Immediate Treatment for Suspected Pulmonary Embolism
Start weight-adjusted intravenous heparin immediately upon clinical suspicion in patients with high or intermediate probability, before diagnostic confirmation, using an initial bolus of 80 IU/kg followed by continuous infusion of 18 IU/kg/hour. 1, 2
Initial Clinical Assessment
When evaluating a patient with suspected PE and risk factors (recent immobility, cancer, or DVT history), recognize that:
- Predisposing factors are present in 80-90% of PE cases, with the most common being immobilization >1 week, previous venous thromboembolism, recent surgery, and lower limb fractures or surgery 3
- Record respiratory rate immediately - PE is rare in the absence of all three: tachypnea (>20/min), pleuritic pain, and arterial hypoxemia 3
- Obtain chest radiography, ECG, and arterial blood gas measurements in all suspected cases 3, 1
Immediate Anticoagulation Protocol
For Hemodynamically Stable Patients
Begin IV heparin without waiting for diagnostic confirmation if clinical probability is high or intermediate 3, 1:
- Initial bolus: 80 IU/kg (or standard dose 5,000-10,000 IU) 3, 1, 2
- Maintenance infusion: 18 IU/kg/hour (or standard 1,300 IU/hour) 3, 1, 2
- Target aPTT: 1.5-2.5 times control (45-75 seconds) 3, 2
aPTT Monitoring Schedule
- First check: 4-6 hours after initial bolus 3, 1
- After dose adjustments: 6-10 hours later 3
- Once therapeutic: Daily monitoring 3, 1
For Hemodynamically Unstable Patients
Administer systemic thrombolysis immediately if systemic hypotension or hemodynamic instability is present 3, 1:
Thrombolytic regimens (stop heparin before administration) 3:
- rtPA: 100 mg over 2 hours 3, 1
- Streptokinase: 250,000 units over 20 minutes, then 100,000 units/hour for 24 hours (plus hydrocortisone to prevent circulatory instability) 3
- Urokinase: 4,400 IU/kg over 10 minutes, then 4,400 IU/kg/hour for 12 hours 3
Diagnostic Workup (Concurrent with Treatment)
- Perform lung scanning within 24 hours of clinical suspicion 3
- Consider leg vein imaging as first-line in patients with previous PE, clinical DVT, or chronic cardiorespiratory disease 3
- Normal D-dimer excludes PE if laboratory offers reliable testing 3
Critical Pitfalls to Avoid
Do not delay anticoagulation waiting for imaging - heparin should be started based on clinical suspicion alone in high/intermediate probability cases 3, 1. The British Thoracic Society explicitly recommends this approach given that untreated PE historically carried 25-35% mortality 3.
Recognize that cancer patients with PE warrant special attention - they have higher rates of concomitant DVT (20.9%) and increased VTE recurrence risk 4. Consider lower extremity imaging even with confirmed PE 4.
Weight-adjusted dosing is superior to standard dosing for achieving therapeutic anticoagulation rapidly 1, 2.
Transition to Oral Anticoagulation
- Start warfarin 5-10 mg daily for 2 days once heparin is therapeutic 3
- Target INR: 2.0-3.0 3
- Discontinue heparin after 5 days if INR ≥2.0 3
- Minimum anticoagulation duration: 3 months 1, 5
For first episode with temporary risk factors, anticoagulation may be discontinued after 3 months; for idiopathic or recurrent PE, consider indefinite anticoagulation 3, 1.