AUTHOR=Eleveld Nick , Hoedemaekers Cornelia W. E. , van Kaam C. Ruud , Leijte Guus P. , van den Brule Judith M. D. , Pickkers Peter , Aries Marcel J. H. , Maurits Natasha M. , Elting Jan Willem J. 

TITLE=Near-Infrared Spectroscopy-Derived Dynamic Cerebral Autoregulation in Experimental Human Endotoxemia—An Exploratory Study

JOURNAL=Frontiers in Neurology

VOLUME=Volume 12 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/neurology/articles/10.3389/fneur.2021.695705

DOI=10.3389/fneur.2021.695705

ISSN=1664-2295

ABSTRACT=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. 
Methods: Continuous-wave NIRS-data were obtained from eleven healthy participants receiving continuous infusion of bacterial endotoxin for 3 hours (Clinicaltrials.gov NCT02922673) under extensive physiological monitoring. Oxygenated-deoxygenated haemoglobin 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 end-of-experiment 7 hours after initiation of endotoxin administration.
Results: Median (IQR) LF-phase difference was 16.2 (3.0–52.6) degrees at baseline and decreased to 3.9 (2.0 – 8.8) degrees at systemic inflammation (p=0.03). LF-phase difference increased from systemic inflammation to 27.6 (12.7–67.5) degrees at end-of-experiment (p=0.005). No significant changes in VLF-phase difference were observed. TSI (mean±SD) increased from 63.7±3.4% at baseline to 66.5±2.8% during systemic inflammation (p=0.03) and remained higher at end-of-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
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.