What is the recommended heparin (unfractionated heparin) regimen for managing pulmonary embolism?

Unfractionated Heparin Regimen for Pulmonary Embolism Management

For patients with pulmonary embolism requiring unfractionated heparin (UFH), treatment should begin with an intravenous bolus of 5000 units followed by a continuous infusion of 1250 units/hour, with subsequent dose adjustments to maintain aPTT at 2-2.5 times the baseline value. 1

Risk Stratification and Initial Treatment Approach

High-Risk PE (with hemodynamic instability)

• UFH is the preferred anticoagulant for high-risk PE with shock or hypotension 2
• Administration:
  • IV bolus of 5000 units
  • Initial continuous infusion of 1250 units/hour
  • Adjust dose to maintain aPTT at 2-2.5 times normal
  • Continue for at least 5-7 days

Intermediate or Low-Risk PE

• While LMWH or fondaparinux is generally preferred over UFH for most patients 2, UFH is specifically indicated in:
  • Patients with severe renal impairment (CrCl <30 mL/min)
  • Patients with morbid obesity
  • Situations where rapid reversal may be needed
  • Cases where primary reperfusion treatment is considered

Dosing and Monitoring Protocol

1. Initial Dosing:

   • Loading dose: 5000 units IV bolus
   • Maintenance: 1250 units/hour continuous IV infusion 1

2. Monitoring:

   • Check aPTT 4-6 hours after bolus and 4-6 hours after any dose change
   • Target aPTT: 2-2.5 times control value (typically 60-80 seconds)
   • Once stable, monitor aPTT daily

3. Dose Adjustment:

   • If aPTT below target: increase infusion rate by 2-3 units/kg/hour
   • If aPTT above target: reduce infusion rate by 2-3 units/kg/hour
   • If aPTT excessively high: stop infusion for 1 hour, then restart at lower rate

Duration and Transition to Oral Therapy

• Continue UFH for at least 5 days 2

• Initiate oral anticoagulation (VKA or NOAC) as soon as possible, preferably on the same day as UFH 2

• For patients transitioning to VKA:

  • Continue UFH until INR is 2.0-3.0 for two consecutive days 2
  • Target INR: 2.0-3.0

• For patients transitioning to NOACs:

  • If using dabigatran or edoxaban: continue UFH for at least 5 days
  • If using rivaroxaban or apixaban: UFH can be discontinued after 1-2 days 2

Special Considerations

Pregnancy

• UFH is preferred over LMWH approaching delivery since its effect can be more easily reversed 2
• Consider reducing dose or discontinuing 4-6 hours before expected delivery time

Monitoring for Complications

• Monitor platelet count for heparin-induced thrombocytopenia (HIT)
• Assess for bleeding complications daily
• Unlike fondaparinux, UFH carries risk of HIT and requires platelet monitoring 2

Common Pitfalls to Avoid

1. Inadequate initial dosing: Starting with too low a dose delays achieving therapeutic anticoagulation
2. Infrequent monitoring: Failure to check aPTT regularly leads to suboptimal anticoagulation
3. Delayed transition to oral therapy: Oral anticoagulants should be started as soon as possible
4. Premature discontinuation: UFH should overlap with VKA until therapeutic INR is achieved
5. Failure to adjust for renal function: Patients with renal impairment may require dose adjustment

The 2020 ESC guidelines strongly recommend LMWH or fondaparinux over UFH for most patients with PE, but UFH remains the anticoagulant of choice for specific situations including high-risk PE with hemodynamic compromise, severe renal impairment, or when rapid reversal potential is needed 2.