Background:The normal range of red cell distribution width (RDW) level is ＜ 15％.Several studies have indicated that a high RDW level was associated with mortality in critically ill patients,and the patients with a high RDW level need increased focus in clinical practice.In view of the difficulty in defining the specific value of high RDW level,the key is to focus on the patient with the level beyond the normal upper limit.This study aimed to determine whether dynamic change of RDW levels,rather than the level itself,is predictive of death in elderly patients with septic shock when RDW level is beyond 15％.Methods:Between September 2013 and September 2015,the elderly septic shock patients with RDW level beyond 15％ were enrolled in this study.The RDW levels were measured at enrollment (day 1),and days 4 and 7 after enrollment.Sequential Organ Failure Assessment (SOFA) scores were recorded simultaneously.Results:A total of 45 patients,including 32 males and 13 females,were included in the final analysis.Based on their hospital outcomes,these patients were divided into the survivor group (n =26) and the nonsurvivor group (n =19).There were no significant differences in age,gender,body mass index,initial level of RDW,Acute Physiology and Chronic Health Evaluation Ⅱ scores,and SOFA scores between survivors and nonsurvivors.At days 4 and 7 measurement,both RDW level (median [interquartile range]:day 4:15.8 [2.0]％ vs.16.7 [2.0]％,P =0.011;and day 7:15.6 [1.8]％ vs.17.7 [2.5]％,P=0.001) and SOFA scores (day 4:7.0 [4.0] vs.16.0 [5.0],P ＜ 0.001,day 7:5.5 [4.0] vs.17.0 [5.0],P ＜ 0.001) were significantly lower in survivors than those innonsurvivors.Dynamic changes of RDW and SOFA scores in survivor group were significantly different from those in nonsurvivor group (all P ＜ 0.05).Continuous increase in RDW level was observed in 10 of the 13 nonsurvivors,but only in 3 of the 26 survivors.The level of RDW7 and dynamic changes significantly correlated with their counterparts of SOFA scores (all P ＜ 0.05),whereas the levels of RDW 1 and RDW4 had no significant correlation with their counterparts of SOFA scores (all P ＞ 0.05).Conclusions:Continuous increase in RDW level,rather than the level of RDW itself,was more useful in predicting hospital death in elderly patients with septic shock when the level of RDW was ＞15％.The dynamic changes of RDW were highly correlated with the SOFA score in the patients.