ECMO - Extracorporeal Membrane Oxygenation ECPR and Special Populations Questions and Answers — Questions and Answers
Question 1: A 58-year-old patient experiences a witnessed in-hospital cardiac arrest (IHCA) with an initial shockable rhythm. After 20 minutes of high-quality CPR and adherence to ACLS protocols, ROSC has not been achieved. Which of the following is the strongest indicator for transitioning to ECPR in this patient?
- The patient's end-tidal CO2 (ETCO2) has remained consistently above 15 mmHg. (Correct answer)
- The patient has a known history of coronary artery disease.
- The arrest was unwitnessed, but CPR was initiated within 5 minutes.
- The patient received three doses of epinephrine per ACLS protocol.
Correct answer: The patient's end-tidal CO2 (ETCO2) has remained consistently above 15 mmHg.
A sustained ETCO2 above 10-15 mmHg during CPR indicates effective chest compressions are generating some degree of pulmonary blood flow and metabolic activity, which is a favorable prognostic sign for ECPR. It suggests a potentially salvageable state, making the patient a better candidate. The other options are either less specific indicators (history of CAD), negative factors (unwitnessed arrest is less favorable), or simply process measures (epinephrine doses).
Question 2: Which of the following represents a unique and immediate challenge when establishing peripheral VA ECMO during active CPR (ECPR)?
- Achieving adequate circuit anticoagulation before initiation.
- Difficulty in identifying and cannulating collapsed femoral vessels. (Correct answer)
- Preventing hypothermia due to the extracorporeal circuit.
- Managing left ventricular distention after flow is established.
Correct answer: Difficulty in identifying and cannulating collapsed femoral vessels.
During cardiac arrest, the absence of pulsatile arterial flow and the collapse of the venous system make vessel identification and cannulation extremely challenging, even with ultrasound guidance. This is a primary procedural hurdle that distinguishes ECPR from elective ECMO initiation and requires a highly skilled team to perform rapidly. Anticoagulation, hypothermia, and LV distention are all important considerations, but they are typically managed after vascular access is secured and ECMO flow has been initiated.
Question 3: When considering VA ECMO for a peripartum patient with refractory cardiogenic shock, which cannulation strategy is generally preferred to ensure adequate systemic and uterine perfusion?
- Central cannulation via sternotomy, as it provides the best possible flow.
- Dual-lumen single cannula in the right internal jugular vein.
- Femoral vein drainage and axillary artery return, to perfuse the upper body and coronaries. (Correct answer)
- Femoral-femoral, to minimize risk to the thoracic structures.
Correct answer: Femoral vein drainage and axillary artery return, to perfuse the upper body and coronaries.
A femoral vein to axillary artery cannulation strategy provides anterograde flow of oxygenated blood to the aortic arch. This ensures perfusion of the coronary arteries and cerebral circulation, which is critical for maternal stability and avoids the differential hypoxia (Harlequin syndrome) associated with femoral-femoral VA ECMO, which could compromise both the mother and the fetus.
Question 4: A 30-year-old patient is placed on VA ECMO for refractory septic cardiomyopathy. Despite achieving target ECMO flows and mean arterial pressure, the patient's lactate remains elevated, and peripheral perfusion is poor. In this scenario of severe vasodilation due to sepsis, which adjunctive management strategy is most critical to improve end-organ perfusion?
- Increasing the ECMO pump flow rate significantly above cardiac output.
- Administering aggressive fluid boluses to increase preload.
- Increasing the sweep gas flow to reduce PaCO2.
- Titrating vasopressor therapy to achieve an adequate mean arterial pressure. (Correct answer)
Correct answer: Titrating vasopressor therapy to achieve an adequate mean arterial pressure.
In refractory septic shock, the underlying pathophysiology is profound vasodilation. While VA ECMO provides circulatory flow, it cannot restore vascular tone. Therefore, concurrent vasopressor therapy is essential to increase systemic vascular resistance (SVR) and achieve a mean arterial pressure (MAP) sufficient for end-organ perfusion. Without adequate MAP, the flow generated by the ECMO pump will not translate to effective tissue oxygen delivery.
Question 5: A 28-year-old patient with blunt chest trauma develops severe ARDS and requires VV ECMO. The patient has multiple rib fractures and a small, stable pulmonary contusion. The trauma team is concerned about bleeding risk. What is the most appropriate initial anticoagulation strategy for this patient?
- Initiate a standard heparin infusion with a target aPTT of 60-80 seconds.
- Start a bivalirudin infusion as it has a more predictable response.
- Use a completely heparin-free circuit and monitor for signs of clotting.
- Withhold systemic anticoagulation for the first 24-48 hours while monitoring for bleeding. (Correct answer)
Correct answer: Withhold systemic anticoagulation for the first 24-48 hours while monitoring for bleeding.
In trauma patients on ECMO, the risk of life-threatening hemorrhage often outweighs the risk of circuit thrombosis, especially in the early phase. A common approach is to withhold systemic anticoagulation for at least 24-48 hours, or until the sources of bleeding are controlled and the patient is stable. Modern heparin-bonded circuits can often tolerate this period without systemic anticoagulation.
Question 6: In patients who undergo ECPR for out-of-hospital cardiac arrest (OHCA), which factor is most strongly associated with favorable neurological outcomes?
- A short 'low-flow' time (duration of CPR until ECMO initiation). (Correct answer)
- Total dose of epinephrine administered by EMS.
- Successful intubation in the field on the first attempt.
- The use of a mechanical CPR device during transport.
Correct answer: A short 'low-flow' time (duration of CPR until ECMO initiation).
The duration of the low-flow state (the time from the start of CPR to the establishment of ECMO flow) is one of the most powerful predictors of survival with good neurological outcome in ECPR. Shorter durations imply less time with suboptimal cerebral perfusion, reducing the risk of anoxic brain injury. ELSO guidelines suggest a goal of establishing ECMO flow within 60 minutes of the onset of cardiac arrest.
ECMO - Extracorporeal Membrane Oxygenation ECPR and Special Populations Questions and Answers
A 58-year-old patient experiences a witnessed in-hospital cardiac arrest (IHCA) with an initial shockable rhythm.
After 20 minutes of high-quality CPR and adherence to ACLS protocols, ROSC has not been achieved.
Which of the following is the strongest indicator for transitioning to ECPR in this patient?