Abstract
Introduction
Bioelectrical impedance analysis (BIA) is a simple, noninvasive method of assessing body composition. BIA operates by sending a low-voltage electric current through the body and measuring the impedance to that current. Parameters obtained from BIA have been used to investigate a range of variables such as nutrition and hydration status in a variety of patient populations. Phase angle is also a unique parameter that is thought to reflect cellular health. BIA parameters can undergo further analysis by bioelectrical impedance vector analysis (BIVA) which can provide information about hydration status. Burn and critical care patients pose a unique challenge because they are particularly sensitive to fluid shifts and metabolic derangements which are associated with poorer outcomes. The utility of BIA and BIVA in this patient population has not been well studied. Thus, we have conducted a systematic review and meta-analysis of the ability of BIVA and BIA parameters to assess cellular health and hydration status in critically ill adults and whether they can be correlated with outcomes.
Methods
A search was performed on PubMed and Google Scholar in accordance with PRISMA guidelines between June 2020-August 2020 utilizing the keywords: bioelectrical impedance analysis, critical care, critical, body composition, phase angle, water, fluid. Inclusion criteria were articles investigating the relationship between BIA, BIVA and outcomes with regards to phase angle, hydration, and fluid status in critically ill adults. Reviews, non-English articles, and studies involving pediatric patients were excluded. A meta-analysis was conducted on the correlation between mean phase angle and mortality.
Results
The final analysis included 21 articles; 4 articles were included in the meta-analysis. Statistically significant correlations were found between phase angle and mortality in 9/13 articles, hospital length of stay in 4/7 articles, ICU length of stay in 5/7 articles, and mechanical ventilation duration in 1/4 articles. For meta-analysis, mean phase angle in survivors and non-survivors was 4.5 and 3.9 respectively, and this difference was statistically significant (Figure 1, p< 0.01). Significant correlations were found between ECW/TBW and mortality in 4/7 articles, and BIVA derived hydration status and mortality in 6/7 articles.
Conclusions
BIA and BIVA may be used as a prognostic indicator for outcomes in critical care patients. Further investigations are needed to explore this relationship in the burn patient population.
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