• L Froese, J Dian, A Gomez, and F A Zeiler.
• Biomedical Engineering, Faculty of Engineering, University of Manitoba, Winnipeg, Canada.
• Acta Neurochir (Wien). 2021 May 1; 163 (5): 1383-1389.

BackgroundImpaired cerebrovascular reactivity appears to be linked to worse global outcome in adult traumatic brain injury (TBI). Literature suggests that current treatments administered in TBI care, in the intensive care unit (ICU), fail to greatly impact recorded cerebrovascular reactivity measures. In particular, the impact of sedation on cerebrovascular reactivity in traumatic brain injury (TBI) remains unclear in vivo. The goal of this study was to preliminarily assess the relationship between objectively measured depth of sedation and cerebrovascular reactivity in TBI.MethodsWithin, we describe a case series of 5 adult TBI patients with TBI, during which objective high-frequency physiology for sedation depth, using bispectral index (BIS), and both intracranial pressure (ICP) and arterial blood pressure (ABP) were recorded. Pressure reactivity index (PRx) and RAP (a metric of cerebral compensatory reserve) were derived. Relationships between cerebrovascular reactivity and compensatory reserve monitoring with BIS metrics were explored using descriptive plots.ResultsA total of 5 cases in our prospectively maintained database with high-frequency physiology for ICP, ABP, and BIS. Through error bar plotting, it can be seen that each patient displays a parabolic relationship between BIS and PRx. This suggests a potential "optimal" depth of sedation where cerebrovascular reactivity is the most intact.ConclusionsThis small series highlights the potential impact of depth of sedation on cerebrovascular reactivity in TBI. It suggests that there may be an individual optimal depth of sedation, so as to optimize cerebrovascular reactivity. Further study of objective depth of sedation and its impact on cerebrovascular physiology in TBI is required.

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