Near-infrared spectroscopy for assessing tissue oxygenation and microvascular reactivity in critically ill patients: a prospective observational study

Abstract

BackgroundImpaired microcirculatory perfusion and tissue oxygenation during critical illness are associated with adverse outcome. The aim of this study was to detect alterations in tissue oxygenation or microvascular reactivity and their ability to predict outcome in critically ill patients using thenar near-infrared spectroscopy (NIRS) with a vascular occlusion test (VOT).MethodsProspective observational study in critically ill adults admitted to a 12-bed intensive care unit (ICU) of a University Hospital. NIRS with a VOT (using a 40 % tissue oxygen saturation (StO2) target) was applied daily until discharge from the ICU or death. A group of healthy volunteers were evaluated in a single session. During occlusion, StO2 downslope was measured separately for the first (downslope 1) and last part (downslope 2) of the desaturation curve. The difference between downslope 2 and 1 was calculated (delta-downslope). The upslope and area of the hyperaemic phase (receive operating characteristic (ROC) area under the curve (AUC) of StO2) were calculated, reflecting microvascular reactivity. Outcomes were ICU and 90-day mortality.ResultsPatients (n = 89) had altered downslopes and upslopes compared to healthy volunteers (n = 27). Mean delta-downslope was higher in ICU non-survivors (2.8 (0.4, 3.8) %/minute versus 0.4 (−0.8, 1.8) in survivors, p = 0.004) and discriminated 90-day mortality (ROC AUC 0.72 (95 % confidence interval 0.59, 0.84)). ICU non-survivors had lower mean upslope (141 (75, 193) %/minute versus 185 (143, 217) in survivors, p = 0.016) and AUC StO2 (7.9 (4.3, 12.6) versus 14.5 (11.2, 21.3), p = 0.001). Upslope and AUC StO2 on admission were significant although weak predictors of 90-day mortality (ROC AUC = 0.68 (0.54, 0.82) and 0.70 (0.58, 0.82), respectively). AUC StO2 ≤ 6.65 (1st quartile) on admission was independently associated with higher 90-day mortality (hazard ratio 7.964 (95 % CI 2.211, 28.686)). The lowest upslope in the ICU was independently associated with survival after ICU discharge (odds ratio 0.970 (95 % CI 0.945, 0.996)).ConclusionsIn critically ill patients, NIRS with a VOT enables identification of alterations in tissue oxygen extraction capacity and microvascular reactivity that can predict mortality.Trial registrationNCT02649088, www.clinicaltrials.gov, date of registration 23rd December 2015, retrospectively registered.Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-016-1500-5) contains supplementary material, which is available to authorized users.

Dynamic tracking of microvascular hemoglobin content for continuous perfusion monitoring in the intensive care unit: pilot feasibility study

“…Sublingual microcirculation has been evaluated extensively using handheld videomicroscopy [31], and alterations to the microvascular perfusion characteristics are seen following ICU interventions [32][33][34][35], and correlated with adverse ICU outcomes [36,37]. Dynamic assessments of peripheral perfusion using LDF [38,39] or StO2-derived vascular occlusion tests [40,41] also correlate with ICU outcomes, signifying the importance of the microcirculation in the pathophysiology of critical illness.…”

“…Given the substantial between-patient heterogeneity observed in this cohort, larger sample sizes will be required with the addition of healthy volunteers as a comparison group; MHC signal complexity also suggests that the best metrics for characterizing microvascular dysfunction are not yet established. Furthermore, studies have shown that microvascular monitoring may not discriminate between survivors and non-survivors during initial evaluation, and that metrics will only separate later in ICU stay [41,66]. Thus, the prognostic ability of MHC monitoring is best evaluated with daily assessment to correlate MHC signal with ICU outcomes.…”

Assessment of the peripheral microcirculation in patients with and without shock: a pilot study on different methods

“…Dynamic VOT parameters had a higher accuracy in detecting microvascular dysfunction in critically ill patients than static values [30,36]. In a mix critically ill adults' population, Donati et al showed that the desaturation rate tended to be slower in the late ischemic phase in patients with sepsis, hypotension, high lactate levels or with norepinephrine administration (conditions of a likely hemodynamic instability) [37]. Although our study, involving a smaller population, evidenced similar descending slope rates between shock and non-shock patients, we observed lower values of StO 2 min in patients with shock compared with patients without shock, probably due to the imbalance between supply and demand of oxygen and lower auto regulatory reserve [38].…”

Studies on Polarised Light Spectroscopy

“…This may be particularly useful in conditions where a challenged microcirculation is part of the pathological mechanisms behind the tissue morbidity. Techniques for monitoring alterations in microcirculation of the skin have therefore, in recent years, been playing an increasingly important part in burn care (14); postoperative monitoring of free flaps (15) (16)(17)(18)(19); intensive care (20); and diagnosis of peripheral vascular (21) -and skin diseases (22). In some cases it is the viability of the skin itself that is of interest, whereas in other cases, the microcirculation of the skin can be used as a target for assessing the state of the underlying tissue, or even the whole body.…”