What is the initial treatment for an inpatient with acute pulmonary embolism?

Initial Treatment for Acute Pulmonary Embolism in Inpatients

Immediately initiate weight-based intravenous unfractionated heparin with an 80 U/kg bolus followed by 18 U/kg/hour continuous infusion as soon as PE is suspected—do not wait for diagnostic confirmation in patients with intermediate or high clinical probability. 1, 2

Immediate Anticoagulation Protocol

First-Line: Weight-Based Unfractionated Heparin (UFH)

• Initial bolus: 80 U/kg IV push 1, 2
• Continuous infusion: 18 U/kg/hour 1, 2
• Target aPTT: 1.5-2.5 times control (45-75 seconds or 46-70 seconds depending on laboratory calibration) 3, 1, 2
• Critical timing: Start heparin immediately when PE is suspected—untreated PE carries high mortality risk and subtherapeutic anticoagulation in the first 24 hours increases recurrence rates 1

aPTT Monitoring and Dose Adjustments

• First aPTT check: 4-6 hours after initiating infusion 3, 1
• After dose changes: 6-10 hours later 3
• Once therapeutic: Daily monitoring 3

Adjustment nomogram: 1

• aPTT <35 seconds (<1.2× control): Give 80 U/kg bolus; increase infusion by 4 U/kg/h
• aPTT 35-45 seconds (1.2-1.5× control): Give 40 U/kg bolus; increase infusion by 2 U/kg/h
• aPTT 46-70 seconds (1.5-2.3× control): No change—therapeutic range
• aPTT 71-90 seconds (2.3-3.0× control): Decrease infusion by 2 U/kg/h
• aPTT >90 seconds (>3.0× control): Stop infusion for 1 hour, then decrease by 3 U/kg/h

Alternative Anticoagulation Options for Hemodynamically Stable Patients

For stable patients without massive PE, low molecular weight heparin (LMWH) or fondaparinux are acceptable alternatives: 1

• Enoxaparin: 1.0 mg/kg subcutaneously every 12 hours OR 1.5 mg/kg once daily 1
• Tinzaparin: 175 U/kg subcutaneously once daily 1
• Fondaparinux: Weight-adjusted dosing 1, 4
  • 5 mg if <50 kg
  • 7.5 mg if 50-100 kg
  • 10 mg if >100 kg
  • Given subcutaneously once daily

Thrombolytic Therapy for High-Risk PE

For hemodynamically unstable patients (sudden collapse with raised jugular venous pressure, hypotension, or shock), administer thrombolytic therapy immediately: 3, 2

Thrombolysis Regimens

• rtPA: 100 mg IV over 2 hours 3
• Streptokinase: 250,000 units IV over 20 minutes, then 100,000 units/hour for 24 hours (plus hydrocortisone to prevent circulatory instability) 3
• Urokinase: 4,400 IU/kg IV over 10 minutes, then 4,400 IU/kg/hour for 12 hours 3

Critical instruction: Stop heparin before thrombolysis; resume at maintenance dose after completion 3

Transition to Oral Anticoagulation

Warfarin Initiation

• Start warfarin simultaneously with heparin on day 1 of treatment 1, 2
• Initial dose: 5-10 mg daily for first 2 days 3, 2, 5
• Target INR: 2.0-3.0 throughout treatment 3, 1, 2, 5
• INR monitoring: Every 1-2 days initially until stable in therapeutic range 3, 5

Heparin Discontinuation Criteria

Continue heparin for at least 5 days AND until INR ≥2.0 for at least 24 hours on two consecutive measurements: 1, 2

This dual therapy period is essential—discontinuing heparin before adequate oral anticoagulation creates a dangerous gap in anticoagulation. 1

Risk Stratification and Supportive Care

Immediate Bedside Assessment

• Perform bedside transthoracic echocardiography in hemodynamically unstable patients to assess for right ventricular strain and differentiate PE from other acute conditions 2
• Administer supplemental oxygen to maintain adequate saturation 2
• Consider diuretics for pulmonary congestion and volume overload 2

Contraindications to Anticoagulation

• If anticoagulation is contraindicated, consider inferior vena cava filter placement 2

Critical Pitfalls to Avoid

1. Never use fixed-dose heparin without weight adjustment—this leads to delayed achievement of therapeutic anticoagulation and increased recurrence rates 1

2. Never delay heparin while awaiting diagnostic tests in patients with suspected PE—early therapeutic anticoagulation prevents recurrent thromboembolism 1, 2

3. Never stop heparin before INR is therapeutic for 24 hours—this creates a gap in anticoagulation 1, 2

4. Avoid subcutaneous heparin in massive PE—use continuous IV infusion for predictable anticoagulation 1

5. Do not miss PE in high-risk populations: elderly patients, those with severe cardiorespiratory disease, or patients presenting with isolated dyspnea without cough, sputum, or chest pain 3, 2

6. Avoid beta-blockers or calcium channel blockers in patients with frank cardiac failure 2

Laboratory Considerations

• aPTT reagents vary between laboratories—each facility should calibrate their aPTT range to correspond to anti-Xa activity of 0.3-0.6 IU/mL 1
• In cases of heparin resistance (aPTT not responding to appropriate doses), measure anti-Xa levels directly 1