What are the guidelines for monitoring an Extracorporeal Membrane Oxygenation (ECMO) circuit?

ECMO Circuit Monitoring Guidelines

Implement standardized, continuous multimodal monitoring of the ECMO circuit focusing on neurological surveillance, hemodynamic parameters, oxygenation targets, and circuit function to detect complications early and reduce morbidity and mortality. 1, 2

Neurological Monitoring (Highest Priority for Mortality Prevention)

Continuous cerebral oximetry is mandatory for all ECMO patients, especially those on peripheral VA ECMO at risk for differential hypoxia. 1, 2, 3 This represents the single most important monitoring intervention given the 19% acute brain injury risk in VA ECMO patients. 2

Serial Clinical Neurological Assessment

• Perform bedside nursing neurological assessments every 1-4 hours based on acute brain injury risk. 1
• Conduct daily assessment by a neurologist or neurointensivist when available. 1
• Use standardized scoring tools including Glasgow Coma Scale and Confusion Assessment Method. 1
• Assess mental status, brainstem reflexes (pupillary light response, oculocephalic, corneal, cough/gag reflexes), and motor examination when sedation is lightened. 1
• Implement pupillometry if available for objective pupil assessment. 1, 3

Advanced Neuromonitoring

• Obtain intermittent EEG and somatosensory evoked potentials (SSEP) in all comatose patients. 1, 2, 3
• Use continuous EEG when available to detect non-convulsive seizures in comatose patients. 1
• Monitor for asymmetric cerebral desaturation (right-left differences) and duration of desaturation as better markers for acute brain injury detection. 1
• Obtain early neuroimaging for patients at risk of acute brain injury based on physical examination and neuromonitoring findings. 1

Hemodynamic Monitoring

Blood Pressure Targets

Maintain mean arterial pressure >70 mmHg to ensure adequate cerebral and end-organ perfusion. 1, 2, 3 However, individualize based on specific conditions:

• For acute ischemic stroke: Allow permissive hypertension (BP ≤220/120 mmHg) if the heart can tolerate the increased afterload. 1, 2
• For intracerebral hemorrhage: Target systolic BP <140 mmHg and MAP <90 mmHg due to anticoagulation-associated bleeding risk. 1, 2
• Monitor pulse pressure in the first 24 hours of VA ECMO; low pulse pressure (<20 mmHg) is associated with acute brain injury. 1

ECMO Flow Parameters

Target initial ECMO flow of 3-4 L/min immediately post-cannulation, gradually increasing as tolerated. 2, 3

Maintain arteriovenous oxygen difference between 3-5 cc O₂/100ml blood as the most reliable flow parameter. 2, 3 This is superior to absolute flow rates for assessing adequacy of support.

Differential Hypoxemia Monitoring (Critical for VA ECMO)

Obtain arterial blood gases from a right radial arterial line to best represent cerebral oxygenation. 2 This site approximates what the brain receives in peripheral VA ECMO.

Monitor for wide pulse pressure on right radial arterial line, which indicates significant left ventricular ejection reaching the upper body and suggests a distal mixing point. 2

When differential hypoxemia is detected, immediately increase ECMO flow to move the mixing point proximally toward the innominate artery. 2

Oxygenation and Ventilation Targets

Arterial Oxygen Management

Perform serial arterial blood gas sampling in the first 24 hours of ECMO. 1, 3

Avoid arterial hypoxemia (PaO₂ <70 mmHg) for 24-48 hours in VA ECMO, especially in patients at high risk for reperfusion injury. 1, 2, 3 Hypoxemia is associated with acute brain injury, particularly intracerebral hemorrhage. 1

Avoid severe arterial hyperoxia (PaO₂ >300 mmHg). 2, 3 Mild hyperoxemia (PaO₂ 100-120 mmHg) may be acceptable, but severe hyperoxemia increases mortality risk.

Target arterial oxygen saturation of 92-97% by adjusting ECMO sweep gas oxygen percentage. 3

Carbon Dioxide Management

Avoid rapid changes in carbon dioxide levels within the first 24 hours of ECMO support to prevent cerebrovascular complications. 3

Temperature Monitoring

Continuously monitor core temperature and actively prevent fever (>37.7°C). 1, 3

Consider mild-moderate hypothermia (33-36°C) for 24-48 hours in VA ECMO patients, especially those undergoing ECPR (extracorporeal cardiopulmonary resuscitation). 1, 2, 3 This may improve neurological outcomes in patients with prolonged cerebral ischemia and hypoperfusion.

Do not use hypothermia in VV ECMO patients. 1 There is no data supporting benefit and potential harm.

Sedation Monitoring

Use standardized sedation protocols with validated scoring systems such as the Richmond Agitation Sedation Scale. 1

Prefer intermittent (as-needed) analgo-sedation over continuous infusion. 1

Consider short-acting, non-benzodiazepine sedatives. 1

Perform daily reassessment of sedation goals, stepwise sedation weaning, and sedation interruptions to improve neurological examinations and acute brain injury diagnosis. 1

Circuit-Specific Monitoring

Membrane Pressure Monitoring

Monitor pre- and postmembrane pressures every 4 hours to detect oxygenator thrombosis. 4 An increase in pressure drop across the oxygenator at a preset flow rate suggests clot formation requiring component replacement.

Maintain intra-circuit pressures within physiological range (0-150 mmHg) for safety. 5

Flow Monitoring for Obstruction Detection

Monitor shunt flow continuously as an early indicator of distal circuit obstruction. 6, 7 Elevations in shunt flow indicate increased distal resistance from oxygenator obstruction or other circuit problems.

Use over-the-tube ultrasound flow probes for continuous, non-contact flow monitoring. 6, 7 This avoids risks of air embolism and infection associated with intermittent pressure measurements.

Common Pitfalls and Caveats

• Do not rely solely on fixed, dilated pupils before cannulation as an absolute contraindication to ECMO. 1 Patients receiving epinephrine during CPR frequently have fixed, dilated pupils but can achieve favorable neurological outcomes.

• Recognize that acute brain injury incidence is likely higher than clinical detection. 1 Autopsy studies show 68% of ECMO non-survivors had developed acute brain injury, with only 9 of 10 brains exhibiting injury at autopsy.

• Avoid tissue plasminogen activator (tPA) in ECMO patients with acute ischemic stroke due to high bleeding risk with systemic anticoagulation. 1 Instead, pursue mechanical thrombectomy for large vessel occlusion.

• Balance anticoagulation carefully: 42% of VV-ECMO patients experience thrombotic events, 37% experience bleeding events, and 21% experience both. 2

• Monitor for fluid overload, which is associated with increased mortality by the third day of ECMO. 3 Strive for daily negative fluid balance after ECMO flows are optimized and the patient is hemodynamically stable.