Changes In Extracellular Water Research Articles

Brain elastography in aging relates to fluid/solid trendlines

The relatively new tools of brain elastography have established a general trendline for healthy, aging adult humans, whereby the brain’s viscoelastic properties ‘soften’ over many decades. Earlier studies of the aging brain have demonstrated a wide spectrum of changes in morphology and composition towards the later decades of lifespan. This leads to a major question of causal mechanisms: of the many changes documented in structure and composition of the aging brain, which ones drive the long term trendline for viscoelastic properties of grey matter and white matter? The issue is important for illuminating which factors brain elastography is sensitive to, defining its unique role for study of the brain and clinical diagnoses of neurological disease and injury. We address these issues by examining trendlines in aging from our elastography data, also utilizing data from an earlier landmark study of brain composition, and from a biophysics model that captures the multiscale biphasic (fluid/solid) structure of the brain. Taken together, these imply that long term changes in extracellular water in the glymphatic system of the brain along with a decline in the extracellular matrix have a profound effect on the measured viscoelastic properties. Specifically, the trendlines indicate that water tends to replace solid fraction as a function of age, then grey matter stiffness decreases inversely as water fraction squared, whereas white matter stiffness declines inversely as water fraction to the 2/3 power, a behavior consistent with the cylindrical shape of the axons. These unique behaviors point to elastography of the brain as an important macroscopic measure of underlying microscopic structural change, with direct implications for clinical studies of aging, disease, and injury.

Delayed post-dialysis recovery times are associated with relative changes in intracellular and extracellular fluid ratios between different body compartments.

Hemodialysis patient groups have advocated reducing dialysis fatigue and symptoms. We investigated whether compartmental fluid shifts were associated with peri-dialytic fatigue and symptoms. Sessional dialysis records of patients reporting both a short and delayed recovery (<1 h and ≥1 h) with corresponding bioimpedance measurements were reviewed. One hundred and twenty-four patients reported both short and delayed recovery times, mean age 66.0 ± 14.8 years, 66.1% male. Differences between sessions included higher distress thermometer [4 (1-6) vs. 3 (0-5)], fatigue [4 (0-9) vs. 2 (0-7)], total symptom scores [20.5 (12.3-34.5) vs. 16 (7-28)], change in extracellular water to total body water ratios between body compartments [right leg/left arm 2.36 (1.23-4.19) vs. 1.28 (0.12-2.01), all p < 0.01] with delayed recovery, and more hemodialysis than hemodiafiltration sessions (χ2 4.6, p = 0.02). Sessions with prolonged recovery times were associated with more peri-dialytic symptoms, psychological distress, and hemodialysis mode, and greater changes in compartmental fluid shifts.

Comparison of series and parallel reactance to identify changes in intracellular water in response to physical training in athletes during a sports season

Cross-sectional evidence has demonstrated that parallel reactance obtained by bioelectrical impedance analysis (BIA) may be an alternative to the regularly used series of measurements to predict intracellular water (ICW) in athletes. However, we are not aware of any studies that have determined the predictive role or compared the effectiveness of both series and parallel reactance for tracking ICW changes during an athletic season. The main aim of this study was to determine the predictive role and compare both series and parallel reactance (Xc) in tracking ICW during an athletic season. This longitudinal study analyzed 108 athletes in the preparatory and competitive periods. Using dilution techniques, total body water (TBW) and extracellular water (ECW) were determined and ICW was calculated. Resistance (R), Xc, and impedance (Z) standardized for height were obtained through BIA spectroscopy using a frequency of 50kHz in a series array and then mathematically transformed in a parallel array. Multiple regression analyses showed that only changes in parallel Xc and capacitance (CAP) (P < 0.05) were predictors of delta ICW during the sports season. In contracts, this was not the case for Xcs. Both changes in R and Z, series and parallel, predicted similarly the changes in ECW and TBW (P < 0.05) in athletes. Our findings highlight the potential of parallel BIA values to detect changes in body water compartments over a competitive season. These data provide preliminary evidence that changes in parallel Xc/H, and ultimately CAP, represent valid markers of alterations in cell volume during a sports season.

Phase angle as an index of physiological status: validating bioelectrical assessments of hydration and cell mass in health and disease.

Bioelectrical impedance (BI) is a practical method to assess body composition in health and disease. This method relies on the passive conduction of an applied, safe, low-level alternating current through water and electrolytes in the body. Using a phase-sensitive device, BI yields measurements of impedance (Z) and its components, resistance (R) and reactance (Xc), that are related geometrically as phase angle (PhA). In vitro studies provide empirical evidence relating BI measurements to physiological variables. Cooking raw food samples results in greater decreases in PhA, predominantly Xc, with smaller reductions R indicating destruction of cell membrane integrity with simultaneous movement of fluid from intracellular to extracellular space. Infusion of saline into a cell-free model shows a proportional decrease in R with increases in volume. Saline infusion in a composite model of cells disproportionately decreases Xc and PhA, compared to R, demonstrating greater relative expansion of extracellular water (ECW) with a lesser relative increase in total fluid volume. Surgical patients treated with fluid infusion and diuresis demonstrate changes in Xc predominantly indicating relative changes in ECW with lesser variations in R indicating fluctuations in total fluid volume. Proteomics studies disclose strong independent associations of PhA with protein markers of fluid overload and protein proliferation. Interpretations of PhA measurements for body cell mass should be examined in the context of hydration status.

Differences in extracellular fluid volume between acute heart failure patients with and without high systolic blood pressure.

Some reports have suggested that hypertensive acute heart failure (AHF) is caused by intravascular congestion, not interstitial congestion. We evaluated the differences in extracellular fluid volume assessed by bioelectrical impedance analysis (BIA) between AHF patients with and without high systolic blood pressure (sBP). This prospective single-centre study (UMIN000030266) included 178 patients hospitalized due to AHF between September 2017 and August 2018. We calculated extracellular water (ECW), intracellular water (ICW), total body water (TBW), and ECW-to-TBW ratio (oedema index: EI) by BIA and evaluated conventional parameters as follows: weight, N-terminal pro brain natriuretic peptide values, and echocardiography parameters on admission and before discharge. One-year outcomes included all-cause death and re-admission due to heart failure. We compared patients with sBP>140mmHg on admission [clinical scenario 1 (CS1) group] and with sBP of ≤140mmHg on admission (non-CS1 group). The mean age of the patients was 79.5±11.1years, and 48.9% of the patients were female. EI on admission of 83 patients in the CS1 group was lower than that of 95 patients in the non-CS1 group. The change in EI from admission to before discharge was no significant in the CS1 group but was significant in the non-CS1 group. Comparing the changes from admission to before discharge between the CS1 and the non-CS1 group, delta ECW, delta ICW, delta TBW, and delta EI of the CS1 group were significantly smaller than those of the non-CS1 group. During the 1-year follow-up period after discharge of the 178 patients, the numbers of deaths and re-admissions due to acute HF were 26 (15%) and 49 (28%), respectively. Patients with high EI before discharge [>0.408 (median)] had significantly more cardiac events than patients with low EI [hazard ratio (HR): 2.15, 95% confidence interval (CI): 1.30-3.55]. Cox regression analysis revealed that higher EI as a continuous variable was significantly associated with worse outcome in non-CS1 group (HR: 1.46, 95% CI: 1.13-1.87), but not significantly associated with worse outcome in CS1 group (HR: 1.29, 95% CI: 0.98-1.69). EI on admission in patients with high sBP was not elevated, and changes in ECW, ICW, TBW, and EI in patients with high sBP were smaller than those in patients without high sBP. EI measured by BIA could distinguish AHF with interstitial or intravascular congestion.

Estimation of fluid status using three multifrequency bioimpedance methods in hemodialysis patients.

Segmental eight-point bioimpedance has been increasingly used in practice. However, whether changes in bioimpedance analysis components before and after hemodialysis (HD) using this technique in a standing position is comparable to traditional whole-body wrist-to-ankle method is still unclear. We aimed to investigate the differences between two eight-point devices (InBody 770 and Seca mBCA 514) and one wrist-to-ankle (Hydra 4200) in HD patients and healthy subjects in a standing position. Thirteen HD patients were studied pre- and post-HD, and 12 healthy subjects once. Four measurements were performed in the following order: InBody; Seca; Hydra; and InBody again. Electrical equivalent models by each bioimpedance method and the fluid volume estimates by each device were also compared. Overall, total body water (TBW) was not different between the three devices, but InBody showed lower extracellular water (ECW) and higher intracellular water (ICW) compared to the other two devices. When intradialytic weight loss was used as a surrogate for changes in ECW (∆ECW) and changes in TBW (∆TBW), ∆ECW was underestimated by Hydra (-0.79 ± 0.89 L, p < 0.01), InBody (-1.44 ± 0.65 L, p < 0.0001), and Seca (-0.32 ± 1.34, n.s.). ∆TBW was underestimated by Hydra (-1.14 ± 2.81 L, n.s.) and InBody (-0.52 ± 0.85 L, p < 0.05) but overestimated by Seca (+0.93 ± 3.55 L, n.s.). Although segmental eight-point bioimpedance techniques provided comparable TBW measurements not affected by standing over a period of 10-15 min, the ECW/TBW ratio appeared to be significantly lower in InBody compared with Seca and Hydra. Results from our study showed lack of agreement between different bioimpedance devices; direct comparison of ECW, ICW, and ECW/TBW between different devices should be avoided and clinicians should use the same device to track the fluid status in their HD population in a longitudinal direction.

Effect of Empagliflozin Versus Placebo on Body Fluid Balance in Patients With Acute Myocardial Infarction and Type 2 Diabetes Mellitus: Subgroup Analysis of the EMBODY Trial

BackgroundThe development of heart failure is associated with fluid balance, including that of extracellular water (ECW) and intracellular water (ICW). This study determined whether sodium–glucose cotransporter 2 inhibitors affect fluid balance and improve heart failure in patients after acute myocardial infarction. Methods and ResultsEMBODY was a prospective, randomized, double-blinded, placebo-controlled trial of Japanese patients with acute myocardial infarction and type 2 diabetes. Overall, 55 patients who underwent bioelectrical impedance analysis were randomized to receive once daily 10 mg empagliflozin or placebo 2 weeks after acute myocardial infarction onset. We investigated the time course of body fluid balance measured using the bioelectrical impedance analysis device, InBody. The primary end points were changes in body fluid balance from weeks 0 to 24. Changes between baseline and week 24 in the empagliflozin and placebo groups were –0.21 L (P = .127) and +0.40 L (P = .001) in ECW (P = .001) and –0.23 L (P = .264) and +0.74 L (P < .001) in ICW (P < .001), respectively. In a stratified analysis, the rise in ECW and ICW was significantly attenuated in the empagliflozin group in contrast to the placebo group in participants with a body mass index of 25 or higher but not in those with a body mass index of less than 25. ConclusionsEarly sodium–glucose cotransporter 2 inhibitor administration may attenuate changes in ECW and ICW.

Optimal current frequency for the detection of changes in extracellular water in patients on hemodialysis by measurement of total body electrical resistance.

Measurement of total body electrical resistance (TBER) to an alternating current is useful to monitor extracellular water (ECW) in patients on hemodialysis (HD). Which current frequency is preferable is subject of ongoing debate. The aim of this study was to quantify the implications of TBER measurements at current frequencies ranging from 0 to 1000kHz for ECW monitoring in patients on HD. Bioimpedance spectroscopy measurements were performed in 39 patients on HD using the Body Composition Monitor (BCM, Fresenius Medical Care). TBER data at 5, 50, 200, 500, and 1000kHz were compared with the extrapolated TBER at 0kHz (TBER0) assessed by Cole-Cole analysis. Sensitivity of each TBER configuration was evaluated at individual level, by assessment of the smallest ultrafiltration (UF) volume that induced a significant change in TBER, i.e. a change in TBER≥2.7%. TBER precision was very high for all frequencies, with coefficients of variation of 0.25%-0.28%. Baseline TBER decreased with increasing current frequency. TBER was 2.9% lower at 5kHz(P<0.001), 11.6% lower at 50kHz, and up to 22.0% lower at 1000kHz. This pattern is attributed to a progressive increase in intracellular current conduction at higher frequencies. Sensitivity to volume changes induced by UF also decreased with increasing current frequency. At 0 and 5kHz, an UF volume≤0.5L was sufficient to induce a significant increase in TBER in 87% of patients. This decreased to 69% at higher frequencies. ECW monitoring by TBER requires measurement at 5kHz or less to ensure optimal performance.

Changes in extracellular water and left ventricular mass in peritoneal dialysis patients.

BackgroundIncreasing number of peritoneal dialysis (PD) patients are reported to have increased left ventricular hypertrophy (LVH), a major risk factor for cardiovascular mortality. We wished to determine which factors were most associated with changes in left ventricular mass index (LVMI).MethodsWe reviewed patient and treatment factors in prevalent PD patients with repeat echocardiograms 18 to 24 months apart, with corresponding bioimpedance measurements of extracellular water (ECW) and serum N-terminal pro-brain natriuretic peptide (NT-proBNP).ResultsWe studied 60 patients (34 males, 35 with diabetes) who were treated with PD for a median of 14 months (2.5–26.3 months). All but one had LVH; on repeat echocardiography, there was no overall change in LVMI (106 [84–127] g/m2 vs. 108 [91–122] g/m2) despite a loss of residual renal function. Left ventricular mass increased in 34 (56.7%), and the percent change in LVMI was associated with percent change in NT-proBNP (r = 0.51, p = 0.017) and ECW/height (r = 0.32, p = 0.029), but not with ECW/total body water or changes in systolic or mean arterial pressure, urine output, 24-hour PD ultrafiltration, or net sodium balance. Only ECW/height remained independently associated with the percent change in LVMI in a multivariable model (odds ratio, 1.25; 95% confidence interval, 1.08–1.36; p = 0.007). ConclusionIn this observational longitudinal report, a reduction in ECW/height was associated with regression of LVMI, whereas an increased ECW/height was associated with increased LVMI. As there was no corresponding association with systolic or mean arterial pressure, then volume expansion would appear to be a more significant factor in determining LVH than blood pressure.

Changes in extracellular water with hemodialysis and fall in systolic blood pressure.

Introduction:Intra-dialytic hypotension (IDH) remains the most common complication with outpatient hemodialysis (HD) sessions. As fluid is removed during HD, there is contraction of the extracellular volume (ECW). We wished to determine whether the fall in ECW was associated with a fall in systolic blood pressure (SBP).Methods:We retrospectively reviewed the records of adult dialysis outpatients attending for their midweek sessions who had corresponding pre- and post-HD bioimpedance measurements of ECW.Result:We reviewed 736 patients, median age 67 (54–76) years, 62.8% male, 45.7% diabetic with a median dialysis vintage of 24.4 (9.2–56.8) months. The percentage fall in ECW (ECW%) was associated with post-dialysis systolic blood pressure (SBP) (r = −0.14, p < 0.001). Patients with SBP falls of >20 mmHg had a greater fall in ECW% compared to patients with stable SBP 7.6 (4.6–10.1) vs 6.0 (4.0–8.5), p < 0.001). Patients with greater dialyzer urea clearance had greater fall in ECW% (r = 0.19, p < 0.001). In a logistic model an increased fall in ECW% was associated with weight loss (odds ratio (OR) 1.88, 95% confidence limits (CL) 1.62–2.176, p < 0.001), and session duration (OR 1.45 (CL 1.05–1.99), p = 0.024), and negatively with hemodiafiltration compared to hemodialysis (OR 0.37 (0.19–0.74) p = 0.005 and dialysate sodium to plasma gradient (OR 0.95 (CL 0.90–0.99), p = 0.021).Conclusion:We observed an association between the reduction in ECW and SBP with dialysis. Our results would advocate monitoring ECW changes during dialysis and developing biofeedback devices to control ultrafiltration and dialysate sodium to reduce the risk of IDH.

Patient-reported symptoms during dialysis: the effect of pre-dialysis extracellular water and change in extracellular water post-dialysis

BackgroundQuality of life for haemodialysis (HD) patients may be affected by symptoms during dialysis treatments, and patient groups have highlighted the need to improve post-dialysis fatigue and dialysis-related symptoms. As changes in extracellular water (ECW) may lead to cramps and other symptoms, we wished to determine whether there was an association between ECW and intra-dialytic symptoms.MethodsWe reviewed the hospital records of HD patients who completed a self-reported intra-dialytic symptom questionnaire, using a visual analogue scale, who had contemporaneous pre- and postdialysis bioimpedance ECW measurements adjusted to height (aECW).ResultsWe studied dialysis sessions of 506 patients, 314 (62.1%) male, 226 (44.7%) diabetic, mean age 64.6 ± 15.7 years, weight 69.9 ± 17.4 kg, and duration of dialysis treatment 26 (9.6–60.1) months. We divided patients into three groups according to pre-dialysis aECW, and total dialysis symptom scores were greater for those in the lower tertile (25 (10–41) vs middle 18 (8.5–34) vs upper 20 (7–31), p < 0.05). Only feeling cold, dizziness, and low blood pressure were statistically different between the three pre-dialysis aECW groups, and there was no difference in post-dialysis recovery times.We analysed the effect of the fall in aECW pre-to post-dialysis. Patients in the group with the greatest fall in aECW did not report more intra-dialytic symptoms or longer recovery times.ConclusionWe found that patients starting dialysis with lower relative ECW were more likely to report intra-dialytic symptoms than those with greater amounts of fluid to remove, and most commonly reported symptoms were associated with intra-vascular volume depletion.

Does Pulse Wave Velocity Increase Over Time in Hemodialysis Patients?

Objectives: Arterial stiffness, measured by pulse wave velocity (PWV), is reported to be increased in hemodialysis (HD) patients and increases cardiovascular mortality. Previous studies have reported an association between extracellular water (ECW) and PWV. We wished to review whether PWV increases over time and whether this is associated with ECW. Methods: We reviewed repeat aortic PWV measurements using an oscillograph method along with corresponding ECW measured by multifrequency bioimpedance in HD patients a minimum of 5 years apart. Results: Twenty-four patients (16 [66.7%] male and 11 [45.8%] diabetic, mean age 61.7 ± 15.2 years) had PWV and ECW initially measured after 46 (26–124) months of HD and then after 112 (97–202) months. Overall, there was no change in PWV or ECW (9.4 ± 2.2 vs. 8.1 ± 2.5 cm/s; 14.7 ± 2.5 vs. 15.2 ± 2.9 L, respectively), whereas the ECW/total body water ratio increased (0.399 ± 0.015 vs. 0.408 ± 0.021, p < 0.05). We found no association between changes in PWV and ECW (r = −0.05, p = 0.84), whereas there was an association with the change in peri-dialytic systolic blood pressure (SBP) (r = 0.59, p = 0.007). Conclusion: In our small observational study, there was no overall change in PWV, after 5 years of HD, with PWV increasing in 50% and falling in 50%. Changes in PWV were not associated with changes in ECW but were associated with changes in peri-dialytic SBP. Our study demonstrates that PWV does not increase in all HD patients with time, and interventional studies are required to determine whether targeted blood pressure control reduces PWV in HD patients.

Low Intracellular Water, Overhydration, and Mortality in Hemodialysis Patients.

Background: In hemodialysis patients, extracellular water (ECW) overload predicts all-cause and cardiovascular mortality. The primary aim of the present study was to analyze changes in post-dialysis (i.e., following removal of excess ECW) ECW, intracellular water (ICW), and the overhydration (OH) parameter over time. Additionally, the association of these parameters with mortality was explored. Patients and methods: Prospective study of prevalent hemodialysis patients (n = 124) followed for a median of 20 (interquartile range (IQR) 8–31) months. In three visits, inflammation (C-reactive protein) and post-dialysis fluid status (bioimpedance, BIS) were assessed. Results: During follow-up, the overhydration (OH) parameter increased (−0.696 ± 1.6 vs. 0.268 ± 1.7 L; p = 0.007) at the expense of a decrease in intracellular water (ICW) (19.90 ± 4.5 vs. 18.72 ± 4.1 24 L; p = 0.006) with a non-significant numerical increase in ECW/ICW ratio (0.795 ± 0.129 vs. 0.850 ± 0.143; p = 0.055). Baseline ICW positively correlated with muscle mass and energy intake and negatively with C-reactive protein and it was lower in those who died than in survivors (15.09 ± 2.36 vs. 18.87 ± 4.52 L; p = 0.004). In Kaplan–Meier analysis, patients with low baseline ICW (≤17 L) and high ECW/ICW ratio (≥0.84) were at an increased risk of death. Baseline ICW was also associated with the risk of death in adjusted Cox proportional hazards models (HR 0.62 (0.40–0.98) p = 0.04). Conclusions: In hemodialysis patients, the post-dialysis OH parameter increased over time while ICW decreased, without changes in ECW. Low baseline post-dialysis ICW correlated with muscle wasting and inflammation and was an independent risk factor for mortality.

Changes in aortic pulse wave velocity in peritoneal dialysis do not mirror changes in extracellular water measured by bioimpedance.

Pulse wave velocity is a measurement of arterial stiffness and associated with increased cardiovascular mortality. Previous reports in peritoneal dialysis have linked increased pulse wave velocity with an expansion in extracellular water. As cardiovascular mortality is increased in peritoneal dialysis patient, we wished to determine whether changes in pulse wave velocity mirrored changes in extracellular water. We repeated aortic pulse wave velocity and bioimpedance-derived extracellular water measurements in peritoneal dialysis patients attending for assessment of peritoneal membrane function. Sixty-six patients, 41 males (62.1%), mean age of 66.2 ± 13.9 years, median duration of peritoneal dialysis treatment (14.3 (3.1-31.9) months) had repeated measurement 6.4 (5.8-10.2) months apart, with no significant change in aortic pulse wave velocity (10.1 ± 3.2 to 9.9 ± 2.8 m/s). In univariate analysis, the initial aortic pulse wave velocity was associated with extracellular water (r = 0.26, p = 0.034) and serum N-terminal pro brain-type natriuretic peptide (r = 0.25, p = 0.04), and on follow-up, aortic pulse wave velocity with N-terminal pro brain-type natriuretic peptide (r = 0.31, p = 0.01). Aortic pulse wave velocity increased in 50% of patients, and these patients had greater serum C-reactive protein 3(2-10) versus 2(1-4) mg/L, and ferritin (778(444-1099) versus 585(313-811), p < 0.05), but there were no differences in either absolute or adjusted extracellular water. Both log C-reactive protein (odds ratio 4.7 (95% confidence limits 1.3-17.1), p = 0.019) and prescription of calcium channel blockers (odds ratio 4.9 (95% confidence limits 1.2-19.1), p = 0.024) were independently associated with an increase in aortic pulse wave velocity. We did not find an independent association between a change in aortic pulse wave velocity and extracellular water, suggesting that changes in aortic stiffness in peritoneal dialysis patients are more complex than simply following changes in extracellular water.

Perioperative fluid dynamics evaluated by bioelectrical impedance analysis predict infectious surgical complications after esophagectomy

BackgroundTransthoracic esophagectomy, among the most invasive surgeries, is highly associated with postoperative infectious complications which adversely affect postoperative management including fluid dynamics. The aim of the study is to evaluate the utility of perioperative bioelectrical impedance analysis (BIA) measurements for the patients after transthoracic esophagectomy.MethodMulti-frequency BIA measurements were conducted in 24 patients undergoing transthoracic esophagectomy preoperatively, at 1 h after surgery, and twice daily for the following 7 days. The amounts of extracellular water (ECW), internal cellular water (ICW), total body water (TBW), and fat-free mass (FFM) were calculated. Changing trends in variables were analyzed, and the patients were subdivided according to the presence of infectious surgical adverse events to identify differences in fluid dynamics.ResultsECW was the major body fluid compartment showing an increase after surgery, and peaked on postoperative day (POD) 2. Twelve patients experienced infectious complications. The peaks of changes in ECW and ECW/TBW appeared earlier and their values at the highest peak were significantly lower in the group without infectious complications on POD 2. The ICW/FFM value showed a mild decrease as compared to POD1 and then gradually recovered. It was significantly lower even before surgery and showed the most significant stratification on POD2. ECW/TBW of 48% and ICW/FFM of 37% on POD2 were predictive cut-off values for infectious adverse events with high area-under receiver operating characteristic (ROC) curves: 0.80 or higher.ConclusionBIA measurements are useful for monitoring fluid retention and may predict infectious complications in the early phase after transthoracic esophagectomy.Trial registrationRegistry name: UMIN-CTR, ID: UMIN000030734, Registered on January 9, 2018, retrospectively registered.

P5407Body-composition analysis of patients with acute heart failure - preliminary results from the SCALE HF trial

Abstract Background Guidance for intensified diuretic therapy in acute heart failure (AHF) is mainly based on body weight measurement, frequently leading to a short episode of dehydration with kidney failure after recompensation. In addition, patients often present immobilized due to severe health issues making weight measurement stressful. Purpose Bioelectrical impedance analysis (BIA) may be a more direct approach to guide intensified diuretic therapy analysing patient's body composition. We hypothesized that patient's weight loss during therapy correlates with loss of body water measured by BIA. Therefore, we tested if this method could be an alternative to daily weight measurement. Methods We conducted an observational, single-centre study to evaluate and monitor body composition of patients hospitalised with AHF, adjudicated according to current ESC/HFA guidelines by a cardiologist. We used an eight-electrode, segmental, multi-frequency body composition analyser, previously validated against air displacement plethysmography, whole body MRI, deuterium and sodium bromide dilution. We investigated patients until hospital discharge or latest one day after ending intensified diuretic therapy. Disease specific properties, BIA and weight measurement were assessed daily. Furthermore, we investigated BIA raw data. Results 390 BIA were applied on 76 patients (47 men; 29 women; mean age 76±11 years; mean weight 75.6±15.7 kg). 34 patients presented with global, 27 with left-heart, 8 with right-heart and 7 with not specified AHF. 44 patients presented with pleural effusion. Pearson correlations showed that total body water (r=0.737, p≤0.001) and extracellular water (r=0.69, p≤0.001) correlated each with total body weight. Changes in total body water accurately (within a range of ± 1kg) reflected changes in total body weight in 40.28% of the patients and changes in extracellular water showed a similarly accurate reflection of total body weight change in 68.06% of the patients. BIA raw-data analysis showed significant changes using Wilcoxon test between measurements at the beginning of intensified diuretic therapy and at its end. We found a significant increase of resistance (mean from 334.6±67.5 to 362.8±69.5 Ohm/m; p=0.021) and reactance (mean from 21.3±7.1 to 24.1±6.2 Ohm/m; p=0.009) standardized to patients height and a non-significant increase of phase angle (mean from 3.6±0.9 to 3.8±0.8 °; p=0.149) during hospitalisation. Conclusion BIA is able to estimate changes in total body weight by analysing changes in extracellular body water in patients under intensified diuretic therapy and raw data analysis seems even more accurate and promising. This data derive from a heterogeneous AHF patient group, needing further investigation. Once validated, wearable BIA connected to an automated device monitoring system would enable an easy to use diuretic therapy monitoring for impaired patients or outpatients and could help reducing care efforts.

Novel equations for bioimpedance spectroscopy to calculate body fluid volume based on the agreement between body weight and extracellular water change before and after hemodialysis as a guide

BackgroundMLT-550N is a device to measure the body fluid volume based on bioimpedance spectroscopy. When extracellular water (ECW) or total body water (TBW) is measured with MLT-550N before and after hemodialysis, the change in ECW (ΔECW) or TBW (ΔTBW) is markedly larger than the change in body weight (ΔW). Good agreements between ΔECW and ΔTBW calculated by Moissl equations with ΔW were reported. The aim of this study was to develop novel equations to calculate the body fluid volume by modifying Moissl equations.MethodsA total of 466 measurements of 351 hemodialysis patients were used to develop the novel equations. The equations were based on the agreement between ΔECW and ΔW as a guide. The volume of intracellular water was postulated to be constant during hemodialysis. For evaluation of the equations, 5485 measurements of 627 patients were used. Agreements between values of two groups were assessed with Lin’s concordance correlation coefficients. The normal edema ratio (ER = ECW/TBW) corrected with the fat ratio (fcER) according to the parameters of normally hydrated lean and adipose tissues was used as the reference for normal hydration. The fluid status at dry weight was considered to be close to normal. The absolute values of the deviated ratio of actual ER (aER) from fcER (dER = (aER−fcER)/fcER) were compared. In this study, 1 L of body water corresponded to 1.02 kg of body fluid according to a previous report.ResultsThe concordance correlations between ΔW and 1.02∙ΔECW or 1.02∙ΔTBW with the novel equations were higher than with the MLT method or Moissl equations (0.896, 0.596 vs. 0.411, 0.375 or 0.813, 0.411, respectively). The median value of dER with the novel equations was the lowest (0.062) compared with those of the MLT method and Moissl equations (0.164 and 0.144) (p < 0.001).ConclusionsThe agreements between ΔECW or ΔTBW and ΔW were improved by the novel equations compared with the MLT method or Moissl equations. Based on the relation between aER and fcER at dry weight, the fluid volume calculated using the novel equations may be more adequate than those with the MLT method or Moissl equations.

Single‐frequency and multi‐frequency bioimpedance analysis: What is the difference?

Bioelectrical impedance analysis is a promising method in determining the body compartments in haemodialysis patients. In this study, we aimed to investigate the agreement between two widely used methods: the single-frequency and multi-frequency bioelectrical impedance analyses. Maintenance haemodialysis patients were enrolled in the study. Single-frequency and multi-frequency bioelectrical impedance analyses were performed consecutively before haemodialysis. A second bioelectrical impedance analysis was performed right after the haemodialysis session. A third bioelectrical impedance analysis was performed one hour after haemodialysis. We used weight change as a measure of fluid removal during haemodialysis session. Bioelectrical impedance analysis estimates from both devices had significant differences. Best agreement was observed between single frequency and multifrequency devices' extracellular water estimates immediately after haemodialysis (mean difference 0.076 L). We found the best agreement between weight change and extracellular water change using single-frequency bioimpedance analysis. Moreover, one hour waiting time did not improve the agreement between weight and extracellular water changes for both devices. Different estimates seem to be caused by different raw impedance data measured by both devices and device-specific equations. There are significant differences among bioelectrical impedance measurements performed with different bioelectrical impedance analyzers. Using open source software might be an important step forward in the development of standardized measurements.

Increase in Extracellular Hydration Status After Initiating Peritoneal Dialysis Electively.

Renal replacement therapy is designed to treat uremic symptoms and correct hypervolemia. We hypothesized that starting peritoneal dialysis (PD) should reduce overhydration, and we measured body composition and hydration status using bioimpedance in PD patients prior to training and then at the first assessment of peritoneal membrane function. We studied 100 consecutive patients with a planned start to PD, without peritoneal infections or mechanical catheter problems, mean age 54.7 ± 17.1 years, 57% male and 25% diabetic. Extracellular water (ECW) overhydration increased from -0.06 (-1.21 to 0.97) L to 0.96 (0.50 to 3.01) L, p < 0.001. Fat mass increased from 22.7 ± 11.1 to 23.7 ± 11.3 kg, p = 0.007). The change in ECW/total body water (TBW) was associated with age (β 0.065, p < 0.001), increasing comorbidity (β 1.107, p = 0.005), faster peritoneal protein transport (β 1.84, p < 0.04), and negatively with serum albumin (β -0.208, p < 0.001), and residual renal function (β -0.725, p = 0.026). Patients who had an increase in ECW/TBW had higher C-reactive protein (CRP) both before starting (16.8 ± 24.1 vs 7.7 ± 18.9 mg/L), and when established on PD (15.0 ± 31.8 vs 4.6 ± 5.1 mg/L), p < 0.05. Rather than a reduction in ECW hydration status, overhydration increased after starting PD. This was greater for older more comorbid patients and those with an inflammatory milieu and lower residual renal function. These factors should be considered when deciding upon initial PD prescriptions to limit ECW overhydration before information on peritoneal membrane function becomes available.

Do Bioimpedance Measurements of Over-Hydration Accurately Reflect Post-Haemodialysis Weight Changes?

Introduction: Bioelectrical impedance spectroscopy (BIS) devices are being used to determine ultrafiltration requirements to achieve target weight for haemodialysis (HD) patients. Pre-dialysis measurements are more convenient for both patients and staff. We wished to compare the changes in pre- and post-dialysis hydration measured by BIS with actual weight loss. Methods: We compared paired BIS measurements made pre and post HD using a BIS device based on a 3-compartmental model, designed to provide information on extracellular water (ECW) excess. Results: BIS was measured in 49 HD patients, 35 male (71.4%) with mean age 67.6 ± 14.2. Weight fell significantly from 69.2 ± 17.8 to 67.6 ± 17.4 kg, and BIS over hydration (OH) from 4.5 ± 3.3.4 to 3.4 ± 2.9 litres, and ECW from 16.8 ± 4.8 to 15.5 ± 4.4 litres, but there was no change in the amount of intracellular water. Weight loss correlated positively with the change in ECW, but exceeded the fall in OH; mean bias -0.58 (95% confidence limits -3.6 to 4.8 kg). Summary: We measured OH pre and post HD, but did not find that the change in OH correlated with changes in body weight. Although there was a correlation between changes in OH and ECW, there was none for weight. Our findings do not support total reliance on pre-dialysis BIS alone for assessing volume status in HD patients, but rather BIS should be considered an aid to clinical assessment of volume status.