Weight changes in critically ill patients evaluated by fluid balances and impedance measurements.
OBJECTIVE
To study simple, rapid, and predictive methods to determine body weight changes in critically ill patients.


METHODS
Prospective, consecutive sample.


METHODS
Medical intensive care unit of a university hospital.


METHODS
Thirty-one consecutive patients.


METHODS
Calculated weight changes, using day-to-day and cumulative fluid balances corrected (in two ways) for insensible losses, were compared with the actual weight changes (mattress bascule). A tetrapolar impedance technique measuring resistance was evaluated for estimating weight changes.


RESULTS
No reliable relationship was found between calculated weight changes using fluid balances corrected for insensible loss and the observed weight changes. An intraindividual relationship was found between actual weight changes and changes in resistance measured with the tetrapolar impedance technique in a group of 24 critically ill patients with large weight changes (11.1 +/- 6.7 kg). No such intraindividual relationship was found in seven patients with small weight changes (3.1 +/- 2.2 kg). In each patient, the slope coefficient of the change in weight and resistance relationship differed; this individual slope coefficient could be an indication for hydration.


CONCLUSIONS
Calculated fluid balances are not predictive for actual weight changes in critically ill patients. Absolute weight measurements are indispensable. Changes in resistance correlated with weight changes in individual patients if weight changes were > 3 kg.
Department of General Internal Medicine, University Hospital Leiden, The Netherlands.
A N
AN
Roos
R G
RG
Westendorp
M
M
Frölich
A E
AE
Meinders
D000293:Adolescent; D000328:Adult; D000368:Aged; D001835:Body Weight; D016638:Critical Illness; D005260:Female; D005544:Forecasting; D006801:Humans; D007902:Length of Stay / Q000706:statistics & numerical data; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D010993:Plethysmography, Whole Body / Q000295:instrumentation / Q000379:methods*; D011446:Prospective Studies; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D015996:Survival Rate; D014870:Water Loss, Insensible; D014882:Water-Electrolyte Balance