Extracorporeal Membrane Oxygenation (ECMO) Current Use and Evolving Applications

Introduction
1. Extracorporeal membrane oxygenation (ECMO) is increasingly being used for severe forms of respiratory failure.
2. Indications of ECMO have expanded beyond acute respiratory distress syndrome (ARDS) to include bridging therapy for pulmonary hypertensive crises, lung transplantations, and refractory hypoxemic/hypercarbic respiratory failure

Principles and Circuitry

                                                                                                        N Engl J Med 2011; 365:1905-1914

Types:
1. Venovenous ECMO (VV-ECMO)
     A. Respiratory support
2. Venoarterial ECMO (VA-ECMO) 
     A. Respiratory and hemodynamic support
3. Arteriovenous ECMO
     A. CO2 removal
Cannulation
1. Two site
     A. Pros: Easier to prime
     B. Cons: Re-circulation, immobility, poor nutrition, lack of physical therapy
2. Single site
     A. Pros: less re-circulation, better mobility, physical therapy, nutrition
     B. Cons: need fluoroscopy, echocardiography for priming

                                                                                                      N Engl J Med 2011; 365:1905-1914

ECMO for ARDS

1. Most commonly accepted indication

2. Indications:

    A. PaO2/FiO2 <80 mmHg

    B. pH <7.15

    C. End-inspiratory plateau airway pressures >35 cm of H2O despite optimized sedation and ventilator management

3. Contraindications:

No absolute, but advanced age, multiple organ failures, severe comorbid disease should be considered

4. Advantages:

    A. Prevent ventilator-associated lung injury

    B. Facilitates low tidal volume ventilation

    C. Lung rest

        a. Tidal volume <6 mL/kg of predicted body weight (PBW)

        b. End-inspiratory plateau pressures <20 cm H2O

        c. ECCO2R

ECMO as Bridge to Lung Transplantation

1. Invasive mechanical ventilation and ECMO are associated with high post-transplant mortality

2. Decompensation requiring either during waiting periods of 12 ~ 24 months is a tipping point that reduces likelihood of long-term survival

3. Adequate gas exchange eliminates risk of ventilator-associated complications

4. Aggressive physical therapy while on ECMO support may increase patients’ pre-transplant conditioning

ECMO for Pulmonary Hypertension

1. Patients with pulmonary arterial hypertension in acute crisis or progressive RV failure have high morbidity and mortality

    A. Too rapid for effective pulmonary vasodilator therapy  

    B. May need lung transplantation

2. VA-ECMO as bridging therapy allows organ function to be preserved

    A. Acute decompensation = pulmonary vasodilators + ECMO 

    B. Lung transplant patients = pulmonary vasodilators weaned

3. Problem: 

    A. Upper body O2 delivery limited in Femoral vessel ECMO 

        a. Branch an IJV reinfusion cannula off the arterial cannula --> Venoarterial-venous ECMO

        b. VA ECMO through upper body

            1) IJV --> R’t subclavian artery

ECMO for COPD and Status Asthmaticus

1. Patients requiring MV for COPD exacerbations have in-hospital mortality of up to 30% and survivors have unfavorable consequences

2. Extracorporeal CO2 removal (ECCO2R) in acute exacerbations of COPD is an evolving and potential future application of extracorporeal technology

3. ECCO2R may compensate for exertional dyspnea that limits physical activity, physical rehabilitation can be enhanced

4. Better mobility when coupled with an upper-body, dual-lumen cannula

Alternative Uses

1. Diffuse alveolar hemorrhage attributed to vasculitis, collagen vascular disease, and others

2. Bleeding, especially alveolar hemorrhage

3. Massive pulmonary embolism when thrombolysis is contraindicated or ineffective

4. Amniotic fluid emboli after Cesarean-section

Future

1. Milder forms of ARDS

2. Bridge to recovery and transplant to permit reduced sedative use, increased physical therapy to improve long-term benefits

3. Liberation from mechanical ventilators

4. Decrease the size and existing extracorporeal technology