ICU 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

Practice free in your browser3,800+ exam-style questions with rationales. No account, no ads. Also free on the App Store and Google Play.

For education and exam preparation only. Follow your institution’s protocols. Study aid with typical adult values; follow your institution's protocols and current AHA guidelines.