How to diagnose and treat suspected pulmonary thromboembolism?

Diagnosis and Treatment of Suspected Pulmonary Embolism

Start weight-adjusted intravenous heparin immediately (80 IU/kg bolus, then 18 IU/kg/hour) in all patients with intermediate or high clinical suspicion of PE while awaiting diagnostic confirmation, and proceed with systemic thrombolysis (rtPA 100 mg over 2 hours) for hemodynamically unstable patients. 1, 2

Initial Clinical Assessment

Assess clinical probability systematically by evaluating three classic presentations and major risk factors 1, 2:

Classic Presentations to Recognize:

• Sudden collapse with elevated jugular venous pressure (faintness/hypotension) 1, 2
• Pulmonary hemorrhage syndrome (pleuritic pain and/or hemoptysis) 1, 2
• Isolated dyspnea without cough, sputum, or chest pain 1, 2

High-Risk Populations Where PE is Easily Missed:

• Elderly patients 1, 2
• Patients with severe pre-existing cardiorespiratory disease 1, 2
• Patients presenting with isolated breathlessness only 1, 2

Key Clinical Features:

• Most patients are breathless and/or tachypneic (respiratory rate >20/min) 1, 2
• PE is rare in patients under age 40 without risk factors 1, 2

Score Clinical Probability (+1 point for each):

Question 1: Are other diagnoses unlikely?

• On clinical grounds 1
• After basic investigations (chest X-ray, ECG, arterial blood gases) 1

Question 2: Is a major risk factor present?

• Recent immobilization or major surgery 1, 2
• Recent lower limb trauma and/or surgery 1, 2
• Clinical deep vein thrombosis 1, 2
• Previous proven DVT or PE 1, 2
• Pregnancy or post-partum 1, 2
• Major medical illness 1, 2

Immediate Anticoagulation

Begin weight-adjusted intravenous heparin immediately in patients with intermediate or high clinical probability (score ≥1) without waiting for diagnostic confirmation 1, 2:

Initial Heparin Dosing:

• Bolus: 80 IU/kg intravenously 1, 2
• Maintenance infusion: 18 IU/kg/hour 1, 2
• Target APTT: 1.5-2.5 times control (45-75 seconds) 1

APTT Monitoring Schedule:

• First check: 4-6 hours after initial bolus 1, 2
• After any dose change: 6-10 hours later 1
• Once therapeutic: Daily 1, 2

Alternative standard dosing (if weight-based unavailable): 5000-10,000 IU bolus, then 1300 IU/hour maintenance 1, 3

Low Molecular Weight Heparin as Alternative:

• Enoxaparin 1 mg/kg subcutaneously every 12 hours 4, 5
• Dalteparin 100 IU anti-Xa/kg subcutaneously twice daily 4
• LMWH appears at least as effective and safe as unfractionated heparin for PE 6, 5
• Advantage: Fixed dosing without APTT monitoring 5

Thrombolytic Therapy for Hemodynamically Unstable Patients

Administer systemic thrombolysis immediately in patients with hypotension or hemodynamic instability 1, 2:

Thrombolytic Regimens:

rtPA (preferred):

• 100 mg intravenously over 2 hours 1, 2
• Lower risk of hypotension and systemic symptoms compared to streptokinase 1
• Alternative bolus dosing: 0.6 mg/kg over 15 minutes (maximum 50 mg) 1

Streptokinase:

• 250,000 units over 20 minutes 1
• Then 100,000 units/hour for 24 hours 1
• Give hydrocortisone concurrently to prevent circulatory instability 1

Urokinase:

• 4400 IU/kg over 10 minutes 1
• Then 4400 IU/kg/hour for 12 hours 1

Important Thrombolysis Considerations:

• Stop heparin before thrombolytic administration 1
• Resume maintenance heparin after thrombolysis completes 1
• Thrombolysis accelerates clot resolution and normalizes pulmonary artery pressure faster than heparin alone 1
• For massive PE, thrombolysis may reduce mortality by approximately one-half (6% vs 13%) 5

Transition to Oral Anticoagulation

Start warfarin between day 1-3 once PE is confirmed 1:

Warfarin Dosing:

• Initial: 5-10 mg daily for 2 days 1
• Subsequent: 1-10 mg daily adjusted to target INR 1
• Target INR: 2.0-3.0 1, 2
• Monitor INR every 1-2 days initially 1

Heparin Discontinuation:

• Continue heparin for minimum 5 days after starting warfarin 1, 2
• Discontinue heparin only when INR ≥2.0 for at least 24 hours 1

Direct Oral Anticoagulants (DOACs) as Alternatives:

Rivaroxaban:

• 15 mg twice daily with food for first 3 weeks 7
• Then 20 mg once daily with food 7
• No need for parenteral overlap 7

Apixaban:

• 10 mg twice daily for 7 days 8
• Then 5 mg twice daily 8
• No need for parenteral overlap 8

Duration of Anticoagulation

Minimum 3 months anticoagulation for all confirmed PE 2, 5:

At 6-12 Week Follow-Up, Determine Duration:

Discontinue anticoagulation if:

• First episode with temporary/reversible risk factors 1, 2

Continue indefinitely if:

• Idiopathic (unprovoked) PE 1, 2
• Recurrent episode 1, 2
• Consider evaluation for thrombophilic disorder and occult cancer 1

Discharge Criteria and Safety Checklist

Ensure all criteria met before discharge 1:

• INR between 2.0-3.0 1
• General practitioner informed of anticoagulant therapy and proposed duration 1
• Patient educated on anticoagulant side effects and drug interactions 1
• Patient has written warfarin information 1
• Anticoagulation monitoring appointment scheduled 1
• Follow-up review at 6-12 weeks arranged 1
• Specialist advice obtained for females on oral contraception 1

Critical Pitfalls to Avoid

• Never delay anticoagulation while awaiting diagnostic confirmation in intermediate/high probability patients 1, 2
• Do not use thrombolysis routinely in hemodynamically stable patients—reserve for hypotension/shock 1, 5
• Avoid premature heparin discontinuation—must overlap with warfarin for minimum 5 days AND achieve therapeutic INR 1
• Monitor for heparin-induced thrombocytopenia if heparin continued beyond 5 days 1
• Recognize that PE is easily missed in elderly patients and those with isolated dyspnea 1, 2