Bioimpedance analysis versus lung ultrasonography for optimal risk prediction in hemodialysis patients

Abstract

Fluid overload is associated with adverse outcomes in hemodialysis (HD) patients. Two bedside methods are increasingly utilized to evaluate objectively fluid status-bioimpedance and lung ultrasonography, but there is no available direct, head-to-head comparison of their prognostic significance. Importantly, their predictive abilities have never been tested in a HD population, alongside those of a classic model that also incorporates established echocardiographic parameters of increased mortality risk. Between 26 May 2011 and 26 October 2012, we included in the study 173 patients undergoing chronic HD treatment for at least 3 months in a single dialysis unit. Relative fluid overload (RFO) and B-lines score (BLS) were used as candidate predictors. From Cox survival analysis we evaluated the increase in the predictive abilities for all-cause mortality of adding continuous RFO or BLS to a model including conventional predictors . 31 patients (17.9 %) died during a median follow-up of 21.3 (interquartile range 19.9-30.3) months. All Cox models showed good calibration. The C statistic for the all-cause mortality prediction increased significantly when the RFO was included into the baseline model (ΔC statistics 0.058 95 %CI = 0.003-0.114), but not when the BLS was included into the baseline model. Only the model that incorporated RFO showed significantly better risk reclassification abilities than the baseline model (IDI = 3.6 % and continuous NRI = 24.8 %). Fluid overload, as assessed by bioimpedance, and not by lung ultrasonography, improves risk prediction for death, beyond classical and echocardiographic-based risk prediction scores/parameters.

A Simplified Approach to Extravascular Lung Water Assessment Using Point-of-Care Ultrasound in Patients with End-Stage Chronic Renal Failure Undergoing Hemodialysis

“…The presence of pulmonary B lines in patients undergoing chronic hemodialysis has been previously associated with an increase in mortality [19-21]. As a marker of both fluid status and heart function, this technique provides important information on fluid status and could be useful to individualize fluid removal during dialysis, especially in patients with cardiomyopathy.…”

“…The B-line score has a significant discriminating power for 1 year survival unlike overhydration measured by whole body bioimpedance [20]. However, the B-line score did not improve mortality prediction over a baseline model incorporating left ventricular mass index suggesting that the observed increase in mortality is related to cardiac function [21]. …”

Effects of Volume Overload and Current Techniques for the Assessment of Fluid Status in Patients with Renal Disease

“…Zoccali et al [6] first showed that the degree of lung congestion was a better predictor for mortality, cardiovascular events, and hospitalization than the assessment done by the NYHA score, and that it could even improve prediction for mortality but not cardiovascular events. Later, these results were confirmed by Siriopol et al [75], which showed that lung US was associated with prediction of survival even after the adjustments for echocardiographic and bioimpedance parameters, whereas this technique is not able to improve risk prediction for all-cause mortality in hemodialysis patients beyond classical and echocardiographicbased risk prediction scores/parameters [76].…”

“…On the other hand, in an older study, the same group had found that risk prediction for death by assessing fluid status was improved only by using BIA but not by using LUS [76]. Although the majority of the previous observational studies showed a reduction in mortality in ESRD patients, in a recent metaanalysis that included only randomized controlled trials, BIA was not associated with a significant improvement in survival, showing only a better BP control [25].…”

N-Terminal Prohormone of Brain Natriuretic Peptide but not C-Terminal Pre-Pro Vasopressin (Copeptin) Level is Associated with the Response to Antihypertensive Therapy in Haemodialysis Patients

“…Bioimpedance allows quantification of excess extracellular volume by comparison with a healthy population. This safe and noninvasive method can be used to determine hydration status in patients on dialysis therapy, and different from other methods allows the quantification of intracellular and extracellular volumes [6,10,11]. However, this approach is time-consuming and difficult to handle in everyday practice.…”