title: Impact of hyperhydration on the mortality risk in critically ill patients admitted in intensive care units: comparison between bioelectrical impedance vector analysis and cumulative fluid balance recording.
abstract: BACKGROUND
  Studies have demonstrated a positive correlation between fluid overload (FO) and adverse outcomes in critically ill patients. The present study aims at defining the impact of hyperhydration on the Intensive Care Unit (ICU) mortality risk, comparing Bioelectrical Impedance Vector Analysis (BIVA) assessment with cumulative fluid balance (CFB) recording.
  
  
  METHODS
  We performed a prospective, dual-centre, clinician-blinded, observational study of consecutive patients admitted to ICU with an expected length of ICU stay of at least 72 hours. During observational period (72-120 hours), CFB was recorded and cumulative FO was calculated. At the admission and daily during the observational period, BIVA was performed. We considered FO between 5% and 9.99% as moderate and a FO ≥ 10% as severe. According to BIVA hydration scale of lean body mass, patients were classified as normohydrated (>72.7%-74.3%), mild (>71%-72.7%), moderate (>69%-71%) and severe (≤ 69%) dehydrated and mild (>74.3%-81%), moderate (>81%-87%) and severe (>87%) hyperhydrated. Two multivariate logistic regression models were performed: the ICU mortality was the response variable, while the predictor variables were hyperhydration, measured by BIVA (BIVA model), and FO (FO model). A p-value <0.05 was considered to indicate statistical significance.
  
  
  RESULTS
  One hundred and twenty-five patients were enrolled (mean age 64.8 ± 16.0 years, 65.6% male). Five hundred and fifteen BIVA measurements were performed. The mean CFB recorded at the end of the observational period was 2.7 ± 4.1 L, while the maximum hydration of lean body mass estimated by BIVA was 83.67 ± 6.39%. Severe hyperhydration measured by BIVA was the only variable found to be significantly associated with ICU mortality (OR 22.91; 95% CI 2.38-220.07; p < 0.01).
  
  
  CONCLUSIONS
  The hydration status measured by BIVA seems to predict mortality risk in ICU patients better than the conventional method of fluid balance recording. Moreover, it appears to be safe, easy to use and adequate for bedside evaluation. Randomized clinical trials with an adequate sample size are needed to validate the diagnostic properties of BIVA in the goal-directed fluid management of critically ill patients in ICU.
authors.affiliation: Institute of Life Sciences, Sant'Anna School of Advanced Studies, Pisa, Italy. sara.samoni@sssup.it.|Department of Nephrology, Dialysis and Transplantation, San Bortolo Hospital, International Renal Research Institute Vicenza (IRRIV), Viale Rodolfi, 37, 36100, Vicenza, Italy. sara.samoni@sssup.it.
authors.forename: Sara
authors.initials: S
authors.lastname: Samoni
authors.affiliation: Department of Clinical & Experimental Medicine, University of Pisa, Pisa, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Vigo
authors.affiliation: Department of Nephrology, Dialysis and Transplantation, San Bortolo Hospital, International Renal Research Institute Vicenza (IRRIV), Viale Rodolfi, 37, 36100, Vicenza, Italy.
authors.forename: Luis Ignacio Bonilla
authors.initials: LI
authors.lastname: Reséndiz
authors.affiliation: Department of Nephrology, Dialysis and Transplantation, San Bortolo Hospital, International Renal Research Institute Vicenza (IRRIV), Viale Rodolfi, 37, 36100, Vicenza, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Villa
authors.affiliation: Department of Nephrology, Dialysis and Transplantation, San Bortolo Hospital, International Renal Research Institute Vicenza (IRRIV), Viale Rodolfi, 37, 36100, Vicenza, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: De Rosa
authors.affiliation: Department of Nephrology, Dialysis and Transplantation, San Bortolo Hospital, International Renal Research Institute Vicenza (IRRIV), Viale Rodolfi, 37, 36100, Vicenza, Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Nalesso
authors.affiliation: Department of Nephrology, Dialysis and Transplantation, San Bortolo Hospital, International Renal Research Institute Vicenza (IRRIV), Viale Rodolfi, 37, 36100, Vicenza, Italy.|Department of Anaesthesiology and Intensive Care, San Bortolo Hospital, Vicenza, Italy.
authors.forename: Fiorenza
authors.initials: F
authors.lastname: Ferrari
authors.affiliation: Institute of Life Sciences, Sant'Anna School of Advanced Studies, Pisa, Italy.|Department of Clinical & Experimental Medicine, University of Pisa, Pisa, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Meola
authors.affiliation: Department of Nephrology, Dialysis and Transplantation, San Bortolo Hospital, International Renal Research Institute Vicenza (IRRIV), Viale Rodolfi, 37, 36100, Vicenza, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Brendolan
authors.affiliation: Department of Anaesthesia and Intensive Care Unit 6, Cisanello Hospital, Pisa, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Malacarne
authors.affiliation: Department of Anaesthesia and Intensive Care Unit 4, Cisanello Hospital, Pisa, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Forfori
authors.affiliation: Department of Anaesthesiology and Intensive Care, San Bortolo Hospital, Vicenza, Italy.
authors.forename: Raffaele
authors.initials: R
authors.lastname: Bonato
authors.affiliation: Department of Clinical & Experimental Medicine, University of Pisa, Pisa, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Donadio
authors.affiliation: Department of Nephrology, Dialysis and Transplantation, San Bortolo Hospital, International Renal Research Institute Vicenza (IRRIV), Viale Rodolfi, 37, 36100, Vicenza, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Ronco
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003422:Critical Care / Q000379:methods* / Q000592:standards; D016638:Critical Illness / Q000401:mortality / Q000628:therapy; D017097:Electric Impedance; D005260:Female; D005440:Fluid Therapy / Q000379:methods* / Q000592:standards; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012306:Risk; D016896:Treatment Outcome; D014882:Water-Electrolyte Balance / Q000502:physiology
keywords: Bioelectrical impedance vector analysis; Cumulative fluid balance; Fluid overload; Hyperhydration; Intensive care unit; Mortality