Catheter-Related Early Thromboprophylaxis With Enoxaparin (CRETE) Trial

Critical illness and the presence of a central venous catheter (CVC) are the most important
risk factors for deep venous thrombosis (DVT) in children. Catheter-associated thrombosis
(CADVT) is highly prevalent and associated with poor outcomes in critically ill children.
Yet, based on underpowered pediatric trials, prophylaxis against CADVT is not recommended in
children. The recommendation to provide prophylaxis against thrombosis in critically ill
adults should not be applied to children because the hemostatic system and co-morbidities
vastly differ between age groups. Pivotal trials are urgently needed to determine whether
prophylaxis can prevent CADVT and its complications in critically ill children. However, the
timing and extent of reduction in thrombin generation, the biochemical goal of prophylaxis,
needed to prevent CADVT in children are unclear. The goal of this application is to explore
the efficacy of early prophylaxis against CADVT in critically ill children. Aim 1 is to
obtain preliminary evidence on the effect of early prophylaxis on the incidence of CADVT in
critically ill children. Based on the natural history of CADVT, we hypothesize that among
critically ill children, prophylaxis administered <24 hours after catheter insertion
decreases the incidence of ultrasound-diagnosed CADVT compared with no prophylaxis. In this
phase 2a trial, children admitted to the intensive care unit with a newly inserted central
venous catheter will receive enoxaparin adjusted according to anti-Xa activity, a control
group will not receive enoxaparin adjusted according to anti-Xa activity. Enoxaparin has
become the "standard" pediatric anticoagulant for prophylaxis despite the absence of
conclusive data. We will use Bayesian approach to determine whether further trials are
warranted. Aim 2 is to evaluate the effect of an anti-Xa activity-directed prophylactic
strategy on thrombin generation in critically ill children. We hypothesize that among
critically ill children, standard prophylactic dose of enoxaparin adjusted by anti-Xa
activity reduces thrombin generation to <700 nM.min, as measured by ETP. In non-critically
ill adults, prophylactic dose of enoxaparin proven to prevent DVT reduces ETP to <700
nM.min.Endogenous thrombin potential is the best available measure of thrombin generation. We
will measure endogenous thrombin potential and anti-Xa activity at multiple time points then
examine their relationship in all children enrolled in the phase 2a trial. The proposed
research challenges the current paradigm on prophylaxis against CADVT in children. High
quality evidence is needed to prevent CADVT and its complications in this vulnerable
population.

Inclusion Criteria

1. Untunneled CVC inserted in the internal jugular or femoral vein within the past 24
hours

2. Child anticipated to stay in the pediatric intensive care unit ≥48 hours

3. CVC anticipated to be required for ≥24 hours

4. >36 weeks corrected gestational age to <18 years old

Exclusion Criteria

1. Coagulopathy (i.e., international normalized ratio >2.0, activated partial
thromboplastin time >50 seconds or platelet count <50,000/mm3)

2. Known bleeding disorder

3. Clinically relevant bleeding as defined by the International Society on Thrombosis and
Hemostasis (i.e., Hb decreased ≥2 g/dl in 24 hours, required medical or surgical
intervention to restore hemostasis, or in a critical organ system [i.e.,
retroperitoneum, pulmonary, intracranial or central nervous system])

4. <60 days from a clinically relevant bleeding as defined above

5. <7 days after trauma or surgery

6. Anticipated surgery within 48 hours after insertion of the CVC

7. Renal failure (i.e., creatinine clearance <30 mL/min)

8. Presence of epidural catheter

9. Currently taking an antithrombotic agent (e.g., LMWH, UFH at therapeutic doses,
Coumadin or aspirin)

10. Radiologically documented DVT at the site of insertion of the CVC in the previous 6
weeks

11. Known hypersensitivity to heparin or its components, including pork products

12. History of HIT (i.e., positive serotonin release assay)

13. Currently pregnant

14. Currently lactating

15. Prior enrollment in the study

16. Limitation of care