Extracorporeal CPR (eCPR): Indications and Workflows

Extracorporeal cardiopulmonary resuscitation (eCPR) has established itself as a promising rescue strategy for refractory cardiac arrest in recent years. When conventional Advanced Life Support measures fail to achieve Return of Spontaneous Circulation (ROSC), emergency implantation of veno-arterial extracorporeal membrane oxygenation (VA-ECMO) offers the possibility of providing temporary circulatory support – thereby creating a therapeutic window in which reversible causes can be identified and treated. The evidence base is increasingly growing, yet the complexity of the procedure, strict patient selection, and the need for well-coordinated teams make eCPR an intervention that requires well-thought-out protocols and continuous training.

Basic Principle of eCPR

In eCPR, a VA-ECMO is implanted during ongoing resuscitation efforts. Deoxygenated blood is drained via a large-bore venous cannula (typically in the femoral vein), oxygenated extracorporeally through a membrane oxygenator with simultaneous CO₂ elimination, and then pumped back into the systemic circulation via an arterial cannula (typically in the femoral artery). The ECMO system thus takes over both the pumping and gas exchange functions, ensuring a minimal but critical organ perfusion pressure – even in the complete absence of intrinsic cardiac activity.

The central conceptual difference from conventional CPR is that mechanical chest compressions generate only approximately 25–30% of normal cardiac output, whereas a VA-ECMO can deliver flow rates of 3–5 L/min. This increases the chances of survival when the underlying cause of cardiac arrest is potentially reversible.

Indications and Patient Selection

Careful patient selection is the most critical factor for eCPR success. Not every patient with refractory cardiac arrest is a suitable candidate. The decision must be made rapidly but in a structured manner.

Inclusion Criteria

Most eCPR protocols are guided by the following criteria:

• Witnessed cardiac arrest with immediate initiation of basic life support (BLS)
• Initial rhythm: Ventricular fibrillation (VF) or pulseless ventricular tachycardia (pVT) – these rhythms are associated with the highest survival rates in eCPR
• Refractory cardiac arrest: No ROSC after ≥ 3 defibrillation attempts and adequate pharmacological therapy (epinephrine, amiodarone)
• Age: Typically 18–70 (some centers up to 75) years
• Suspected reversible cause: Acute myocardial infarction, pulmonary embolism, hypothermia, intoxication, refractory arrhythmia
• No-flow time < 5 minutes: The time without any circulatory support is a critical prognostic factor
• Low-flow time (duration of CPR to ECMO flow): Ideally < 60 minutes; some protocols accept up to 90 minutes with good CPR quality

Exclusion Criteria

• Unwitnessed cardiac arrest without bystander CPR
• Prolonged no-flow time (> 5–10 minutes)
• Known terminal illness with limited life expectancy
• Severe pre-existing neurological deficits
• Known DNR order (Do Not Resuscitate) or advance directive against intensive care measures
• Severe peripheral arterial disease (makes femoral cannulation difficult or impossible)
• Massive uncontrollable hemorrhage
• Type A aortic dissection
• Prolonged low-flow time > 90–120 minutes (center-specific)

Special Case: Hypothermia

Accidental hypothermia represents a special indication. Significantly extended time windows apply here, as hypothermia itself has neuroprotective effects. The principle "Nobody is dead until warm and dead" remains valid: In hypothermic patients with cardiac arrest, eCPR can be meaningful even after significantly prolonged CPR duration, provided the core temperature is < 30°C and there are no obvious signs of non-survivability (e.g., potassium > 12 mmol/L).

The Time Window: Why Every Minute Counts

The time factor in eCPR is even more critical than in conventional resuscitation. The central metric is the low-flow time – the total duration from the start of CPR to the initiation of ECMO flow. Every additional minute of low-flow time worsens neurological outcome.

Time Benchmarks

• No-flow time: Should be minimized through immediate bystander CPR (goal: < 5 min)
• Decision for eCPR: Should be made within the first 10–20 minutes of resuscitation
• Cannulation and ECMO start: The goal is ECMO flow within 60 minutes of cardiac arrest
• "Golden Hour" concept: The best outcomes are achieved when ECMO flow is established within 60 minutes of the arrest

These time targets require a highly structured system: The indication must be established in parallel with ongoing ACLS resuscitation, the eCPR team must be alerted early, and cannulation must be performed during ongoing CPR.

Cannulation Strategy

Emergency cannulation during ongoing resuscitation is technically demanding and requires a well-coordinated team.

Percutaneous Femoral Cannulation

The percutaneous femoral Seldinger technique is the standard approach:

1. Ultrasound-guided puncture of the femoral vein and femoral artery (ideally ipsilateral; some centers prefer contralateral)
2. Venous drainage cannula: 21–25 Fr, tip ideally at the level of the right atrium (position confirmed via fluoroscopy, TEE, or formula: groin to right ear)
3. Arterial return cannula: 15–17 Fr in the femoral artery
4. Distal limb perfusion cannula (DPC): 6–8 Fr placed antegrade into the superficial femoral artery – mandatory to prevent critical limb ischemia
5. Priming and connection of the ECMO system (modern systems allow priming within 2–3 minutes)
6. Initiation of ECMO flow: Target flow 3–5 L/min, adjusted according to hemodynamics

Surgical Cut-down

In cases of difficult vascular access (obesity, peripheral arterial disease), a surgical cut-down may be necessary. This requires more time and a surgeon experienced in vascular surgery, but should be established as a backup strategy.

Cannulation During Ongoing CPR – Practical Challenges

• Mechanical CPR devices (LUCAS, AutoPulse) significantly facilitate cannulation by ensuring continuous compressions and allowing access to the patient
• Team division: One team continues ACLS measures while a second team performs the cannulation – clear role assignment is essential
• Sterile precautions: Despite the emergency situation, a minimum of sterile technique should be maintained to reduce infections
• Anticoagulation: Heparin bolus (typically 5000 IU unfractionated heparin IV) before or immediately after cannulation, ACT target range 180–220 seconds

Workflow of an eCPR Case: From Cardiac Arrest to ECMO Flow

A typical eCPR workflow can be divided into phases:

Phase 1: Recognition and Initial Resuscitation (Minute 0–10)

• Cardiac arrest is recognized, BLS initiated
• Emergency medical services alerted, AED use or manual defibrillation
• ACLS measures: rhythm analysis, defibrillation for shockable rhythm, epinephrine, amiodarone
• Early evaluation: Is the patient an eCPR candidate?

Phase 2: Activation of the eCPR Team (Minute 10–20)

• No ROSC despite adequate ACLS → decision for eCPR
• Activation of the ECMO team (cardiac surgery, cardiology, intensive care medicine – depending on local structure)
• Apply mechanical CPR device (if not already done)
• Transport to the cannulation site (cardiac catheterization lab, resuscitation bay, OR – center-specific)

Phase 3: Cannulation and ECMO Start (Minute 20–60)

• Ultrasound-guided femoral puncture during ongoing mechanical CPR
• Insertion of venous and arterial cannulae
• Connection and priming of the ECMO system
• Initiation of ECMO flow → hemodynamic assessment
• Insertion of the distal limb perfusion cannula
• Cannula position verification

Phase 4: Post-ECMO Stabilization and Cause Investigation

• Immediately after ECMO start: actively search for and treat reversible causes
• Coronary angiography when acute myocardial infarction is suspected (most common reversible cause in VF/pVT)
• CT angiography when pulmonary embolism is suspected
• Targeted Temperature Management (TTM)
• Laboratory diagnostics: ABG, lactate, potassium, troponin, coagulation status
• Echocardiography: Assessment of cardiac function, pericardial effusion, right heart strain

Complications of eCPR

eCPR is a high-risk procedure. The most relevant complications include:

• Limb ischemia: Most common vascular complication (up to 15–20%), which is why the distal perfusion cannula is mandatory. Regular monitoring via NIRS (near-infrared spectroscopy) or clinical assessment
• Bleeding complications: Due to anticoagulation, cannulation site, coagulopathy following prolonged CPR
• Harlequin syndrome (North-South syndrome): When cardiac function recovers, the heart pumps deoxygenated blood into the ascending aorta while the ECMO delivers oxygenated blood retrogradely from the femoral artery – monitoring right-sided SpO₂ (forehead or right hand) is essential
• Hemolysis: Caused by the centrifugal pump
• Infections: Cannulation site, pneumonia
• Thromboembolic events
• Multi-organ failure following prolonged low-flow

Evidence

The evidence base for eCPR has substantially improved through several randomized controlled trials (RCTs):

• The ARREST trial (University of Minnesota) demonstrated a significant survival benefit for eCPR compared to standard ACLS in refractory shockable rhythm in the prehospital setting. The trial was stopped early due to eCPR superiority.
• The PRAGUE OHCA study found no significant difference in the primary endpoint (neurologically favorable 180-day survival) but showed trends favoring eCPR and had methodological limitations (crossover, late ECMO implantation).
• The INCEPTION trial from the Netherlands also found no significant difference in 30-day survival, although ECMO implantation times were partly prolonged.

The overall assessment of the evidence suggests that eCPR can offer a survival benefit with strict patient selection, short implantation times, and well-coordinated teams – particularly with an initial shockable rhythm and suspected coronary etiology. The AHA guidelines classify eCPR as an intervention that may be considered in specialized centers with appropriate infrastructure and expertise (Class 2b).

Structural Requirements and Team Concept

eCPR is not a procedure that can be implemented ad hoc. The following prerequisites must be in place:

• 24/7 availability of an ECMO team with cannulation competency
• Structured activation protocol with clearly defined triggers
• Pre-defined patient selection criteria (checklists, algorithm cards)
• Regular team training including simulation of the entire process chain
• Post-ECMO infrastructure: Cardiac catheterization lab, ICU with ECMO experience, vascular surgery
• Data collection and quality assurance (ELSO Registry participation recommended)

Team coordination is the decisive success factor. The interplay between emergency medicine, cardiology, cardiac surgery, intensive care medicine, and perfusion must function seamlessly. CRM principles (Crew Resource Management) – clear communication, role assignment, situational awareness – are of enormous importance in eCPR, as complex decisions must be made and invasive procedures performed under extreme time pressure.

Ethical Aspects and Limitations

eCPR raises relevant ethical questions:

• When is the right time to discontinue therapy? The decision to limit therapy on ECMO requires clear criteria (e.g., absent cardiac recovery after 48–72 hours, irreversible neurological damage)
• Informed consent: Consent prior to the procedure is inherently impossible – the decision is made under the principle of presumed consent
• Resource allocation: eCPR is resource-intensive. The question of whether the procedure should be applied broadly or selectively must be discussed at a systemic level
• Organ donation: eCPR can open the possibility of organ donation under controlled conditions in patients without neurological recovery – this aspect also requires ethical reflection and transparent protocols

Summary: Key Points for Clinical Practice

• eCPR is a rescue strategy for refractory cardiac arrest with a suspected reversible cause
• Strict patient selection is the most important success factor
• Shockable initial rhythm, witnessed arrest, short no-flow and low-flow times improve outcome
• Goal: ECMO flow within 60 minutes of cardiac arrest
• Percutaneous femoral cannulation under ultrasound guidance is the standard approach
• The distal limb perfusion cannula is mandatory
• Post-ECMO: immediate search for and treatment of the reversible cause
• Regular team training and structured protocols are indispensable

Practical Training

eCPR is the prime example of how advanced resuscitation concepts build upon a solid ACLS foundation. The structured approach to cardiac arrest – rhythm analysis, differential diagnoses, reversible causes, team coordination – forms the basis upon which complex interventions like eCPR become possible. In the ACLS course by Simulation Tirol, you train these fundamentals in a hands-on, AHA-certified format: from systematic resuscitation algorithms to team communication and structured decision-making for refractory rhythms. Because even if you don't perform cannulation yourself in your clinical practice – the decision of whether and when eCPR is indicated begins with solid ACLS management.