Table 3.
Neurological monitoring tools in patients with ECMO support
Neuromonitoring tool | Evidence |
---|---|
Near infrared spectroscopy (NIRS) | Several studies have shown that a large drop in rSO2 below baseline has been associated with brain injury.15,16 In a systematic review and meta-analysis on the role of rSO2 in ECPR, higher pre-cannulation rSO2 was associated with reduced mortality and better neurological outcomes.17 Asymmetric desaturation (right-left) and the duration of desaturation may be better markers for ABI detection.15 A few studies have utilized NIRS to identify disturbances in autoregulation18,19 |
Transcranial doppler ultrasound | Cerebral blood flow velocities and pulsatility index changes may be an early warning of ABI. In a prospective study of 135 patients, the absence of a pulsatility index was associated with a higher frequency of intraparenchymal hemorrhage and a composite bleeding event.20 However, caution should be exercised in interpreting the pulsatility index, as in another case series of adult VA ECMO, patients’ low or absent pulsatility index was related to their cardiac output.21 Similarly, microembolic signals in transcranial Doppler ultrasound needs further studies, as current evidence lacks correlation with the burden of microembolic signals to ABI22 |
Pupillometry | Automated pupillometry can objectively evaluate pupil size and reactivity and provide reliable prognostication information.23 Analysis of neurologic pupil index in 100 ECMO patients showed that a neurologic pupil index < 3 at any time 24–72 h after cannulation has 100% specificity for 90-day mortality, with 0% false positives;24 however, no pupillometry data on neurological outcomes exist in ECMO. High opiate doses may affect the reliability of pupillometry assessment |
Electroencephalography (EEG) | The American Clinical Neurophysiology Society consensus statement (2015) recommended EEG monitoring for patients on ECMO who are at high risk for neurological complications such as seizures. Early EEG on ECMO can help in identifying non-convulsive seizures with an opportunity for early intervention.25,26 Poor background activity on continuous EEG has been associated with poor outcomes on ECMO27–29 particularly in high-risk groups such as ECPR30,31 |
Somatosensory evoked potential (SSEP) | SSEP measure of cortical activity in response to stimuli in the peripheral nervous system has been utilized for neurological prognostication in comatose patients (especially for cardiac arrest). Application in the setting of ECMO, particularly in ECPR patients, may have a critical role. In a case series of 13 patients, Cho et al. showed that patients with a delayed response had poor neurological outcomes. However, in a subsequent cohort, the N20 responses remained intact despite poor neurological outcomes.29 Further nvestigations are needed to determine the actual value of this diagnostic examination |
Head computed tomography (CT) | Most ECMO centers perform head CTs upon new clinical neurological concerns. However, studies of VV ECMO, VA ECMO, and ECPR have reported routine head CT within 24 h post-cannulation to be beneficial for early diagnosis of subclinical intracranial complications, such as large infarctions, hemorrhage, or edema, which may influence decisions on ECMO support management32–36. Limitations of head CT include poor sensitivity for detecting acute or small infarctions, and inability to transport hemodynamically unstable patients to the CT scanner. Early cessation and judicious resumption of anticoagulation appeared feasible in the cohort of patients with ECMO-associated ischemic stroke and ICH with the use of serial neuroimaging studies if feasible37 |
Brain magnetic resonance imaging (MRI) | More than 30% of patients do not receive head CT scans during ECMO support due to transport restrictions and the lack of available transport personnel.7 The gold standard for diagnosing ABI is represented by 1.5-3 T MRI, which is incompatible with extracorporeal life support circuits and equipment due to safety concerns (heating, migration, and malfunction). Recent advances in low-field (64 mT) and portable MRI technology enable the acquisition of clinically meaningful imaging in the presence of ferromagnetic materials. The safety and feasibility of portable MRI in adults with ECMO support were demonstrated38 |
Serum biomarker | The most studied biomarkers include serum neuron-specific enolase and S100B, with higher values being significant predictors of mortality or neurological complications, especially if measured serially during ECMO support.39,40 However, the optimal timing and frequency of measurement, specific threshold values for outcome prediction, and methods to control for confounding effects have not been standardized |
ABI: acute brain injury; CT: computed tomography; ECMO: extracorporeal membrane oxygenation: ECPR: extracorporeal cardiopulmonary resuscitation; EEG: electroencephalography; ICH: intracranial hemorrhage; MRI: magnetic resonance imaging; NIRS: Near Infrared Spectroscopy; rSO2: regional tissue oxygen saturation; SSEP: somatosensory evoked potential; VA: venoarterial; VV: venovenous.