Estimation of body fluid status by fluid balance and body weight in critically ill adult patients : A systematic review

Background
The charting of daily fluid balances and measurement of body weight changes are two noninvasive methods commonly used in the intensive care unit for estimating body fluid status. The determination of body fluid status plays an important role in the management of critically ill patients where aggressive fluid resuscitation is often required. This can adversely affect patient outcomes if changes in fluid distribution are not detected early in patients who are susceptible to fluid overload.

Aim
To synthesize the best available evidence on the accuracy of daily fluid balance charting compared with the measurement of body weight for the estimation of body fluid status in critically ill adult patients.

Methods
The review considered studies that investigated the accuracy of charting daily fluid balances or changes in body weight measurements or used both noninvasive methods in the estimation of body fluid status. The search sought to identify published, English language studies from 1980 until February 2018. Databases searched included MEDLINE, CINAHL, EMBASE, TRIP, Scopus, TROVE, ProQuest Dissertations, Australian and New Zealand Trials Registry, and Cochrane Central Register of Clinical Trials. Three reviewers independently assessed retrieved studies that matched inclusion criteria using standardized critical appraisal instruments.

Results
The review included 13 cohort studies. Effectiveness of daily fluid balance charting was affected by inaccuracies observed in seven studies. Inability to obtain consecutive daily body weight measurements reduced the accuracy of monitoring changes in five studies. Seven studies found measurement of daily fluid balance inconsistent with changes in body weight.

Linking Evidence to Action
The accuracy of charting fluid balance is suspect. Measurement of body weight is hard to accomplish. A combination of the two commonly used methods is more likely to be effective in estimating body fluid status than reliance on one single approach.