What are the recommended ECMO (Extracorporeal Membrane Oxygenation) flow and sweep gas flow settings for an adult patient with severe cardiac dysfunction undergoing right atrial thrombus thrombectomy with VA-ECMO (Veno-Arterial Extracorporeal Membrane Oxygenation)?

ECMO Flow and Sweep Gas Settings for VA-ECMO During Right Atrial Thrombus Thrombectomy

For an adult patient with severe cardiac dysfunction undergoing right atrial thrombus thrombectomy with VA-ECMO, initiate ECMO flow at 3-4 L/min immediately post-cannulation and gradually increase as tolerated, while maintaining arteriovenous oxygen difference between 3-5 cc O₂/100ml blood and targeting mixed venous saturation (SvO₂) above 66%. 1

Initial Flow Rate Management

Target ECMO flow of 3-4 L/min immediately after cannulation, avoiding immediate maximization of flow to prevent sudden increases in left ventricular afterload that could precipitate hypertensive crisis or worsen cardiac recovery. 1

• Gradually increase flow as tolerated based on hemodynamic response rather than immediately maximizing to full support 1
• Monitor arteriovenous O₂ difference as the most 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%, recognizing this is a hemoglobin-dependent parameter 1
• Evaluate the ratio of O₂ delivery to consumption (DO₂:VO₂), targeting above 3 1

Sweep Gas Flow Management

Titrate sweep gas FiO₂ to maintain arterial O₂ saturation of 92-97%, avoiding early hyperoxia (PaO₂ >300 mmHg) which is associated with mortality and poor neurological outcomes. 1, 2

• Avoid arterial hypoxemia (PaO₂ < 70 mmHg), particularly in the first 24-48 hours of VA-ECMO support 3, 2
• Avoid severe arterial hyperoxia (PaO₂ > 300 mmHg), especially in VA-ECMO where reperfusion injury risk is high 3, 2
• For patients with hypercapnia (PaCO₂ > 45 mmHg), avoid rapid changes in PaCO₂ within the first 24 hours of ECMO support to prevent cerebrovascular complications 3, 1, 2
• Perform serial arterial blood gas sampling in the first 24 hours of ECMO support 3, 2

Hemodynamic Targets and Monitoring

Maintain mean arterial pressure (MAP) > 70 mmHg while continuously monitoring for signs of left ventricular distension, which is a critical complication in peripheral VA-ECMO due to increased afterload. 3, 1

• Use right radial arterial line for blood gas sampling as it best represents cerebral perfusion in peripherally cannulated patients 1
• Continuously monitor ECMO flow, arterial blood pressure, and perform repeated echocardiography 3
• Monitor for left ventricular distension by assessing for narrow pulse pressure from the right radial arterial line, which suggests a mixing point proximal to the innominate artery 1
• Wean vasoactive inotropic support as tolerated after cannulation to reduce cardiac workload 1

Critical Complications to Monitor

Watch for Harlequin syndrome (differential hypoxia), which occurs in approximately 10% of peripherally cannulated VA-ECMO patients, by using continuous cerebral oximetry to follow trends and enable early detection. 3, 1

• Monitor central venous oxygen saturation (SvO₂) and lactate levels continuously 3
• Maintain accurate recording of fluid intake and output, as positive fluid balance is an independent predictor of poor outcomes in ECMO patients 3
• Strive for a daily negative fluid balance after ECMO flows are optimized and the patient is hemodynamically stable 1
• Monitor for fluid overload, which is frequent in ECMO patients and associated with increased mortality by the third day 1

Left Ventricular Unloading Considerations

If signs of LV distension develop despite flow optimization (evidenced by pulmonary congestion, elevated pulmonary artery pressures, or echocardiographic findings), 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
• Support ejection with inotropic agents to attenuate LV distension 1
• Choose the least invasive but most effective venting strategy based on patient condition 1

Ventilation Management During VA-ECMO

Maintain mechanical ventilation despite ECMO support to ensure lung expansion and prevent Harlequin syndrome, using lung-protective ventilation strategies with low ventilatory pressure and respiratory rate. 1

• Titrate FiO₂ to maintain arterial O₂ saturation >92% 1
• Use PEEP greater than 10 cmH₂O to maintain alveolar inflation and prevent pulmonary edema and atelectasis 1
• Employ lung-protective ventilation with tidal volume of 6 ml/kg predicted body weight 3

Common Pitfalls to Avoid

• Never immediately maximize ECMO flow as this increases left ventricular afterload abruptly, potentially worsening cardiac recovery and precipitating complications 1
• Avoid hypovolemia which may induce venous collapse during extracorporeal blood extraction, causing cannula 'suctioning' and 'chatter' that result in flow reduction and hemolysis 3
• Do not allow excessive fluid administration as positive fluid balance by the third day of ECMO is associated with increased mortality 3, 1
• Avoid early hyperoxia (PaO₂ >300 mmHg) which is associated with mortality and poor neurological outcomes 1, 2