Medic Basics

Shock and circulation

Massive Pulmonary Embolism Algorithm

PE with shock or arrest: support the RV, then reperfuse

Reviewed by Alex G, BSN, RN, CEN, CCRN, CMC, NREMT-P · From the Reference tab of the app

Each step lists what to do, then the choices that lead on. In the app the algorithm is tapped through one decision at a time.

1 Call for help: shock or arrest?

  • Call the rapid response or code team and page the PE response team (PERT); without one, ICU, cardiology and cardiac surgery
  • Monitor and defibrillator pads on; oxygen for SpO₂ 90% or more, high-flow nasal oxygen rather than intubation
  • Two large-bore IVs; arterial line at a compressible site (radial) if it does not delay treatment
  • Type and screen, CBC, coagulation, fibrinogen, creatinine, troponin, BNP, lactate, blood gas

Cardiac arrest → step 2Shock: SBP under 90 (or a fall of 40 or more) for 15 minutes, or a pressor needed → step 3No hypotension → step 4

2 Cardiac arrest from PE

  • High-quality CPR and ACLS; PEA and asystole are the usual rhythms
  • Confirmed PE: lysis, surgical or catheter embolectomy are reasonable (2a); suspected PE: lysis may be considered (2b, AHA 2025)
  • Lytic per local protocol (no guideline dose): often alteplase 50 mg IV push, repeated once after 15 minutes without ROSC; tenecteplase is one push by STEMI weight bands
  • After a lytic, continue CPR for at least 60–90 minutes before stopping (ESC 2019, ERC 2025)
  • ECPR candidate: call the ECMO team now and place a mechanical CPR device

ROSC → step 5No ROSC: ECPR available → step 6

3 Heparin and RV support; safe to go to CT?

  • Not yet anticoagulated: UFH 80 units/kg IV bolus, then 18 units/kg/h, before imaging unless bleeding (ESC 2019, ERC 2025); AHA/ACC 2026 prefers LMWH unless ECMO is likely
  • Norepinephrine first, titrated to MAP 65 or more; a peripheral start is acceptable
  • Fluid only if not volume loaded (small collapsing IVC, low CVP): 250–500 mL over 15–30 minutes, then reassess
  • Low cardiac output once MAP holds: add dobutamine 2.5–5 mcg/kg/min

Stable enough to travel to CT → step 7Too unstable for CT, or CT not available → step 8Breathing failing: intubation unavoidable → step 9

4 No hypotension yet: anticoagulate and watch

  • Anticoagulate: LMWH is preferred, even if lysis or a catheter procedure may follow (AHA/ACC 2026, class 1); ESC 2019 keeps UFH for imminent instability or CrCl 30 or less
  • PERT review (categories C–D): high severity score, RV strain on CT or echo, high troponin or BNP
  • Syncope, brief hypotension or normotensive shock (high lactate, AKI) is category D: advanced therapy can be considered (2b)
  • ICU or step-down bed; reassess HR, BP, SpO₂, mentation, lactate and urine output often

SBP under 90 or a pressor needed → step 3Cardiac arrest → step 2

5 After reperfusion: ICU care

  • Trend MAP, heart rate, lactate and urine output; echo for RV recovery
  • Bleeding watch for 24 hours: puncture sites, hemoglobin, fibrinogen, neuro checks
  • Anticoagulation per the team: LMWH, then a DOAC once stable and no procedure is planned (AHA/ACC 2026)
  • IVC filter only if anticoagulation is impossible; follow up for chronic thromboembolic disease

End of this path.

6 VA-ECMO for refractory shock or arrest

  • Refractory shock (category E2) or arrest: VA-ECMO is reasonable where available (2a, AHA/ACC 2026 and AHA 2025)
  • Call the ECMO team early; compressions continue until flow starts (mechanical CPR frees the groins)
  • ECMO buys time: the PERT then chooses catheter or surgical clot removal, or anticoagulation alone
  • Right radial arterial line; heparin per the ECMO team

End of this path.

7 CT pulmonary angiography: is it PE?

  • Travel with a critical care nurse, pressor running, push-dose epinephrine, airway kit and defibrillator
  • An RV:LV diameter ratio of 1 or more on CT means RV strain

PE confirmed → step 10No PE → step 11

8 Bedside echo: is the RV dilated and failing?

  • Signs: RV larger than the LV, D-shaped septum, McConnell sign, clot in transit in the right heart
  • Leg compression ultrasound: a DVT plus RV failure supports PE
  • In shock with suspected PE, RV failure on echo justifies reperfusion without CT (ESC 2019)

RV dilated and failing → step 10RV not dilated: PE is unlikely to be the cause → step 11

9 If intubation cannot be avoided

  • Most experienced operator; PERT and ECMO team told first; CPR and the code cart ready
  • Norepinephrine running and push-dose epinephrine drawn up before induction
  • Reduced-dose induction: etomidate 0.15–0.2 mg/kg or ketamine 0.5–1 mg/kg, with rocuronium 1–1.2 mg/kg
  • Preoxygenate with HFNC or NIV; after the tube: tidal volume 6 mL/kg, low PEEP (about 5), a rate that prevents hypercapnia
  • Inhaled nitric oxide or epoprostenol if available

Stable enough for CT → step 7Too unstable for CT → step 8

10 Can the patient have systemic thrombolysis?

  • Absolute (ESC 2019): any brain bleed or stroke of unknown cause, ischemic stroke within 6 months, brain tumor
  • Also absolute: major trauma, surgery or head injury within 3 weeks; active bleeding; a bleeding disorder
  • Relative: TIA within 6 months, oral anticoagulant, pregnancy or first week postpartum, noncompressible puncture, traumatic CPR
  • Also relative: SBP over 180, advanced liver disease, infective endocarditis, active peptic ulcer

No contraindication: systemic lysis → step 12Contraindicated, high bleeding risk, or the PERT prefers a catheter or surgery → step 13

11 Look for another cause of shock

End of this path.

12 Systemic thrombolysis: is the shock improving?

  • Alteplase 100 mg IV over 2 hours (ESC 2019; 2a for category E, AHA/ACC 2026)
  • Crashing or peri-arrest: 0.6 mg/kg over 15 minutes, max 50 mg (ESC accelerated regimen)
  • Pause the heparin infusion during alteplase; restart without a bolus once the aPTT is 2 times normal or less (label)
  • No new punctures or IM injections; vital signs and neuro checks every 15 minutes; watch sites, hemoglobin, back or flank pain

Shock improving → step 5Still in shock or worse → step 13Cardiac arrest → step 2

13 Catheter or surgical clot removal

  • Catheter-directed lysis or mechanical thrombectomy: lysis contraindicated, bleeding risk high, or lysis failed (2a for category E1, AHA/ACC 2026)
  • Surgical embolectomy: the same reasons, or clot in transit in the right heart or across a PFO
  • The PERT picks what the hospital can do fastest; transfer early if neither is available
  • Travel with pressors running, push-dose epinephrine, defibrillator and blood

Improving after clot removal → step 5Refractory shock → step 6Cardiac arrest → step 2

Drugs in this algorithm

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