title: Assessment of hydration status using bioelectrical impedance vector analysis in critical patients with acute kidney injury.
abstract: The state of hyperhydration in critically ill patients with acute kidney injury (AKI) is associated with increased mortality. Bioelectrical impedance vector analysis (BIVA) appears to be a viable method to access the fluid status of critical patients but has never been evaluated in critical patients with AKI. The objective of this study is to evaluate the hydration status measured using BIVA in critical patients under intensive care at the time of AKI diagnosis and to correlate this measurement with mortality.
  
  
  
  We assessed the fluid status measured using BIVA in 224 critical patients at the time of AKI diagnosis and correlated it with mortality. To interpret the results, BIVA Software 2002 was used to plot the data from the patients studied on the 95% confidence ellipses of the RXcplane for comparisons between groups (non-survivors, survivors). Variables such as mechanical ventilation, vasoactive drug, and sepsis, among others, were collected.
  
  
  
  The impedance vector analysis conducted using BIVA Software 2002 indicated changes in the body compositions of patients according to the 95% confidence ellipse between the vectors R/H and Xc/H of the group of survivors and the group of deceased patients. Hotelling's test (T2= 21.2) and the F test (F = 10.6) revealed significant differences (p < 0.001) between the two groups. These results demonstrate that patients who died presented with a greater hydration volume at the time of AKI diagnosis compared with those who survived. In addition to the hydration status measured using BIVA, the following were also correlated with death: diagnosis at hospitalization, APACHE II score, length of hospital stay, RIFLE score, maximum organ failure, sepsis type, hemoglobin, and AF.
  
  
  
  The fluid status assessment measured using BIVA significantly demonstrated the difference in hydration between survivors and non-survivors among critically ill patients with AKI.
authors.affiliation: Post-graduation Program in Health and Behavior, Catholic University of Pelotas, R. Gonçalves Chaves 377, sala 411, CEP 960515-560 Pelotas, RS, Brazil. Electronic address: achise70@gmail.com.
authors.forename: Ana Cláudia da Rosa
authors.initials: ACDR
authors.lastname: Hise
authors.affiliation: Post-graduation Program in Health and Behavior, Catholic University of Pelotas, R. Gonçalves Chaves 377, sala 411, CEP 960515-560 Pelotas, RS, Brazil. Electronic address: cristinagbs@hotmail.com.
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Gonzalez
mesh_terms: D058186:Acute Kidney Injury / Q000453:epidemiology* / Q000503:physiopathology*; D001938:Brazil / Q000453:epidemiology; D016638:Critical Illness / Q000453:epidemiology; D017097:Electric Impedance; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D000074267:Organism Hydration Status / Q000502:physiology*; D011446:Prospective Studies; D016019:Survival Analysis; D014882:Water-Electrolyte Balance / Q000502:physiology*
keywords: Acute kidney injury; Bioelectrical impedance analysis; Critical patient; Fluid status; Prognostic factor