MD Jaiswal Lecture Hoag

Introduction to ECMO for ARDS

  • Acute Respiratory Distress Syndrome (ARDS)

    • Clinical definition involves criteria that leads to critical care management strategies.

  • Ventilator Induced Lung Injury (VILI)

    • Understanding mechanisms and impacts of mechanical ventilation in ARDS patients.

  • Strategies to Improve Mortality

    • ARDS Net guidelines and protocols to manage serious cases.

    • Use of prone positioning, neuromuscular blocking agents (NMBA).

  • Salvage Strategies (No proven mortality benefit)

    • Pressure control strategies, APRV, nitric oxide (iNO), Flolan, and ECMO as salvage options.

Definition and Physiology of ARDS

  • Clinical Definition (Old Definition)

    • Key Criteria:

      • Bilateral infiltrates on chest X-ray (CXR)

      • PaO2/FiO2 ratio <200

      • Pulmonary capillary wedge pressure (PCWP) <18

      • Non-cardiogenic pulmonary edema (Bernard et al., 1994).

Berlin Criteria for ARDS

  • Classification of ARDS Severity:

    • Mild ARDS: PaO2/FiO2 ratio <300

    • Moderate ARDS: PaO2/FiO2 ratio <200

    • Severe ARDS: PaO2/FiO2 ratio <100

  • Physiological Changes:

    • Endothelial injury and protein-rich edema influx.

    • Impaired removal of edema leading to complications like fibrosing alveolitis.

Mortality and Complications in ARDS

  • Mortality Rate: 40% to 60%.

    • Hypoxemia is not the direct cause of death; mortality stems from advanced fibroproliferative phase and mechanical ventilation complications.

    • Complications include multisystem organ failure, especially due to VILI.

Mechanisms of Ventilator Induced Lung Injury (VILI)

  • Types of Injuries:

    • Atelectrauma: Lung collapse due to low lung volume ventilation.

    • Baro/volutrauma: Injury from hyperinflation and overdistention when using high volume ventilation (Slutsky, NEJM 2013).

Management Strategies in ARDS

  • ARDS Network (ARDSNet)

    • Low tidal volume ventilation strategy at 6 ml/kg.

    • Plateau pressure should be maintained <30 mmHg.

    • Use of NMBA, prone positioning as effective management methods.

    • Evidence of Mortality Benefit: Strategies include Low Tidal Volume and prone positioning.

ARDS Network Trials

  • Notable Trials:

    • Multi-center studies comparing tidal volumes of 6 ml/kg versus traditional volumes of 12 ml/kg proved that lower tidal volumes effectively reduced morbidity and mortality.

    • Compliance with protocols critical during the first 24-48 hours for improved outcomes.

Lung Protective Strategies

  • Implementation of low tidal volume strategy at 6 ml/kg with plateau pressure <30.

  • PEEP Strategies: Use high/low PEEP to manage oxygenation without significant mortality benefit observed between the two.

  • Monitoring for complications with higher PEEP, such as hemodynamic compromise.

Prone Positioning in ARDS

  • Effectiveness: Prone positioning improves survival rates, P/F ratios, and reduces lung overdistension; implementation should occur within 48 hours of ARDS diagnosis.

  • Duration of prone therapy recommended for a minimum of 48-72 hours.

Neuromuscular Blocking Agents (NMBA) in ARDS

  • NMBA enhances lung protective ventilation and improves patient outcomes in severe ARDS (PaO2/FiO2 <120).

    • Associated with increased ventilator-free days and reduced incidence of barotrauma.

ECMO in Severe ARDS

  • Definition: Extracorporeal Membrane Oxygenation (ECMO) provides mechanical support for cardiac/pulmonary failure; derived from cardiac surgery techniques.

  • Types of ECMO:

    • VA ECMO: For cardiogenic shock.

    • VV ECMO: For severe respiratory failure.

  • Clinical Indications: Used in severe respiratory failure, ARDS due to various underlying causes.

EOLIA Trial

  • Overview: The EOLIA trial studies ECMO's effectiveness in severe ARDS; supported findings favoring early initiation of ECMO over conventional care methods.

  • Conclusions: Early ECMO initiation might not significantly reduce 60-day mortality, but could offer benefits as a rescue therapy.

Future Directions and Considerations

  • Careful patient selection and timing for ECMO are crucial.

  • Detailed monitoring of the patient's condition, including compliance with lung protective strategies.

  • Highlights the importance of evolving standards and guidelines for ARDS management worldwide.