Case 8

A 52-year-old man with severe ARDS on VV ECMO is found by the night nurse to be in pulseless electrical activity (PEA). The ECMO circuit appears to be functioning: the pump is running at 4.2 L/min, there is a visible color change between drainage (dark) and return (bright red) blood, and the sweep gas is flowing at 5 L/min. The bedside monitor shows a narrow-complex electrical rhythm at 72 bpm but no palpable pulse and the arterial line tracing is flat.

The ECMO circuit is functioning normally. On VV ECMO, does a functioning circuit provide adequate support during cardiac arrest? Explain your reasoning.

No. VV ECMO provides NO direct circulatory support. Blood is drained from and returned to the venous circulation—it does not bypass the heart. The circuit provides gas exchange (oxygenation and CO₂ removal) but depends entirely on the native heart to generate cardiac output and systemic perfusion. During cardiac arrest, even though the ECMO circuit is oxygenating blood and returning it to the venous system, there is no forward flow through the systemic circulation because the heart is not pumping. Therefore, the patient needs hemodynamic support (CPR) in addition to the respiratory support that the functioning ECMO circuit provides.

Which of the following is the correct approach to this patient’s PEA arrest?

A. No ACLS needed since the ECMO circuit is providing support; troubleshoot cause of arrest

B. Start CPR and provide ACLS without additional respiratory support while troubleshooting the cause

C. Immediately clamp the ECMO circuit and proceed with standard ACLS

D. Increase ECMO blood flow to 6 L/min to compensate for the cardiac arrest

The correct approach is to start CPR and provide full ACLS without additional respiratory support while troubleshooting the cause of arrest. Since the ECMO circuit is functioning (confirmed by gas flow, blood flow, and color change), gas exchange is being provided extracorporeally. The patient only needs hemodynamic support. ACLS is performed per standard protocols (CPR, epinephrine, evaluation of reversible causes), but additional respiratory interventions (like increasing ventilator settings) are not necessary because the circuit is handling gas exchange.

Choice A is wrong because VV ECMO does not provide circulatory support. Choice C is wrong because the functioning circuit is helping with gas exchange and should not be clamped. Choice D is wrong because increasing ECMO flow does not provide circulatory support in VV configuration.

List four potential reversible causes of PEA arrest in this patient that should be investigated.

Reversible causes of PEA arrest on VV ECMO to investigate:

(1) Tension pneumothorax—particularly concerning in ARDS patients on mechanical ventilation; check for absent breath sounds, tracheal deviation, and perform needle decompression if suspected.

(2) Hypovolemia—occult bleeding (GI, retroperitoneal, cannula site) is common on ECMO due to anticoagulation.

(3) Cardiac tamponade—especially if there has been a recent procedure or if the patient has a pericardial effusion. Bedside echocardiography is critical.

(4) Hyperkalemia or metabolic derangement—renal dysfunction is common on ECMO, particularly if hemolysis is present, and can lead to fatal arrhythmias. Additional considerations include myocardial infarction, pulmonary embolism, and drug effects.

Of course there are many more. Consider your Hs and Ts.

Despite 15 minutes of ACLS, the patient remains in PEA. What should be considered at this point?

If the patient has refractory cardiac arrest despite 15 minutes of ACLS, conversion from VV to VA ECMO should be considered, provided resources and expertise are available. VA ECMO provides both respiratory and circulatory support. Conversion typically involves adding an arterial return cannula (e.g., in the femoral artery) while maintaining the existing venous drainage. This allows the circuit to generate systemic perfusion independent of native cardiac function. The decision to convert should involve the ECMO team and consider the underlying cause of arrest, the patient’s prognosis, and whether the arrest is likely reversible.

How would the management of cardiac arrest differ if this patient were on VA ECMO with a functioning circuit instead of VV ECMO?

On VA ECMO with a functioning circuit, the management of cardiac arrest is fundamentally different. Because VA ECMO provides both respiratory AND circulatory support (blood is drained from the venous system and returned to the arterial system, bypassing the heart and lungs), the patient may be adequately supported even with cardiac standstill. In this scenario, ACLS is NOT needed.

The clinician should:

(1) Verify the circuit is functioning (gas flow, blood flow, color change).

(2) Increase blood flow if needed depending on patient assessment and hemodynamic response.

(3) Troubleshoot the cause of the arrest. Only if the VA ECMO circuit itself is also malfunctioning would full ACLS be required.

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