The importance of bioelectrical impedance in the critical pediatric patient

Phase angle as a prognostic indicator in critically ill children: A systematic review

Phase angle (PhA) may reflect the integrity of cellular membranes, hydration status, and total body cell mass. Studies have shown that PhA can be used as a good predictor for evaluation of disease severity in critically ill adults. However, there is a lack of studies assessing the association between PhA and clinical outcomes in critically ill children. This systematic review described the association between PhA at pediatric intensive care unit (PICU) admission with clinical outcomes in critically ill children. The search was conducted using PubMed/Medline, Scopus, Web of Science, EMBASE and LILACS until July 22, 2022. Studies that evaluate the association between PhA at PICU admission in critically ill children and clinical outcomes were eligible. Data regarding population, study design, setting, bioelectrical impedance analysis (BIA) protocol used, PhA classification, and outcome analysis were extracted. Risk of bias was assessed by Newcastle-Ottawa Scale. Among the 4669 articles screened, five prospective studies were included. The studies have shown association between lower values of PhA at PICU admission with longer PICU and hospital length of stay, duration of mechanical ventilation, septic shock, and higher mortality risk. Small sample size, different clinical conditions, and methodological differences of the studies regarding BIA equipment and cutoffs of PhA were observed. Although the studies have limitations, the PhA has a potential role in predicting clinical outcomes in critically ill children. Larger studies with standardized PhA protocols and other relevant clinical outcomes are necessary.

Body composition in pediatric patients

Undernutrition is highly prevalent in children who are critically ill and is associated with increased morbidity and mortality, including a higher risk of infection due to transitory immunological disorders, inadequate wound healing, reduced gut function, longer dependency on mechanical ventilation, and longer hospital stays compared with eutrophic children who are critically ill. Nutrition care studies have proposed that early interventions targeting nutrition assessment can prevent or minimize the complications of undernutrition. Stress promotes an acute inflammatory response mediated by cytokines, resulting in increased basal metabolism and nitrogen excretion and leading to muscle loss and changes in body composition. Therefore, the inclusion of body composition assessment is important in the evaluation of these patients because, in addition to the nutrition aspect, body composition seems to predict clinical prognosis. Several techniques can be used to assess body composition, such as arm measurements, calf circumference, grip strength, bioelectrical impedance analysis, and imaging examinations, including computed tomography and dual-energy x-ray absorptiometry. This review of available evidence suggests that arm measurements seem to be well-established in assessing body composition in children who are critically ill, and that bioelectrical impedance analysis with phase angle, handgrip strength, calf circumference and ultrasound seem to be promising in this evaluation. However, further robust studies based on scientific evidence are necessary.

Phase angle as a marker of outcome in hospitalized pediatric patients. A systematic review of the evidence (GRADE) with meta-analysis

Phase angle (PhA) is a valuable tool for evaluating the nutritional and inflammatory status, which can accompany acute and severe disorders. PhA is a cellular health biomarker, whose value is particularly substantial due to the negative consequences of these situations in the pediatric population. Relevant literature was collected with the aim of comprehensively analysing the evidence on the association between an altered PhA can serve as a predictive-marker for mortality and poor-outcomes in at-risk-pediatric patients. Understanding this relationship could have significant implications for identifying high-risk individuals and implementing timely interventions. A systematic review with meta-analysis was conducted in the primary electronic databases from inception until January 2023. Overall, four studies with a total of 740 patients were eligible for our analysis. Evidence demonstrates that PhA is associated with nutritional status, reflecting undernutrition and changes in body composition related to illness. This review suggests that PhA can indeed be used as an indicator of nutritional status and a tool for predicting prognosis, including mortality and poor-outcomes, in hospitalized pediatric patients. A low PhA was associated with a significant mortality risk [RR:1.51;95%CI (1.22-1.88),p = 0.0002;I2 = 0%,(p = 0.99)] and an increased complications risk [OR:8.17;95%CI (2.44-27.4),p = 0.0007;I2 = 44%,(p = 0.18)]. These findings highlight the importance of taking a comprehensive approach to clinical nutrition, integrating multiple evaluation aspects to establish an accurate diagnosis and personalized therapeutic plans. While PhA emerges as a valuable tool for assessing the risk of malnutrition and as a prognostic-indicator for poor-outcomes in pediatric patients. Further future studies are needed to focus on investigating this relationship in larger and diverse population to strengthen the evidence base.

Brazilian Reference Percentiles for Bioimpedance Phase Angle of Healthy Individuals

Objectives

The present study was designed to estimate phase angle percentile curves for a broad age range of healthy individuals.

Methods

This is a cross-sectional study of healthy Brazilian individuals aged five to 80. InBodyS10 was used to assess phase angle. Reference curves were stratified by sex and estimated using Generalized additive models for location, scale, and shape as a continuous function of age. The phase angle determinants analyzed were physical activity, age, BMI, and SES variables.

Results

Data were analyzed from 2,146 individuals, 1,189 (55.2%) of whom were female. In both sexes, the phase angles showed a similar pattern (an increasing trend from childhood to the teenage phase, followed by stabilization during adult ages and a decrease in old adults). In female, the relationship between phase angle and age were associated with BMI and family income. In the male, the relationship between phase angle and age were associated with skin color and family income.

Conclusions

To the best of our knowledge, it is the first attempt to apply the GAMLSS technique to estimate phase angle percentiles in a healthy population covering most of the life cycle. We also showed that there are different phase angle determinants according to sex.

The Use of Bioelectrical Impedance Analysis Measures for Predicting Clinical Outcomes in Critically Ill Children

Background

The study aimed to investigate the association of bioelectrical impedance analysis (BIA) for predicting clinical outcomes in critically ill children.

Methods

This single-center prospective observational study included patients admitted to a mixed Pediatric Intensive Care Unit (PICU). All patients underwent anthropometric measurement and BIA measurements in the first 24 h of admission. The patients were classified into different groups based on body mass index (BMI) for age. Electronic hospital medical records were reviewed to collect clinical data for each patient. All the obtained data were analyzed by the statistical methods.

Results

There were 231 patients enrolled in our study, of which 31.6% were diagnosed with malnutrition. The phase angle (PhA) of 90-day survivors was significantly higher than that of the non-survivors (4.3° ± 1.1°vs. 3.1° ± 0.9°, P = 0.02). The age-adjusted Spearman partial correlation analysis showed a weak negative correlation between PhA and duration of medical ventilation (r_s = -0.42, P < 0.05). Furthermore, length of stay in PICU has a very weak correlation with ECW/TBW (r_s = 0.29, P < 0.05), and a negative correlation with protein (r_s = -0.27, P < 0.05). Multivariate analysis found that PhA was a significant predictor associated with the 90-day mortality when it was adjusted for PRISM III score (adjusted OR = 1.51, CI: 1.10–2.07, p = 0.01). The area under the ROC (AUROC) of PhA for predicting 90-day mortality was 0.69 (95% CI: 0.53–0.85, p < 0.05), and the cutoff value of PhA was 3.0°, with a sensitivity and specificity of 83 and 53%, respectively.

Conclusion

BIA-derived PhA was found to be an independent predictor of 90-day mortality among critically ill children. A low PhA was associated with a prolonged duration of medical ventilation.

Using bioelectrical impedance analysis in children and adolescents: Pressing issues

Single- and multifrequency bioelectrical impedance analysis (BIA) has gained popularity as a tool to assess body composition and health status of children and adolescents, but many questions and misconceptions remain. This review addresses pressing issues researchers and health care providers may encounter when using BIA in the young population. The importance of choosing population-specific and device-specific equations to estimate body composition as well as the use of BIA in longitudinal analyses are discussed. When specific equations are not available, raw bioimpedance values (i.e., resistance, reactance, and impedance) can be used to compute bioimpedance parameters, such as phase angle, impedance ratio, and bioelectrical impedance vector analysis. As interpreting these parameters is challenging, suggestions are provided on the use of reference data, cut-off points, and adjustment factors. Furthermore, unsolved technical and analytical issues are listed. Based on existing issues and potential for future development, a greater interaction between industry and academic researchers to improve the validity of BIA measurements among children and adolescents across their developmental stages is encouraged.

Comparison of body water status and its distribution in patients with non-septic infection, patients with sepsis, and healthy controls

Objective

Although fluid resuscitation is the cornerstone of treatment for sepsis, the role of body water status in sepsis is poorly understood. This study aimed to understand how body water and its distribution are modified in patients with sepsis and those with non-septic infection compared to healthy individuals.

Methods

Two groups of adults presumed to have non-septic infection (n=87) and sepsis (n=54) were enrolled in this prospective study in a single emergency department, and they were compared to sex-, age-, and height-matched (1:3 ratio) healthy controls (n=11,190) from retrospective data in a health promotion center. Total body water (TBW), intracellular water (ICW), and extracellular water (ECW), determined using direct segmental multi-frequent bioelectrical impedance analysis (InBody S10) were expressed as indices for normalization by body weight (BW). The ratio of ECW to TBW (ECW/TBW) was evaluated to determine body water distribution.

Results

TBW/BW, ICW/BW, and ECW/BW were significantly higher in the non-septic infection group than in the healthy group (P<0.001), but ECW/TBW was not significantly different (P=0.690). There were no differences in TBW/BW and ICW/BW between the sepsis and healthy groups (P=0.083 and P=0.963). However, ECW/BW and ECW/TBW were significantly higher in the sepsis group than in the healthy group (P<0.001).

Conclusion

Compared to the healthy group, the ratio of body water to BW was significantly increased in the non-septic infection group, while ECW/BW and ECW/TBW were significantly increased in the sepsis group. These indices could be utilized as diagnostic variables of body water deficit in septic patients.