Abstract
IntroductionNear-infrared spectroscopy (NIRS) noninvasively measures peripheral tissue oxygen saturation (StO2). NIRS may be utilized along with a vascular occlusion test, in which limb blood flow is temporarily occluded and released, to quantify a tissue bed's rate of oxygen exchange during ischemia and recovery. The objective of this study was to test the hypothesis that NIRS-derived StO2 measures (StO2 initial, StO2 occlusion and StO2 recovery) identify patients who are in shock and at increased risk of organ dysfunction (Sequential Organ Failure Assessment (SOFA) score ≥ 2 at 24 hours) and dying in the hospital.MethodsThis prospective, observational study comprised a convenience sample of three cohorts of adult patients (age > 17 years) at three urban university emergency departments: (1) a septic shock cohort (systolic blood pressure < 90 after fluid challenge; the "SHOCK" cohort, n = 58), (2) a sepsis without shock cohort (the "SEPSIS" cohort, n = 60) and emergency department patients without infection (n = 50). We measured the StO2 initial, StO2 occlusion and StO2 recovery slopes for all patients. Outcomes were sepsis syndrome severity, organ dysfunction (SOFA score at 24 hours) and in-hospital mortality.ResultsAmong the 168 patients enrolled, mean initial StO2 was lower in the SHOCK cohort than in the SEPSIS cohort (76% vs 81%), with an impaired occlusion slope (-10.2 and 5.2%/minute vs -13.1 and 4.4%/minute) and an impaired recovery slope (2.4 and 1.6%/second vs 3.9 and 1.7%/second) (P < 0.001 for all). The recovery slope was well-correlated with SOFA score at 24 hours (-0.35; P < 0.001), with a promising area under the curve (AUC) for mortality of 0.81. The occlusion slope correlation with SOFA score at 24 hours was 0.21 (P < 0.02), with a fair mortality AUC of 0.70. The initial StO2 was significantly but less strongly correlated with SOFA score at 24 hours (-0.18; P < 0.04), with a poor mortality AUC of 0.56.ConclusionsNIRS measurements for the StO2 initial, StO2 occlusion and StO2 recovery slope were abnormal in patients with septic shock compared to sepsis patients. The recovery slope was most strongly associated with organ dysfunction and mortality. Further validation is warranted.Trial registrationNCT01062685
Highlights
Near-infrared spectroscopy (NIRS) noninvasively measures peripheral tissue oxygen saturation (StO2)
Outcomes We examined the association of StO2 parameters in relation to three patient-oriented outcomes: (1) presence of shock, as defined above, assessed at the time of enrollment; (2) in-hospital mortality, defined as vital signs status at hospital discharge; and (3) organ dysfunction at 24 hours assessed on the basis of the Sequential Organ Failure Assessment (SOFA) scores calculated at the time of enrollment and 24 hours later [6]
We examined the correlation between the NIRS parameters at initial presentation and the total SOFA score and found a correlation between StO2 initial slope (Spearman’s r correlation coefficient = -0.18; P < 0.04), occlusion slope (Spearman’s r correlation coefficient = 0.21; P < 0.02) and recovery slope (Spearman’s r correlation coefficient = -0.35; P < 0.001)
Summary
Near-infrared spectroscopy (NIRS) noninvasively measures peripheral tissue oxygen saturation (StO2). NIRS may be utilized along with a vascular occlusion test, in which limb blood flow is temporarily occluded and released, to quantify a tissue bed’s rate of oxygen exchange during ischemia and recovery. The objective of this study was to test the hypothesis that NIRS-derived StO2 measures (StO2 initial, StO2 occlusion and StO2 recovery) identify patients who are in shock and at increased risk of organ dysfunction (Sequential Organ Failure Assessment (SOFA) score ≥ 2 at 24 hours) and dying in the hospital. Current international consensus guidelines for the resuscitation of patients with severe sepsis and septic shock recommend aggressive, invasive, protocol-directed care titrating to centrally monitored parameters [3]. A noninvasive and reproducible measure of tissue hypoxia would be a valuable asset in the resuscitation armamentarium
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