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Randomized trial of standard vs high-dose enoxaparin and sodium chloride for preventing clots in critically ill ICU patients at high risk of thrombosis

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What is this trial about?

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

Patients who are treated in the Intensive care unit (ICU) and have a high chance that blood‑clot prevention (called thromboprophylaxis) may not work are the focus of this research. In these very ill patients, clots can form in the veins of the legs (known as deep venous thrombosis) or travel to the lungs, causing a pulmonary embolism. At the same time, medicines that stop clots can sometimes cause serious bleeding, referred to as major bleeding, and both clotting problems and bleeding can lead to death.

The study compares two dose levels of a blood‑thinner called enoxaparin. One group receives the usual (standard) dose, while another group receives a higher dose. A separate group receives a harmless saline injection (sodium chloride) that looks the same but does not contain the active medicine. The main goal is to see which dose better prevents clots while keeping bleeding risks low.

Participants are given their assigned injection once each day for about four weeks. Doctors check their health regularly during this period and again several months later to find out whether clots, serious bleeding, or death have occurred. The study follows each person for up to six months to collect this information.

The research process

The trial runs in 6 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Randomization and Assignment

    After you agree to join the study, you are assigned by chance to one of two groups. One group receives the standard dose of enoxaparin, and the other group receives a higher dose. The study is double‑blind, which means neither you nor the treating team knows which medication you are receiving.

  2. Step 2

    Baseline Assessment

    Before the first injection, the study staff record your medical history, perform routine blood tests, and confirm that you meet the study criteria for critically ill patients at high risk for clotting problems.

  3. Step 3

    Daily Study Medication

    Each day you receive a subcutaneous injection (an injection under the skin).

    If you are in the standard‑dose group, the injection contains enoxaparin 40 mg. If you are in the high‑dose group, the injection contains a higher amount of the same medication (dose not specified in the provided information).

    If you are assigned to the placebo group, the injection contains sodium chloride 3.6 mg, which looks the same as the active drug.

    Injections are given once daily for as long as you remain in the intensive care unit (ICU) or until a maximum of 28 days, whichever comes first.

  4. Step 4

    Ongoing Monitoring

    Every day the medical team checks for signs of blood clots, bleeding, and any other health changes.

    If symptoms suggest a clot or major bleeding, additional tests such as ultrasound or blood work may be performed.

  5. Step 5

    Day 28 Evaluation

    On the 28th day after starting the study medication, a final assessment is performed.

    The team determines whether you experienced any clot (venous thrombosis), major bleeding, or death. This combined result is the primary outcome of the trial.

  6. Step 6

    Extended Follow‑Up (Day 180)

    Approximately six months after the start of the study (Day 180), an additional follow‑up may be conducted to evaluate longer‑term health outcomes.

Who can join the trial?

5 criteria

  • Age 18 years or older.
  • Currently admitted to an ICU (Intensive Care Unit, a special hospital area for very sick patients).
  • Has at least two of the following risk factors for thromboprophylaxis failure (meaning usual blood‑clot prevention may not work): body mass index (BMI) greater than 30 kg/m² (a measure of weight relative to height, >30 is considered obesity), augmented renal clearance (kidney filtering rate higher than 130 mL/min/1.73 m²), a personal history of cancer treated within the past 6 months, a personal history of venous thrombosis (deep‑vein clot or lung clot known as pulmonary embolism), presence of a jugular or femoral central venous catheter (a tube placed in a large vein in the neck or thigh), ongoing vasopressor therapy (medicines that keep blood pressure up), or being intubated (having a breathing tube).
  • Signed an informed consent form (a document that shows you understand the study and agree to take part).
  • Is affiliated with the French Social Security System (required for participants in France).

Who cannot join the trial?

19 criteria

  • Pregnant or breastfeeding women, or a positive pregnancy test within the three days before the study start.
  • Anyone already taking part in another research study that uses blood‑thinning medicines.
  • Patients who have been in the intensive care unit for more than 72 hours before they would be entered into the study.
  • Women who have given birth within the past six weeks.
  • People who weigh less than 50 kg (about 110 pounds).
  • People who need blood‑thinning medication as a treatment (called therapeutic anticoagulation).
  • Anyone with a current bleeding problem, such as bleeding caused by a clotting disorder, a serious bleed, a stomach ulcer, or any wound that could bleed easily.
  • People whose platelet count is below 50 × 10⁹ per litre – platelets are the cells that help blood clot.
  • Those who had major surgery or a serious injury in the last 15 days, or who received spinal or epidural anesthesia within the past 24 hours.
  • Anyone with a previous brain bleed, a large recent stroke, a known brain malformation or tumor, or an acute infection of the heart lining (called infectious endocarditis).
  • Patients with severe kidney failure, measured as a creatinine clearance under 30 mL/min – this is a test of how well the kidneys work.
  • Patients with low‑oxygen COVID‑19 pneumonia.
  • People who are allergic to heparin (a common blood thinner), low‑molecular‑weight heparin, or any of the ingredients in these medicines.
  • Those who have had a type II heparin‑induced low platelet count, known as heparin‑induced thrombocytopenia.
  • Anyone allergic to protamine (a drug used to reverse heparin) or its ingredients.
  • Patients who are extremely ill and are expected to die during the current hospital stay (called moribund).
  • People who are in prison or who are cared for in an institutional psychiatric facility.
  • Individuals under legal guardianship or curatorship.
  • In France only: people who are classified as “vulnerable” under the French Public Health Code (article L.1121‑6).
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Investigated drugs

Enoxaparin is an injectable blood‑thinner that helps prevent the formation of clots. In this study it is given under the skin to critically ill patients who are at high risk of developing dangerous blood clots. The trial is comparing a standard dose of enoxaparin with a higher dose to see which one works better at stopping clots while keeping bleeding risks low. Researchers are looking at how well each dose prevents clotting events, major bleeding, or death over 28 days.

What is already known about the treatment

  • Enoxaparin

    Enoxaparin is given by subcutaneous injection, which means a small needle is used to place the medicine just under the skin, and it is an approved drug that is widely used in hospitals today. It is used to prevent blood clots in patients who are at high risk, such as those in intensive‑care units. The medicine works by attaching to a natural protein called antithrombin and helping it block clotting factors, which reduces the formation of clots. Enoxaparin belongs to the class of low‑molecular‑weight heparins.

  • Sodium chloride

    Sodium chloride is also given by subcutaneous injection in the same way as the active drug, but it contains only a sterile salt solution and serves as a placebo in the trial. It is an approved medical ingredient that is commonly used to replace lost electrolytes or as a harmless control in studies. It has no effect on clotting and simply adds a small amount of salt water to the body. Sodium chloride is classified as an isotonic saline solution.

Investigated diseases

Critically ill medical patients at high risk for thromboprophylaxis failure - These patients are admitted to an intensive care unit for serious medical conditions and have factors that make preventive blood thinners less effective. They may develop clot formation in deep veins of the legs, in central venous catheters, or in the lungs. The condition can evolve from isolated distal leg clots to larger proximal clots and pulmonary embolism if not addressed. The risk increases with immobility, inflammation, and certain underlying diseases. Ongoing monitoring is needed to detect new clot events.
Trial detailsLast updated 21 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-524864-40-00Protocol codeERASME-HIPRO-2025Estimated enrolment600 patientsSponsorHopital Erasme

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