Reviewed by DR. Sabrina Berdouk

You’re in resus. The patient is hypotensive, tachycardic, gasping. CT (or echo) screams PE. The right ventricle is huge and unhappy.

This is the moment where clarity beats complexity.

This post is a practical, physiology-rooted cheat sheet for high-risk (massive) PE – the patient who is shocked or in arrest because of a pulmonary embolism.

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1. Clinical frame: Who are we talking about?

Before you do anything fancy, make sure you’re in the right territory.

ESC High-Risk (Massive) PE:

• Hypotension / shock (or arrest)
• PE on imaging (or very high suspicion + RV strain on echo)
• You’re convinced the PE is driving the haemodynamic collapse
• In this zone, the default is reperfusion (thrombolysis)
  • You should need a good reason not to lyse

If the PE is an incidental finding on a CT done for sepsis or cardiogenic shock – that’s not this post. Here, we’re in the land of:

“This clot is killing them. How do I stop it now without killing them in another way?”

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2. First 30–60 minutes: what actually helps?

In the chaos, keep one mantra in your head:

Lyse – Anticoag – Norad – O₂ – CPR

Let’s walk through each.

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A. Thrombolysis – the center of gravity

If you remember nothing else:

High-risk PE + shock from PE = you need a good reason not to give tPA.

• ESC guidelines: Class I recommendation for systemic thrombolysis in high-risk PE
• This is one of the very few class I life-saving things in PE

Easy case (no one argues):

• 25-year-old, day 3 post knee arthroscopy
• Massive PE on CT, SBP 70, tachycardic
• No major bleeding risk
• → Just lyse. You are trying to stop them dying in front of you.

Hard case (the 3 a.m. agony):

• Polytrauma
• Small traumatic SAH, resolving SDH
• Recent laparotomy
• Now in shock with massive PE

Here, the risk–benefit conversation is brutal. But it’s still worth stressing:

• Not lysing in high-risk PE is rarely “safe” – it’s just a different risk (death from PE vs bleeding).
• You may still decide no tPA – but that decision deserves serious cognitive bandwidth, not a reflex “they have a head bleed so no”.

Dosing (alteplase – example regimen)

• Unstable but with a pulse:
  • 10 mg IV bolus, then 90 mg over 2 hours
• Cardiac arrest from suspected PE:
  • 50 mg IV bolus during CPR
  • Many will consider a repeat bolus if no ROSC after a period

(Always follow your local protocols – doses here are typical examples, not a replacement for them.)

Physiology: why lyse?

Massive PE does this:

1. Big clot suddenly blocks pulmonary arteries → RV afterload skyrockets
2. RV dilates, wall stress ↑, RV perfusion ↓ → RV ischemia / failure
3. Dilated RV pushes the IV septum left → LV gets underfilled
4. LV stroke volume drops → low cardiac output → hypotension → shock

Norad, fluids, inotropes – all of that is just playing with the plumbing.
Only reperfusion (thrombolysis, thrombectomy, embolectomy) actually removes the obstruction.

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B. Anticoagulation – stop the situation getting worse

Also an ESC Class I recommendation.

Even if you lyse, you still need anticoagulation to stop new clot formation.

In the ICU, unfractionated heparin (UFH) is usually your friend:

• Short half-life
• Quickly off if bleeding starts or you need a procedure
• Reversible (protamine)

LMWH has pros:

• More predictable anti-Xa effect
• Less monitoring needed

…but:

• Harder to stop
• Not ideal if the patient is unstable, may go to theatre, or you’re worried about bleeding after lysis.

Bedside rule of thumb:

Sick PE in ICU + procedures/bleeding/lysis on the table → start a UFH infusion.

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C. Fluids: the “no litre bolus” rule

Massive PE is an RV problem, not a “they need more fluid” problem.

What happens if you throw in a big crystalloid bolus?

1. RV is already dilated and struggling against huge afterload
2. You increase RV volume and wall tension
3. Septum bows further into LV cavity
4. LV filling gets worse → cardiac output drops further
5. RV may become more ischemic

So:

• No reflex “1 L crystalloid” for hypotension.
• If they might be dry (e.g. sepsis, vomiting, poor intake), use small test boluses:
  • 200–250 mL
  • Reassess BP, echo, lactate, clinical picture
  • Stop if no clear benefit

Think:

“This is an RV under pressure, not an empty LV that wants a bucket of saline.”

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D. Noradrenaline (then adrenaline): your real resus fluid

In massive PE, noradrenaline is usually the right first go-to drug.

Why it works:

• α1: ↑SVR → ↑aortic diastolic pressure → better coronary perfusion → RV gets more oxygen
• β1: a bit more contractility → RV squeeze improves

The effect at the bedside:

• BP picks up
• Coronary perfusion improves
• You gain time to make a properly weighed decision about thrombolysis.

Typical scenario:

• You’re 90% sure it’s a PE
• Patient is hypotensive, tachycardic, mottled
• CT is booked but not done
• → Don’t wait. Start norad.

If:

• Norad dose is climbing
• Echo shows RV really failing

Then:

Adrenaline is a good add-on inotrope – gives you β1 inotropy plus some α support.

What about milrinone & the inodilators?

Milrinone, dobutamine, etc:

• Can reduce pulmonary vascular resistance (good for RV)
• But are vasodilatory, and can drop systemic BP massively

Starting milrinone 0.5 mcg/kg/min in someone with a BP of 60/40 from PE is…

Basically a leap of faith – and the wrong faith.

Save inodilators for:

• Later in the ICU course
• When BP is secure with vasopressors
• When you’re fine-tuning RV function, not fighting for basic survival

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E. Oxygenation – help the RV, don’t kill it with intubation

Why oxygen matters physiologically:

• Hypoxia and hypercapnia trigger hypoxic pulmonary vasoconstriction
• This increases PVR → RV afterload goes up further
• Giving O₂ and reducing CO₂ reduces PVR, easing RV workload

But the big trap is intubation.

Why intubation is dangerous in massive PE

Induction often causes:

• Loss of sympathetic tone → vasodilation and ↓SVR
• Positive pressure → ↑intrathoracic pressure → ↓venous return / preload
• A sick RV that was just holding on suddenly:
  • Gets less preload
  • Less coronary perfusion
  • Loses catecholamine drive

Result:

PEA on induction – you’ve just tipped them over.

So:

• Use non-invasive strategies first:
  • High-flow nasal oxygen
  • NIV (if tolerated and not making them worse)
  • Awake proning if feasible

If you must intubate:

• Resuscitate first: norad running, maybe tPA on board
• Get everything ready:
  • Vasopressors drawn up and infusing
  • Try to avoid deep vasodilatory induction
  • Keep apnea time as short as possible

Think:

“Reperfuse or at least resuscitate the RV before you take away their sympathetic tone.”

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F. CPR in massive PE – not just “standard arrest”

In PE arrest:

• You need high-quality CPR for any chance of forward flow.
• But in PE specifically, repetitive compressions may also:
  • Mechanically disrupt or shift clot more distally
  • Sometimes leading to stuttering ROSC episodes

So don’t give up too early, especially if you’ve given thrombolysis – the drug needs time to work.

Beware mechanical CPR devices

If:

• tPA is on board
• There’s trauma or concern for liver injury

Then:

• Mechanical CPR devices can generate large, repetitive forces
• tPA + liver lac + mechanical pounding = high risk of catastrophic haemorrhage

Use manual CPR in this setting where possible.

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3. ICU-phase add-ons: less sexy early, useful later

Once you’ve survived the first hour and they’re in ICU, more tools appear.

A. Inhaled nitric oxide

• Selective pulmonary vasodilator → reduces PVR without systemic hypotension
• Can unload the RV in ventilated patients
• Evidence is limited and mixed, but physiologically sensible and usually low risk

Use it as:

A rescue/adjunct in ventilated patients with RV failure and hypoxaemia, not as a replacement for reperfusion.

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B. Mechanical / catheter-based interventions

These are not part of the first 30–60 minutes of resus.

They come into play when:

• You’ve kept them alive long enough, and
• Thrombolysis is contraindicated or has clearly failed

Catheter-directed lysis

• tPA infused directly into pulmonary arteries
• Theoretical benefits:
  • Lower total tPA dose
  • Higher local concentration at the clot
• But: if you infuse tPA peripherally, it still ends up in the pulmonary circulation.

Evidence so far is underwhelming for dramatic advantages.

Mechanical thrombectomy

This one is physiologically appealing:

• Suck out large bits of clot →
  • RV afterload falls
  • BP and oxygenation can improve rapidly

But reality check:

• Large catheters, almost ECMO-sized, into pulmonary arteries
• Procedure time around ~90 minutes in trials like PEERLESS
• Patient has to be:
  • Alive
  • Stabilised enough to tolerate transfer and time on the table

How to think about it:

Great option for: failed lysis, absolute contraindication to lysis, and a patient who is “sick but not dying this second”.
Not the answer to “BP 60/40, peri-arrest, no norad yet”.

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C. VA-ECMO – the big gun

VA-ECMO can be magic in the right context:

• Bypasses the RV and pulmonary arteries
• Supports circulation and oxygenation while:
  • Lysis works
  • Or thrombectomy/embolectomy happens

But:

• Rarely available outside major centres
• Requires expertise, logistics, and time

In practice:

If you have ECMO, involve them early in crashing PE.
If you don’t, don’t fantasise – focus on what you can do well: lyse, heparin, norad, O₂, good ICU care.

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D. PERT teams – helpful, but don’t let them slow you down

PERT = Pulmonary Embolism Response Team (ICU, EM, cardiology, IR, etc).

They’re useful for:

• Grey-zone cases
• Intermediate-risk PE
• Long-term planning, follow-up, chronic thromboembolic disease

But two common traps in massive PE:

1. Outsourcing an obvious decision
   • Patient in shock
   • Massive PE
   • No major contraindication
   • → They need thrombolysis.
   Delaying to ask a committee is dangerous.
   This is your decision at the bedside.
2. Remote advice for a patient they’ve never seen
   • IR/surgical options may be suggested
   • But the patient is actually improving on anticoagulation and vasopressors

The person holding the stethoscope, watching the numbers and the skin and the lactate, is often better placed to judge trajectory than three people on a speakerphone.

Use PERT as:

An advisory tool — not a reason to pause when the need for reperfusion is clear.

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E. Surgical pulmonary embolectomy

On paper:

• ESC: Class I recommendation (but low-quality evidence)
• Option when:
  • Thrombolysis is contraindicated
  • Or failed

In reality:

• You’re taking someone who is almost dead
• Anaesthetising them
• Opening the chest
• Putting them on bypass with large-dose heparin

Two big issues:

1. Contraindications to lysis often also apply to large-dose heparin
2. The “Goldilocks problem”:
   • Not sick enough → surgery won’t take them
   • Too sick → anaesthetics says they’ll die on induction

So:

Embolectomy has a niche role in the right centre; it’s not your everyday fallback plan.

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4. A simple bedside mental algorithm

When you’re in resus or ICU with a crashing PE, run this in your head:

Step 1 – Confirm the frame

• Hypotension / shock / arrest?
• PE on imaging or very high suspicion + RV strain on echo?
• No alternative cause that fully explains the collapse?

→ If yes, you’re in high-risk PE territory.

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Step 2 – Immediate actions

• Give oxygen (liberally)
• Start noradrenaline early – don’t wait for BP to fall further
• Avoid big fluid boluses – no automatic “1 L”
• Start UFH infusion (or plan heparin around thrombolysis if already given)

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Step 3 – Reperfusion decision (don’t dawdle)

Ask yourself:

1. Is there a clear indication for thrombolysis?
   • High-risk PE causing shock/arrest → usually yes
2. Is there an absolute contraindication that truly outweighs near-term death from PE?

If no major contraindication →

Give tPA.

If contraindicated or tPA fails →

Consider mechanical thrombectomy / surgical embolectomy / VA-ECMO
(where available, and only if patient is stable enough to get there).

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Step 4 – If they arrest

• Start high-quality CPR
• Give 50 mg tPA bolus (per local protocol)
• Continue CPR for a prolonged period (up to 60–90 minutes)
  • Thrombolysis needs time to work
  • PE arrests can have late ROSC

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Step 5 – ICU course

• Adjust norad ± adrenaline according to RV function and BP
• Consider inhaled nitric if ventilated with RV failure
• Serial echo to track RV recovery
• Watch closely for bleeding post-lysis and on heparin
• Reassess:
  • Do they need upgrade to mechanical thrombectomy?
  • Are they actually improving and can we just continue anticoagulation and supportive care?