An. Roos et al., WEIGHT CHANGES IN CRITICALLY ILL PATIENTS EVALUATED BY FLUID BALANCESAND IMPEDANCE MEASUREMENTS, Critical care medicine, 21(6), 1993, pp. 871-877
Objective. To study simple, rapid, and predictive methods to determine
body weight changes in critically ill patients. Design: Prospective,
consecutive sample. Setting: Medical intensive care unit of a universi
ty hospital. Patients: Thirty-one consecutive patients. Interventions:
Calculated weight changes, using day-to-day and cumulative fluid bala
nces 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 cha
nges. Measurements and Main Results: No reliable relationship was foun
d between calculated weight changes using fluid balances corrected for
insensible loss and the observed weight changes. An intraindividual r
elationship was found between actual weight changes and changes in res
istance 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 wi
th small weight changes (3.1 +/- 2.2 kg). In each patient, the slope c
oefficient of the change in weight and resistance relationship differe
d; this individual slope coefficient could be an indication for hydrat
ion. Conclusions: Calculated fluid balances are not predictive for act
ual weight changes in critically ill patients. Absolute weight measure
ments are indispensable. Changes in resistance correlated with weight
changes in individual patients if weight changes were >3 kg.