PURPOSE: Severe sepsis results in acute organ failure and mortality. Impaired tissue perfusion is thought pathogenic in sepsis-induced organ failure despite resuscitation to macrodynamic endpoints. We hypothesized that regional microvascular responses to ischemia correlate with global tissue hypoxia and predict outcome.
METHODS: We studied human subjects with severe sepsis, 24 hours after ICU admission. Stagnant forearm ischemia was induced by a vascular cuff at 250 mm Hg for 5 minutes. Near Infrared Spectroscopy (NIRS) measured thenar tissue oxygen saturation (StO2) before, during and after ischemia. The microvascular reoxygenation rate was calculated as the rate of rise of StO2 in the first 14 seconds after cuff deflation. We collected clinical data including serum lactates and Sequential Organ Failure Assessment (SOFA) scores. Severe organ failure was defined as SOFA > 10, and is associated with 50% mortality.
RESULTS: We enrolled 46 subjects, including 28 (61%) men. The mean subject age was 57 years (range 27-89). The mean SOFA score was 7.3 (SD 4.3). 28-day in-hospital mortality was 19.6%. The median initial serum lactate was 2.55 mEq/L (range 0.7-14.9); and was not different between survivors and non-survivors. 24 hours after ICU admission, lactate in survivors (median 2.0 mEq/L, range 0.9-3.9) was lower than in non-survivors (median 11.2 mEq/L, range 2.9-16 mEq/L; p= 0.035). At this timepoint, the mean microvascular reoxygenation rate in survivors (2.8 %/sec SD 1.2) was higher than that in non-survivors (1.6 %/sec SD1.4; p = 0.001). There were significant correlations between microvascular reoxygenation rates and contemporaneous lactates (Spearman r = -0.44; p = 0.04) and organ failure (Pearson r = -0.449; p = 0.002). Microvascular reoxygenation rates had a high discriminative ability to predict mortality (Area under curve 73%) and severe organ failure (Area under curve 69%).
CONCLUSIONS: Thenar microvascular dysfunction that persists after resuscitation reflects global hypoxia and is a strong predictor of outcome.
CLINICAL IMPLICATIONS: Tissue Reoxygenation Rate might be a good target for resuscitation in severe sepsis.
DISCLOSURE: The following authors have nothing to disclose: Surya Bhatt, Bryon Johnson, Angela Delsing, Alicia Gerke, Kevin Doerschug
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