title: Electronic bed weighing vs daily fluid balance changes after cardiac surgery.
abstract: OBJECTIVE
  The purpose of this study is to establish the validity and reliability of measuring weight in critically ill patients with electronic weighing beds.
  
  
  METHODS
  All patients admitted to a private intensive care unit (ICU) after cardiac surgery over a 7-month period were weighed on admission and then twice daily (1200 and 2400 hours) using electronic weighing beds (Hill-Rom, Batesville, AR). For each measurement, nonremovable items were recorded, and an average value was deducted from measured weight. We compared differences in body weights (BWs) between 2 consecutive 12-hour periods with the corresponding fluid balance (FB). In addition, we compared weights obtained with electronic weighing beds with those obtained with a regular calibrated scale on ICU discharge.
  
  
  RESULTS
  We obtained data in 103 patients for 414 (75.5%) of 548 of all possible BW measurements. On average, we identified a total of 3.5 kg (SD, 1.4) of nonremovable items on patients' beds. The correlation between 12-hourly changes in BW and FB was weak (r = 0.28; 95% confidence interval [CI], 0.17-0.39), even after correction for insensible fluid losses (r = 0.27; 95% CI, 0.15-0.38) and when only values obtained in intubated patients were taken into account (r = 0.34; 95% CI, 0.16-0.49). Similarly, limits of agreements were wide (95% CI, -3.3 to 3.5 kg). There was also poor agreement between weights obtained on electronic beds and those obtained on the regular scale on ICU discharge (95% CI, -7.6 to 7.6 kg).
  
  
  CONCLUSIONS
  Body weight measured by electronic weighing beds does not seem sufficiently robust or accurate to replace daily FB in ICU. The clinical value of purchasing such beds remains uncertain.
authors.affiliation: Intensive Care Unit, Department of Intensive Care, Austin Health, 3084 Heidelberg Australia; Warringal Private Hospital, 3084 Heidelberg Australia.
authors.forename: Antoine Guillaume
authors.initials: AG
authors.lastname: Schneider
authors.forename: Christopher
authors.initials: C
authors.lastname: Thorpe
authors.forename: Kerrin
authors.initials: K
authors.lastname: Dellbridge
authors.forename: George
authors.initials: G
authors.lastname: Matalanis
authors.forename: Rinaldo
authors.initials: R
authors.lastname: Bellomo
mesh_terms: D018806:APACHE; D000368:Aged; D001513:Beds; D001835:Body Weight; D002138:Calibration; D006348:Cardiac Surgical Procedures; D016638:Critical Illness; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D007902:Length of Stay / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D014882:Water-Electrolyte Balance
keywords: Body weight; Intensive care units; Water electrolyte balance; Weights and measures