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Here is a comprehensive overview of Extracorporeal Membrane Oxygenation (ECMO):

ECMO — Overview

ECMO provides mechanical cardiorespiratory support to patients with severe cardiac and/or pulmonary failure when conventional therapies are exhausted. It works by draining venous blood, passing it through an oxygenator (artificial lung), and returning oxygenated blood to the patient.

Configurations

ModeFull NamePrimary Support
VV ECMOVenovenousRespiratory only (gas exchange); requires intact cardiac function
VA ECMOVenoarterialCardiac + respiratory; used in cardiogenic shock
V-AV ECMOVeno-arteriovenousHybrid; flexible transitions between circulatory and respiratory support
ECMO configurations
VA, VV, and V-AV ECMO circuit configurations

Brief History

  • 1953 — John Gibbon develops the heart-lung machine
  • 1972 — First successful cardiac ECMO use (2-year-old, cardiac failure post-Mustard procedure); J.D. Hill reports first prolonged ECMO in an adult ICU patient
  • 1975 — Robert Bartlett (the "father of modern ECMO") saves a neonate with meconium aspiration
  • 2009 — H1N1 pandemic triggers major expansion of adult ECMO for ARDS
  • Technology shift: roller pumps → centrifugal pumps; silicone membranes → polymethylpentene (PMP) oxygenators; open surgical cannulation → percutaneous bedside approach

Indications

VV ECMO (Respiratory Failure)

  • Severe ARDS (PaO₂/FiO₂ < 100 mmHg with PEEP > 5 cm H₂O) — ~40% mortality without ECMO
  • Viral/bacterial pneumonia (H1N1, COVID-19), bridge to lung transplant
  • Murray score and Berlin criteria guide candidacy

VA ECMO (Cardiac Failure)

  • Cardiogenic shock refractory to dual inotropes ± IABP/Impella
  • Postcardiotomy failure (inability to wean from bypass)
  • Acute MI with mechanical complications (VSR, acute MR, RV failure)
  • Fulminant myocarditis (~67% survival), peripartum cardiomyopathy
  • Massive pulmonary embolism with obstructive shock
  • Refractory ventricular arrhythmias
  • ECPR (CPR-ECMO) — ~29% survival to discharge in adults
  • High-risk PCI support

Key Management Points

Respiratory (VV ECMO)

  • Lung-protective ventilation: low tidal volume, PEEP ~10 cm H₂O, RR 10, FiO₂ 40%
  • Sweep gas adjusted to keep PCO₂ 35–45 mmHg, pH 7.35–7.45
  • Prone positioning can be performed concurrently
  • Steroids (DEXA-ARDS/Meduri protocols) often continued

Cardiac (VA ECMO)

  • Inotropes maintain LV pulsatility and aortic valve opening:
    • Dobutamine (β₁ agonist, reduces afterload)
    • Milrinone (PDE-3 inhibitor — preferred for RV failure/pulmonary HTN)
    • Epinephrine (severe shock requiring strong inotropy)
  • Loss of pulsatility → LV distention → pulmonary congestion, aortic root thrombus, coronary malperfusion
  • Inhaled nitric oxide for RV failure/pulmonary hypertension

Anticoagulation

  • Systemic heparin (institution-specific PTT/anti-Xa goals)
  • May be withheld short-term in high bleeding risk (especially VV)
  • HIT → switch to argatroban or bivalirudin
  • Flow > 4 L/min reduces thrombosis risk

Cannulation

TypeSitesNotes
PeripheralFemoral vein/artery, internal jugularPercutaneous, bedside; limits mobility if femoral
CentralDirect aorta/RA via sternotomy or axillaryPost-cardiac surgery; requires OR skill
ECMO circuit components
ECMO circuit: pump head, oxygenator, blood warmer
VA ECMO cannulation
Peripheral VA ECMO cannulation — femoral artery and vein

Complications

ComplicationDetails
BleedingMost common; from anticoagulation + cannula sites
HemolysisMechanical shear; monitor LDH, free Hgb, transmembrane pressures
InfectionCannula-site and circuit infections
Extremity ischemiaFemoral artery cannulation → distal limb ischemia; prevent with antegrade distal perfusion cannula
Stroke/CVAThromboembolism or hemorrhage from altered coagulation
DVTImmobility + vascular trauma; duplex at 24h post-decannulation
Low flow / chuggingHypovolemia, cannula malposition, or circuit thrombosis
Spinal cord ischemiaRare; turbulent mixing zone in peripheral VA ECMO
LV distention (VA ECMO)Retrograde flow impedes LV emptying → may need Impella or atrial septostomy

Outcomes (ELSO Registry)

  • Adult respiratory failure (VV ECMO): ~60% survival to discharge
  • Adult cardiac failure (VA ECMO): varies by indication; myocarditis ~67%, postcardiotomy ~30%, ECPR ~29%
  • Bridge to transplant/LVAD: 45–66% survive to discharge

Key Trials

  • CESAR trial: 63% vs. 47% survival (ECMO vs. standard care) for severe ARDS — supported use at specialized centers
  • EOLIA trial: No statistically significant mortality difference (35% vs. 46%, P = .09) but 28% crossover to ECMO; widely interpreted as supporting early ECMO in severe ARDS
Sources: Sabiston Textbook of Surgery, 20e; Miller's Anesthesia, 10e; Fishman's Pulmonary Diseases and Disorders
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