Comparison of cerebral metabolic rate of oxygen, blood flow, and bispectral index under general anesthesia

Abstract

Significance: The optical measurement of cerebral oxygen metabolism was evaluated.

Aim: Compare optically derived cerebral signals to the electroencephalographic bispectral index (BIS) sensors to monitor propofol-induced anesthesia during surgery.

Approach: Relative cerebral metabolic rate of oxygen ( ${\mathrm{rCMRO}}_2$ ) 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.

Results: In 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%], ${\mathrm{rCMRO}}_2$ 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%), ${\mathrm{rCMRO}}_2$ (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, ${\mathrm{rCMRO}}_2$ , and rCBF was witnessed in the majority of the cases (14/18 and 12/18 for rCBF and 19/21 and 13/18 for ${\mathrm{rCMRO}}_2$ in the initial and final part, respectively). These changes were also correlated in time ( $R>0.69$ to $R=1$ , $p\text{-}\text{values}<0.05$ ).

Conclusions: Optics can reliably monitor ${\mathrm{rCMRO}}_2$ in such conditions.

Keywords: bispectral index; cerebral blood flow; cerebral metabolic rate of oxygen; cerebral physiological changes; diffuse correlation spectroscopy; diffuse optics; near-infrared spectroscopy; propofol-induced anesthesia; time-resolved spectroscopy.