The Quantitative Associations Between Near Infrared Spectroscopic Cerebrovascular Metrics and Cerebral Blood Flow: A Scoping Review of the Human and Animal Literature

Abstract

Cerebral blood flow (CBF) is an important physiologic parameter that is vital for proper cerebral function and recovery. Current widely accepted methods of measuring CBF are cumbersome, invasive, or have poor spatial or temporal resolution. Near infrared spectroscopy (NIRS) based measures of cerebrovascular physiology may provide a means of non-invasively, topographically, and continuously measuring CBF. We performed a systematically conducted scoping review of the available literature examining the quantitative relationship between NIRS-based cerebrovascular metrics and CBF. We found that continuous-wave NIRS (CW-NIRS) was the most examined modality with dynamic contrast enhanced NIRS (DCE-NIRS) being the next most common. Fewer studies assessed diffuse correlation spectroscopy (DCS) and frequency resolved NIRS (FR-NIRS). We did not find studies examining the relationship between time-resolved NIRS (TR-NIRS) based metrics and CBF. Studies were most frequently conducted in humans and animal studies mostly utilized large animal models. The identified studies almost exclusively used a Pearson correlation analysis. Much of the literature supported a positive linear relationship between changes in CW-NIRS based metrics, particularly regional cerebral oxygen saturation (rSO2), and changes in CBF. Linear relationships were also identified between other NIRS based modalities and CBF, however, further validation is needed.

Prognostic value of near-infrared spectroscopy regional oxygen saturation and cerebrovascular reactivity index in acute traumatic neural injury: a CAnadian High-Resolution Traumatic Brain Injury (CAHR-TBI) Cohort Study

“…Further, there was no identifiable threshold value of rSO 2 at which outcomes following TBI worsened. This is somewhat surprising given the existing body of evidence indicating a relationship between rSO 2 and measures of CBF or CBV [ 8 ]. A key factor to take into consideration is that in these studies it was typical that relative changes in CBV/CBF were associated with changes in rSO 2 .…”

“…While advantageous due to its noninvasive nature and relatively high spatial resolution, the association of NIRS parameters and outcomes following TBI remains unclear [ 7 ]. There is a substantive body of the literature supporting an association between NIRS parameters and cerebral blood flow (CBF) but threshold values at which outcomes worsen have not been identified [ 8 ].…”

Non-invasive estimation of in vivo optical properties and hemodynamic parameters of domestic animals: a preliminary study on horses, dogs, and sheep

“…Indeed, accurate estimate of S t O 2 can be of paramount importance for example during surgical or diagnostic procedures especially in large animals (e.g., horse) where prolonged general anesthesia may lead to reduced oxygen uptake and altered gas exchange in the lungs that, combined with prolonged compression and immobility of skeletal muscle, can lead to impaired blood flow, tissue hypoxia and subsequent myopathies ( 21 , 22 , 64–66 ). Like in human applications, precise assessment of S t O 2 can be also of vital impact when monitoring cerebral functions (e.g., in dog, cat, or rabbit) intraoperatively during anesthesia ( 67 ). Similarly, this tool has also helped to investigate cortical hemodynamics and functions after motor, cognitive, and somatosensory stimuli in dogs and sheep ( 28–33 ).…”

Optimal bispectral index level of sedation and cerebral oximetry in traumatic brain injury: a non-invasive individualized approach in critical care?

“…This is evidenced by pre-clinical literature providing only validation for ICP and NIRS-based cerebrovascular reactivity indices as true measures of the lower limit of autoregulation in several different animal models [31]. This strong association between NIRS and cerebral blood flow/cerebral blood volume is also supported by the growing objective body of literature supporting a moderate/strong correlation between NIRS measures and cerebral blood flow [49,50]. Similarly, time-series and multi-variate clustering analysis has demonstrated strong co-variance between NIRSbased measures and standard PRx [26,28,29].…”