title: Near-infrared spectroscopy for assessing tissue oxygenation and microvascular reactivity in critically ill patients: a prospective observational study.
abstract: Impaired 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).
  
  
  
  Prospective 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, StO2downslope 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.
  
  
  
  Patients (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 StO2on 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)).
  
  
  
  In critically ill patients, NIRS with a VOT enables identification of alterations in tissue oxygen extraction capacity and microvascular reactivity that can predict mortality.
  
  
  
  NCT02649088, www.clinicaltrials.gov , date of registration 23rd December 2015, retrospectively registered.
authors.affiliation: Anesthesia and Intensive Care Unit, Department of Biomedical Sciences and Public Health, Università Politecnica delle Marche, Ancona, Italy. a.donati@univpm.it.
authors.forename: Abele
authors.identifier: 0000-0001-6792-8741
authors.initials: A
authors.lastname: Donati
authors.affiliation: Anesthesia and Intensive Care Unit, Department of Biomedical Sciences and Public Health, Università Politecnica delle Marche, Ancona, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Damiani
authors.affiliation: Anesthesia and Intensive Care Unit, Department of Biomedical Sciences and Public Health, Università Politecnica delle Marche, Ancona, Italy.
authors.forename: Roberta
authors.initials: R
authors.lastname: Domizi
authors.affiliation: Anesthesia and Intensive Care Unit, Department of Biomedical Sciences and Public Health, Università Politecnica delle Marche, Ancona, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Scorcella
authors.affiliation: Anesthesia and Intensive Care Unit, Department of Biomedical Sciences and Public Health, Università Politecnica delle Marche, Ancona, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Carsetti
authors.affiliation: Anesthesia and Intensive Care Unit, Department of Biomedical Sciences and Public Health, Università Politecnica delle Marche, Ancona, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Tondi
authors.affiliation: Anesthesia and Intensive Care Unit, Department of Biomedical Sciences and Public Health, Università Politecnica delle Marche, Ancona, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Monaldi
authors.affiliation: Anesthesia and Intensive Care Unit, Department of Biomedical Sciences and Public Health, Università Politecnica delle Marche, Ancona, Italy.
authors.forename: Erica
authors.initials: E
authors.lastname: Adrario
authors.affiliation: Anesthesia and Intensive Care Unit, Department of Biomedical Sciences and Public Health, Università Politecnica delle Marche, Ancona, Italy.
authors.forename: Rocco
authors.initials: R
authors.lastname: Romano
authors.affiliation: Anesthesia and Intensive Care Unit, Department of Biomedical Sciences and Public Health, Università Politecnica delle Marche, Ancona, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Pelaia
authors.affiliation: Bloomsbury Institute of Intensive Care Medicine, Division of Medicine, University College London, London, UK.
authors.forename: Mervyn
authors.initials: M
authors.lastname: Singer
mesh_terms: D000328:Adult; D000368:Aged; D016638:Critical Illness / Q000401:mortality* / Q000628:therapy; D005260:Female; D017052:Hospital Mortality / Q000639:trends; D006801:Humans; D008297:Male; D008833:Microcirculation / Q000502:physiology*; D055806:Microvessels / Q000000981:diagnostic imaging* / Q000378:metabolism; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology*; D011446:Prospective Studies; D019265:Spectroscopy, Near-Infrared / Q000379:methods*
keywords: Critical illness; Microcirculation; Near-infrared spectroscopy; Tissue oxygenation; Vascular occlusion test