsequent CVC placement, secondary prophylaxis strategy, recurrent VTE, and bleeding. Risk factors for recurrence and effectiveness of secondary prophylaxis were evaluated using survival and binomial models. Among 373 patients with an index CVC-VTE, 239 (64.1%) had subsequent CVC placement; 17.4% (65/373) of patients had recurrent VTE, of which 90.8% (59/65) were CVC-associated. On multivariable survival analysis, each additional CVC (hazards ratio [HR] 12.00; 95% confidence interval [CI] 2.78-51.91), congenital heart disease (HR 3.70; 95% CI 1.97-6.95), and total parenteral nutrition dependence (HR 4.02; 95% CI 2.23-7.28) were associated with an increased hazard of recurrence. Full dose anticoagulation for secondary prophylaxis was associated with decreased odds of recurrent CVC-VTE (odds ratio [OR] 0.35; 95% CI 0.19-0.65) but not prophylactic dosing (OR 0.61; 95% CI 0.28-1.30). Only 1.3% of CVCs experienced major bleeding with prophylactic or full-dose anticoagulation. In summary, children with CVC-VTE are at increased risk for recurrent VTE. Secondary prophylaxis with full-dose anticoagulation was associated with a 65% reduction in odds of thrombotic events.