What is the immediate treatment for a patient with pulmonary embolism?

Immediate Treatment of Pulmonary Embolism

Begin anticoagulation with unfractionated heparin (UFH) or low molecular weight heparin (LMWH) immediately upon suspicion of PE, even before diagnostic confirmation is complete, unless absolute contraindications exist. 1, 2

Risk Stratification Determines Treatment Intensity

The immediate management pathway depends critically on hemodynamic status at presentation:

High-Risk PE (Hemodynamically Unstable)

For patients presenting with hypotension, shock, or cardiac arrest, systemic thrombolytic therapy is the standard of care and should be administered immediately. 1, 3, 2

• Initiate UFH with weight-adjusted bolus (80 IU/kg) followed by continuous infusion (18 IU/kg/hour) without delay 1
• Administer systemic thrombolysis concurrently: rtPA 100 mg over 2 hours, or streptokinase 250,000 units over 20 minutes followed by 100,000 units/hour for 24 hours 1
• Stop heparin before thrombolysis, then resume maintenance dosing afterward 1
• Provide supplemental oxygen for SaO2 <90%, escalating from conventional oxygen to high-flow nasal cannula to non-invasive ventilation as needed 3
• Use vasopressors (norepinephrine and/or dobutamine) to maintain blood pressure, but avoid aggressive fluid challenges which worsen right ventricular failure 1, 3, 2
• If thrombolysis is contraindicated or fails, proceed immediately to surgical pulmonary embolectomy 1, 2
• Consider percutaneous catheter-directed treatment as an alternative to surgery when thrombolysis fails 1

Intermediate-Risk and Low-Risk PE (Hemodynamically Stable)

For stable patients, anticoagulation alone is sufficient initial therapy—thrombolysis is not routinely indicated. 1, 2

• Prefer LMWH or fondaparinux over UFH for most stable patients 1, 2
• LMWH dosing does not require monitoring in most cases, unlike UFH which requires APTT monitoring every 4-6 hours initially 1
• UFH target: APTT 1.5-2.5 times control (45-75 seconds), corresponding to anti-Xa activity 0.3-0.6 IU/mL 1
• Provide supplemental oxygen if SaO2 <90% 3
• Monitor closely for hemodynamic deterioration—if this occurs despite anticoagulation, escalate immediately to rescue thrombolytic therapy 3, 2

Transition to Oral Anticoagulation

Begin oral anticoagulation early, overlapping with parenteral therapy:

• Direct oral anticoagulants (DOACs) such as rivaroxaban or apixaban are preferred over warfarin in eligible patients 2, 4
• Rivaroxaban dosing for PE: 15 mg twice daily with food for 21 days, then 20 mg once daily 4
• If using warfarin, start 5-10 mg daily for 2 days, overlap with heparin for at least 5 days, and discontinue heparin only when INR ≥2.0 for 24 hours 1
• Target INR for warfarin: 2.0-3.0 1

Critical Pitfalls to Avoid

• Never delay anticoagulation while awaiting diagnostic imaging in patients with high clinical probability of PE 1, 2
• Never use aggressive fluid boluses in PE patients with right ventricular dysfunction—this worsens hemodynamics and can precipitate cardiovascular collapse 3, 2
• Never delay thrombolysis in hemodynamically unstable patients while attempting other interventions—this increases mortality 3
• Never achieve subtherapeutic anticoagulation in the first 24 hours—failure to reach therapeutic APTT (>1.5 times control) is associated with 25% risk of recurrent thromboembolism 1, 5
• Never use DOACs in patients with severe renal impairment (CrCl <30 mL/min for rivaroxaban) or antiphospholipid antibody syndrome 2, 4
• Never use invasive mechanical ventilation as first-line for hypoxemia—positive pressure ventilation worsens right ventricular failure 3
• Never routinely place IVC filters—these are only indicated when anticoagulation is absolutely contraindicated 2

Special Considerations

• In pregnancy, use therapeutic LMWH based on early pregnancy weight—never use DOACs or warfarin 2
• Consider refractory hypoxemia from right-to-left shunting through patent foramen ovale as a cause of persistent desaturation despite oxygen therapy 3
• For patients requiring intubation, use lung-protective ventilation (6 mL/kg tidal volume, plateau pressure <30 cm H2O) and avoid hypotension-inducing anesthetic agents 3