Synopsis
Move from a non-specific presentation to a defensible pulmonary embolism diagnosis using clinical probability, D-dimer and the right imaging test without delaying treatment in an unstable patient.
- Think PE with otherwise unexplained acute dyspnoea, pleuritic chest pain, haemoptysis, syncope, tachycardia, hypoxaemia or signs of DVT; none is diagnostic in isolation.
- First assess physiological stability and plausible alternatives. Obtain chest radiography to look for another cause, but a normal film neither proves nor excludes PE.
- When overall clinical suspicion is low and another diagnosis is feasible, NICE says the 8-item PERC rule may be considered to decide whether further PE investigation is needed; do not use PERC in moderate or high suspicion.
Key red flags
Cardiac arrest, obstructive shock, persistent systolic hypotension, rising lactate, altered consciousness or rapidly escalating oxygen need suggests high-risk PE or another immediately reversible cause.
Investigation priorities
Identify instability and competing emergencies before probability scoring.
Management branches
The clinician judges overall PE probability low and another diagnosis is feasible.
- Confirm the patient is stable and that PE is not moderate/high probability by gestalt.
- Consider all 8 PERC items. If every item is negative, further PE testing may be unnecessary under NICE NG158.
Key medicines
Interim therapeutic enoxaparin (example parenteral option)1 mg/kg subcutaneously every 12 hours is a common treatment regimen for symptomatic PE; use actual product strength and adjust/choose an alternative for severe renal impairment.
Controlled oxygenTitrate to SpO2 94–98% for most acutely ill adults, or 88–92% if at risk of hypercapnic respiratory failure pending blood gases.