Treating acute pulmonary embolism with anticoagulant therapy (Guideline) - PulmCCM
Apr 092012
Treating Acute Pulmonary Embolism with Anticoagulant Therapy
from the ACCP Guidelines, 9th Ed.


The ACCP‘s new 9th edition of their authoritative clinical practice guidelines for prevention and treatment of venous thromboembolism (VTE) were published in February 2012. PulmCCM’s commentary is only appropriate as a reference for those who have read and are familiar with the original document, which is linked below. PulmCCM is not affiliated with ACCP. (See also the other sections of the 9th edition recommendations.)

Here we review the section on treating acute pulmonary embolism (PE) with antithrombotic / anticoagulant therapy.


How to Treat Pulmonary Embolism With Anticoagulation Therapy

If I suspect pulmonary embolism, but am waiting for test results (like CT-angiography or ultrasound) to help make the diagnosis, should I treat empirically with parenteral anticoagulants?*

ACCP suggests the following for empirically treating patients with parenteral anticoagulants when there is clinical suspicion of acute pulmonary embolism:

  • If your patient has a high clinical suspicion for acute pulmonary embolism, begin treatment with parenteral anticoagulants while waiting for test results (Grade 2C, suggestion based on consensus).
  • For intermediate clinical suspicion for acute PE, treat with parenteral anticoagulants while waiting if the test results will be delayed >4 hours (Grade 2C).
  • If there’s a a low clinical suspicion for PE, don’t treat empirically with anticoagulants as long as results will come back within 24 hours (Grade 2C).

* ACCP-recommended parenteral anticoagulants include low molecular weight heparin (e.g., enoxaparin), fondaparinux, intravenous or subcutaneous unfractionated heparin.


Once the diagnosis of acute PE is made, how should I treat my patient? 

  • When pulmonary embolism is confirmed, begin treatment with parenteral anticoagulants (Grade 1B, strong recommendation on moderate strength evidence).
  • Begin warfarin (Coumadin) the same day as parenteral anticoagulation; delay is not advised (Grade 1B).
  • Continue parenteral anticoagulation for at least 5 days, even if the INR reaches 2.0 earlier (Grade 1B).
  • Continue parenteral anticoagulation until the INR is at least 2.0 for 24 hours or more (Grade 1B).


Which parenteral anticoagulant is best for a patient with acute pulmonary embolism?

ACCP suggests low-molecular weight heparin (enoxaparin or Lovenox) or fondaparinux instead of unfractionated heparin (Grade 2B-C suggestions). Caveats to this are patients in whom subcutaneous absorption may not be adequate, or patients who are being considered for thrombolytic therapy: they should receive IV unfractionated heparin.

In those patients treated with low molecular weight heparin (LMWH like enoxaparin), ACCP suggests using once-daily dosing rather than twice-daily dosing. (Grade 2C, suggestion based on consensus or weak evidence)

However (hat tip to Mike Scheer in Fargo, ND for pointing this out), the FDA-approved once-daily dose of enoxaparin for acute PE is 1.5 mg/kg, and 1 mg/kg for twice daily dosing. Was the ACCP recommending we exceed the FDA-approved dose? Their remarks in the document are a bit unclear to me:

This recommendation only applies when the approved once-daily regimen uses the same daily dose as the twice-daily regimen (ie, the once-daily injection contains double the dose of each twice-daily injection). It also places value on avoiding an extra injection per day.

I emailed with Elie Akl, the corresponding author, and he wrote back:

No, we are not recommending to go above the FDA approved 1.5mg/kg once daily dose for enoxaparin. In fact, the recommendation doesn’t cover enoxaparin 1.5 mg/kg as the panel didn’t feel sufficiently confident about its efficacy. Another way to say it is that this recommendation doesn’t apply to Lovenox.

That seems to be make the recommendation a tacit endorsement of tinzaparin (Innohep), the only low molecular weight heparin currently FDA approved for treatment for acute PE that is dosed once-daily. If enoxaparin is chosen instead, I am taking this to mean we are being advised to stay with the FDA-approved twice daily dosing of 1 mg/kg (and check anti-Xa levels when appropriate), as before.

How soon is it safe to discharge a patient with acute pulmonary embolism?

Patients with low-risk pulmonary embolism (see below) who have good support at home, are likely to follow up, and can inject parenteral anticoagulants (or their family, or home nursing, can inject them) should be discharged home “early,” which means as early as the day of diagnosis, rather than staying in the hospital for 5 days (Grade 2B, suggestion based on moderate strength evidence). These patients can be safely discharged home from the emergency department without hospital admission, the ACCP has suggested.

How do I identify patients with acute PE who are “low-risk”?

The Pulmonary Embolism Severity Index (PESI) is a validated tool the ACCP mentions as a reasonable method of identifying people with low-risk PE. (Click the link for an online calculator.) Scores on the PESI < 85 without hypoxia, systolic BP < 100, severe chest pain, bleeding, thrombocytopenia < 70,000, severe liver or kidney disease, or PE while on anticoagulation suggest low risk PE. There’s also a simplified PESI calculator; a score of 0 suggests low-risk PE.


Kearon C et al. Antithrombotic Therapy for VTE Disease: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. CHEST 2012;141 (suppl 2): e419-e494S

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  7 Responses to “Treating acute pulmonary embolism with anticoagulant therapy (Guideline)”

  1. The above statements regarding lovenox dosing appear to suggest we use a 2 mg/kg once a day dose versus the APPROVED dose of 1.5 mg/kg once a day. The CHEST guidelines reference APPROVED dosing of LMWH where the total once a day dose is equivalent to the bid total daily dose. Unfortunately, this language may cause over dosing errors with once a day lovenox. Lovenox 2mg/kg once daily has never been studied in RCTs and should not be advocated (per the manufacturer clinical experts).

    • Mike: Thanks for making this very important point. I revised that section of the post (above) to draw attention to this question and I’ve also emailed Elie Akl, the corresponding author to ask for clarification. -Matt

  2. Is there ever any differentiation between LMWH and IV unfractionated heparin? A common regional practice is to use IV UFH for “large” pulmonary clots. Am I correct that this distinction is not made in the guidelines and, if anything, LMWH is actually preferred unless the patient may be a thrombolytic candidate?

  3. Is there any evidence to treat with subcutaneus unfractionated heparin for acute PE?

  4. can anyone clarify the following?

    1) When is unfractionated Heparin preferred over LMWH ?

    2) What is the difference of efficacy in Unfractionated Heparin and LMWH in Massive PE? Any clinical trial comparing this?

  5. What happens if there is a patient with previous dvt or pe that is being treated with coumadin. They have been therapeutic but become subtherapeutic. Is it necessary to bridge these patients?

  6. No I dont think so , I had a patient who had no access whatso ever and we decided to give him big doses of S/Q UFH and recheck PTT in 2-3 hrs after the dose and then come up with a dosing protocol for that , never were able to figure out what is the correct dose for that, he died from CRI and ESRD complications

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