Venoarterial ECMO in Cardiogenic Shock

Keebler ME, Haddad EV, Choi CW, et al.
Venoarterial Extracorporeal Membrane Oxygenation in Cardiogenic Shock. JACC Heart Fail 2018;6:503-15.

The following are key points to remember about this state-of-the-art review of venoarterial extracorporeal membrane oxygenation (ECMO) in cardiogenic shock:

  1. ECMO can be administered through a venous-arterial circuit or venous-venous circuit. Venous-venous ECMO is primarily used in isolated pulmonary disease.
  2. Cannulation can be central or peripheral; hybrid approaches are possible. In femoral artery cannulation, limb ischemia can be minimized by directing a portion of the oxygenated blood to the cannulated distal limb. Peripheral arm cannulation permits increased mobility in some patients.
  3. Indication for ECMO is refractory cardiogenic shock in patients likely to benefit due to potentially reversible underlying etiology. ECMO provides a unique modality for treating refractory hypoxemia from pulmonary failure while supporting the right ventricle.
  4. A decision to use ECMO in any patient must ultimately be informed by patient-specific risk factors, the underlying diagnosis, expected duration of support, and the viability of an exit strategy. Early consultation with palliative care specialists should be considered in light of the high mortality and complication rates with ECMO.
  5. The Survival After Venoarterial ECMO risk score can aid in determining the utility versus futility of ECMO. It is calculated from 10 clinical parameters; the final score falls into 1 of 5 categories with a corresponding estimated survival ranging from 75% (Class I) to 18% (Class V).
  6. Ideal timing of ECMO use is after less-invasive technologies have been exhausted but before onset of significant end-organ dysfunction.
  7. The primary goal of patient management is restoration of tissue and end-organ perfusion:
    • Venous-arterial ECMO flow rate should initially be 50-70 ml/kg/min with mean arterial pressure >60 mmHg.
    • Arterial line should be placed for monitoring, ideally in the right arm. Higher pulsatility indicates possible myocardial recovery. Low or absent pulsatility indicates the left ventricle (LV) is ejecting small volumes or is not ejecting, which increases risk for blood stasis and thrombus formation.
    • Gas exchange can be adjusted via ECMO circuit or mechanical ventilation; hypoxemia, hyperoxia, and respiratory acidosis should be avoided. CO2 clearance can be regulated by adjusting the sweep gas flow relative to blood flow through the membrane filter to remove excess CO2 or by decreasing it if alkalosis develops.
    • LV preload reduction can be improved with intra-aortic balloon pump or Impella (Abiomed; Danvers, MA) if pulmonary edema persists despite diuresis, inotropes, and ECMO. Other options include atrial septostomy and direct LV venting.
    • Volume optimization is crucial for support of LV decompression and improves end-organ function. More positive fluid balances have been associated with worse outcomes. Dialysis filter may be placed directly in the ECMO circuit.
    • Prevention of upper body hypoxia may be realized by various means: adjusting ventilator settings, using central or hybrid cannulation, or decreasing the LV output to reduce mixing of oxygenated and deoxygenated blood.
    • Systemic anticoagulation is recommended unless active bleeding requiring blood transfusions is present.
    • Adjustment of drug dosages may be needed due to altered pharmacokinetics and dynamics especially for analgesics, sedatives, and antimicrobial agents.
    • Calorie and protein nutrition should continue as feasible.
  8. An algorithmic approach to weaning of ECMO is recommended. Lower levels of inotropes and vasopressors at weaning are associated with improved outcomes.
  9. The following complications have been reported with ECMO: neurologic complications (13.3% overall; 50% on imaging studies), limb ischemia, compartment syndrome, infection, hemolysis, bleeding, renal failure, systemic inflammatory response syndrome, and decreased quality of life.
  10. In the United States, costs for ECMO generally exceed $100,000 per patient, but data suggest that percutaneous circulatory support including ECMO results in decreased mortality and in-hospital costs.

Clinical Topics: Cardiac Surgery, Heart Failure and Cardiomyopathies, Invasive Cardiovascular Angiography and Intervention, Cardiac Surgery and Heart Failure, Acute Heart Failure, Mechanical Circulatory Support, Interventions and Imaging, Angiography, Nuclear Imaging

Keywords: Extracorporeal Membrane Oxygenation, Shock, Cardiogenic, Heart Ventricles, Carbon Dioxide, Oxygen, Respiration, Artificial, Arterial Pressure, Catheterization, Femoral Artery, Respiratory Insufficiency, Risk Factors, Pulmonary Edema, Intra-Aortic Balloon Pumping, Angiography, Cardiac Surgical Procedures, Hyperoxia, Acidosis, Respiratory, Alkalosis, Respiratory, Thrombosis

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