title: Elevated Red Cell Distribution Width Is Associated With Decreased Ventilator-Free Days in Critically Ill Patients.
abstract: BACKGROUND
  Elevated red cell distribution width (RDW) is associated with mortality in a variety of respiratory conditions. Recent data also suggest that RDW is associated with mortality in intensive care unit (ICU) patients. Although respiratory failure is common in the ICU, the relationship between RDW and pulmonary outcomes in the ICU has not been previously explored. Therefore, our goal was to investigate the association of admission RDW with 30-day ventilator-free days (VFDs) in ICU patients.
  
  
  METHODS
  We performed a retrospective analysis from an ongoing prospective, observational study. Patients were recruited from medical and surgical ICUs of a large teaching hospital in Boston, Massachusetts. The RDW was assessed within 1 hour of ICU admission. Poisson regression analysis was used to investigate the association of RDW (normal: 11.5%-14.5% vs elevated: >14.5%) with 30-day VFD, while controlling for age, sex, race, body mass index, Nutrition Risk in the Critically Ill score, the presence of chronic lung disease, Pao2/Fio2ratio, and admission levels of hemoglobin, mean corpuscular volume, phosphate, albumin, C-reactive protein, and creatinine.
  
  
  RESULTS
  A total of 637 patients comprised the analytic cohort. Mean RDW was 15 (standard deviation 4%), with 53% of patients in the normal range and 47% with elevated levels. Median VFD was 16 (interquartile range: 6-25) days. Poisson regression analysis demonstrated that ICU patients with elevated admission RDW were likely to have 32% lower 30-day VFDs compared to their counterparts with RDW in the normal range (incidence rate ratio: 0.68; 95% confidence interval: 0.55-0.83: P < .001).
  
  
  CONCLUSIONS
  We observed an inverse association of RDW and 30-day VFD, despite controlling for demographics, nutritional factors, and severity of illness. This supports the need for future studies to validate our findings, understand the physiologic processes that lead to elevated RDW in patients with respiratory failure, and determine whether changes in RDW may be used to support clinical decision-making.
authors.affiliation: 1 Tufts University School of Medicine, Boston, MA, USA.|2 Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA, USA.
authors.forename: Tiffany M N
authors.initials: TMN
authors.lastname: Otero
authors.affiliation: 3 Department of Surgery, Massachusetts General Hospital, Boston, MA, USA.|4 Harvard Medical School, Boston, MA, USA.
authors.forename: D Dante
authors.initials: DD
authors.lastname: Yeh
authors.affiliation: 4 Harvard Medical School, Boston, MA, USA.|5 Department of Medicine, Massachusetts General Hospital, Boston, MA, USA.
authors.forename: Ednan K
authors.initials: EK
authors.lastname: Bajwa
authors.affiliation: 6 Department of Anesthesiology, Tufts Medical Center, Boston, MA, USA.
authors.forename: Ruben J
authors.initials: RJ
authors.lastname: Azocar
authors.affiliation: 6 Department of Anesthesiology, Tufts Medical Center, Boston, MA, USA.
authors.forename: Andrea L
authors.initials: AL
authors.lastname: Tsai
authors.affiliation: 7 Department of Nutrition and Food Services, Massachusetts General Hospital, Boston, MA.
authors.forename: Donna M
authors.initials: DM
authors.lastname: Belcher
authors.affiliation: 2 Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA, USA.|4 Harvard Medical School, Boston, MA, USA.
authors.forename: Sadeq A
authors.initials: SA
authors.lastname: Quraishi
mesh_terms: D018806:APACHE; D001900:Boston; D003422:Critical Care; D016638:Critical Illness / Q000401:mortality / Q000628:therapy*; D004909:Erythrocyte Indices; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000706:statistics & numerical data*; D012131:Respiratory Insufficiency / Q000097:blood* / Q000401:mortality / Q000503:physiopathology* / Q000628:therapy; D012189:Retrospective Studies; D012307:Risk Factors
keywords: ICU; RDW; VFD; critical care; mechanical ventilation; red blood cell distribution width