No relationship between red blood cell distribution width and microcirculatory alterations in septic patients

BACKGROUND: Increased red cell distribution width (RDW), a quantitative measure of erythrocyte size variability, has been associated with increased mortality in critically ill patients. METHODS: In this post-hoc analysis of prospectively collected data, we studied 122 septic patients with and without shock who had undergone sublingual microcirculatory assessment using Sidestream Dark Field (SDF) videomicroscopy. Patient demographics, comorbidities, the Acute Physiology and Chronic Health Evaluation (APACHE) II score on admission and the Sequential Organ Failure Assessment (SOFA) score on the day of the microcirculatory assessment were collected. The RDW was retrospectively collected on the day of the microcirculatory evaluation from the routine daily blood count analysis. RESULTS: Median patient age was 68[55-77] years, and median APACHE II and SOFA scores were 22[17-28] and 10[8-12], respectively; ICU mortality was 43. On the day of the microcirculatory analysis, the median RDW was 13.8[12.8-15.5] and was elevated (>13.4) in 74 (61) patients. There was no correlation between RDW and microcirculatory parameters (functional capillary density, r2 = 0.12; proportion of small perfused vessels, r2 = 0.17; mean flow index, r2 = 0.14). RDW was not related to disease severity, the presence of shock or survival. CONCLUSIONS: RDW is not associated with microcirculatory alterations or prognosis in septic patients