Digital archive of theses discussed at the University of Pisa


Thesis etd-06192014-103029

Thesis type
Tesi di specializzazione (5 anni)
Thesis title
Fluid management in the Intensive Care Unit. The role of Bioelectrical Impedance Vector Analysis in the assessment of hydration status and to evaluate the impact of fluid overload on the outcome in critically ill patients.
Course of study
relatore Prof. Donadio, Carlo
relatore Prof. Ronco, Claudio
  • hydration status
  • intensive care
  • fluid overload
  • mortality
  • bioelectrical impedance vector analysis
Graduation session start date
Background: Clinical trials have shown a positive correlation between fluid overload and adverse outcomes in critically ill patients admitted to ICU. Nevertheless, there is not currently a single method that can provide an accurate and timely assessment of whole body hydration status. The aim of this study is to evaluate the role of BIVA in assessment of hydration status and to assess the impact of hyperhydration on outcomes in ICU patients.

Methods: This is a prospective, dual-center study in critically ill patients. Anthropometric, medical history and laboratory data of each patient admitted in ICU with an expected length of stay of 72 hours or more were recorded. Assessments of body fluid status was performed using Bioelectric Impedance Vectorial Analysis (BIVA), using a single frequency analyzer, at the baseline and daily for a period of 72-120 hours. Patients were considered normohydrated if BIVA hydration level was 72.7%-74.3% of fat-free body mass, dehydrated and hyperhydrated if hydration level was respectively <72.7% and >74.3%. According to BIVA numerical scale, dehydration and hyperhydration was classified into mild, moderate and severe.

Results: Four-hundred and eighty three BIVA measurements were taken in 114 pts. Logistic regression analysis found significant association between ICU mortality and maximum hydration level reached in observation period (MAX HYD), either in patients with or without AKI (OR 1.26; 95% CI 1.08-1.45; p=0.01). Cox model showed a significant association between long-term mortality and both MAX HYD (OR 1.14; 95% CI 1.02-1.27; p=0.01) and percentage of days in which patients was hyperhydrated (OR 12.82; 95% CI 1.03-158.92; p =0.04), either in patients with or without AKI.

Conclusions: Our study confirms and expands literature data of a correlation between ICU mortality and long-term mortality with hyperhydration. Failing a method to assess whole body fluid status, we believe that the routinely use of BIVA beside to current clinical-structural methods may help physician to individuate patients’ ideal dry weight. However, RCTs that evaluate fluid administration and diuretic therapy taking into account also hydration status are needed in order to assess the precise role of BIVA in goal-directed fluid management in ICU.