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

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 11 healthy participants receiving a continuous infusion of bacterial endotoxin for 3 h (ClinicalTrials.gov 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.Results: The median (inter-quartile range) LF phase difference was 16.2° (3.0–52.6°) at baseline and decreased to 3.9° (2.0–8.8°) at systemic inflammation (p = 0.03). The LF phase difference increased from systemic inflammation to 27.6° (12.7–67.5°) 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 ± 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.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.

Cerebral Autoregulation Assessment Using the Near Infrared Spectroscopy ‘NIRS-Only’ High Frequency Methodology in Critically Ill Patients: A Prospective Cross-Sectional Study

“…Interestingly, for the whole ICU study population, the LF-phase shift was low (12° (q1–q3 2.2–34)). So far, our ‘NIRS-only’ methodology has been applied in only two small studies [ 9 , 22 ]. In eleven healthy subjects, the baseline LF-phase shift was between 30° and 40° and decreased to values around 20° during hypercapnia.…”

Identifying Cognitive Impairment in Elderly Using Coupling Functions Between Cerebral Oxyhemoglobin and Arterial Blood Pressure

“…Kainerstorfer et al ( 2015 ) demonstrated the reliability of non-invasive measurement of cerebral autoregulation in microvascular systems using NIRS. Currently, NIRS has been used to observe cerebral autoregulation in patients with subarachnoid hemorrhage (Budohoski et al, 2016 ), acute neurological injury (Rivera et al, 2017 ), and sepsis patients (Eleveld et al, 2021 ). Therefore, in the present study, NIRS was employed to investigate cerebral autoregulation function in subjects with cognitive dysfunction.…”

“…Coupling function between the ABP and cerebral oxygenation signals was established based on dynamical Bayesian inference. Very-low-frequency (VLF, 0.02–0.07 Hz) and low-frequency (LF, 0.07–0.20 Hz) oscillation of oxyhemoglobin has shown to be robust parameter for evaluating cerebral autoregulation (Kainerstorfer et al, 2015 ; Eleveld et al, 2021 ). Spontaneous oscillations in the VLF interval are mainly associated with hemodynamic fluctuations that originate from spontaneous cortical neural activity, and the spontaneous oscillations in the LF interval are believed to reflect vasomotor and sympathetic activity (Vermeij et al, 2014 ).…”

Table_1.DOCX

“…Kainerstorfer et al (2015) demonstrated the reliability of non-invasive measurement of cerebral autoregulation in microvascular systems using NIRS. Currently, NIRS has been used to observe cerebral autoregulation in patients with subarachnoid hemorrhage (Budohoski et al, 2016), acute neurological injury (Rivera et al, 2017), and sepsis patients (Eleveld et al, 2021). Therefore, in the present study, NIRS was employed to investigate cerebral autoregulation function in subjects with cognitive dysfunction.…”

“…Coupling function between the ABP and cerebral oxygenation signals was established based on dynamical Bayesian inference. Very-lowfrequency (VLF, 0.02-0.07 Hz) and low-frequency (LF, 0.07-0.20 Hz) oscillation of oxyhemoglobin has shown to be robust parameter for evaluating cerebral autoregulation (Kainerstorfer et al, 2015;Eleveld et al, 2021). Spontaneous oscillations in the VLF interval are mainly associated with hemodynamic fluctuations that originate from spontaneous cortical neural activity, and the spontaneous oscillations in the LF interval are believed to reflect vasomotor and sympathetic activity (Vermeij et al, 2014).…”