Positive fluid status has been consistently associated with worse prognosis in critically ill adult patients.However, observational studies showed poor agreement between fluid balance and body weight changes. The objective of the study is to compare the measurements of FB and BW over time and to assess correlation with ICU mortality.

Positive fluid status has been consistently associated with worse prognosis in critically ill adult patients. Daily and cumulative fluid balance (FB) is a routine nursing activity in intensive care unit (ICU). In view of the potential for errors in the calculation of FB totals and the problem of accounting for insensible fluid losses, measurement of body weight (BW) changes is an alternative non-invasive method commonly used for estimating body fluid status. Its accuracy over FB assumes a one kilogram change in BW equates to a one liter gain or loss in body fluid volume. However, observational studies showed poor agreement between those measurements, particularly among individuals staying more than a week in ICU possibly due to muscle and fat loss as well as bone demineralization. The objective of the study is to compare the measurements of FB and BW over time and to assess correlation with ICU mortality.

Inclusion Criteria:

• Individuals aged >18 years-old admitted to ICU;
• Expected length of ICU stay superior to 24 hours.

Exclusion Criteria:

• Individuals receiving oral diet;
• Actual body weight superior to 227kgs or 501lb.

All adult patients consecutively admitted to the ICU from June to October 2018 are eligible if expected length of ICU stay is superior to 24 hours and no oral nutritional is being offered.