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Evaluation of Enoxaparin for Prevention of Localized Intravascular Coagulopathy in Children with Slow-Flow Vascular Malformations Undergoing Interventional Procedures

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This study focuses on slow-flow vascular malformations in children and adolescents. Vascular malformations are abnormalities in blood vessels or lymphatic vessels that are present at birth but may not be visible until later in life. Slow-flow vascular malformations specifically refer to abnormal formations of veins or lymphatic vessels that have slow blood flow through them. During procedures to treat these malformations (such as sclerotherapy, which involves injecting medicine directly into the malformation), patients can develop a condition called localized intravascular coagulopathy, which is an abnormal blood clotting process that occurs within the malformation.

The purpose of this study is to evaluate whether the medication enoxaparin (a type of blood thinner) can effectively and safely prevent this abnormal blood clotting when given before procedures in children with these vascular malformations. Enoxaparin works by interfering with the formation of blood clots. The study will also examine how the treatment affects certain markers of damage to the lining of blood vessels (called endothelial damage markers).

Participants in this study will be children and adolescents aged 0 to 18 years who have been diagnosed with venous malformations or low-flow venous/lymphatic malformations and are scheduled to undergo a procedure such as sclerotherapy, cryoablation (freezing of tissue), or electroporation (using electrical pulses to treat the malformation). Some participants will receive enoxaparin before their procedure, while others will not, and researchers will compare outcomes between these groups.

The research process

The trial runs in 8 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Randomization and group assignment

    You will be randomly assigned to one of two groups in this trial. This is like a coin flip to determine whether you will receive the medication (enoxaparin) or not during your procedure.

    The study will evaluate if enoxaparin helps prevent blood clotting complications during percutaneous procedures (procedures that involve inserting instruments through the skin) for slow-flow vascular malformations.

  2. Step 2

    Pre-procedure baseline tests

    Blood samples will be collected to establish your baseline values for localized intravascular coagulopathy (a condition where blood clotting is disrupted in a specific area) and endothelial damage (damage to the inner lining of blood vessels).

    These tests will measure levels of substances like D-dimer, fibrinogen, and platelets, which help evaluate how your blood clots.

  3. Step 3

    Scheduled procedure

    You will undergo one of the following percutaneous procedures for your vascular malformation: sclerotherapy (injection of a solution to shrink blood vessels), cryoablation (using extreme cold to treat the malformation), or electroporation (using electrical pulses to treat the malformation).

    If you're in the treatment group, you'll receive enoxaparin (a blood-thinning medication) as a preventive measure. The medication is given as an injection under the skin.

  4. Step 4

    Enoxaparin administration (for treatment group only)

    If assigned to the treatment group, you will receive enoxaparin sodium injections. The dosage will depend on your weight and condition.

    Enoxaparin comes in pre-filled syringes with various strengths (ranging from 20 mg to 100 mg) and will be administered according to your doctor's prescription.

  5. Step 5

    Post-procedure monitoring

    After your procedure, you will be monitored for signs of bleeding or other complications.

    The medical team will conduct a subjective assessment of bleeding (checking for visible signs of bleeding), measure your hemoglobin levels (to detect potential internal bleeding), and classify any hemorrhage if it occurs.

  6. Step 6

    Follow-up blood tests

    Additional blood samples will be taken at scheduled times to monitor your body's response to the procedure and treatment.

    These tests will check for changes in your blood clotting factors and indicators of blood vessel damage.

  7. Step 7

    Pain and inflammation assessment

    Your pain levels will be evaluated during the follow-up period.

    The medical team will also assess the degree of inflammation and check for the development of phleboliths (small calcifications in veins) or deep vein thrombosis (blood clots in deep veins).

  8. Step 8

    Study completion

    The study will continue until September 15, 2025, though the overall research project extends to June 15, 2027.

    Your participation will conclude after completing all scheduled follow-up visits and assessments.

Who can join the trial?

7 criteria

  • You must be between 0 and 18 years old
  • You must have a venous malformation or a low-flow venous/lymphatic malformation (abnormal formations of veins or lymph vessels that have slow blood flow)
  • You must be scheduled to have one of these procedures:
    • Sclerotherapy (a procedure where medicine is injected into abnormal vessels to shrink them)
    • Cryoablation (a procedure that uses extreme cold to destroy abnormal tissue)
    • Electroporation (a procedure that uses electrical pulses to treat the malformation)
    • Your parents or legal guardians must sign an informed consent form allowing you to participate in the study
    • If you are 12 years or older, you must also agree to participate in the study by signing an assent form

Who cannot join the trial?

9 criteria

  • You cannot participate if you don't have a venous malformation (a type of abnormal blood vessel growth) or a low-flow venous/lymphatic malformation (abnormal vessels containing blood or lymph fluid that flow slowly).
  • You cannot join if you're not a pediatric patient (a child).
  • You will be excluded if you're not scheduled to undergo a percutaneous interventional procedure (a minimally invasive treatment done through the skin) for your vascular malformation.
  • You cannot participate if you have a known allergy or sensitivity to enoxaparin (the blood-thinning medication being studied) or similar medications.
  • You will be excluded if you have active major bleeding or a high risk of uncontrolled bleeding.
  • You cannot join if you have severe kidney problems, as this might affect how the medication works in your body.
  • If you're currently taking other blood-thinning medications that cannot be stopped for the study, you cannot participate.
  • You will be excluded if you're pregnant or breastfeeding.
  • You cannot participate if you have any condition that, in the opinion of the researchers, would make it unsafe for you to be in the study.
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Investigated drugs

Enoxaparin is a blood-thinning medication that helps prevent blood clots. In this trial, it's being studied as a preventive treatment for localized intravascular coagulopathy (a blood clotting disorder) in children with slow-flow vascular malformations (abnormal blood vessel formations) who are undergoing minimally invasive procedures. The medication works by interfering with the blood's clotting process.

What is already known about the treatment

Enoxaparin – A low molecular weight heparin administered by subcutaneous injection that is used to prevent blood clotting during medical procedures. It is widely recognized in medical literature as an effective anticoagulant for various conditions including prevention of deep vein thrombosis. In this trial, enoxaparin is being studied as a prophylactic treatment for localized intravascular coagulopathy in children with slow-flow vascular malformations who are undergoing percutaneous procedures. It works by binding to and accelerating the activity of antithrombin III, which inhibits clotting factors and prevents blood clot formation. Enoxaparin belongs to the pharmacological class of anticoagulants and is considered a standard of care in many anticoagulation protocols.

Investigated diseases

  • Venous malformation

    A venous malformation is a type of vascular anomaly characterized by abnormally formed veins with thin walls and enlarged chambers. These malformations are present at birth, though they may not be visible until later in life, and tend to grow proportionally with the child. They can cause pain, swelling, and functional impairment depending on their location and size. As venous malformations grow, they can develop localized intravascular coagulopathy, a condition where blood clotting is disrupted within the malformation. Over time, calcified clots called phleboliths may form within the malformed veins, which can be a distinctive feature on imaging.

  • Low-flow venous/lymphatic malformation

    Low-flow venous/lymphatic malformations are congenital vascular anomalies consisting of abnormally formed vessels containing both venous and lymphatic components. These malformations expand slowly over time and can cause symptoms like swelling, pain, and compression of surrounding structures. The lymphatic component may cause clear fluid-filled vesicles on the skin or mucous membranes, while the venous component appears as bluish masses under the skin. These malformations can infiltrate tissues, including muscles, bones, and occasionally internal organs, causing progressive dysfunction of affected areas. They frequently result in localized blood clotting abnormalities within the malformation that can worsen during interventional procedures.

Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-521196-32-00Protocol codeFSJD-PEaRL-X-2025Estimated enrolment60 patientsSponsorFundacio Sant Joan De Deu

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