Bioelectrical impedance analysis during deresuscitation: correlation and agreement with cumulative fluid balance in ICU patients

Bioelectrical impedance analysis (BIA) is a promising tool to evaluate the body composition of critically-ill patients. The present study aimed to assess its value as a fluid management monitoring tool during standardized deresuscitation strategy. A historical cohort of critically-ill adult patients with fluid overload and continuous renal replacement therapy was used to explore both relationship and agreement between changes in cumulative fluid balance and BIA-derived hydration variables within the 5 days following initiation of deresuscitation strategy using net ultrafiltration. Correlations were described using Spearman’s rank correlation coefficient, and agreement using Bland–Altman analysis for repeated measurements. Sixty-one couples of fluid shift measurements from 30 patients were analyzed. The deresuscitation strategy induced a negative mean (± SD) cumulative fluid balance (− 4.2 ± 3.8 L) and a significant decrease in extra- and intracellular water (P < 0.001). Decreases in extra- and intracellular water were independent of weight variations inputted in the BIA device. Total body water (rho = 0.63), extracellular water (rho = 0.68), and intracellular water (rho = 0.67) were significantly correlated with cumulative fluid balance (all P values < 0.001). The limits of agreement did not allow interchangeability for a delta of 2L between cumulative fluid balance and BIA-derived hydration variables (P > 0.05). BIA hydration-derived variables are significantly correlated with cumulative fluid balance but the large limits of agreements exclude interchangeability of the measures.