SignificanceThe optical measurement of cerebral oxygen metabolism was evaluated.AimCompare optically derived cerebral signals to the electroencephalographic bispectral index (BIS) sensors to monitor propofol-induced anesthesia during surgery.ApproachRelative cerebral metabolic rate of oxygen (rCMRO2) and blood flow (rCBF) were measured by time-resolved and diffuse correlation spectroscopies. Changes were tested against the relative BIS (rBIS) ones. The synchronism in the changes was also assessed by the R-Pearson correlation.ResultsIn 23 measurements, optically derived signals showed significant changes in agreement with rBIS: during propofol induction, rBIS decreased by 67% [interquartile ranges (IQR) 62% to 71%], rCMRO2 by 33% (IQR 18% to 46%), and rCBF by 28% (IQR 10% to 37%). During recovery, a significant increase was observed for rBIS (48%, IQR 38% to 55%), rCMRO2 (29%, IQR 17% to 39%), and rCBF (30%, IQR 10% to 44%). The significance and direction of the changes subject-by-subject were tested: the coupling between the rBIS, rCMRO2, and rCBF was witnessed in the majority of the cases (14/18 and 12/18 for rCBF and 19/21 and 13/18 for rCMRO2 in the initial and final part, respectively). These changes were also correlated in time (R > 0.69 to R = 1, p-values < 0.05).ConclusionsOptics can reliably monitor rCMRO2 in such conditions.
One sedative drug to induce anesthesia during surgery is propofol. It diminishes the cerebral metabolic rate of oxygen (CMRO2), preventing memory formation and is coupled with a decrease in the cerebral blood flow (CBF). Anesthesia depth is commonly monitored by the bispectral index (BIS) to avoid awareness. Optical hybrid near-infrared spectroscopies have the potential to assess CMRO2 and other physiological signals (i.e. CBF). Optical signals acquired alongside BIS in surgeries were compared to it and provided additional information. Overall, agreement was found at different levels (group analysis, single subject analysis and simultaneity in time of changes).
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