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The following is a summary of “Clinical outcomes and peripheral tissue oxygen saturation monitoring of the knee region by near-infrared spectroscopy in circulatory shock: a prospective observational cohort study,” published in the March 2025 issue of Critical Care by Varis et al. 

Researchers conducted a retrospective study to examine whether peripheral tissue oxygen saturation (StO₂), measured with near-infrared spectroscopy (NIRS), non-invasively indicated tissue hypoperfusion and predicted organ dysfunction and mortality.  

They enrolled individuals with circulatory shock from April 2019 to May 2023 in 3 intensive care units (ICU). Adults meeting circulatory shock criteria within 24 hours of ICU admission were included. Continuous 48-hour peripheral StO₂ monitoring (INVOS™) was performed at the knee. Mean StO₂ and areas below set thresholds quantified hypoperfusion burden. The primary outcome was Sequential Organ Failure Assessment (SOFA) score change, categorized as improvement or non-improvement from enrolment to day 7 or ICU discharge, with death within 7 days classified as non-improvement and secondary outcomes included 90-day mortality.  

The results showed that 256 individuals were included, though enrolment was non-consecutive due to factors like the COVID-19 pandemic. The median 48-hour mean peripheral StO₂ was 68.3% (interquartile range [IQR] 57.5–74.1) in those with SOFA improvement (n = 171) and 63.5% (IQR 52.7–70.8, P = 0.020) in non-improvers (n = 85). Among 90-day survivors, the median was 68.7% (IQR 58.2–74.5), compared to 60.9% (IQR 49.5–67.1, P < 0.001) in non-survivors. No significant differences were found in areas below predefined StO₂ thresholds between SOFA-improvers and non-improvers, but all areas were larger in 90-day non-survivors. The 90-day mortality rate was 27.0% (n = 69). Multivariable analysis showed an association between 48-hour mean StO₂ and 90-day mortality (Odds ratio [OR] 0.97, 95% confidence interval [CI 95%] 0.94–1.00, P = 0.047), but this association was no longer significant after excluding the last 6 hours of StO₂ registration for individuals who died during monitoring (n = 29, OR 0.97, CI 95% 0.94–1.00, P = 0.062).  

Investigators concluded that lower peripheral StO₂ was associated with increased 90-day mortality patients with critical illness with circulatory shock 

Source: ccforum.biomedcentral.com/articles/10.1186/s13054-025-05363-1