Synopsis
Recognise high-risk PE from haemodynamic instability and deliver resuscitation, anticoagulation and time-critical reperfusion while avoiding delays caused by routine stable-PE workflows.
- Prefer the term high-risk PE: risk is defined by haemodynamic instability, not by 'saddle' position or clot size on CT.
- Recognise cardiac arrest, obstructive shock or persistent hypotension (commonly systolic BP below 90 mmHg or a fall of at least 40 mmHg for more than 15 minutes not explained by another cause).
- Start ABCDE/ALS, controlled oxygen, monitoring, IV/IO access and immediate critical-care/PE-team input; treat competing reversible causes in parallel.
Key red flags
PE commonly presents with pulseless electrical activity; very low ETCO2 despite a confirmed airway, appropriate ventilation and high-quality compressions may support but does not prove the diagnosis.
Investigation priorities
Track shock and detect peri-arrest deterioration.
Management branches
Obstructive shock or persistent hypotension with PE confirmed or overwhelmingly likely.
- Start ABCDE, controlled oxygen, continuous monitoring, 2 IV/IO lines and immediate critical-care/PE-team activation. Take reperfusion bloods without delaying treatment.
- Use cautious 250–500 mL crystalloid only if clinically underfilled and reassess; avoid repeated large boluses that distend the failing RV. Start vasoactive support in critical care when hypotension persists.
Normotensive PE with RV dysfunction and/or myocardial injury but no shock.
Key medicines
Alteplase for massive PEBody weight at least 65 kg: 10 mg IV over 1–2 minutes, then 90 mg by IV infusion over 2 hours (total 100 mg). Below 65 kg: total dose must not exceed 1.5 mg/kg; follow the current Actilyse PE dosing table.
Unfractionated heparinRCUK 2025 gives 80 units/kg IV during the diagnostic process unless bleeding or an absolute contraindication is present; continue with a specialist-prescribed IV infusion titrated to the service's APTT or anti-Xa target rather than an unmonitored fixed rate.