• Frederick Sieber, Karin Neufeld, Esther S Oh, Allan Gottschalk, and Nae-Yuh Wang.
• Department of Anesthesiology and Critical Care Medicine, Johns Hopkins Bayview Medical Center, 4940 Eastern Avenue, Baltimore, MD, 21224, USA. fsieber1@jhmi.edu.
• BMC Anesthesiol. 2020 May 28; 20 (1): 129129.

BackgroundThis study determined whether the relationship between predicted propofol effect site concentration (Ce) and observer's assessment of alertness/sedation scale (OAA/S) or Bispectral Index (BIS) was similar comparing cognitively intact vs impaired patients undergoing hip fracture repair with spinal anesthesia and sedation.MethodsFollowing informed consent baseline mini-mental status exam (MMSE), Clinical Dementia Rating (CDR) and geriatric depression scale (GDS) were obtained. Intraoperatively OAA/S, BIS, and propofol (timing and exact amounts) administered were recorded. Cerebrospinal fluid was collected for Alzheimer's (AD) biomarkers. Mean Ce level (AvgCe) during surgery was calculated using the area under the Ce measurement series from incision to closure, divided by surgical time. Average OAA/S (AvgOAA/S), and BIS (AvgBIS) were similarly calculated. Pearson correlations of AvgCe with AvgOAA/S and AvgBIS were calculated overall and by CDR. Nonparametric locally weighted scatterplot smoothing (LOWESS) fits of AvgOAA/S and AvgBIS on AvgCe were produced, stratified by CDR. Multivariable regression incorporating baseline cognitive measurements or AD biomarkers assessed AvgOAA/S or AvgBIS associations with AvgCe.ResultsIn 186 participants AvgBIS and AvgOAA/S correlated with AvgCe (Pearson ρ = - 0.72; p < 0.0001 and Pearson ρ = - 0.81; p < 0.0001, respectively), and remained unchanged across CDR levels. Association patterns of AvgOAA/S or AvgBIS on AvgCe guided by LOWESS fits and modeled through regression, were similar when stratified by CDR (p = 0.16). Multivariable modeling found no independent effect on AvgBIS or AvgOAA/S by MMSE, CDR, GDS, or AD biomarkers after accounting for AvgCe.ConclusionsWhen administering sedation in conjunction with spinal anesthesia, cognitive impairment does not affect the relationship between predicted propofol AvgCe and AvgOAA/S or AvgBIS.

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