Bioimpedance as a measure of fluid status in critically ill patients: A systematic review

Abstract

Objective Precise measurements of fluid status lack valid methods. Bioimpedance is an attractive diagnostic tool because it is noninvasive, quick, and relatively cheap. This systematic review aims to assess the existing evidence of bioimpedance as an accurate measure of fluid status in critically ill patients. Data sources PubMed and Embase up till March 2021 were systematically searched (PROSPERO: CRD42020157436). Study selection Eligibility criteria were studies reporting original data from cohorts of adult patients in intensive care units and doing at least one whole‐body bioimpedance and one reference test. In addition, studies assessing internal reproducibility were included. Data extraction An extraction form was designed for the purpose. Data synthesis Nine hundred five studies were screened for eligibility, and 28 studies, comprising 1482 individual patients, were included in the final analysis. Eight studies compared bioimpedance with a gold standard, and two of those reported the results adequate. We found a low mean difference, but the 95% limits of agreements had wide limits. The remaining studies applied different surrogates as reference tests. Correlations ranged from 0.05 to 0.99. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) certainty of evidence for all outcomes was very low. Conclusions The accuracy of bioimpedance as a measure for fluids in critically ill patients in the intensive care unit cannot be determined. Due to the lack of a gold standard, numerous studies compared bioimpedance with surrogate outcomes with great variability in both designs and results. Assessing the internal reproducibility of bioimpedance had the same limitations, but the studies overall reported good internal reproducibility.

Bioimpedance spectroscopy fluid analysis in acute high-risk abdominal surgery, a prospective clinician-blinded observational feasibility study

“…Several studies on critical care and surgical patients have been conducted, with different methods of body composition analysis and mixed results [ 23 ]. In this study, we employed bioimpedance spectroscopy using the BCM device, which measures at 50 frequencies and utilizes a unique body composition model for determining fluid overload or overhydration to directly predict TBW, ECW, and ICW.…”

“…3 ), adding to the method's credibility. However, a recent systematic review questioned the accuracy of measurements due to a lack of gold standards, where numerous studies, like the present, compared measurements with surrogate parameters with significant variability in design [ 23 ].…”

“…and is currently recommended for evaluating fluid status in haemodialysis patients [ 18 , 19 ]. Data regarding BIA use in critically ill patients and septic [ 20 ] and burn patients [ 21 , 22 ] is available but controversial due to mixed results [ 23 , 24 ]. BIA has not been studied specifically in patients undergoing AHA surgery.…”

Diagnosis of Fluid Overload: From Conventional to Contemporary Concepts

“…However, BIA-guided decongestive therapy has not shown to be superior compared to standard care with respect to outcome [69][70][71][72]. In critically ill patients, the accuracy of BIA as a measure of hydration status remains unclear at this time [73]. A key limitation of BIA is its inability to detect the location of extracellular volume expansion (e.g., pleural effusion vs. pulmonary edema vs. ascites vs. venous congestion).…”

Bioimpedance as a measure of fluids in patients with septic shock. A prospective observational study

“…Bioelectrical impedance analysis is an attractive diagnostic tool because it is non‐invasive, easy to use, quick, relatively cheap, and safe 8–12 . Nevertheless, the validity of Bioimpedance measurements in this population has not yet been established 13 …”