Table 3.

Current non-invasive clinical technologies for neurologic monitoring in patients on ECMO.

Monitoring technique	Description
Neurological pupil index (NPi)	• Automatedly assesses pupil size • Neurological deterioration is always associated with a sudden drop in NPi value below 2.8–3.0 • Influenced by ambient light and high concentrations of opioids
Cerebral near-infrared spectroscopy	• Monitors of regional oxygen saturation (rSO2) • Decreases from baseline (>25% drop) and a large right-left rSO2 difference (>10%) may predict acute neurologic injury • Affected by ambient light and skin color
Electroencephalography (EEG)	• Assess neurologic status • Continuous EEG can detect non-convulsive seizures or status epilepticus • Occurrence of suppressed EEG background is associated with poor neurological outcome and mortality • Early Standard EEG can be used for prognostication • As the results of EEG depend on technician's experience and expertise, quantitative EEG can be applied in the future studies
Transcranial doppler (TCD) ultrasound	• Measures the pattern of cerebral blood flow, hemodynamic reserve, and microembolic signals • Effectiveness of TCD is uncertain with continuous, non-pulsatile, arterial flow in some patients on venoarterial ECMO • Detects intracranial artery microembolic signals, which may eventually lead to acute ischemic stroke
Biomarkers	• Serum protein biomarkers of cerebral injury, such as NSE, and S100B • Serial measurement can increase diagnostic accuracy • Serum half-life of NSE is long, and can be affected by hemolysis or cancer • S100B can be released from not only brain but also heart, bone and adipose tissue
Neuroimaging	• Cranial CT is the main technology for revealing and excluding acute cerebral injury • MRI is limited due to hardware incompatibility

ECMO, extracorporeal membrane oxygenation; NSE, neuron-specific enolase; CT, computerized tomography; MRI, magnetic resonance imaging.