Summary by Katrina Augustin, MD, BSN-RN

Expert Reviewed by Christina Creel-Bulos, MD, BSN-RN, Emory ECMO Center Medical Director

Winter is here

To some that may evoke thoughts of peppermint lattes, festive gatherings, and feelings of nostalgia, but to others, it represents long shifts caring for patients with severe respiratory failure refractory to conventional management through a feared “tripledemic”.

…So, let’s talk

Venovenous Extracorporeal Membrane Oxygenation (VV ECMO) to the rescue

VV ECMO has demonstrated trends towards increased survival in ARDS compared to conventional treatment (PMID: 30642776, PMID: 29791822). There has been increased utilization of ECMO during the COVID-19 pandemic and its applications continue to expand with it recently being incorporated into the ASA practice guidelines for management of the difficult airway (PMID: 34762729). However, despite increased utilization, implementation of this therapy is limited by lack of universal availability as well as nuanced patient selection and constantly evolving relative contraindications.

While this continues to be an evolving topic, the goal of this post is to discuss patient selection for VV ECMO and when to call for help if working at a non-ECMO center.

So, who will benefit from VV ECMO to the rescue?

There are several commonly cited prediction scores such as the RESP (Respiratory ECMO Survival Prediction) score and PRESERVE (Predicting death for severe acute respiratory distress syndrome on VV ECMO) score that have been used to predict in-hospital survival when on VV ECMO. However, they have many limitations.

• Only included patients already cannulated for VV ECMOàLimits generalizability to determine if a patient is “ECMO ELIGIBLE”
• Focused on a population level rather than individual levelà limits clinical utility at bedside when determining if “your” patient is eligible
• At best provide moderate discrimination between survivors and non-survivors

While these prediction scores may not be the magic bullet we are looking for to definitively tell us who to cannulate, they can be used to provide additional support to the decision-making process.

Eligibility charts incorporating patients age, etiology of respiratory failure, chronic co-morbidities, and acute clinical derangements can also assist with determining a patient suitability and expected outcomes on ECMO; however, they can quickly become complex and time consuming.

Ultimately, patient selection for VV ECMO is nuanced and frequently determined on a case-by-case basis by a multidisciplinary team incorporating individual patient characteristics and indication for ECMO with support from prediction scores such as RESP.

So, how do I know if my patient might be a ECMO candidate?

Murray Score

Used in the CESAR Trial. You can see it here.

Discussion of Specific Contraindications

Older Age

• Very institution dependent (typical age cut off 65-75), less physiological reserve & increasing mortality with older age

CNS Hemorrhage/Significant CNS Dysfunction

• Needs to be a clinical evaluation of degree

Contraindications to Anticoagulation (AC)

• Relative⇢it is feasible to do VV ECMO without AC (PMID: 32173339); determine on case-by-case basis with discussion of risks/benefits

Immunosuppression

• Associated with increased mortality on VV ECMO
• Determine on case-by-case basis, Outcomes vary depending on etiology of immunosuppression (malignancy/solid organ transplant, autoimmune disease, untreated HIV) (PMID: 33725377)

Prolonged Mechanical Ventilation (MV)>7 days

• Multiple studies showing increased mortality with prolonged ventilation prior to ECMO (PMID: 24693864)
• MV>7 days before ECMO compared to those with <7 days had a 77% mortality rate vs 38% (p< 0.001) PMID: 28525416)
• However others studies in COVID 19 populations showing there may be benefit even up to 10 days after initiation of MV (PMID: 35508314, PMID: 35024972)

Cardiogenic Shock (CS)

• May need venoarterial ECMO for cardiac support, see exception below

Multi-Organ Failure (i.e. anticapted non-recovery)

• Elevated SOFA score associated with increased mortality (PMID: 36213640)
• AKI not an exclusion (PMID: 32243267)
• Patient with shock liver, AKI, elevated lactate, and high dose vasopressors likely poor prognosis

Obesity

• No longer considered contraindication, potentially even increased survival (“obesity paradox”) due to protective factors and/or earlier decompensation with less severe parenchymal disease (PMID: 31663965)

**Per ELSO contraindications to ECMO should become more stringent as capacity diminishes

So now that we discussed the basics… Let’s talk about a couple of nuances with VV ECMO.

Bridge to transplant

• VV ECMO can be used as a bridge to lung transplant ideally the patient is already being worked up for a transplant
• Consider “Awake ECMO” cannulation in non-intubated patient; facilitates prehabilitation prior to transplant
• Careful with “bridge to decision” on individuals with questionable lung transplant candidacy decision should involve multidisciplinary team, discussion of decannulation options including palliative care, and include a clear discussion of duration of ECMO support offered

Secondary Right ventricular failure

• 25% of patients with ARDS develop RV failure

• In isolated RV failure due to ARDS, VV ECMO can be effective by increasing 02 delivery, reducing hypoxic vasoconstriction, and decreases hypercarbia/acidosis with resultant decreased PVR & improved myocardial contractility
• In special circumstances can consider VV ECMO via a double lumen cannula like Protek duo that allows additional RV support (inlet RA, outlet PA=true RVAD) as a bridge to recovery or transplant

Trauma

• Can have favorable outcomes, especially in younger patients
• As always consider patient specific indication and comorbidities
• Use caution if significant TBI in addition to pulmonary insult

Difficult Airways

• VV ECMO is included in the difficult airway algorithm. An emergent consult can be lifesaving if you are at an institution that has access to ECMO or have a mobile unit nearby
• Consider it in patients with difficult to establish airways (difficult anatomy, severe pulmonary hemorrhage, negative pressure pulmonary edema)
• Asthma patients that you are unable to ventilate due to severe obstructive physiology

Remember Medicine is both an ART and a SCIENCE,

and when it comes to VV ECMO it is no different. The decisions to “cannulate or not” as well as “when to remove care” can quickly become emotional for staff caring for the patient as well as family members. The decisions are best made as a team looking at the “big picture.”

The Bottom Line:

• Aggressively optimize medical management early, call ECMO referral center EARLY
• Young, with single organ failure due to reversible cause, call early
• Old, with chronic comorbidities and multiorgan failure, likely will not benefit
• Utilize a team-based decision-making process and decide on a case-by-case basis incorporating the reversibility of disease process, acute clinical condition, and chronic comorbidities

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Scott Weingart, MD FCCM

Editor-in-Chief, at EMCrit.org

An ED Intensivist from NY.
Professor
Nassau University Medical Center
No conflicts of interest (coi).

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