PURPOSE:
Monitoring of fluid balance (FB) can be
achieved by subtracting recorded fluid output from input or by measuring
changes in body weight (BW). The latter approach is difficult in the
critically ill. Recently, hospital beds have become available with the ability
to directly weigh patients in the intensive care unit (ICU) patients directly.
We sought to compare FB estimates obtained by these 2 methods in a cohort of
critically ill patients.
MATERIALS AND METHODS:
Between November 2010 and May 2011, all
patients admitted in our ICU for more than 2 consecutive days and nursed on a
Hill-Rom (Batesville, Ind) Total Care bed were weighed daily at midnight hours.
Fluids charting was done by electronic spreadsheet with automated 24 hours
calculation. Differences in BW and FB between 2 consecutive days were
compared using correlation and Bland-Altman analysis. Corrections for
unmeasured fluids losses were performed using a predetermined formula based
on peak temperature and intubation status.
RESULTS:
We obtained complete data in 160 (31%) of 504
admissions exceeding 2 days (153 patients) resulting in 435 data points. The change in BW over 24 hours and FB for the
same period was only weakly correlated before (r = 0.34; P < .001;
Fig. 1) or after correction for insensible fluid losses (r = 0.34; P < .001).
On Bland-Altman plot, the mean bias was small (0.07 kg), but the 95% limits of
agreement, very large (-5.8 and 6.0 kg). The lack of agreement increased with
the magnitude of the changes.
CONCLUSION:
- Obtaining daily weights in ICU patients proved difficult.
- Compliance was poor.
- The correlation between changes in BWs and FB was weak.
Further studies are required to establish if
accurate and reproducible daily weighing of ICU patients is feasible.
Reference:
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