Near-Infrared Spectroscopy-Derived Dynamic Cerebral Autoregulation In Experimental Human Endotoxemia-An Exploratory Study

Cerebral perfusion may be altered in sepsis patients. However, there are conflicting findings on cerebral autoregulation (CA) in healthy participants undergoing the experimental endotoxemia protocol, a proxy for systemic inflammation in sepsis. In the current study, a newly developed near-infrared spectroscopy (NIRS)-based CA index is investigated in an endotoxemia study population, together with an index of focal cerebral oxygenation.

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Methods: Continuous-wave NIRS data were obtained from 11 healthy participants receiving a continuous infusion of bacterial endotoxin for 3 h ( NCT02922673) under extensive physiological monitoring. Oxygenated-deoxygenated hemoglobin phase differences in the (very)low frequency (VLF/LF) bands and the Tissue Saturation Index (TSI) were calculated at baseline, during systemic inflammation, and at the end of the experiment 7 h after the initiation of endotoxin administration.

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Results: The median (inter-quartile range) LF phase difference was 16.2?degrees (3.0-52.6 degrees) at baseline and decreased to 3.9 degrees(& nbsp;)(2.0-8.8 degrees) at systemic inflammation (p = 0.03). The LF phase difference increased from systemic inflammation to 27.6 degrees (12.7-67.5 degrees) at the end of the experiment (p = 0.005). No significant changes in VLF phase difference were observed. The TSI (mean +/- SD) increased from 63.7 & PLUSMN; 3.4% at baseline to 66.5 +/- 2.8% during systemic inflammation (p = 0.03) and remained higher at the end of the experiment (67.1 +/- 4.2%, p = 0.04). Further analysis did not reveal a major influence of changes in several covariates such as blood pressure, heart rate, PaCO2, and temperature, although some degree of interaction could not be excluded.

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Discussion: A reversible decrease in NIRS-derived cerebral autoregulation phase difference was seen after endotoxin infusion, with a small, sustained increase in TSI. These findings suggest that endotoxin administration in healthy participants reversibly impairs CA, accompanied by sustained microvascular vasodilation.