Introduction: Nutritional and fluid status assessment is important for clinical management of critically ill children. Routinely this is accomplished by anthropometrics and documentation of intake and output, but there are limited tools available for accurate assessment. Bioimpedance Spectroscopy (BIS) measures body fluid composition, including total body water (TBW), extracellular fluid (ECF), and intracellular fluid (ICF). Our study objective was to determine if nutritional and fluid status correlate with changes in ICF and ECF respectively. Methods: This single center prospective study was conducted over a six-month period at a tertiary Pediatric Intensive Care Unit (PICU). All patients admitted longer than two weeks were consented and enrolled. Weekly weight change, fluid intake, net fluid balance, and caloric intake were collected from electronic medical records. BIS measurements were performed weekly using ImpediMed SBF7 device and TBW, ICF, and ECF were recorded. Sequential weekly data was collected until the patient was discharged. Repeated measures correlations were done for relevant clinical and BIS covariates. Results: Based upon sample size calculations, 40 patients were enrolled. Using repeated measures correlation analysis, weekly weight change positively correlated with TBW (r = 0.39, p < 0.001), ECF (r = 0.43, p < 0.001), and ICF (r = 0.31, p < 0.001). Weekly fluid intake had a positive correlation with TBW (r = 0.12, p = 0.026), ECF (r = 0.23, p = 0.01), and ECF/ICF ratio (r = 0.12, p = 0.046). Weekly caloric intake had a negative correlation with ECF/ICF ratio (r = -0.23, p = 0.014). Weekly net fluid balance had positive correlation with TBW (r = 0.34, p < 0.001), ECF (r = 0.35, p < 0.001), and ICF (r = 0.31, p < 0.001). Conclusions: TBW, ICF, ECF, and ECF/ICF ratio as measured by BIS have statistically significant correlation with clinically measured parameters such as weekly weight change, total fluid intake, fluid balance, and caloric intake. A high ECF/ICF ratio is reflective of fluid overload, and a lower ratio correlates well with higher caloric intake. This single center study suggests that BIS can be used as a non-invasive modality to evaluate fluid and nutritional parameters.
Mirza et al. (Sun,) studied this question.