Initial Treatment for Pulmonary Embolism
The initial treatment for a patient diagnosed with pulmonary embolism should be immediate anticoagulation, preferably with low molecular weight heparin (LMWH), fondaparinux, or direct oral anticoagulants (DOACs) such as apixaban or rivaroxaban, with treatment approach determined by risk stratification. 1
Risk Stratification
Risk assessment is crucial for determining the appropriate treatment approach:
High-Risk PE (with hemodynamic instability)
- Characterized by shock or hypotension
- Requires immediate intravenous unfractionated heparin (UFH)
- Initial bolus: 80 IU/kg followed by infusion at 18 IU/kg/hour 1
- Consider systemic thrombolysis if no contraindications exist 2, 1
Non-High-Risk PE (hemodynamically stable)
- Intermediate-risk: Evidence of right ventricular dysfunction (RVD) and/or myocardial injury
- Low-risk: No evidence of RVD or myocardial injury
- Treatment options:
- LMWH
- Fondaparinux
- Direct initiation of DOACs (apixaban or rivaroxaban) 1
Anticoagulation Protocols
Unfractionated Heparin (UFH)
- Initial dose: 80 IU/kg bolus followed by 18 IU/kg/hour infusion 1
- Alternative dosing: 5,000-10,000 IU bolus followed by 1,300 IU/hour 2
- Adjust to maintain APTT at 1.5-2.5 times control (45-75 seconds) 2
- APTT monitoring:
- 4-6 hours after initial bolus
- 6-10 hours after any dose change
- Daily when in therapeutic range 2
Low Molecular Weight Heparin (LMWH)
- Preferred for most non-high-risk PE patients
- Weight-adjusted dosing
- No routine monitoring required
- Preferred in cancer patients 1
Direct Oral Anticoagulants (DOACs)
- Apixaban: 10 mg twice daily for 7 days, followed by 5 mg twice daily 1
- Rivaroxaban: Can be initiated without prior parenteral anticoagulation
- Not recommended for patients with hemodynamic instability who may require thrombolysis or pulmonary embolectomy 3
Vitamin K Antagonists (Warfarin)
- Initial dose: 5-10 mg daily for 2 days, then adjusted to maintain INR 2.0-3.0 2
- Start concurrently with parenteral anticoagulation
- Continue parenteral anticoagulation until INR ≥2.0 for at least 24 hours 1
- Discontinue heparin 5 days after starting warfarin if INR at least 2.0 2
Thrombolytic Therapy
Indications
- High-risk PE with hemodynamic instability 2, 1
- May be considered in selected intermediate-risk PE patients without elevated bleeding risk 2
Agents and Dosing
- Alteplase (rtPA): 100 mg over 2 hours 1
- Streptokinase: 250,000 units over 20 minutes, then 100,000 units/hour for 24 hours 2
- Urokinase: 4,400 IU/kg over 10 minutes, then 4,400 IU/kg/hour for 12 hours 2
Contraindications
- Hemorrhagic stroke (any time)
- Ischemic stroke within 6 months
- Central nervous system damage or neoplasms
- Recent major trauma/surgery/head injury
- GI bleeding within the last month
- Known active bleeding 1
Special Populations
Pregnancy
- LMWH is the treatment of choice
- DOACs and warfarin are contraindicated due to teratogenicity 1
Cancer
- LMWH preferred over VKAs or DOACs for at least 6 months
- Continue treatment while cancer is active 1
Severe Renal Insufficiency
- Avoid DOACs
- Consider UFH with careful monitoring 1
Common Pitfalls and Caveats
- Delayed anticoagulation: Initiate treatment immediately upon diagnosis to prevent mortality
- Inadequate dosing: Ensure proper weight-based dosing of anticoagulants
- Premature discontinuation of parenteral anticoagulation: Continue until oral anticoagulation is therapeutic
- Failure to risk stratify: High-risk patients require more aggressive treatment approaches
- Inappropriate use of DOACs: Avoid in hemodynamically unstable patients who may require thrombolysis 3
- Overlooking PE in certain populations: PE is easily missed in elderly patients, those with severe cardiorespiratory disease, or when breathlessness is the only symptom 2
By following this structured approach to the initial management of pulmonary embolism, clinicians can optimize outcomes and reduce the risk of complications and mortality.