What is the current evidence and protocol for pre-hospital Extracorporeal Membrane Oxygenation (ECMO)?

Pre-Hospital ECMO: Current Evidence and Protocols

Pre-hospital ECMO is an emerging rescue therapy with limited evidence but may be considered for selected patients with cardiac arrest, particularly those with cardiac diagnoses, when implemented by experienced teams with appropriate resources and systems.

Current Evidence Base

The evidence for pre-hospital ECMO implementation remains limited. The most recent guidelines from the American Thoracic Society (2024) suggest the use of venovenous ECMO (VV-ECMO) in selected patients with severe ARDS, but this recommendation is conditional with low certainty of evidence 1. This recommendation is primarily focused on in-hospital settings rather than pre-hospital environments.

For cardiac arrest scenarios, the American Heart Association (2015) suggests that extracorporeal membrane oxygenation with resuscitation may be considered for infants and children with cardiac diagnoses who have in-hospital cardiac arrest (IHCA) in settings that provide the expertise, resources, and systems to optimize ECMO use 1. However, there is insufficient evidence to recommend for or against routine ECMO use in infants and children without cardiac diagnoses who have IHCA 1.

Patient Selection Criteria

Patient selection for pre-hospital ECMO should be highly selective and focus on:

• Patients with potentially reversible etiologies of respiratory or cardiac failure
• Very severe hypoxemia (PaO₂/FiO₂ ratio < 80 mm Hg) or hypercapnia (pH < 7.25 with PaCO₂ > 60 mm Hg) despite optimal conventional management
• Early in their course of illness (< 7 days)
• Few risk factors for futility of treatment 1
• Cardiac arrest patients with cardiac diagnoses 1

Implementation Considerations

Pre-hospital ECMO implementation faces significant challenges:

• Resource Requirements: ECMO is extremely resource-intensive regarding equipment, trained personnel, and costs 1
• Team Expertise: Requires specialized teams with experience in ECMO initiation, management, and transport
• System Integration: Necessitates coordination between pre-hospital services and ECMO-capable centers
• Logistical Challenges: Transportation of patients on ECMO requires specialized vehicles and equipment

Current Protocols

While standardized protocols for pre-hospital ECMO are still evolving, the general approach includes:

1. Conventional Therapy First: Less invasive therapies should be attempted before ECMO consideration, including:

   • Lung-protective ventilation
   • Higher PEEP
   • Neuromuscular blockade
   • Prone positioning 1

2. ECMO Initiation Decision: Based on failure to respond to conventional therapy and meeting selection criteria

3. ECMO Configuration Selection:

   • VV-ECMO for respiratory failure without hemodynamic compromise
   • VA-ECMO for cardiac arrest or cardiogenic shock 2

4. Transport Considerations:

   • Specialized transport teams
   • Continuous monitoring during transport
   • Protocols for managing complications during transport

Outcomes and Complications

The evidence regarding outcomes of pre-hospital ECMO is limited. The most recent systematic reviews have found:

• Heterogeneity in mortality outcomes across studies 1
• Potential complications including significant bleeding, vascular injuries, and thrombotic events
• Concerns about resource allocation and health equity 1

Future Directions

The field of pre-hospital ECMO is evolving rapidly:

• Technological advances may lead to more portable and user-friendly ECMO systems 3
• Ambulatory ECMO is showing promise as a bridge to definitive treatment 4
• Research is needed to better define patient selection criteria and standardize protocols for pre-hospital implementation

Conclusion

Pre-hospital ECMO remains an emerging therapy with significant implementation challenges. While it shows promise for selected patients, particularly those with cardiac diagnoses experiencing cardiac arrest, its widespread adoption in pre-hospital settings requires further research, technological advancement, and system development. Centers considering pre-hospital ECMO should ensure they have the necessary expertise, resources, and systems to optimize outcomes.