Impact of dry weight determined by calf bioimpedance ratio on carotid stiffness and left ventricular hypertrophy in hemodialysis patients

Effect of bioelectrical impedance technology on the prognosis of dialysis patients: a meta-analysis of randomized controlled trials

Managing patient 'dry weight' according to clinical standards has deficiencies. Research has focused on the effectiveness of using bioelectrical impedance technology for fluid management in dialysis patients. Whether bioelectrical impedance monitoring can improve dialysis patients prognoses remain controversial. We performed a meta-analysis of randomized controlled trials to determine whether bioelectrical impedance was effective in improving dialysis patients prognoses. The primary outcome was all-cause mortality (13.6 ± 9.1 months). Secondary outcomes were left ventricular mass index (LVMI), arterial stiffness assessed using Pulse Wave Velocity (PWV), and N-terminal brain natriuretic peptide precursor (NT-proBNP). Of 4,641 citations retrieved, we identified 15 eligible trials involving 2763 patients divided into experimental (n = 1386) and control (n = 1377) groups. In 14 studies with mortality data, the meta-analysis showed that bioelectrical impedance intervention reduced the risk of all-cause mortality (rate ratios [RR]: 0.71; 95% confidence interval [CI]: 0.51, 0.99; p = .05; I2 = 1%). Subgroup analysis of patients on hemodialysis (RR: 0.72; 95% CI: 0.42, 1.22; p = .22) and peritoneal dialysis (RR: 0.62; 95% CI: 0.35, 1.07; p = .08) showed no significant mortality difference between intervention and control groups. It reduced the risk of all-cause mortality in the Asian population (RR: 0.52; p = .02), and reduced NT-proBNP (mean difference [MD]: -1495.73; p = 0.002; I²=0%) and PWV (MD: -1.55; p = .01; I²=89%). Bioelectrical impedance intervention reduced the LVMI in hemodialysis patients (MD: -12.69; p < .0001; I²=0%). Our analysis shows that in dialysis patients, bioelectrical impedance technology intervention could reduce, but not eliminate, the risk of all-cause mortality. Overall, this technology can improve the prognosis of dialysis patients.

Incidence of hospital admissions in bioimpedance-guided fluid management among maintenance hemodialysis patients-Results of a randomized controlled trial

INTRODUCTION

Hemodialysis is life-sustaining in kidney failure. However, proper regulation of body fluids depends on an accurate estimate of target weight. This trial aims to compare clinical endpoints between target weight estimation guided by bioimpedance spectroscopy and usual care in hemodialysis patients.

METHODS

This is an open-label, parallel-group, controlled trial that randomized, through a table of random numbers, adult patients on maintenance hemodialysis to target weight estimation based on monthly clinical evaluation alone or added to evaluation by bioimpedance twice a year. The primary outcome was survival, and the secondary outcomes were the rate of hospital admissions, change in blood pressure (BP), and antihypertensive drugs load. Participants were followed for 2 years. Survival analysis was performed using Kaplan-Meier estimator and Log-rank test, and hospital admissions were analyzed by the incidence-rate ratio.

FINDINGS

One hundred and ten patients were randomized to the usual care (52) or bioimpedance (58) groups, with a mean age of 57.4 (15.4) years, 64 (58%) males. There was no difference between the groups at baseline. Survival was not significantly different between groups (log-rank test p = 0.68), but the trial was underpowered for this outcome. There was also no difference between the groups in the change in systolic or diastolic BP or in the number of antihypertensive drugs being used. The incidence rate of hospital admissions was 3.1 and 2.1 per person-year in usual care and bioimpedance groups, respectively, with a time-adjusted incidence rate ratio of 1.48 (95% CI: 1.20-1.82, p = 0.0001) and attributable fraction of risk among exposed individuals of 0.32 (95% CI: 0.17-0.45).

DISCUSSION

The inclusion of bioimpedance data to guide the estimation of target weight in hemodialysis patients had no detectable impact on survival or BP control, but significantly reduced the incidence rate of hospital admissions. The study was registered at ClinicalTrials.gov Identifier: NCT05272800.

Effect of oral nutritional supplementation combined with impedance vectors for dry weight adjustment on the nutritional status, hydration status and quality of life in patients on chronic hemodialysis: A pilot study

BACKGROUND & AIMS

Protein energy wasting frequently affect hemodialysis patients and contribute to the development of overhydration. The objective of this study was to assess the effect of oral nutritional supplementation (ONS) combined with bioelectrical vector analysis (BIVA) on the nutritional and hydration status and the quality of life (QoL) in hemodialysis (HD) patients.

METHODS

Thirty-two chronic HD patients were included in a 6-month randomized pilot study. Patients in SUPL group received a simultaneous intervention consisting of a personalized diet, 245 mL/d ONS and dry weight adjustment through BIVA. Patients in CON group received a personalized diet and dry weight adjustment by BIVA. Anthropometrical, biochemical, dietary, QoL, handgrip strength (HGS) and bioimpedance measurements were performed. Malnutrition Inflammation Score (MIS) was applied.

RESULTS

At the end of the intervention, moderate undernutrition decreased by 43.8% in SUPL group while in CON group, severe undernutrition increased by 13% (p < 0.04 between groups). In the adjusted covariance analysis, SUPL compared to CON group, increased HGS (Δ 2.8 Kg vs Δ -1.8 Kg, p = 0.003), serum albumin (Δ 0.29 g/dL vs Δ -0.03 g/dL, p = 0.04) and serum transferrin (Δ 4.7 mg/dL vs Δ -0.7 mg/dL, p = 0.0007). The increase in QoL was significantly higher in SUPL group. Dry weight was achieved in 100% of patients in SUPL and 95% in CON group.

CONCLUSIONS

ONS combined with BIVA for dry weight adjustment, improved nutritional status, QoL and achieved dry weight in HD patients.

Effect of Improving Volume Overload on Home Blood Pressure Variability in Hemodialysis Patients

Blood pressure variability is an independent predictor of adverse clinical events in hemodialysis patients. Volume overload is one of the most important factors affecting blood pressure homeostasis. In the present study, we explored the effects of dry weight reduction on home blood pressure variability in volume overload hemodialysis patients. Hemodialysis patients with volume overload had their dry weight gradually decreased under the guidance of bioimpedance methods, which was represented by calf-bioimpedance ratio (Calf-BR). Home blood pressure was measured on waking up and at bedtime for 1 week at baseline and at the end of the two-month study. Coefficient of variation was used to define home blood pressure variability. Thirty-eight hemodialysis patients had their dry weight significantly decreased from 60.7 ± 11.3 to 59.6 ± 10.7 kg (P = 0.003) accompanied with a significant reduction in calf-BR (0.828 ± 0.023 vs. 0.786 ± 0.020, P<0.001). The systolic and diastolic blood pressure decreased significantly. Moreover, the whole-day, morning, and evening systolic blood pressure variability gradually and significantly decreased by the end of the study (5.6 ± 2.1% versus 4.0 ± 1.7%, P<0.001; 7.7 ± 3.5% vs. 6.3 ± 2.7%, P = 0.005; 7.5 ± 2.8% vs. 5.9 ± 2.3%, P = 0.002, respectively). Diastolic blood pressure variability parameters were unchanged. The interdialytic weight gain and the incidence of adverse events were similar throughout the study period. Gradual dry weight reduction by bioimpedance methods improved home blood pressure variability in hemodialysis patients with chronic fluid overload.

Evaluation of one year of frequent dialysis on fluid load and body composition using calf bioimpedance technique

OBJECTIVE

The primary aim of this study was to evaluate the effect of increased frequency of dialysis (FHD) on change in fluid status and body composition using segmental bioimpedance.

APPROACH

Twelve stable HD patients were switched from 3 times/week to 6 times/week HD (FHD). Systolic blood pressure (SBP), body mass and body mass index (BMI) were measured pre- and post-HD. Calf resistance (R ₅) at 5 kHz was measured using a multifrequency bioimpedance device (Hydra 4200). Calf resistivity (ρ  =  R ₅ * area/length), normalized resistivity (CNR  =  ρ/BMI) and calf extracellular volume (cECV) were calculated. Fat mass was measured by Futrex body composition analyzers (Futrex 6100, Futrex Tech, Inc.). All measurements were performed at baseline (BL) and monthly for up to one year.

MAIN RESULTS

Nine patients completed one year of FHD. Compared to BL, body weight and cECV decreased, and CNR increased significantly by the first month but did not change thereafter. SBP pre-HD decreased significantly by the end of the first month with further reduction until month 12. Additionally, antihypertensive medication decreased significantly from baseline by month 4 and remained stable from month 6 throughout the rest of the study. The post-HD CNR in five of nine patients reached the range of normal (>18.5 10^-2 * Ohm * m³ kg^-1 for males and  >19.1 10^-2 * Ohm * m³ kg^-1 for females) after 1 year FHD. In patients who returned to 3 times/week dialysis, CNR decreased significantly in the first week, and this was associated with increases in body weight and SBP.

SIGNIFICANCE

Reduction of fluid overload with no alteration of body composition was observed in this study. Accordingly, improving fluid status was confirmed by reducing BP and use of antihypertensive drugs together with increase in CNR. Measurement of fluid status by CNR in hemodialysis patients is a new method to quantitatively assess hydration potentially creating a target for volume of fluid removal.

Low dialysate sodium levels for chronic haemodialysis

BACKGROUND

Cardiovascular (CV) disease is the leading cause of death in dialysis patients, and strongly associated with fluid overload and hypertension. It is plausible that low dialysate [Na+] may decrease total body sodium content, thereby reducing fluid overload and hypertension, and ultimately reducing CV morbidity and mortality.

OBJECTIVES

This review evaluated harms and benefits of using a low (< 138 mM) dialysate [Na+] for maintenance haemodialysis (HD) patients.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 7 August 2018 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

Randomised controlled trials (RCTs), both parallel and cross-over, of low (< 138 mM) versus neutral (138 to 140 mM) or high (> 140 mM) dialysate [Na+] for maintenance HD patients were included.

DATA COLLECTION AND ANALYSIS

Two investigators independently screened studies for inclusion and extracted data. Statistical analyses were performed using random effects models, and results expressed as risk ratios (RR) for dichotomous outcomes, and mean differences (MD) or standardised MD (SMD) for continuous outcomes, with 95% confidence intervals (CI). Confidence in the evidence was assessed using GRADE.

MAIN RESULTS

We included 12 studies randomising 310 patients, with data available for 266 patients after dropout. All but one study evaluated a fixed concentration of low dialysate [Na+], and one profiled dialysate [Na+]. Three studies were parallel group, and the remaining nine cross-over. Of the latter, only two used a washout between intervention and control periods. Most studies were short-term with a median (interquartile range) follow-up of 3 (3, 8.5) weeks. Two were of a single HD session, and two of a single week's HD. Half of the studies were conducted prior to 2000, and five reported use of obsolete HD practices. Risks of bias in the included studies were often high or unclear, lowering confidence in the results.Compared to neutral or high dialysate [Na+], low dialysate [Na+] had the following effects on "efficacy" endpoints: reduced interdialytic weight gain (10 studies: MD -0.35 kg, 95% CI -0.18 to -0.51; high certainty evidence); probably reduced predialysis mean arterial blood pressure (BP) (4 studies: MD -3.58 mmHg, 95% CI -5.46 to -1.69; moderate certainty evidence); probably reduced postdialysis mean arterial BP (MAP) (4 studies: MD -3.26 mmHg, 95% CI -1.70 to -4.82; moderate certainty evidence); probably reduced predialysis serum [Na+] (7 studies: MD -1.69 mM, 95% CI -2.36 to -1.02; moderate certainty evidence); may have reduced antihypertensive medication (2 studies: SMD -0.67 SD, 95% CI -1.07 to -0.28; low certainty evidence). Compared to neutral or high dialysate [Na+], low dialysate [Na+] had the following effects on "safety" endpoints: probably increased intradialytic hypotension events (9 studies: RR 1.56, 95% 1.17 to 2.07; moderate certainty evidence); probably increased intradialytic cramps (6 studies: RR 1.77, 95% 1.15 to 2.73; moderate certainty evidence).Compared to neutral or high dialysate [Na+], low dialysate [Na+] may make little or no difference to: intradialytic BP (2 studies: MD for systolic BP -3.99 mmHg, 95% CI -17.96 to 9.99; diastolic BP 1.33 mmHg, 95% CI -6.29 to 8.95; low certainty evidence); interdialytic BP (2 studies:, MD for systolic BP 0.17 mmHg, 95% CI -5.42 to 5.08; diastolic BP -2.00 mmHg, 95% CI -4.84 to 0.84; low certainty evidence); dietary salt intake (2 studies: MD -0.21g/d, 95% CI -0.48 to 0.06; low certainty evidence).Due to very low quality of evidence, it is uncertain whether low dialysate [Na+] changed extracellular fluid status, venous tone, arterial vascular resistance, left ventricular mass or volumes, thirst or fatigue. Studies did not examine cardiovascular or all-cause mortality, cardiovascular events, or hospitalisation.

AUTHORS' CONCLUSIONS

It is likely that low dialysate [Na+] reduces intradialytic weight gain and BP, which are effects directionally associated with improved outcomes. However, the intervention probably also increases intradialytic hypotension and reduces serum [Na+], effects that are associated with increased mortality risk. The effect of the intervention on overall patient health and well-being is unknown. Further evidence is needed in the form of longer-term studies in contemporary settings, evaluating end-organ effects in small-scale mechanistic studies using optimal methods, and clinical outcomes in large-scale multicentre RCTs.

Impedance ratio: a novel marker and a powerful predictor of mortality in hemodialysis patients

PURPOSE

Impedance ratio (Imp-R) obtained by multifrequency bioimpedance analysis (BIA) has been shown to be associated with volume and nutrition status. In this prospective study, the predictive role of Imp-R for mortality in hemodialysis (HD) patients was investigated.

METHODS

Multifrequency (5-50-100-200 kHz) BIA was applied to 493 prevalent HD patients in March-April 2006. Imp-R was defined as the ratio of 200-5 kHz impedance values. Demographical, clinical and laboratory data at the time of the analysis were recorded. All-cause and cardiovascular (CV) mortality were assessed during 3 years of follow-up.

RESULTS

Mean age was 57.7 ± 13.9 years, HD duration 52.1 ± 42.6 months and prevalence of diabetes 21.7 %. Imp-R was negatively correlated with nutritional markers including albumin, creatinine and hemoglobin levels. In addition, there was a positive correlation between Imp-R and age, ratio of extracellular water to total body water and high-sensitive C-reactive protein. Over a mean follow-up period of 27.9 ± 11.1 months, 93 deaths (52 from CV reasons) were observed. In the multivariate analysis, Imp-R was significantly associated with all-cause and CV mortality after adjustments [HR 1.13, 95 % CI (1.04-1.23); p = 0.004 and HR 1.15, 95 % CI (1.03-1.27); p = 0.01, respectively]. The risk of all-cause mortality was 3.4 times higher in the fourth quartile of Imp-R (>83.5 %) compared to the first Imp-R quartile (<78.8 %) as reference. Cutoff value of Imp-R for all-cause mortality was 82.0 % with a sensitivity of 65.5 % and specificity of 64 %.

CONCLUSION

Impedance ratio measured by multifrequency in standardized conditions BIA is an independent and powerful predictor of both all-cause and CV mortality in hemodialysis patients.

Bioimpedance can solve problems of fluid overload

Bioimpedance (BI) techniques for measuring normal hydration status (NHS) can be generally classified as (1) by frequency as single frequency at 50 kHz, BI analysis, and multifrequency BI spectroscopy and (2) by method as whole body (wrist to ankle) measurement and calf BI spectroscopy. The aim of this article was to review current BI methods for clinical practice in patients with end-stage of kidney disease. BI vector analysis using whole-body single-frequency BI at 50 kHz may be useful for population studies to indicate a range of degree of fluid loading and of nutritional status. Whole body multifrequency BI spectroscopy is used to estimate extracellular (ECV), intracellular fluid volume, and total body water in dialysis patients. The whole-body BI model is used in the body composition monitor (BCM). The whole-body BI model is established with ECV, intracellular fluid volume, and body weight based on parameters from regression analysis in healthy subjects to calculate fluid overload in dialysis patients. Calf BI methods have been developed to measure NHS by 2 ways: (1) continuous measurement of the intradialytic resistance curve until flattening occurs; (2) calf normalized resistivity in the range of healthy subjects (18.5 × 10(-2) Ω m(3)/kg in male and 19.1 × 10(-2) Ω m(3)/kg in female). In general, for population studies, BI vector analysis or ECV/total body water may be useful; BCM is a commercially available device that can certainly guide volume reduction safely over time. For more exact measure of fluid overload, calf BI methods appear to be most accurate, but these are at present research tools. BI techniques are not only useful in assessing NHS but also in the study of nutrition and body composition.

Acute effects of haemodialysis on central venous and arterial pressure characteristics

AIM

Haemodynamic stability of patients during haemodialysis (HD) sessions is of pivotal importance and accurate determination of dry weight remains a challenge. Little information is available about central venous and aortic pressure during dialysis. In this pilot study we used a non-invasive technique to describe the changes in central venous pressure (CVP) during dialysis.

METHODS

An ultrasound-assisted pressure-manometer was used at the cephalic vein during haemodialysis to quantify CVP. Central aortic pressure changes were assessed as aortic augmentation index and subendocardial viability ratio. Bioimpedance was applied to measure total body water, as well as extracellular and intracellular water before and after HD. Measurements were performed prior during and after 1 and 2 h on HD.

RESULTS

Ten patients were included with a median age of 72 years (23-82). Haemodialysis reduced the weight by 2.0 kg, corresponding to a measured decrease in total body water of 1.9 L. The mean CVP showed a significant decrease (9.0-0.8 cmH₂O; P = 0.0005) during dialysis. The significant drop in CVP was found during the first hour (9-2.8 cmH₂O). Starting and stopping dialysis was reflected by a reduction of 2.6 cmH₂O and a rise of 2.8 cmH₂O (n.s.). Aortic augmentation index decreased from 26.1% to 21.0% (n.s.). Subendocardial viability ratio increased from 126% to 156% (P < 0.05) during HD, and decreased to 139% direct after HD (n.s.).

CONCLUSION

This is the first study that illustrates a prominent reduction of CVP during the first hour of haemodialysis. Non-invasive CVP measurement is feasible during haemodialysis and adds another piece in the puzzle of factors involved in haemodynamic stability.