Initial Treatment for Suspected Pulmonary Embolism
For patients with suspected pulmonary embolism and high-risk factors (recent surgery, cancer, or history of DVT), immediately initiate weight-adjusted intravenous heparin with an 80 IU/kg bolus followed by 18 IU/kg/hour continuous infusion before diagnostic confirmation, targeting an aPTT of 1.5-2.5 times control. 1, 2
Immediate Anticoagulation Protocol
Start anticoagulation based on clinical suspicion alone—do not wait for diagnostic confirmation. 1, 2
Standard IV Heparin Dosing:
- Initial bolus: 80 IU/kg (or 5,000-10,000 IU if weight-based dosing unavailable) 1, 2
- Maintenance infusion: 18 IU/kg/hour (or 1,300 IU/hour) 1, 2
- Target aPTT: 1.5-2.5 times control (45-75 seconds) 1, 3
aPTT Monitoring Schedule:
- First check: 4-6 hours after initial bolus 1, 2
- After dose adjustments: 6-10 hours later 1
- Once therapeutic: Daily monitoring 1, 2
Risk Stratification and Treatment Escalation
Hemodynamically Stable Patients:
Continue standard heparin as above while pursuing diagnostic confirmation with chest imaging within 24 hours. 1, 2
Hemodynamically Unstable Patients (Systolic BP <90 mmHg):
Thrombolytic therapy is mandatory for patients with hypotension or shock. 1, 3
Preferred thrombolytic regimen—rtPA: 3
Stop heparin before initiating thrombolysis. 1, 3
After thrombolysis completion, resume heparin at maintenance dose (1,280 IU/hour or 18 IU/kg/hour) once aPTT falls below twice the upper limit of normal. 3
Alternative thrombolytic agents if rtPA unavailable: 1, 3
- Streptokinase: 250,000 units over 20 minutes, then 100,000 units/hour for 24 hours (must give hydrocortisone concurrently to prevent circulatory instability) 1, 3
- Urokinase: 4,400 IU/kg over 10 minutes, then 4,400 IU/kg/hour for 12 hours 1
Critical Risk Factors Requiring Immediate Action
Your patient population with recent surgery, cancer, or prior DVT represents the highest-risk group—these factors are present in 80-90% of PE patients. 1
Major risk factors that mandate immediate heparin initiation: 1, 2
- Recent immobilization >1 week
- Recent major surgery (particularly orthopedic, abdominal, or thoracic)
- Active malignancy
- Previous documented DVT or PE
- Recent lower limb trauma or surgery
Transition to Oral Anticoagulation
Begin warfarin 5-10 mg daily on day 1 of heparin therapy. 1
Continue heparin for minimum 5 days AND until INR ≥2.0 for 24 hours. 1
Target INR: 2.0-3.0 1
Minimum anticoagulation duration: 3 months 2, 4, 5
For patients with cancer or recurrent PE, consider indefinite anticoagulation with low-molecular-weight heparin rather than warfarin. 4
Common Pitfalls to Avoid
Do not delay anticoagulation waiting for imaging. The mortality benefit of immediate treatment far outweighs bleeding risk in high-probability patients. 1, 2
Do not use inferior vena cava filters in patients who can receive anticoagulation. Filters are reserved only for patients with absolute contraindications to anticoagulation or recurrent PE despite adequate anticoagulation. 1
Do not assume heparin prophylaxis prevents fatal PE. In one series of lung resection patients, 17 of 23 fatal PE cases occurred despite prophylactic heparin. 6 Therapeutic anticoagulation is required for suspected PE.
Monitor platelet counts. If platelets fall below 100,000/mm³, discontinue heparin immediately due to heparin-induced thrombocytopenia risk. 7