When to Call for ECMO – A Resident's Quick Guide: Indications, Timing, and Contraindications in Critical Care

Dr Neeraj Manikath , claude.ai

Abstract

Extracorporeal membrane oxygenation (ECMO) has evolved from an experimental rescue therapy to a mainstream intervention in critical care medicine. For residents managing critically ill patients, the decision of when to initiate ECMO discussions can be life-saving, yet the narrow therapeutic window and complex patient selection criteria make this one of the most challenging clinical decisions. This review provides a practical framework for recognizing appropriate ECMO candidates, understanding optimal timing, and identifying absolute contraindications. We emphasize early recognition and consultation rather than delayed salvage therapy, with specific focus on ARDS and cardiogenic shock scenarios commonly encountered in critical care practice.

Keywords: ECMO, ARDS, cardiogenic shock, critical care, patient selection, timing

Introduction

The fundamental question facing critical care residents is not whether they can manage ECMO independently—that requires specialized training and institutional expertise—but rather when to recognize that conventional therapy is failing and ECMO consultation is warranted. The difference between rescue ECMO (high mortality, resource-intensive) and bridge ECMO (reasonable outcomes, planned intervention) often lies in this early recognition.

Pearl #1: Think ECMO before the patient is "too sick for ECMO"—the sickest patients rarely benefit from ECMO.

ECMO Fundamentals: A Quick Primer

Veno-Venous (VV) ECMO

Purpose: Respiratory support only
Indication: Severe respiratory failure with adequate cardiac function
Cannulation: Typically femoral-jugular or bicaval dual-lumen

Veno-Arterial (VA) ECMO

Purpose: Combined cardiac and respiratory support
Indication: Cardiogenic shock ± respiratory failure
Cannulation: Peripheral (femoral-femoral) or central (atrial-aortic)

Oyster #1: Many residents confuse the indications. Remember: VV = lungs only, VA = heart ± lungs. If there's any cardiac involvement requiring support, think VA-ECMO.

Part I: ARDS and VV-ECMO

Primary Indications for VV-ECMO in ARDS

1. Refractory Hypoxemia

Threshold criteria (consider if ANY present despite optimal ventilation):

PaO₂/FiO₂ < 80 mmHg for > 6 hours
PaO₂/FiO₂ < 50 mmHg for > 3 hours
Unable to maintain SaO₂ > 88% despite FiO₂ 1.0

Hack #1: Use the "ECMO phone call" rule: If you're spending more time adjusting the ventilator than managing other aspects of care, and oxygenation targets remain unmet, it's time to call.

2. Ventilator-Induced Lung Injury (VILI) Risk

Consider ECMO consultation when requiring:

Plateau pressure > 30 cmH₂O despite PEEP optimization
Driving pressure > 15 cmH₂O
PEEP > 15 cmH₂O with recruitment strategies failing
pH < 7.20 with protective ventilation

Pearl #2: ECMO isn't just about oxygenation—it's about lung protection. Sometimes adequate oxygenation with injurious ventilation is worse than ECMO with ultra-protective ventilation.

3. Severe Respiratory Acidosis

pH < 7.20 despite optimized ventilation
Permissive hypercapnia not tolerated (e.g., increased intracranial pressure)

ARDS-Specific Clinical Scenarios

Scenario 1: The "Honeymoon Period" Patient

Clinical picture: 22-year-old with viral pneumonia, initially stable on BIPAP, now requiring intubation with rapidly worsening oxygenation.

Key decision point: This is when ECMO works best—before multi-organ failure develops.

Action: Early consultation when P/F ratio drops below 150 with high PEEP requirements.

Scenario 2: The "ARDS + Pregnancy" Patient

Clinical picture: 28-week pregnant patient with H1N1 pneumonia and severe ARDS.

Special considerations:

Maternal mortality approaches 100% with conventional therapy in severe cases
ECMO allows protective ventilation while maintaining fetal viability
Earlier consultation threshold recommended (P/F < 100)

Hack #2: Pregnancy is not a contraindication to ECMO—it's often an indication for earlier consultation.

Part II: Cardiogenic Shock and VA-ECMO

Primary Indications for VA-ECMO

1. Acute Myocardial Infarction with Cardiogenic Shock

Consider when:

Lactate > 4 mmol/L despite optimal medical therapy
Inotrope/vasopressor requirement increasing
Mixed venous saturation < 60%
Cardiac power output < 0.6 W

Pearl #3: In AMI with cardiogenic shock, VA-ECMO is often a bridge to revascularization, not definitive therapy. Early cath lab activation is crucial.

2. Acute Myocarditis with Hemodynamic Compromise

Threshold for consultation:

New-onset heart failure with EF < 30%
Ventricular arrhythmias refractory to medical therapy
Rising troponins with hemodynamic instability

3. Post-Cardiotomy Shock

Consider when unable to wean from bypass or:

Cardiac index < 2.0 L/min/m² despite maximal support
Need for > 3 inotropes/vasopressors
Evidence of end-organ hypoperfusion

4. Refractory Cardiac Arrest

ECPR (Extracorporeal CPR) criteria:

Witnessed arrest with immediate high-quality CPR
Initial shockable rhythm
Age < 65 years (relative)
No-flow time < 5 minutes, low-flow time < 30 minutes
Reversible cause suspected

Oyster #2: ECPR sounds appealing but has strict criteria. Most arrested patients you encounter will NOT be ECPR candidates. Don't delay conventional resuscitation for ECMO consultation.

Cardiogenic Shock Clinical Scenarios

Scenario 3: The "Acute MI + Mechanical Complication"

Clinical picture: 65-year-old with STEMI, successful PCI, but develops acute mitral regurgitation with pulmonary edema and shock.

Decision framework:

Emergent echo to define anatomy
Early VA-ECMO as bridge to surgical repair
Don't wait for "optimal" medical management

Scenario 4: The "Fulminant Myocarditis"

Clinical picture: Previously healthy 30-year-old with viral prodrome, now in cardiogenic shock with EF 15%.

Key points:

High recovery potential with aggressive support
Earlier ECMO consultation warranted
Bridge to recovery vs. bridge to transplant decision can be deferred

Part III: Timing - The Critical Window

The "Golden Hour" Concept in ECMO

Early consultation (best outcomes):

Patient meets criteria but still responsive to conventional therapy
Organ function preserved
Lactate < 4 mmol/L
Adequate urine output maintained

Salvage therapy (poor outcomes):

Multi-organ failure established
Prolonged high-dose vasopressor requirement
Irreversible neurologic injury
Lactate > 8 mmol/L

Hack #3: Use the "lactate trend" as your timing guide. Rising lactate despite therapy = call ECMO. Falling lactate = continue conventional therapy but stay vigilant.

Institutional Factors Affecting Timing

High-Volume ECMO Centers

Earlier consultation appropriate
24/7 availability
Transport team capable

Limited ECMO Experience

Higher threshold for consultation
Earlier involvement of transfer teams
Focus on patient optimization during transport

Pearl #4: Know your institutional capabilities. A good ECMO program will guide you on appropriate timing—use their expertise early rather than late.

Part IV: Contraindications - When NOT to Call

Absolute Contraindications

1. Irreversible Neurologic Injury

Fixed pupils with absent brainstem reflexes
Extensive cerebral infarction on imaging
Brain death criteria met

2. Irreversible End-Organ Failure

End-stage liver disease (MELD > 30) without transplant candidacy
End-stage renal disease with limited functional status
Advanced malignancy with poor prognosis

3. Prolonged High-Pressure Ventilation (VV-ECMO)

Plateau pressures > 30 cmH₂O for > 7 days
Evidence of irreversible pulmonary fibrosis

4. Prolonged CPR Without ROSC

60 minutes of CPR without specialized circumstances
Asystole as initial rhythm with prolonged downtime

Relative Contraindications (Requires Case-by-Case Discussion)

1. Advanced Age

Chronologic age less important than physiologic age
Consider functional status and comorbidities
Some centers use age > 65 as relative contraindication for ECPR

2. Severe Bleeding Risk

Recent major surgery (< 7 days)
Active GI bleeding
Recent stroke (< 7 days)
Platelet count < 50,000 (relative)

Oyster #3: Don't let relative contraindications prevent the conversation with ECMO specialists. They can help weigh risks vs. benefits better than residents can alone.

3. Prolonged Intensive Care Stay

21 days of mechanical ventilation (VV-ECMO)
Multiple failed organ supports
ICU-acquired weakness/deconditioning

4. Irreversible Underlying Disease

Advanced COPD with FEV₁ < 25% predicted
Pulmonary fibrosis with DLCO < 25%
Advanced heart failure without transplant candidacy

The "Futility" Discussion

When ECMO consultation becomes futile:

Multi-organ failure with increasing organ dysfunction scores
Lactate > 15 mmol/L despite maximal therapy
pH < 7.0 with multiple vasopressors
Family/patient goals inconsistent with aggressive intervention

Hack #4: Sometimes the most important ECMO decision is NOT to pursue it. Use ECMO specialists to help frame goals-of-care discussions when appropriate.

Part V: Practical Clinical Pearls and Hacks

Assessment Pearls

Pearl #5: The "eyeball test" matters. If a patient looks like they're dying despite optimal numbers, trust your clinical judgment and call early.

Pearl #6: Lactate clearance > absolute lactate value. A lactate of 6 that's falling is better than a lactate of 4 that's rising.

Pearl #7: Mixed venous saturation < 60% in cardiogenic shock is often the earliest sign that VA-ECMO may be needed.

Communication Hacks

Hack #5: When calling ECMO, lead with: "I have a patient who may need ECMO consultation" rather than "I need ECMO for this patient." Let the specialists help determine appropriateness.

Hack #6: Have three pieces of information ready: (1) Why conventional therapy is failing, (2) What the reversible pathology might be, (3) What the functional baseline was.

Hack #7: Document ECMO discussions in real-time. Families and teams need to understand the rationale, even if ECMO is ultimately not pursued.

Logistical Pearls

Pearl #8: Blood bank preparation takes time. If you're thinking ECMO, give blood bank a heads-up early—they'll need to prepare multiple units and factor concentrates.

Pearl #9: ECMO consultation doesn't equal ECMO cannulation. Many consultations result in optimized conventional therapy rather than ECMO initiation.

Pearl #10: Geographic factors matter. A borderline ECMO candidate at a high-volume center may be different from the same patient at a referring hospital 6 hours away.

Part VI: Special Populations and Considerations

Pediatric Considerations

Different size-based criteria for flows and oxygenation targets
Higher success rates in respiratory failure
Different cannulation strategies
Family dynamics often more complex

Pregnancy and ECMO

Physiologic changes affect ECMO management
Multidisciplinary team essential (maternal-fetal medicine, cardiac surgery, ECMO)
Delivery timing decisions complex
Higher bleeding risk but not absolute contraindication

Trauma Patients

Massive transfusion protocol interaction with ECMO
Neurologic injury assessment challenging
Damage control surgery principles apply
High bleeding risk requires careful consideration

Oyster #4: Special populations require specialist input early. Don't try to adapt general ECMO criteria independently.

Part VII: Quality Improvement and System-Based Practice

Institutional ECMO Programs

Components of successful programs:

Dedicated ECMO coordinator
24/7 availability with response time standards
Multidisciplinary team approach
Regular case review and quality metrics
Education and simulation programs

Metrics That Matter

Consultation-to-cannulation time
Pre-ECMO lactate and organ function
Survival to hospital discharge
Functional neurologic outcomes
Resource utilization

Pearl #11: Good ECMO programs track their "near miss" cases—patients who were consulted but didn't require ECMO. This helps calibrate appropriate consultation thresholds.

Part VIII: Future Directions and Emerging Evidence

Evolving Indications

ECMO as bridge to lung transplant in acute respiratory failure
ECMO for severe acute respiratory distress in non-ARDS conditions
Prophylactic ECMO for high-risk procedures
ECMO for refractory status asthmaticus

Technology Advances

Smaller, more biocompatible circuits
Improved pumps with lower hemolysis rates
Better anticoagulation strategies
Percutaneous cannulation techniques

Research Priorities

Optimal timing algorithms
Biomarkers for patient selection
Weaning protocols and criteria
Long-term functional outcomes

Conclusion: A Framework for ECMO Decision-Making

The resident's role in ECMO decision-making is not to be the final arbiter of candidacy, but to recognize when conventional therapy is failing and expert consultation is warranted. The key principles are:

Think early, not late: ECMO works best before irreversible injury occurs
Focus on reversibility: What can ECMO bridge the patient to?
Know your limits: Use specialist expertise to guide complex decisions
Consider the whole patient: Technical candidacy must align with patient values and goals
Don't let perfect be the enemy of good: Sometimes ECMO consultation clarifies that conventional therapy should be optimized rather than abandoned

Final Pearl: The best ECMO consultation is often the one that results in better conventional management rather than ECMO cannulation.

The decision to pursue ECMO represents one of the most complex risk-benefit calculations in critical care medicine. By understanding the indications, timing, and contraindications outlined in this review, residents can contribute meaningfully to these life-and-death decisions while recognizing when specialist expertise is essential.

Final Hack: Develop a relationship with your institutional ECMO team before you need them. Understanding their thought processes and decision-making frameworks will make you a better intensivist, whether or not your patients ultimately require ECMO.

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Conflict of Interest Statement: The authors have no financial conflicts of interest to declare related to ECMO technology or pharmaceutical interventions discussed in this review.

Monday, August 11, 2025