How should Extracorporeal Cardiopulmonary Resuscitation (ECPR) flow rates be managed to avoid complications such as hypertension crisis and increased cardiac workload?

Management of ECPR Flow Rates to Avoid Hypertension and Cardiac Workload Complications

ECMO flow should not be increased immediately to the maximum level in ECPR patients, but rather should be carefully titrated to balance adequate perfusion while minimizing complications such as hypertension crisis and increased cardiac workload. 1

Initial Flow Rate Management

• Begin with a goal of 3-4 L/min ECMO flow after cannulation, gradually increasing as tolerated rather than immediately maximizing flow 1
• Monitor arteriovenous O₂ difference as a reliable parameter for setting ECMO flow goals, maintaining between 3-5 cc O₂/100ml of blood 1
• Assess mixed venous saturation (SvO₂), targeting above 66%, and the ratio of O₂ delivery to consumption (DO₂:VO₂) above 3, though these are hemoglobin-dependent parameters 1
• Use right radial arterial line for blood gas sampling as it best represents cerebral perfusion in peripherally cannulated patients 1

Hemodynamic Considerations

• Peripheral VA-ECMO increases left ventricular afterload, which can negatively impact cardiac recovery and should be carefully managed 1
• Maintain mean arterial pressure (MAP) that provides adequate cerebral and end-organ perfusion while minimizing LV afterload to ensure circulatory support and cardiac recovery 1
• Consider weaning vasoactive inotropic support as tolerated after cannulation to reduce cardiac workload 1
• Monitor for LV distension, which can be attenuated by supporting ejection with inotropic agents 1

Flow Optimization Strategies

• Gradually increase ECMO flow to avoid sudden increases in afterload that could precipitate hypertensive crisis 1, 2
• Higher ECMO blood flow rates resulting in higher SvO₂ decrease pulmonary artery pressure, cardiac output, and right heart workload - this can be beneficial but must be achieved gradually 2
• Avoid rapid changes in PaCO₂ within the first 24 hours of ECMO support, as this can lead to cerebrovascular complications 1
• Strive for a daily negative fluid balance after ECMO flows are optimized and the patient is hemodynamically stable 1

Monitoring for Complications

• Continuously monitor for signs of Harlequin syndrome (differential upper and lower torso oxygenation), which occurs in approximately 10% of peripherally cannulated patients 1
• Assess for narrow pulse pressure from right radial arterial line, suggesting a mixing point proximal to the innominate artery, versus wide pulse pressure indicating more distal mixing point 1
• Watch for signs of LV distension, which can lead to ventricular stasis, pulmonary congestion, and myocardial ischemia 1
• Monitor for fluid overload, which is frequent in ECMO patients and associated with increased mortality by the third day 1

LV Unloading Considerations

• If signs of LV distension develop despite flow optimization, consider additional mechanical circulatory support for LV unloading 1
• Options include percutaneous therapies such as intra-aortic balloon pump (IABP), Impella, or pulmonary artery venting via the internal jugular vein 1
• Choose the least invasive but most effective venting strategy based on patient condition 1
• Note that IABP or Impella is contraindicated in the presence of hypoxemic respiratory failure as they would exacerbate hypoxemic cerebral perfusion 1

Ventilation Management During ECPR

• Maintain mechanical ventilation despite ECMO support to ensure lung expansion and prevent Harlequin syndrome 1
• Titrate FiO₂ to maintain arterial O₂ saturation >92% 1
• Employ lung-protective ventilation strategies with low ventilatory pressure and respiratory rate 1
• Use PEEP greater than 10 cmH₂O to maintain alveolar inflation and prevent pulmonary edema and atelectasis 1

Avoiding Common Pitfalls

• Avoid early hyperoxia (PaO₂ >300 mmHg), which is associated with mortality and poor neurological outcomes 1
• Target arterial O₂ saturation of 92-97% by manipulating the ECMO sweep gas FiO₂ 1
• Prevent excessive fluid administration, as positive fluid balance by the third day of ECMO is associated with increased mortality 1, 3
• Recognize that low-flow time (duration of mechanical CPR until VA-ECMO support) strongly correlates with survival, emphasizing the importance of rapid but careful establishment of appropriate flow 4