ECMO

what is ecmo?

Extracorporeal Membrane Oxygenation (ECMO) is a form of Extracorporeal Life Support (ECLS) given to patients when their heart and/or lungs are not able to provide the body with enough blood flow and oxygen.

During ECMO, the heart and lungs are bypassed and the blood is oxygenated outside the body (extracorporeal) by an artificial lung and circulates with the help of an external pump, allowing the heart and lungs to rest.

See introduction to ECMO produced by the Alfred for more information

<-----------

Patients will have two large bore cannulas inserted into main vessels in the neck, chest or legs.

One cannula will be the inflow cannula: this takes blood from patient's body and delivers it to the ECMO machine

One will be the outflow cannula: this takes oxygenated blood from the ECMO machine back to the patient.

Patients are placed on ECMO when they have conditions that cause acute and/or severe REVERSIBLE cardiac and/or lung failure with a high risk of death.

ECMO does not fix a disease, it just allows the body to rest while more time is allowed to discuss and arrange treatment options.

vv ecmo

Bypasses lungs only

Venovenous (VV) ECMO provides lung support only, so the patient's heart must still function well enough to meet the body's needs. Two cannulas are placed into veins in spots close to or inside the heart. Blood from the ECMO system returns to the body before the heart, and the patient's own heart pumps the blood throughout the body.

Patients may be placed on VV ECMO for the following conditions:

-> pneumonia

-> ARDS

-> acute GVHD

-> pulmonary contusion

-> smoke inhalation

-> status asthmaticus

-> airway obstruction

-> aspiration

-> bridge to lung transplant

-> drowning

va ecmo

Bypasses the heart and lungs

Venoarterial (VA) ECMO provides support for the patient's heart and lungs by allowing most of a patient's blood to move through the circuit without going through the patient's heart. This type of ECMO takes blood out of a large vein and returns it into a large artery, allowing oxygen-rich blood to circulate through the body even if the heart is too weak to pump it.

Patients may be placed on VA ECMO for the following conditions:

-> graft failure post heart or heart lung transplant

-> non-ischaemic cardiogenic shock

-> failure to wean post CPB

-> bridge to LVAD

-> drug OD

-> sepsis

-> PE

-> cardiac or major vessel trauma

-> massive pulmonary haemorrhage

-> pulmonary trauma

-> acute anaphylaxis (2)

why do we commonly scan ecmo patients in ct?

stroke

Patients on ECMO have high risk of both ischaemic stroke and haemorrhagic stroke.

Ischaemic: ECMO circuits can carry a risk of increased blood clotting which can cause emboli in patients and can result in ischaemic strokes in the brain.

Haemorrhagic: Patients are put on anticoagulants to reduce clotting. This can lead to bleeds throughout the brain.

Thus, the risk of thromboembolism, should be carefully balanced against the risk of bleeding. (1)

bleeds

Due to the need for thrombolysis while on ECMO, there is an increased potential for large bleeds in the brain and body.

infection

Introduction of infection is high to the patient via the cannula sites.

prognositication

Can this patient recover from this event and will they be able to maintain life while off ECMO?

ischaemic limbs

The cannula can result in damage/blockage to major arteries they are inserted into. This has potential to disrupt supply to the affected limb causing ischaemia

investigating cause for ecmo

In emergency settings, patients may be placed on ECMO without a diagnostic scan being conducted prior.

?cause for cardiac arrest

?cause for respiratory arrest

In emergency settings, patients may be placed on ECMO without a diagnostic scan being conducted prior.

?cause for cardiac arrest

?cause for respiratory arrest

We commonly perform the following CT scans on ECMO patients to assist in the diagnosis of these conditions:

C- Brain
CTA Head/Neck
CTA Chest
CAP studies (Arterial, Venous, Dual-phase, Delayed)
CTA limbs

important considerations for non-contrast ct

patient transport

Patient will either be transported with the circuit next to them while on the CT table (above)

Transported on an orange ECMO board on which the circuit sits (below)

The second option is often favourable as there is less movement that may involve putting any tension on the cannulas.

breath holds

Patients will often be ventilated or hand bagged. This is important as it may effect the ability to do breath holds for scans of the chest.

Some patients may be too unwell for a breath hold.

type of scan protocol used

We try to limit the table speed for the patients to account for all the attachments and minimize any ECMO cannula movement.

NO FLASH SCANS FOR ECMO

additional important considerations for post contrast ct

contrast delivery and an ecmo circuit

The pathway of contrast delivery typically follows this pattern in an ECMO circuit

PIVC --> Inflow cannula -> ECMO circuit --> Outflow cannula --> Systemic arteries

This additional step through the ECMO circuit will require increased contrast volumes and time delays.

How can we reduce these problems ---------->

can the circuit be slowed or stopped?

If the circuit can be stopped/clamped, then the contrast will not flow into the circuit and will flow around the patient as it would in a non-ECMO C+ scan.

If the circuit is slowed then less volume will go into the circuit therefore reducing the amount of contrast needed and the amount of time it may take to reach the areas of interest.

This can only be done on patients who have sufficient cardiac output available to pump the contrast through the body and will not be suitable for everyone.

See considerations we need to take into account if the circuit is still active

PIvc site

Where will the contrast enter the patient vasculature?

Will this be before or after the inflow cannular?

Do we need a line in upper or lower limb to show particular pathology?

inflow cannula location

Where is the inflow cannular?

Important to know this in relation to the PIVC.

Will contrast have to move through the ECMO circuit before being delivered back to the patient and to vessel of interest?

May need extra volume/scan delay time if the contrast is moving through the circuit.

outflow cannula location

Where will the contrast be put back into the vasculature once it has travelled through the ECMO machine?

cardiac output

Can the patients heart still pump contrast efficiently if flows are lowered/stopped?

If flows are stopped the patient must have cardiac output to ensure the contrast can be moved through the body.

If the cardiac output it to low then the ECMO circuit cannot be stopped

ecmo circuit volume

What is the volume of blood is being moved through the ECMO circuit?

Can effect the dilution of the contrast

When needed, in ECMO patients you may use up to 6ml/kg to account for this dilution.

flow rates

At what speed is the flood moving through the ECMO circuit?

How will this effect the time delay for the scan.

All these considertions are to be discussed with the radiologist and the icu team prior to the patient coming to ct.

FIonas ecmo presentation

case examples

CTA Chest for assessment of cardiac anatomy post arrest.

ECMO flows stopped for scan. Clamps were placed on the ECMO cannulas by the perfusion team. Once flows in ECMO circuit were confirmed to be 0, contrast was given to the patient. As the patient had high cardiac output the contrast moved through the body as it would in a non-ECMO CTA.

Details of contrast below:

Scan delay: 14s

11mls 70% C @ 1.5ml/s

20mls saline

Weight: 6.3kg

PIVC: R wrist: 20G

references

Themas K, Zisis M, Kourek C, Konstantinou G, D'Anna L, Papanagiotou P, Ntaios G, Dimopoulos S, Korompoki E. Acute Ischemic Stroke during Extracorporeal Membrane Oxygenation (ECMO): A Narrative Review of the Literature. J Clin Med. 2024 Oct 9;13(19):6014. doi: 10.3390/jcm13196014. PMID: 39408073; PMCID: PMC11477757.
https://www.elso.org/home.aspx

Page updated

Google Sites

Report abuse