What is the recommended immediate treatment for pulmonary embolism?

Immediate Treatment of Pulmonary Embolism

Begin therapeutic anticoagulation immediately upon suspicion of PE—do not wait for imaging confirmation when clinical probability is intermediate or high. 1, 2

Risk-Based Treatment Algorithm

The immediate treatment of PE is determined by hemodynamic status, which stratifies patients into high-risk (shock/hypotension), intermediate-risk (stable with RV dysfunction), or low-risk (stable without RV dysfunction) categories. 1

High-Risk PE (Shock or Persistent Hypotension)

Systemic thrombolysis is the first-line treatment for high-risk PE unless absolutely contraindicated. 3, 1, 2

Immediate Actions:

• Start unfractionated heparin (UFH) immediately with weight-adjusted dosing: 80 U/kg IV bolus followed by 18 U/kg/h continuous infusion, targeting aPTT 1.5–2.5 times control. 3, 1, 2
• Administer systemic thrombolysis with alteplase 100 mg IV over 90 minutes for hemodynamically unstable patients not in cardiac arrest. 2
• For cardiac arrest with confirmed massive PE, give alteplase 50 mg IV bolus. 2
• Provide oxygen to correct hypoxemia. 1
• Use vasopressors (norepinephrine and/or dobutamine) for hypotension—avoid aggressive fluid boluses as they worsen right ventricular failure. 1, 2

Alternative Reperfusion:

• Surgical pulmonary embolectomy is indicated when thrombolysis is contraindicated or has failed. 3, 1, 2
• Catheter-directed therapy may be considered when systemic thrombolysis is contraindicated, has failed, or experienced interventional expertise is available. 2

Common Pitfall: Do not withhold thrombolysis due to relative contraindications when the patient faces imminent mortality—untreated high-risk PE carries ~50% 90-day mortality. 2

Intermediate-Risk PE (Stable with RV Dysfunction)

Anticoagulation alone is the standard treatment—routine thrombolysis is NOT recommended. 1, 2

Immediate Actions:

• Initiate LMWH or fondaparinux (preferred over UFH) for hemodynamically stable patients. 3, 1
• Example dosing: enoxaparin 1 mg/kg SC every 12 hours. 2
• Reserve rescue thrombolysis only for patients who develop hemodynamic deterioration during anticoagulation. 1, 2
• Ensure close monitoring in an appropriate care setting. 2

Low-Risk PE (Stable, No RV Dysfunction)

LMWH or fondaparinux is preferred over UFH for initial anticoagulation. 3, 1

Immediate Actions:

• Start LMWH (e.g., enoxaparin 1 mg/kg SC q12h) or fondaparinux (weight-based dosing) immediately. 3, 2
• Early discharge and outpatient management are acceptable when no medical or social contraindications exist. 1, 2

Anticoagulation Dosing Details

Unfractionated Heparin (for high-risk PE or severe renal impairment):

• Initial bolus: 80 U/kg IV (or fixed dose 5,000–10,000 units). 3, 1
• Continuous infusion: 18 U/kg/h. 3, 1
• Adjust based on aPTT measured 4–6 hours after initiation: 3

aPTT Result	Adjustment
<35 s (<1.2× control)	80 U/kg bolus; increase infusion by 4 U/kg/h
35–45 s (1.2–1.5× control)	40 U/kg bolus; increase infusion by 2 U/kg/h
46–70 s (1.5–2.3× control)	No change
71–90 s (2.3–3.0× control)	Decrease infusion by 2 U/kg/h
>90 s (>3.0× control)	Stop infusion 1 hour; decrease by 3 U/kg/h

Common Pitfall: Subtherapeutic anticoagulation in the first 24 hours increases recurrence risk—use weight-based nomograms to achieve therapeutic levels rapidly. 3

Transition to Long-Term Anticoagulation

• Direct oral anticoagulants (DOACs) are preferred over warfarin for eligible patients (apixaban, rivaroxaban, edoxaban, dabigatran). 1, 2, 4
• Do NOT use DOACs in severe renal impairment, pregnancy/lactation, antiphospholipid antibody syndrome, or mechanical heart valves. 1, 2
• If warfarin is used, overlap with parenteral anticoagulation for at least 5 days and until INR ≥2.0 on two consecutive days, targeting INR 2.5 (range 2.0–3.0). 2

Duration of Anticoagulation

Clinical Scenario	Minimum Duration
Provoked PE (surgery, trauma)	3 months, then stop [2]
First unprovoked PE	≥3 months; strongly consider indefinite therapy [2]
Recurrent VTE	Indefinite [2]
Cancer-associated PE	≥6 months with LMWH preferred; continue while cancer active [2]

Re-evaluate at 3–6 months to balance bleeding versus recurrence risk. 2

Special Considerations

IVC Filters:

• Reserved for absolute contraindication to anticoagulation or recurrent PE despite therapeutic anticoagulation. 1, 2
• Routine filter use is NOT recommended. 1, 2

Severe Renal Impairment:

• Use UFH instead of LMWH or fondaparinux. 1, 5
• Avoid DOACs. 1, 2

Critical Pitfall: Do not delay anticoagulation while awaiting imaging in high-probability patients—empirical treatment saves lives. 2, 6