The association of red cell distribution width at hospital discharge and out-of-hospital mortality following critical illness*

Abstract

Objectives: Red cell distribution width is associated with mortality and bloodstream infection risk in the critically ill. In hospitalized patients with critical illness, it is not known if red cell distribution width can predict subsequent risk of all-cause mortality following hospital discharge. We hypothesized that an increase in red cell distribution width at hospital discharge in patients who survived to discharge following critical care would be associated with increased postdischarge mortality.

Design: Two-center observational cohort study

Setting: : All medical and surgical ICUs at the Brigham and Women's Hospital and Massachusetts General Hospital.

Patients: We studied 43,212 patients, who were 18 years old or older and received critical care between 1997 and 2007 and survived hospitalization.

Interventions: None.

Measurements and main results: The exposure of interest was red cell distribution width within 24 hours of hospital discharge and categorized a priori in quintiles as less than or equal to 13.3%, 13.3-14.0%, 14.0-14.7%, 14.7-15.8%, and more than 15.8%. The primary outcome was all-cause mortality in the 30 days following hospital discharge. Secondary outcomes included 90-day and 365-day mortality following hospital discharge. Mortality was determined using the U.S. Social Security Administration Death Master File, and 365-day follow-up was present in all cohort patients. Adjusted odds ratios were estimated by multivariable logistic regression models with inclusion of covariate terms thought to plausibly interact with both red cell distribution width and mortality. Adjustment included age, race, gender, Deyo-Charlson Index, patient type (medical vs surgical), sepsis, and number of organs with acute failure. In patients who received critical care and survived hospitalization, the discharge red cell distribution width was a robust predictor of all-cause mortality and remained so following multivariable adjustment. Patients with a discharge red cell distribution width of 14.0-14.7%, 14.7-15.8%, and more than 15.8% have an odds ratio for mortality in the 30 days following hospital discharge of 2.86 (95% CI, 2.25-3.62), 4.57 (95% CI, 3.66-5.72), and 8.80 (95% CI, 7.15-10.83), respectively, all relative to patients with a discharge red cell distribution width less than or equal to 13.3%. Following multivariable adjustment, patients with a discharge red cell distribution width of 14.0-14.7%, 14.7-15.8%, and more than 15.8% have an odds ratio for mortality in the 30 days following hospital discharge of 1.63 (95% CI, 1.27-2.07), 2.36 (95% CI, 1.87-2.97), and 4.18 (95% CI, 3.36-5.20), respectively, all relative to patients with a discharge red cell distribution width less than or equal to 13.3%. Similar significant robust associations post multivariable adjustments are seen with death by days 90 and 365 postdischarge. Estimating the receiver-operating characteristic area under the curve shows that discharge red cell distribution width has moderate discriminative power for mortality 30 days following hospital discharge (area under the curve = 0.70; SE 0.006; 95% CI, 0.69-0.71; p < 0.0001).

Conclusion: In patients treated with critical care who survive hospitalization, an elevated red cell distribution width at the time of discharge is a robust predictor of subsequent all-cause patient mortality. Increased discharge red cell distribution width likely reflects the presence of proinflammatory state, oxidative stress, arterial underfilling, or a combination, thereof which may explain the observed impact on patient survival following discharge. Elevated red cell distribution width at hospital discharge may identify ICU survivors who are at risk for adverse outcomes following hospital discharge.