## First-Line Anticoagulation in Haemodynamically Stable PE **Key Point:** Low-molecular-weight heparin (LMWH) is the preferred initial anticoagulant for haemodynamically stable PE in most clinical settings, including outpatient management. ### Rationale for LMWH 1. **Predictable pharmacokinetics** — Once-daily or twice-daily dosing based on weight; no monitoring required 2. **Subcutaneous administration** — Can be given as outpatient therapy 3. **Superior efficacy** — Non-inferior or superior to UFH in preventing recurrent thromboembolism [cite:Harrison 21e Ch 297] 4. **Reduced HIT risk** — Lower incidence of heparin-induced thrombocytopenia (HIT) vs UFH 5. **Cost-effective** — Especially for outpatient PE management ### When UFH is Preferred Over LMWH | Clinical Scenario | Reason | | --- | --- | | Haemodynamic instability / shock | Shorter half-life; reversible with protamine | | Severe renal impairment (CrCl < 30 mL/min) | LMWH cleared renally; UFH hepatically metabolised | | Massive PE requiring thrombolysis | UFH allows rapid reversal if bleeding occurs | | Pregnancy | Both acceptable; UFH preferred in first trimester | **High-Yield:** LMWH is the standard of care for outpatient and inpatient stable PE; UFH reserved for haemodynamic instability, renal failure, or imminent need for invasive procedures. ### Transition to Oral Anticoagulation LMWH or UFH is continued for minimum 5 days, then transitioned to: - **Warfarin** (target INR 2–3) — requires 5-day overlap with parenteral anticoagulant - **DOAC** (apixaban, rivaroxaban, dabigatran, edoxaban) — direct oral anticoagulants, increasingly preferred for long-term PE management **Clinical Pearl:** In this stable patient, LMWH allows early discharge and outpatient follow-up, reducing hospital stay and cost while maintaining efficacy.
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