The relationship between chronic volume overload and elevated blood pressure in hemodialysis patients: use of bioimpedance provides a different perspective from echocardiography and biomarker methodologies

Association of Bioimpedance Parameters with Increases in Blood Pressure during Hemodialysis

BACKGROUND

Intradialytic hypertension, defined as an increase in BP from pre- to post-hemodialysis (HD), affects 5%-15% of patients receiving maintenance HD and is associated with cardiovascular and all-cause mortality. Hypervolemia is believed to be a major etiological factor, yet the association of more objective biomarkers of volume status with intradialytic hypertension is not well described.

METHODS

In a post hoc analysis of the Frequent Hemodialysis Network Daily Trial ( n =234), using data from baseline, 1-, 4-, and 12-month visits ( n =800), we used random-effects regression to assess the association of bioimpedance estimates of volume (vector length) with post-HD systolic BP (continuous) and any increase in systolic BP (categorical) from pre- to post-HD. We adjusted models for randomized group; age; sex; self-reported race; Quételet (body mass) index; vascular access; HD vintage; hypertension; history of heart failure; diabetes; residual kidney function (urea clearance); pre-HD systolic BP; ultrafiltration rate; serum-dialysate sodium gradient; and baseline values of hemoglobin, phosphate, and equilibrated Kt/V urea.

RESULTS

The mean age of participants was 50±14 years, 39% were female, and 43% were Black. In adjusted models, shorter vector length (per 50 Ω/m) was associated with higher post-HD systolic BP (2.9 mm Hg; 95% confidence interval [CI], 1.6 to 4.3) and higher odds of intradialytic hypertension (odds ratio 1.66; 95% CI, 1.07 to 2.55). Similar patterns of association were noted with a more stringent definition of intradialytic hypertension (>10 mm Hg increase from pre- to post-HD systolic BP), where shorter vector length (per 50 Ω/m) was associated with a higher odds of intradialytic hypertension (odds ratio 2.17; 95% CI, 0.88 to 5.36).

CONCLUSIONS

Shorter vector length, a bioimpedance-derived proxy of hypervolemia, was independently associated with higher post-HD systolic BP and risk of intradialytic hypertension.

Benefits of BNP/NT-proBNP serum level evaluation for dry weight adjustment in pediatric hemodialysis patients

BACKGROUND

Dry weight (DW) adjustment in children on hemodialysis (HD) can be challenging. It relies on clinical evaluation and additional supports. Our aim was to study the benefits of cardiac biomarker assessment, in addition to the more commonly used technique, bioimpedance spectroscopy (BIS), and clinical signs for DW prescription in pediatric HD patients.

METHOD

Observational study including 41 children on HD in three pediatric HD centers in the Paris region. During one session, BIS was performed before the session and serum levels of BNP and NT-proBNP were analyzed before and after the session.

RESULTS

Median pre-dialysis level of BNP was 87 ng/L [24-192] and NT-proBNP 968 ng/L [442-4828]. Cardiac biomarker levels showed positive correlation with the BIS hydration status evaluation (p = 0.004). The most appropriate cutoff for pre-dialysis BNP to detect significant overhydration (OH) was 165 ng/L (sensitivity 0.67, specificity 0.84). Based on the BIS evaluation, only 32% of patients with high blood pressure (BP) had OH, whereas in the normal BP group, 33% had significant OH.

CONCLUSIONS

DW prescription for children on HD should not only rely on clinical evaluation, particularly BP, but should also include additional helpful parameters. BIS is well-validated in children, but it has limitations in non-cooperative patients, and its cost can limit its use in some settings. Cardiac biomarkers, especially BNP, were well-correlated to hydration status evaluated by BIS, and thus could add valuable information for individual patient management and DW assessment. A higher resolution version of the Graphical abstract is available as Supplementary information.

Lung Ultrasound Estimates the Overhydration and Benefits Blood Pressure Control in Normal or Mild Symptomatic Hemodialysis Patients

Introduction

Lung ultrasound (LUS) is used for dry weight guidance by assessment of pulmonary congestion in hemodialysis (HD) patients. The aim of this study was to estimate amounts of accumulated fluid by total LUS scores (TLUSS), which were scarcely reported in HD patients who were normal or had a mild functional abnormality. In addition, the correlations between the LUS score of each area and TLUSS were determined to suggest fewer specific areas valuable to shorten the examination time of LUS.

Methods

This cohort study was conducted in adult HD patients who have New York Heart Association Classes I-II. LUS and multifrequency bioimpedance (BIA) were performed at baseline and the individual prescribed dry weight was set. Then each LUS was conducted at 28 areas of bilateral intercostal spaces and calculated as TLUSS weekly for eight weeks in which dry weight was adjusted. The second BIA was also measured at week eight. The difference of pre-HD weight and target weight (weight gain; WG) represented the amount of fluid accumulation.

Results

Twenty patients with a mean age of 62.2±14.0 years were enrolled. One hundred and sixty-six LUS were performed in which forty episodes of them were simultaneously measured with BIA. Optimum dry weight adjusted by TLUSS which benefited in mean reductions of blood pressure, and cardiothoracic ratios. WG amounts were significantly correlated with TLUSS (r=0.38), and with extracellular fluid (r=0.35) and overhydration fluid (r=0.39) assessed by BIA. Estimations of mean fluid overload were 2.18 (TLUSS ≤15), 2.72 (TLUSS 16-24), 3.17 (TLUSS 25-33), 3.65 (TLUSS 34-38) and 5.03 (TLUSS ≥39) in liters. The cut-off points of sum scores of 12 specific lung areas represented the none-mild were <8, moderate at 8-16, and severe pulmonary congestions were >16.

Conclusion

TLUSS estimated accumulated fluid useful for volume and blood pressure controls. Performance of LUS in 12 specific lung areas may reduce spending time and support routine uses of LUS in clinical practice.

Chronic Kidney Disease and Heart Failure-Everyday Diagnostic Challenges

Is advanced chronic kidney disease (CKD) a cardiac “no man’s land”? Chronic heart failure (HF) is widely believed to be one of the most serious medical challenges of the 21st century. Moreover, the number of patients with CKD is increasing. To date, patients with estimated glomerular filtration rates <30 mL/min/1.73 m² have frequently been excluded from large, randomized clinical trials. Although this situation is slowly changing, in everyday practice we continue to struggle with problems that are not clearly addressed in the guidelines. This literature review was conducted by an interdisciplinary group, which comprised a nephrologist, internal medicine specialists, and cardiologist. In this review, we discuss the difficulties in ruling out HF for patients with advanced CKD and issues regarding the cardiotoxicity of dialysis fistulas and the occurrence of pulmonary hypertension in patients with CKD. Due to the recent publication of the new HF guidelines by the European Society of Cardiology, this is a good time to address these difficult issues. Contrary to appearances, these are not niche issues, but problems that affect many patients.

Characteristics of bioimpedance-determined fluid shifts according to intradialytic blood pressure difference

This study was designed to identify the fluid spaces that are most changed during ultrafiltration (UF) according to intradialytic blood pressure (BP) difference. BP data were collected five times (before hemodialysis [HD] and 1–4 h of HD). Intradialytic BP difference was calculated as the highest minus lowest of these BP measurements. Intradialytic systolic BP (SBP) difference over 20 mm Hg and diastolic BP (DBP) difference over 10 mm Hg were defined as wide intradialytic SBP difference (SYS-W) and DBP difference (DIA-W), respectively. We measured the various fluid spaces before HD and 1–4 h of HD, and 30 min after HD using a portable, whole-body bioimpedance spectroscopy (BIS). In this study, 85 prevalent patients aged over 18 years with a fixed dry weight (65.38 ± 12.45 years, 54.18% men, 52.50% patients with diabetes), undergoing HD had participated. 1) Mean relative reduction of extracellular water (ECW) was significantly higher in SYS-W than in narrow intradialytic SBP difference (SYS-N) patients from 1 h to 30 min after HD. 2) Mean relative reduction of intracellular water (ICW) was significantly lower in DIA-W than in narrow intradialytic DBP difference (DIA-N) patients from 1 h to 30 min after HD. 3) ECW of patients with SYS-W was significantly lower than that of patients with SYS-N. Patients with SYS-W have the characteristics of fluid shifts in which reduction of ECW was steeper than patients with SYS-N whereas fluid shifts of ICW were lower in patients with DIA-W than patients with DIA-N.

Body Fat Plays an Important Role in of Bioimpedance Spectroscopy-Based Dry Weight Measurement Error for Patients with Hemodialysis

Accurate dry weight (DW) estimation is important for hemodialysis patients. Although bioimpedance spectroscopy (BIS) is commonly used to measure DW, the BIS-based DW frequently differs from the clinical DW. We analyzed the characteristics of patients whose BIS-based DWs were over- and underestimated. In this retrospective cohort study, we evaluated 1555 patients undergoing maintenance hemodialysis in Chungnam National University Hospital. The gap (DWCP-BIS) was calculated by comparing the BIS and clinical DWs. We analyzed the clinical characteristics of patients with positive (n = 835) and negative (n = 720) gaps. Compared with other patients, the DWCP-BIS-positive group had higher extracellular water (ECW) level and extracellular/intracellular water index (E/I) and had lower weight, body mass index (BMI), lean tissue index (LTI), fat tissue index (FTI), fat mass (FAT), and adipose tissue mass (ATM). The DWCP-BIS-negative group exhibited elevated BMI, FTI, FAT, and ATM; however, it had lower height, ECW, and E/I. Linear regression analysis revealed that FAT significantly predicted DWCP accuracy. The clinical DW of patients with a low fat mass tended to be underestimated, while the clinical DW of patients with comparatively large fat reserves tended to be overestimated. These characteristics will aid in the reduction of BIS-based DW errors.

Are there any further modalities for prediction of subclinical volume overload in advanced stages of chronic kidney disease?

BACKGROUND

Subclinical volume overload in chronic kidney disease (CKD) patient represents a debatable issue. Although many tools were used to detect volume overload in such patients, many non-specific results were due to presence of comorbidities. Bioimpedance spectroscopy is an objective fluid status assessment method, which is shown superior to classical methods in many studies. Combining some of these tools may improve their accuracy and specificity. Inferior vena cava collapsibility index (IVCCI) with brain natriuretic peptide (BNP) can be combined for more specific volume assessment. This study was performed to assess the usage of combined IVCCI and BNP levels in CKD patients to predict subclinical volume overload.

METHODS

One hundred and ten patients with CKD (stages 4 and 5) not on dialysis and having normal left ventricular systolic function were included in this study. Exclusion criteria were: (1) patients with other causes of raised BNP than volume overload and (2) patients on diuretics. A complete medical history was obtained, and thorough examination and laboratory tests were performed for all included patients. IVCCI and BNP serum levels were evaluated. The patients who exhibited an overhydration (OH)/extracellular water (ECW) ratio of >15% were considered to have volume overload.

RESULTS

Twenty-six patients (23.6%) had subclinical hypervolemia as diagnosed by OH/ECW ratio of >15%. IVCCI ≤ 38% had higher diagnostic performance than BNP ≥ 24 pg/mL. Combining both IVCCI ≤ 38% and BNP ≥ 24 pg/mL increased the specificity and positive predictive value for detection of subclinical hypervolemia.

CONCLUSION

Combined elevated BNP level and decreased IVCCI are more precise tools for subclinical volume overload detection in CKD patients.

Multi-Method Complex Approach for Hydration Assessment Does Not Detect a Hydration Difference in Hemodialysis versus Peritoneal Dialysis Patient

Assessment of hydration status is essential in monitoring the effectiveness of renal replacement therapy and is usually based on physical examination. However, comparisons of hydration status achieved with different dialysis methods are not conclusive. We compared the hydration status of patients on chronic hemodialysis (HD, n = 60) and peritoneal dialysis (PD, n = 20) in a comprehensive assessment including physical examination and additional methods. The mean age of the 80 chronically dialyzed patients (53 males, 27 females) was 58.1 ± 13.9 years. The clinical evaluation took into account the presence of peripheral edema, dyspnea, and crackling over the lung fields. Additional tests included lung ultrasound, electrical bioimpedance (performed in 79 patients), impedance cardiography, ultrasound assessment of large abdominal vessels (performed in 79 patients), select echocardiographic parameters (obtained in 78 patients), and serum NT-proBNP concentration. Residual diuresis volume was significantly higher in the PD group. We found no significant differences between the two groups in any other baseline characteristics or in the results of the clinical examination or additional tests. The use of different methods for assessing hydration does not allow differentiation of patients treated with dialysis in terms of the dialysis technique used. Therefore, it seems reasonable to use common algorithms to objectify the hydration status of these patients.

Evaluation of Hypervolemia in Children

Hypervolemia is a condition with an excess of total body water and when sodium (Na) intake exceeds output. It can have different causes, such as hypervolemic hyponatremia (often associated with decreased, effective circulating blood volume), hypervolemia associated with metabolic alkalosis, and end-stage renal disease. The degree of hypervolemia in critically ill children is a risk factor for mortality, regardless of disease severity. A child (under 18 years of age) with hypervolemia requires fluid removal and fluid restriction. Diuretics are able to increase or maintain urine output and thus improve fluid and nutrition management, but their benefit in preventing or treating acute kidney injury is questionable.

Factors related to peripheral arterial disease in patients undergoing hemodialysis: the potential role of monocyte chemoattractant protein-1

Peripheral arterial disease (PAD) is substantially prevalent among patients in the end stage of renal disease (ESRD). We considered factors related to peripheral arterial disease in patients undergoing hemodialysis including the important role of monocyte chemoattractant protein-1 (MCP-1) serum concentrations. We studied 150 patients in on-line-predilution hemodiafiltration. Dialysis sufficiency was defined by Kt/V for urea. PAD was defined using clinical criteria, ankle-brachial index and Doppler ultrasound in the lower limbs. MCP-1 serum concentrations were measured using enzyme-linked immunoabsorbed assay (ΕLISA). We performed chi-square tests and logistic regression analysis to investigate risk factors for the prevalence of PAD in these patients including MCP-1 serum concentrations. The patients with manifested PAD had elevated MCP-1, higher BP, higher arterial stiffness markers, higher markers of malnutrition, uncontrolled metabolic acidosis, bone disease and lower obtained dialysis adequacy than the patients without PAD. The association between PAD manifestation and high MCP-1 was found significant (x² = 9.6, p = 0.001). The built logistic regression analysis showed that the high MCP-1 increased the risk for PAD 3.2 (95% C.I 1.3-8.2) folds after adjustment for confounders. PAD was also significantly associated with non-administration of vitamin D agents during dialysis (x² = 3.5, p = 0.04).Malnutrition, low-grade inflammation mainly defined by high MCP-1 serum concentrations, metabolic acidosis and bone disease were included in significant predictors for peripheral arterial disease in patients undergoing hemodiafiltration. The obtained dialysis sufficiency and the therapy during dialysis sessions seem to play an additional role in the demonstration of peripheral vascular disease in these patients.

Influence of dry weight reduction on anemia in patients undergoing hemodialysis

Objective

Volume load in patients undergoing hemodialysis correlates with renal anemia, with reductions in volume load significantly improving hemoglobin levels. We performed a prospective controlled study to assess the effect of post-dialysis dry weight reduction, resulting from the gradual enhancement of ultrafiltration, on renal anemia in this patient population.

Methods

Sixty-four patients with renal anemia on maintenance hemodialysis were randomized to an ultrafiltration group, in which dry weight was gradually reduced by slightly increasing the ultrafiltration volume while maintaining routine hemodialysis, and a control group, in which patients underwent conventional dialysis while routine ultrafiltration was maintained. After 28 weeks, post-dialysis weight and levels of hematocrit, hemoglobin, C-reactive protein, serum albumin, serum ferritin, and transferrin saturation were compared.

Results

All parameters were similar at baseline between the two groups and remained unchanged at week 28 in the control group compared with baseline. In contrast, the ultrafiltration group showed a significant reduction in post-dialysis weight and C-reactive protein concentration and a significant increase in hematocrit, hemoglobin, albumin, serum ferritin, and transferrin saturation.

Conclusions

Dry weight reduction resulting from enhanced ultrafiltration may improve renal anemia in patients undergoing hemodialysis.

The relationship between hydration status, male sexual dysfunction and depression in hemodialysis patients

Background

Disturbances in sexual function are common among dialysis patients. Normal erections require a complex balance of physiological, psychological, emotional, hormonal, neurological and vascular factors. This study examined a possible association of overhydration (OH) with male sexual dysfunction and depression in hemodialysis (HD) patients.

Patients and methods

This cross-sectional study assessed hydration status by whole-body bioimpedance spectroscopy in patients on maintenance HD for more than 12 months. Patients were categorized according to OH to extracellular water (ECW) ratio: OH/ECW ratio >0.15 and OH/ECW ratio ≤0.15. Sexual function was assessed using the International Index of Erectile Function (IIEF) score. Psychological status was evaluated using the Beck Depression Inventory (BDI) score. Serum sex hormones were determined.

Results

Of 39 stable participants on HD, 53.8% were overhydrated (OH/ECW ratio >0.15) and 46.2% not overhydrated (OH/ECW ratio ≤0.15). Of participants with OH/ECW ratio >0.15, 85.7% had mild to severe ED, and 71.4% had abnormal BDI scores, ranging from mild mood disturbance to severe depression. Compared to patients with OH/ECW ratio ≤0.15, BDI scores, serum estradiol and plasma hsCRP were higher (18.48±8.34 vs 10.61±5.46, p<0.001; 140.10±44.51 vs 126.10±32.26, p=0.034; and, 17.70±12.14 vs 9.76±8.79, p=0.013; respectively) in those with OH/ECW ratio >0.15, while their IIEF score, serum total testosterone and dehydroepiandrosterone (DHEA) were lower (12.81±7.31 vs 41.44±23.79, p<0.001; 8.97±5.43 vs 14.10±8.30, p=0.013; and 85.31±55.14 vs 133.3±95.48, p=0.029; respectively). The OH/ECW ratio correlated inversely with the IIEF score (r=−0.69, p<0.001) and positively with BDI scores (r=0.64, p<0.001). IIEF scores were inversely correlated with BDI scores (r=−0.54, p<0.001).

Conclusion

OH in HD patients was found to be associated with a higher prevalence of sexual dysfunction and depression, lower serum levels of total testosterone and DHEA, and higher levels of serum estradiol.

Assessing Extracellular Volume in Hemodialysis Patients Using Intradialytic Blood Pressure Slopes

BACKGROUND/AIMS

Extracellular volume (ECV) overload is a mortality risk factor in hemodialysis patients, but no standard approach exists to objectively assess this clinically. We aimed to quantify relationships between slopes of repeated intradialytic blood pressure (BP) measurements and ECV.

METHODS

In a cross-sectional study of 71 hemodialysis patients, we calculated BP slopes from all intradialytic measurements using Gaussian regression. We measured extracellular and total body water (TBW) with bioimpedance spectroscopy. We analyzed unconditional and conditional associations between BP slope and volume metrics with mixed linear models and sensitivity analyses using non-linear intradialytic BP trajectory.

RESULTS

Mean systolic intradialytic BP slope (IBPS) was -0.06 (0.1) mm Hg/min. Post-dialysis extracellular water (ECW)/weight was the volume metric mostly strongly associated with slope (r = 0.34, p = 0.007 for unconditional analysis; β = 1.45, p = 0.001 for conditional analysis). Among subjects with post-dialysis systolic BP ≥130 mm Hg, the association strengthened (r = 0.40, p = 0.006; β = 1.42, p = 0.003). ECV was more strongly associated with the BP slope than with pre-dialysis, post-dialysis, or delta systolic BP (r = -0.07, 0.19, 0.28; p = 0.6, 0.1, 0.03). In nonlinear models, BP trajectory also had the strongest association with post-dialysis ECW/body weight (p < 0.001).

CONCLUSIONS

In hypertensive hemodialysis patients, measurements of ECV excess are more strongly associated with IBPSs than with pre-dialysis, post-dialysis, or change in systolic BP. Among varying volume metrics, post-dialysis ECW/weight has the strongest association with these slopes. Determining IBPS is a novel method to optimize clinical assessment of ECV in hemodialysis patients.

The Relationship of Residual Renal Function with Cardiovascular Morbidity in Hemodialysis Patients and the Potential Role of Monocyte Chemoattractant Protein-1

BACKGROUND

Residual renal function (RRF) provides several benefits to patients on dialysis. Monocyte chemoattractant protein-1 (MCP-1) plays an important role in atherosclerotic lesions. We considered the relationship between RRF and cardiovascular morbidity and the significant role of MCP-1 serum concentrations in hemodiafiltration (HDF) patients.

METHODS

We enrolled 76 patients on on-line HDF. RRF was defined by interdialytic urine output, and we studied the patients in two groups according to the preservation or not of urine output. MCP-1 levels were measured using enzyme-linked immunosorbent assay. χ2 tests were applied for the association between RRF and left ventricular hypertrophy (LVH), coronary artery disease (CAD), peripheral artery disease (PAD), and systolic and diastolic cardiac dysfunction. We built an adjusted model using logistic regression analysis for the factors which might impact on the loss of urine output.

RESULTS

χ2 tests showed a significant association between the loss of urine output and LVH, diastolic dysfunction, and PAD (χ2 = 7.4, p = 0.007; χ2 = 14.3, p = 0.001; χ2 = 4.2, p = 0.03, respectively), although the association with CAD and systolic dysfunction was found to be nonsignificant. The patients without RRF had significantly higher MCP-1, and the urine volume was inversely associated with MCP-1 (r = -465, p = 0.03). In the built adjusted model, the elevated MCP-1 was found to be a significant predictor for the loss of RRF.

CONCLUSION

The loss of RRF was significantly associated with LVH, diastolic dysfunction, and PAD in HDF patients. The increased MCP-1, affected by the lack of urine, may act as an additional underlying factor on this relationship, reflecting a progressive inflammation/oxidative stress condition.

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

BACKGROUND/AIMS

Volume overload, frequently clinically asymptomatic is considered as a causative factor limiting the effectiveness of antihypertensive therapy in haemodialysis (HD) patients. Therefore, the aim of this study was to assess plasma levels of N-terminal fragment of the prohormone brain natriuretic peptide (NT-proBNP) and a C-terminal portion of the precursor of vasopressin (CT-proAVP, copeptin), surrogate markers of volume overload in HD patients in relation to the number of antihypertensive drugs used in the hypertension treatment.

METHODS

One hundred and fifty adult HD patients (92 males) were enrolled into this study. Clinical data concerning blood pressure (BP) measurements prior haemodialysis session and pharmacotherapy were collected from all patients. In addition to routine laboratory parameters, plasma levels of NT-proBNP and CT-proAVP were measured, and daily sodium and water consumption were estimated with a portion-size food frequency questionnaire.

RESULTS

Among 145 (96.7%) hypertensive HD patients, 131 were receiving antihypertensive medication. Despite antihypertensive therapy, 31.0% had inadequate BP control. Plasma concentration of NT-proBNP was associated with systolic (R=0.19; p=0.02) but not diastolic BP values and with the number of received antihypertensive drugs (R=0.21; p=0.01). The highest NT-proBNP values were observed in patients receiving 3 or more antihypertensive drugs. In contrast, no significant correlation was found between plasma CT-proAVP concentrations and BP values as well as and the number of antihypertensive drugs. Receiver operator curve analysis showed that NT-proBNP values over 13,184 pg/mL predicted the use of at least 3 antihypertensive drugs in maximal doses in the therapy of hypertension, similar analyses performed for CT-proAVP showed much less specificity.

CONCLUSIONS

1. Increased levels of NT-proBNP seems to be a better biomarker of multidrug antihypertensive therapy requirement than CT-proAVP. 2. Whether estimation of NT-proBNP in these patients will be also better biomarker than copeptin in the prediction of cardiovascular complications related to hypertension needs further investigations.

Modern peptide biomarkers and echocardiography in cardiac healthy haemodialysis patients

BACKGROUND

In this prospective study, we aimed to assess the haemodynamic changes before and after haemodialysis (HD) in cardiac healthy subjects on chronic HD by imaging methods and endocrine markers of fluid balance.

METHODS

Mid-regional pro-atrial natriuretic peptide (MR-proANP), N-terminal prohormone of brain natriuretic peptide (NT-proBNP), vasopressin (AVP) and copeptin (CT-proAVP), metanephrines and normetanephrines, renin and aldosterone, standard transthoracic echocardiography and diameter of vena cava inferior (VCID) were performed in 20 patients with end stage renal disease (CKD5D) before and after HD and were stratified in residual excretion (RE, less or more 0.5 l) and ultrafiltration rate (UF, less or more 2 l).

RESULTS

Copeptin was significantly higher in patients before HD. Copeptin was inversely correlated with haemodialysis treatment adequacy (KT/v), RE and UF, but was not significantly influenced by age, gender and body mass index (BMI). MR-proANP was significantly reduced by haemodialysis by 27% and was inversely correlated with KT/v, but there was a significant influence by UF, RE, age, gender and BMI. NT-proBNP was significantly higher in patients before HD and was not influenced by RE and UF. Renin, aldosterone, metanephrines and normetanephrines did not demonstrate significant differences. Echocardiographic parameters and VCID were significantly correlated with RE, UF and copeptin.

CONCLUSION

Modern biomarkers will provide cardiovascular risk assessment, but elimination (UF), RE and other factors may influence the serum concentrations, e.g. in patients with renal impairment. The interpretation will be limited by altered reference ranges, and will be restricted to individual courses combined with clinical and echocardiographic data.

Investigation of optimum N-terminal probrain natriuretic peptide level in patients on maintained hemodialysis

Background: Serum N-terminal probrain natriuretic peptide (NT-proBNP) level is known to be strongly associated with fluid overload, and serves as a guide for fluid management in patients on hemodialysis (HD). This study aimed at investigating the relationship between NT-proBNP level and blood pressure (BP), ultrafiltration/dry weight ratio as well as hemoglobin, and to explore the optimal cutoff point of NT-proBNP level in Chinese patients on HD.

Methods: A total of 306 patients on maintained HD for stage 5 chronic kidney disease (CKD) were included in this prospective study. Their average ultrafiltration/dry weight ratio and BP before dialysis were recorded. The serum NT-proBNP, hemoglobin, serum calcium, and phosphorus were detected. The cutoff value for NT-proBNP level was calculated using receiver operating characteristic (ROC) analysis.

Results: The high NT-proBNP level was associated with high BP and ultrafiltration/dry weight ratio, and low hemoglobin level. The optimal cutoff point of NT-proBNP level for patients on maintained HD was 5666 pg/mL, with a sensitivity of 78.5%, specificity of 43.9%, and area under the curve (AUC) of 0.703 (<0.001).

Conclusions: NT-proBNP level ≤5666 pg/mL was recommended to achieve the target BP, hemoglobin level, and ultrafiltration/dry weight ratio in patients on maintained HD with an ejection fraction (EF) >50%.

Comparison of multiple fluid status assessment methods in patients on chronic hemodialysis

PURPOSE

Control of hydration status is an important constituent of adequate and efficient hemodialysis (HD) treatment. Nevertheless, there are no precise clinical indices for early recognition of small changes in fluid status of patients undergoing chronic hemodialysis therapy. This study aimed to evaluate and compare the widely used and reliable method of indexed inferior vena cava diameter (IVCDi) with established and more recently available techniques (bioelectrical impedance analysis [BIA], continuous blood volume monitoring [Crit-line], and the B-line score [BLS] with lung ultrasonography) for estimating the hydration status of patients on HD.

METHODS

Fifty-three patients undergoing chronic HD thrice weekly were included in the study. Evaluation of hydration status methods (IVCDi, BLS, BIA, and Crit-line) was performed thrice weekly before and after HD. Receiver operating characteristic curve analysis was performed to evaluate the discriminative power of (methods) the BLS, BIA, and Crit-line for predicting over- and underhydration of patients, as determined by the reference method, IVCDi.

RESULTS

BLS showed the most promising results in predicting overhydration, as determined by IVCDi, compared with BIA and Crit-line and presented a sensitivity of 77% and specificity of 74%. The accuracy of the BLS was higher than that of BIA (0.81 vs. 0.71, p = 0.032) and Crit-line (0.61, p = 0.001). BLS also showed more promising results in predicting underhydration, as determined by IVCDi, than BIA and Crit-line and presented a sensitivity of 78% and a specificity of 73%. The accuracy of the BLS was higher than that of BIA (0.83 vs. 0.76, p = 0.035) and Crit-line (0.50, p < 0.001).

CONCLUSIONS

The BLS is a useful and easily performed technique that has recently become available for accurate evaluation of dry weight and fluid status in patients with end-stage renal disease undergoing chronic HD. This method might help recognize asymptomatic lung congestion in these patients.

Evaluation and Treatment of Hypertension in End-Stage Renal Disease Patients on Hemodialysis

Hypertension is one of the most common cardiovascular comorbidities in end-stage renal disease patients on hemodialysis. Its complex pathophysiology is related to extracellular volume overload, increased vascular resistance stemming from factors related to uremia or abnormal signaling from the failing kidneys, as well as the unique blood pressure changes that take place during and between hemodialysis treatments. Despite the changing nature of blood pressure over time in hemodialysis patients, hypertension diagnosed in or out of the hemodialysis unit is associated with increased cardiovascular morbidity and mortality. This review details the causes of hypertension in hemodialysis patients and provides an updated review of the clinical consequences and management of hypertension.

Preservation of residual kidney function in hemodialysis patients: reviving an old concept

Residual kidney function (RKF) may confer a variety of benefits to patients on maintenance dialysis. RKF provides continuous clearance of middle molecules and protein-bound solutes. Whereas the definition of RKF varies across studies, interdialytic urine volume may emerge as a pragmatic alternative to more cumbersome calculations. RKF preservation is associated with better patient outcomes including survival and quality of life and is a clinical parameter and research focus in peritoneal dialysis. We propose the following practical considerations to preserve RKF, especially in newly transitioned (incident) hemodialysis patients: (1) periodic monitoring of RKF in hemodialysis patients through urine volume and including residual urea clearance with dialysis adequacy and outcome markers such as anemia, fluid gains, minerals and electrolytes, nutritional, status and quality of life; (2) avoidance of nephrotoxic agents such as radiocontrast dye, nonsteroidal anti-inflammatory drugs, and aminoglycosides; (3) more rigorous hypertension control and minimizing intradialytic hypotensive episodes; (4) individualizing the initial dialysis prescription with consideration of an incremental/infrequent approach to hemodialysis initiation (e.g., twice weekly) or peritoneal dialysis; and (5) considering a lower protein diet, especially on nondialysis days. Because RKF appears to be associated with better patient outcomes, it requires more clinical and research focus in the care of hemodialysis and peritoneal dialysis patients.

Fluid volume expansion and depletion in hemodialysis patients lack association with clinical parameters

BACKGROUND

Achievement of normal volume status is crucial in hemodialysis (HD), since both volume expansion and volume contraction have been associated with adverse outcome and events.

OBJECTIVES

The objectives of this study are to assess the prevalence of fluid volume expansion and depletion and to identify the best clinical parameter or set of parameters that can predict fluid volume expansion in HD patients.

DESIGN

This study is cross-sectional.

SETTING

This study was conducted in three hemodialysis units.

PATIENTS

In this study, there are 194 HD patients.

METHODS

Volume status was assessed by multifrequency bio-impedance spectroscopy (The Body Composition Monitor, Fresenius) prior to the mid-week HD session.

RESULTS

Of all patients, 48 % (n = 94) were volume-expanded and 9 % of patients were volume-depleted (n = 17). Interdialytic weight gain was not different between hypovolemic, normovolemic, and hypervolemic patients. Fifty percent of the volume-expanded patients were hypertensive. Paradoxical hypertension was very common (31 % of all patients); its incidence was not different between patient groups. Intradialytic hypotension was relatively common and was more frequent among hypovolemic patients. Multivariate regression analysis identified only four predictors for volume expansion (edema, lower BMI, higher SBP, and smoking). None of these parameters displayed both a good sensitivity and specificity.

LIMITATIONS

The volume assessment was performed once.

CONCLUSIONS

The study indicates that volume expansion is highly prevalent in HD population and could not be identified using clinical parameters alone. No clinical parameters were identified that could reliably predict volume status. This study shows that bio-impedance can assist to determine volume status. Volume status, in turn, is not related to intradialytic weight gain and is unable to explain the high incidence of paradoxical hypertension.

The source of net ultrafiltration during hemodialysis is mostly the extracellular space regardless of hydration status

Fluid shifts are common in patients undergoing chronic hemodialysis (HD) during the intradialytic periods, as several liters of fluid are removed during ultrafiltration (UF). Some patients have experienced frequent intradialytic hypotension (IDH). However, the characteristics of fluid shifts and which fluid space is affected remain controversial. Therefore, we designed this study to evaluate the fluid spaces most affected by UF and to determine whether hydration status influences the fluid shifts during HD. This was a prospective cohort study of 40 patients undergoing HD. We measured the patient's fluid spaces using a whole-body bioimpedance apparatus to evaluate the changes in the fluid spaces before HD and 1-4 hours of HD and 30 minutes after HD. UF achieved during HD by the 40 patients (age, 60.0 ± 5.2 years; 50% men; 50% of patients with diabetes; body weight, 61.3 ± 10.5 kg) was 2.18 ± 0.78 L (measured fluid overload, 2.15 ± 1.24 L). 1) Mean relative reduction of total body water and extracellular water was reduced from the start to the end of HD. 2) However, mean relative reduction of intracellular water was not reduced from the start to the end of HD. 3) No significant differences in fluid shifts were observed according to hydration status. The source of net UF during HD is mostly the extracellular space regardless of hydration status. Thus, IDH may be related to differences in the interstitial fluid shift to the vascular space.

The impact of the peritoneal glucose load index on hydration status and inflammation in peritoneal dialysis patients

Objective

To evaluate the impact of the peritoneal glucose load (PGL) on hydration status and inflammation in peritoneal dialysis (PD) patients.

Methods

This cross-sectional study evaluated stable PD patients using a novel PGL index (PGLI), which was calculated as the net glucose content (g) in the PD solutions administered in the daily PD prescription divided by the dry body weight (kg) assessed by whole-body bioimpedance spectroscopy. The relationship between PGLI and glycosylated haemoglobin (HbA1c), fluid overload (FO), and inflammatory markers was investigated.

Results

A total of 43 stable PD patients participated in the study. Significant positive correlations were found between PGLI and HbA1c, FO, plasma high sensitivity C-reactive protein (hsCRP), and plasma interleukin-6 (IL-6) levels. HbA1c, FO, plasma hsCRP and plasma IL-6 levels were significantly higher in patients with PGLI >3 g/kg/day compared with those with PGLI ≤3 g/kg/day.

Conclusions

PGLI values >3 g/kg/day may be associated with poor glycaemic control, over hydration and augmented inflammation. PGLI might be a useful tool for the quantitative assessment of the PGL and could be applied when managing PD patients.

Effects of Crit-Line® monitor use on patient outcomes and epoetin alfa dosing following onset of hemodialysis: a propensity score-matched study

BACKGROUND

The Crit-Line® monitor (CLM) is a device for monitoring hematocrit, oxygen saturation and change in intravascular blood volume during hemodialysis. Prior studies have evaluated CLM use in dialysis patients, but not specifically in those new to dialysis.

METHODS

In this retrospective analysis, 199 patients initiating dialysis at 8 facilities routinely using CLM were compared with 796 propensity score-matched non-CLM patients initiating dialysis at facilities not using CLM. Outcomes were considered over the first 180 days on dialysis.

RESULTS

Overall, the CLM group had higher StdKt/V (p = 0.06) and received lower doses of intravenous iron than the non-CLM group (p < 0.001). Erythropoiesis-stimulating agent doses were lower in the CLM group in months 1-5. Serum iron and transferrin saturation levels were higher overall for the CLM group than the non-CLM group (p = 0.004 and 0.01, respectively). Hemoglobin levels and time to first hospitalization were similar for both groups.

CONCLUSION

Use of CLM is associated with lower erythropoiesis-stimulating agent and iron use in incident hemodialysis patients.

Clinical significance of multi-frequency bioimpedance spectroscopy in peritoneal dialysis patients: independent predictor of patient survival

BACKGROUND

It is becoming increasingly evident that the accurate assessment of hydration status is critical to care of a dialysis patient. Using the Body Composition Monitor, different parameters (overhydration (OH), extra-cellular water/total body water (ECW/TBW) or OH/ECW) have been proposed to indicate hydration status. We wished to determine which parameter (if any) was most predictive of all-cause mortality, and if this was independent of nutritional indices.

METHODS

We performed a single-centre retrospective analysis of prospectively collected data of all peritoneal dialysis (PD) patients between 1 January 2008 and 30 March 2012. Record review was undertaken to establish patient survival, clinical and demographic data. Follow-up was continued even after PD technique failure (transfer to haemodialysis) and transplantation.

RESULTS

The study included 529 patients. OH index (OH and OH/ECW) was the independent predictor of mortality in multi-variate analysis. ECW/TBW as a continuous variable was not associated with increased risk of death. In contrast, patients that were severely overhydrated (highest 33%) had hazard ratios (HRs) that were statistically significant irrespective of the parameter used to define hydration. Using OH, severely overhydrated patients had an HR of 1.83 [95% confidence interval (CI) 1.19-2.82, P < 0.01], OH/ECW: 2.09 (95% CI 1.36-3.20, P < 0.001) and ECW/TBW: 2.05 (95% CI 1.31-3.22, P < 0.005).

CONCLUSIONS

Our results also indicated that there was no influence of body mass index (BMI) on the hydration parameter OH/ECW. OH/ECW remained an independent predictor of mortality when the BMI and lean tissue index were included in multivariate model. However, it remains to be determined if correcting the OH status of a patient will lead to improvement in mortality.

Hydration measurement by bioimpedance spectroscopy and blood pressure management in children on hemodialysis

BACKGROUND

Hypertension is frequent in chronic hemodialyzed patients and usually treated by reducing extracellular fluid. Probing dry weight only based on a clinical evaluation may be hazardous, especially in case of volume independent hypertension.

METHODS

We performed a 1-year retrospective study in three pediatric centers to define the relation between blood pressure (BP) and hydration status, assessed by whole-body bioimpedance spectroscopy (BIS). We analyzed 463 concomitant measurements of BP, relative overhydration (rel.OH), and plasma sodium (Napl) in 23 children (mean age 13.9 ± 5.1 years).

RESULTS

Pre-dialytic under-hydration (rel.OH < -7%) was present in 5.4% of the sessions, out of which 24% showed hypertension. Normohydration (rel.OH -7 - +7%) was observed in 62.4% of the sessions, 45.3% of them revealed hypertension. Moderate OH (rel.OH +7 - +15%) was present in 21% of the sessions, 47.4% of them showed normal BP. In 11.2% of the sessions, severe overhydration (rel.OH > +15%) was assessed, however, the majority (73%) showed normal BP. Patient-specific Napl setpoint could not be described. Mean dialysate sodium concentration was higher than mean Napl.

CONCLUSIONS

Hypertension is not always related to overhydration. Therefore, BIS should restrict the practice of "probing dry weight" in hypertensive children. Moreover, sodium dialytic balance needs to be considered to improve BP management.

Comparison and Reproducibility of Techniques for Fluid Status Assessment in Chronic Hemodialysis Patients

BACKGROUND

Several methods have been developed to assess the hydration status in chronic hemodialysis (HD) patients. The aim of this study was to compare body bioimpedance spectroscopy (BIS) with ultrasound (US) lung comet score (ULCs), B-type natriuretic peptide (BNP) and inferior vena cava diameter (IVCD) by US for the estimation of dry weight before and after HD and to analyze all methods in terms of fluid status variations induced by HD. An additional aim of this study was to establish the interoperator reproducibility of these methods.

METHODS

Two nephrologists evaluated BIS, ULCs, IVCD during inspiration (min) and expiration (max), the inferior vena cava collapsibility index (IVCCI) as well as BNP before and after HD in 30 patients. The same operators measured BIS, ULCs and IVCD in 28 HD patients in a blinded fashion.

RESULTS

There was a significant reduction in BIS, ULCs, IVCD and BNP after HD (p < 0.001), but a less significant reduction in IVCCI (p = 0.13). There was a significant correlation between BIS and ULCs, BNP and indexed IVCD (IVCDi)min (p < 0.05) before and after HD, and between BIS and IVCDimax only before HD.

CONCLUSION

All methods were able to describe hyperhydration before and after HD, except for IVCCI after HD. All techniques correlated with BIS before HD. After HD, ULCs correlated better with BIS than IVCD in terms of evaluation of fluid status. It could be expected that the ULCs can give a real-time evaluation of interstitial water. The reproducibility of the measurement of BIS, IVCD and ULCs between the two operators was high.

Volume estimation in dialysis patients: the concordance of brain-type natriuretic peptide measurements and bioimpedance values

Correct estimation of the dialysis patients' hydration status remains an important clinical challenge. Bioimpedance measurements have been validated by various physiological tests, and the use of brain-type natriuretic peptide (BNP) has been validated by inferior vena cava diameter measurements. This is an observational cohort study that evaluated the correspondence between bioimpedance-measured overhydration percentage (OH%) and BNP. We measured predialysis OH% by bioimpedance apparatus (Body Composition Monitor) and BNP by microparticle enzyme-linked immunoassay in 41 prevalent stable hemodialysis patients, 19 (46%) women, aged 58.9 ± 14.5 years. The cohort's average BNP was 2694 ± 3278 pg/mL and 10 (24.4%) of these 41 patients had BNP < 500 pg/mL (average 260.7 ± 108.5). The OH% was 8.5 ± 7.0% among those with a BNP < 500 pg/mL, while the rest of the population had an OH% of 21.4 ± 8.0%, corresponding to excess volumes of 1.6 ± 1.3 and 4.4 ± 3.8 L, respectively. The OH% vs. BNP relationship was best described by the exponential regression of y = 216.4e(0.097x) , predicting a BNP of 216.4 pg/mL at 0% overhydration status (r 0.61). Receiver-operating curves revealed an area under the curve of 0.885 for BNP when the OH% was set ≥15% of overhydration and an area under the curve of 0.918 for OH% when the BNP was set ≥500 pg/mL for being abnormal. We conclude that in our cohort there was a high degree of correspondence between these two tests with an exponential relationship between the measurements.

The dual blockade of the renin-angiotensin system in hemodialysis patients requires decreased dialysate sodium concentration

Purpose

The study evaluated whether the dual blockade of the renin–angiotensin system may influence the sodium balance in hemodialysis.

Methods

The study involved 148 hemodialysis patients (male 85, female 63), mean age 59.6 ± 12.9 years. Participants were randomly selected to receive either angiotensin-converting enzyme inhibitor (ACEI)—subgroup A—or dual blockade ACEI and angiotensin receptor blocker (ARB)—subgroup AA.

Results

At baseline, in the A versus AA subgroups, the pre-dialysis sodium concentrations (mmol/l) were 137.7 ± 0.5 versus 137.9 ± 0.8, the sodium gradients 2.6 ± 0.5 versus 2.9 ± 0.4, interdialytic weight gain (IWG) (kg) 3.1 ± 0.2 versus 3.0 ± 0.3, and thirst inventory score (points) 18.1 ± 1.0 versus 19.0 ± 1.7, respectively. After 3 months of therapy, a decrease in sodium concentration to 134.5 ± 0.5 and the increase of its gradient to 5.5 ± 0.5 were noted in the AA subgroup. An elevation of mean interdialytic weight gain to 3.47 ± 0.2 and thirst score to 21.3 ± 2.1 was observed. No significant changes in subgroup A were found. One month of the dialysate sodium concentration being lowered from 140 mmol/l to 138 mmol/l was associated with reduced serum sodium concentration and gradient, decreased IWG and restored moderate thirst score in the AA subgroup (137.5 ± 0.6 and 2.9 ± 0.6, 3.0 ± 0.5 and 19.2 ± 1.3, respectively).

Conclusions

The dual blockade of the renin–angiotensin system affects sodium balance, increasing the sodium gradient, thus elevating thirst sensation and enhancing interdialytic weight gain. In maintenance hemodialysis patients treated with both ACEI and ARB, lowered dialysate sodium levels should be prescribed.

Dialysis patients' fluid overload, antihypertensive medications, and obesity

Overhydration (OH) is both a major etiology of hypertension in hemodialysis patients and a serious risk factor for mortality. We investigated the association of multiple variables and OH. This is a cross-sectional study of prevalent hemodialysis patients examining the predialysis hydrational status with a portable bioimpedance apparatus to measure the degree of hydration. We completed our study in 79 patients. Patients were overhydrated by 2.6 ± 2.4 L. The mean medication count was 2.4 ± 1.5, and 50.7% had diuretics. We found a significant correlation between OH and systolic blood pressure (r = 0.39; p = 0.0006), each liter of OH generating 3.6 mm Hg. We also found a positive correlation between the use of diuretics and OH (p = 0.003, two-tailed Student's t test) but no correlation between OH and body weight (r < 0.0001; p = 0.99), body mass index (r = -0.17), age (r = 0.089), and vintage (r = 0.05). For every 10% increase in body fat, OH decreased by 1.2 L; residual urine output gave no protection from OH (r = 0.077) and did not correlate with blood pressure (r = 0.01). Overhydration is strongly associated with the use of antihypertensive medications and the use of diuretics in this dialysis population. Obesity seems to afford some protection from OH.

The Relationship between Bioimpedance Analysis, Haemodynamic Parameters of Haemodialysis, Biochemical Parameters and Dry Weight

Adequate fluid management plays an important role in the treatment of haemodialysis patients and the assessment of dry weight is important for efficient therapy. Fluid volume parameters were assessed in adults undergoing haemodialysis for end-stage renal disease, using whole-body multifrequency bioimpedance analysis (BIA), and their relationship to haemodynamic and biochemical parameters of haemodialysis was evaluated. Ultrafiltration volume was correlated with age, sodium, haemoglobin, extracellular water (ECW)/total body water (TBW) ratio and ECW/intracellular water (ICW) ratio. The ECW/TBW ratio was correlated with age, body mass index, dry weight, predialysis systolic and diastolic blood pressure, and ECW/total body weight ratio. The ECW/ICW ratio correlated with age, dry weight, TBW, albumin, adequacy of dialysis and urea removal ratio. The study demonstrated a close relationship between bioimpedance-derived fluid volume parameters and the haemodynamic and biochemical parameters of haemodialysis. It is concluded that multifrequency whole-body BIA may have clinical value in the estimation of dry weight and other haemodynamic parameters of haemodialysis and so may protect patients from the risks associated with under- or over-hydration.

Estimation of normal hydration in dialysis patients using whole body and calf bioimpedance analysis

Prescription of an appropriate dialysis target weight (dry weight) requires accurate evaluation of the degree of hydration. The aim of this study was to investigate whether a state of normal hydration (DW(cBIS)) as defined by calf bioimpedance spectroscopy (cBIS) and conventional whole body bioimpedance spectroscopy (wBIS) could be characterized in hemodialysis (HD) patients and normal subjects (NS). wBIS and cBIS were performed in 62 NS (33 m/29 f) and 30 HD patients (16 m/14 f) pre- and post-dialysis treatments to measure extracellular resistance and fluid volume (ECV) by the whole body and calf bioimpedance methods. Normalized calf resistivity (ρ(N)(,5)) was defined as resistivity at 5 kHz divided by the body mass index. The ratio of wECV to total body water (wECV/TBW) was calculated. Measurements were made at baseline (BL) and at DW(cBIS) following the progressive reduction of post-HD weight over successive dialysis treatments until the curve of calf extracellular resistance is flattened (stabilization) and the ρ(N)(,5) was in the range of NS. Blood pressures were measured pre- and post-HD treatment. ρ(N)(,5) in males and females differed significantly in NS. In patients, ρ(N)(,5) notably increased with progressive decrease in body weight, and systolic blood pressure significantly decreased pre- and post-HD between BL and DW(cBIS) respectively. Although wECV/TBW decreased between BL and DW(cBIS), the percentage of change in wECV/TBW was significantly less than that in ρ(N)(,5) (-5.21 ± 3.2% versus 28 ± 27%, p < 0.001). This establishes the use of ρ(N)(,5) as a new comparator allowing a clinician to incrementally monitor removal of extracellular fluid from patients over the course of dialysis treatments. The conventional whole body technique using wECV/TBW was less sensitive than the use of ρ(N)(,5) to measure differences in body hydration between BL and DW(cBIS).

The risks of high ultrafiltration rate in chronic hemodialysis: implications for patient care

As dialytic practice has evolved, hemodialysis (HD) adequacy has come to be defined in terms of small molecule clearance. A growing body of evidence suggests that fluid dynamics, specifically ultrafiltration rate (UFR), bear clinical and physiological significance and should perhaps play a more central role in titrating HD therapy. Three recent studies have shown an independent association between higher UFR and mortality. Further work is needed to determine whether this relationship represents a direct toxic effect of rapid fluid perturbations or whether this association is a consequence of confounding on the basis of large interdialytic weight gain, as each would prompt a different therapeutic response. This mounting evidence builds the case that fluid management should play a more central role in the dialytic prescription and that more individualized approaches to fluid management should be encouraged.