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Pulmonary embolism

Emergencies

Unstable (shock or hypotension): think massive PE — senior now and consider thrombolysis.

Stable: Wells score decides between CTPA now and D-dimer first. Anticoagulate while waiting if imaging is delayed.

Act now

  1. 1

    Oxygen to target; IV access.

  2. 2

    Haemodynamically unstable: senior and critical care now; consider thrombolysis.

  3. 3

    Stable: calculate the 2-level Wells score.

Assess

  • ABCDE: SpO₂, RR, HR, BP; signs of DVT.
  • Risk factors: surgery, immobility, cancer, previous VTE, pregnancy, oestrogen.
  • Bleeding risk before anticoagulation.

Investigations

  • Wells over 4 (PE likely): CTPA; interim anticoagulation if it can't happen promptly.
  • Wells 4 or less: D-dimer; if positive, CTPA.
  • CTPA unsuitable (e.g. renal impairment, contrast allergy): V/Q scan.
  • ECG, CXR, FBC, U&E, LFT, clotting before anticoagulation.

Manage

  • First choice: apixaban or rivaroxaban.
  • If unsuitable: LMWH for at least 5 days then dabigatran or edoxaban, or LMWH with warfarin for at least 5 days and until INR is 2 or more for 24 hours.
  • Severe renal impairment (CrCl under 15) or established renal failure: LMWH or unfractionated heparin with specialist advice.
  • Low-risk patients can often be managed as outpatients.

Escalate when

  • Hypotension, signs of right ventricular strain with deterioration, or cardiac arrest: senior, critical care and the local PE team.

Doses and prescribing

Apixaban

10 mg oral twice daily for 7 days, then 5 mg twice daily.

Rivaroxaban

15 mg oral twice daily for 21 days, then 20 mg once daily with food.

Alteplase

10 mg IV over 1–2 minutes, then 90 mg over 2 hours (max 1.5 mg/kg if under 65 kg) for massive PE — senior decision.

Check the BNF and your local formulary before prescribing.

Written to current guidance (NICE NG158) · sources checked 14 Nov 2026. We watch NICE for updates weekly.

Sources (2)

Reviewed by Aboodee Alhasso, MPharm MRCPharm IP on 14 Nov 2026

Calculators for this

For healthcare professionals, as an aid to clinical judgement — not a substitute for it. Follow your local policy and ask a senior when in doubt.