Increased interhemispheric asymmetry of cerebral blood flow in comatose adult patients on extracorporeal membrane oxygenation

Extracorporeal membrane oxygenation (ECMO) is a mechanical circulatory support method that is associated with a high burden of neurologic injury, but neurologic examination and imaging of this population presents prohibitive medical and logistical challenges. Diffuse correlation spectroscopy (DCS) can measure relative cerebral blood flow (rBF) non-invasively at the bedside. In this study we observed interhemispheric differences in rBF in response to mean arterial pressure (MAP) changes in adult ECMO recipients. Thirteen patients were recruited (ages 21-78, 7 with cardiac arrest, 4 with acute heart failure, 2 with acute respiratory distress syndrome). They were dichotomized via Glasgow Coma Scale Motor score (GCS-M) into comatose (GCS-M ≤ 4; n=4) and non-comatose (GCS-M > 4; n=9) groups. Comatose patients had more interhemispheric rBF asymmetry (ASYMrBF) vs. non-comatose patients over a range of MAP values (29% [IQR 23-34%] vs. 11% [IQR 8-13%], p=0.009). ASYMrBF in comatose patients resolved near a MAP range of 70-80 mm Hg, while rBF remained symmetric through a wider MAP range in non-comatose patients. Associations between post-oxygenator pCO2 or pH vs. ASYMrBF individually did not meet significance, though the linear model slopes were different between comatose and non-comatose subgroups. Here we have demonstrated asymmetric cerebral autoregulation in comatose ECMO patients.