Dehydration is common and frequently under-diagnosed in chronic malnourished children, leading to life-threatening conditions. In this pilot study we applied bioimpedance vector analysis (BIVA) to determine hydration status in 52 neurologically impaired (NI) paediatric patients (14.08 ± 5.32). Clinical and biochemical data were used to define malnutrition and dehydration. Body composition analysis and hydration were also assessed by BIVA and we considered 143 normal-weight healthy subjects (15.0 ± 1.7), as controls for hydration status assessment. BIVA revealed a pathological hydration status in NI children, showing higher resistance (p < 0.001) and reactance values (p = 0.001) compared to controls. No differences in reactance and resistance were detected between well-nourished and under-nourished subjects. Four patients out of 52 showed mild signs of dehydration; no severe dehydration was detected. Laboratory data, suggestive for dehydration, were similar in well-nourished and under-nourished NI subjects. In conclusion, in our sample of NI paediatrics, dehydration according to clinical signs and laboratory data was under-diagnosed. BIVA showed specific bioelectrical characteristics that could be compatible with impaired hydration status. Further studies are necessary to confirm that BIVA may an applicable tool for defining dehydration status and guiding rehydration in NI children.
Dehydration is common and frequently under-diagnosed in chronic malnourished children leading to life-threatening conditions, such as acute kidney injury or cardiac disease . Since the presence or absence of dehydration symptoms and abnormal laboratory results may not be an accurate way to diagnose dehydration, we propose to use bioelectrical impedance vector analysis (BIVA), which offers the potential for both noninvasive single assessment and serial monitoring of hydration status .
Subjects and methods
Fifty-two patients (31 M/21 F; 14.08 ± 5.32 years) with severe disabilities (34.6% cerebral palsy, 25% epileptic encephalopathy, 40.4% dysmorphic syndromes), were enroled between 1 November 2016 and 1 April 2018.
All patients, living either at home or in sheltered community accommodations, were on anticonvulsive treatment and enteral feeding (bolus 80.8%, continuous 19.2%).
In all patients, nutritional status and body composition analysis were evaluated.
We considered 143 normal-weight healthy subjects, matched for age (15 ± 1.7 yrs) formerly enroled for another study , as controls for hydration status assessment.
The study was performed according to the Declaration of Helsinki, with the approval of the Institutional Review Board, with patients’ parents or tutors written consent.
As previously reported, subjects were defined undernourished if they met BMI-SDS < 2 and at least ≥ 2 biochemical markers positive for malnutrition .
Dehydration was defined as mild to moderate in presence of dry mouth, lips and eyes, fewer tears when crying, reduced urine output (less than four wet diapers in 24 h); severe in presence of excessive sleepiness, sunken eyes, feeling cold, discoloured hands and feet and wrinkled skin. Additional laboratory data included renal function and haemoconcentration.
Physical examination included pubertal stage evaluation and anthropometry: mid upper arm circumference, weight, height and body segment, lengths according to Stevenson’s method, as previously detailed .
Body composition was estimated by bioelectrical impedance (BIA) (BIOSMART, Eupraxia srl, Italy), using an alternating electric current at low intensity (800 μA) and fixed rate frequency at 50 kHz; measurements were performed to the non-dominant side of the body between the ipsilateral wrist and ankle bony prominences . Resistance (R), reactance (Xc) and phase angle were obtained. Body hydration was also assessed by bioimpedance vector analysis (BIVA) [5, 6] a graphical method for interpreting body composition without assuming a constant hydration level of 73% in individuals.
Descriptive statistics (mean, SD, median, 25–75 percentile) were calculated for age, height, weight, BMI-SDS and bioelectrical variables (phase angle, R/h and Xc/h). Differences between well vs under-nourished subjects, and between cases with severe disabilities vs controls, were assessed by Wilcoxon Mann^ = Whitney U-test. Whole-body bioimpedance vectors were analysed by the RXc graph method  using the BIVA software .
Several physiological and pathological factors may contribute to BIVA results, and interpretation may be challenging, nevertheless, longer and shorter vectors indicate, respectively, dehydration and hyperhydration , while vectors falling left of the major axis are associated with a higher cell mass compared to those falling on the right. As shown in Fig. 1, higher resistance (p < 0.001) and reactance (p = 0.001), as well as longer vectors falling on the right of the major axis were observed in NI paediatrics compared to controls, suggesting an impaired hydration status. In five children, who received rehydratation solution besides continous enteral feeding, the reversal of the vector to normal was observed, supporting the role of dehydration on the vector elongation (see supplementary information).
Under-nutrition was identified in 32.7% (17/52) of the patients, although no significant differences in reactance and resistance were observed between well- and under-nourished subjects. Clinical features and body composition of all subjects according to their nutritional status, are reported in Table 1.
Only 4 patients out of 52 showed mild clinical signs of dehydration, however no haemoconcentration was evident from the haematocrit values. Additional laboratory data were comparable regardless of nutritional status (Table 1), suggesting poor accuracy of these biomarkers in identifying individuals dehydrated or at risk.
Subjects with developmental disabilities are at a higher risk for dehydration . They are not able to drink on their own, besides they may have cognitive and/or speech impairment, which makes it hard for their caregivers to understand when they are thirsty . This risk is further increased by loss of cell mass and multiple medications interactions .
The role of hydration in health and disease is crucial and negatively impacts health. Hydration status should be assumed as a routine model, and assessed daily, according to gender, age, physical activity and environmental conditions. Effective assessments are needed to overcome current tools limitations and in our opinion BIA offers the possibility to evaluate body fluid variation, especially when BIVA vectors are applied .
In our sample of NI paediatrics, dehydration according to clinical signs and laboratory data was under-diagnosed. BIVA showed specific bioelectrical characteristics that could be compatible with impaired hydration status related to poor nutritional status faced by these patients. BIA vector migration detected in the children who received rehydratation solution, could support this hypothesis; however, at this time is not possible to define the role of the vector modification on the well being and survival of the patients. Moreover, the alternative explanation could, therefore, lie within the framework of the neural impulses in upper motor neuron disease interfering with BIVA or due to the fibrofatty muscle degeneration.
Other tests, such as D2O, could serve to confirm that BIVA may an applicable tool for defining dehydration status and guiding rehydration in NI children, however, in clinical practice NI children present many different physical, behavioural and emotional problems, that make these test difficult to be performed.
Our pilot study suggests that further research should be conducted to provide health care professionals with simple and reliable tools able to assess body composition and hydration status to avoid worsening of the precarious health conditions, and help lowering the risk of further complications in NI children.
Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
The authors did not receive any funding from public, commercial or not-for-profit agencies to conduct this research.