B-type natriuretic peptide is not a volume marker among patients on hemodialysis

Association of frequent intradialytic hypotension with the clinical outcomes of patients on hemodialysis: a prospective cohort study

Intradialytic hypotension (IDH) is a common complication of hemodialysis (HD), but there is no consensus on its definition. In 2015, Flythe proposed a definition of IDH (Definition 1 in this study): nadir systolic blood pressure (SBP) <90 mmHg during hemodialysis for patients with pre-dialysis SBP <159 mmHg, and nadir SBP <100 mmHg during hemodialysis for patients with pre-dialysis SBP ≥160 mmHg. This prospective observational cohort study investigated the association of frequent IDH based on Definition 1 with clinical outcomes and compared Definition 1 with a commonly used definition (nadir SBP <90 mmHg during hemodialysis, Definition 2). The incidence of IDH was observed over a 3-month exposure assessment period. Patients with IDH events ≥30% were classified as 'frequent IDH'; the others were 'infrequent IDH'. All-cause mortality, cardiovascular mortality, and all-cause hospitalization events were followed up for 36 months. This study enrolled 163 HD patients. The incidence of IDH was 11.1% according to Definition 1 and 10.5% according to Definition 2. The Kaplan-Meier curves showed that frequent IDH patients had higher risks of all-cause mortality (p = 0.009, Definition 1; p = 0.002, Definition 2) and cardiovascular mortality (p = 0.021, Definition 1). Multivariable Cox regression analysis indicated that frequent IDH was independently associated with a higher risk of all-cause mortality (Model 1: HR = 2.553, 95%CI 1.334-4.886, p = 0.005; Model 2: HR = 2.406, 95%CI 1.253-4.621, p = 0.008). In conclusion, HD patients classified as frequent IDH are at a greater risk of all-cause mortality. This highlights the significance of acknowledging and proactively managing frequent IDH within the HD patients.

Variation of brain natriuretic peptide assists with volume management and predicts prognosis of hemodialysis patients

PURPOSE

The objective of this study was to elucidate the spectrum of brain natriuretic peptide (BNP) expression in hemodialysis patients with euvolemic status and investigate its prognostic significance.

METHODS

Patients on chronic hemodialysis were enrolled. The normal range of BNP was measured and analyzed in patients with euvolemic status defined by systolic blood pressure and overhydration. Hemodialysis patients were stratified into groups according to BNP expression at baseline and followed up for 57 months, with all-cause mortality and cardiovascular disease-related death being assessed as primary outcomes.

RESULTS

BNP significantly correlated with overhydration in all patients (r = 0.255, P = .004). In patients with euvolemic state, the average BNP level was 701 (±645) pg/ml, with a 95% confidence interval (CI) of 500-902 pg/ml. In patients with BNP < 902 pg/ml, systolic blood pressure significantly correlated with overhydration. Elevated BNP expression correlated with an increased risk of cardiovascular mortality (HR = 1.871, per 782 pg/ml increase, P = .008). The patients with continuously high levels of BNP showed significantly increased risk of cardiovascular disease-related death during follow-up (HR = 12.845, P = .005).

CONCLUSION

Predialysis measured BNP levels correlate with volume status, and the common range is from 500 to 902 pg/ml in dialysis patients with euvolemic status. Patients with upregulated BNP expression showed an increased risk of cardiovascular death. Key messages What is already known on this topic  The volume management of hemodialysis patients should be judged comprehensively by clinical manifestations and objective examinations. The parameters involved in the evaluation need to be further optimized. What this study adds  In hemodialysis patients, BNP serves as an indicator of volume status. Properly hydrated hemodialysis patients typically exhibit BNP levels ranging from 500 to 902 pg/ml, while persistent BNP elevation is associated with increased mortality. How this study might affect research, practice, or policy  In clinical practice, BNP can be routinely monitored in hemodialysis patients to provide information for volume adjustment and to identify patients with high mortality risk. The potential advantages of implementing targeted BNP management warrant further investigation through intervention studies.

Assessment and Management of Volume Overload Among Patients on Chronic Dialysis

Volume overload is the most common complication in end-stage renal disease (ESRD) patients, being directly related to numerous complications including resistant hypertension, cardiac hypertrophy, congestive heart failure or arterial stiffness, among others. Therefore, volume overload is now considered an important risk factor for hard outcomes, like all-cause or cardiovascular mortality. Relying solely on clinical examination for assessing volume overload in ESRD patients lacks sensitivity and specificity. Numerous efforts have been made to identify new methods that could objectively assess volume status; however, each of them has important limitations. This review aims to discuss the most frequently used methods (biomarkers, inferior vena cava assessment, lung ultrasonography, bioimpedance analysis and blood volume monitoring) and to compare the advantage of each method vs. the overall/ clinical strategy.

Association of N-Terminal Pro-brain Natriuretic Peptide With Volume Status and Cardiac Function in Hemodialysis Patients

Introduction: N-terminal-pro-brain natriuretic peptide (NT-pro BNP) is secreted by cardiomyocytes in cases of cardiac structure disorder and volume overload. However, the relationship between NT-pro BNP level and body fluid status in dialysis patients with reduced cardiac ejection function (EF) is uncertain. Therefore, we aimed to investigate this relationship.

Methods: We enrolled patients who had been receiving hemodialysis for >3 months. Blood sample, transthoracic echocardiographic, and bioimpedance spectroscopy measurements were performed during a midweek non-dialysis day. The predictive value of NT-pro BNP in hemodialysis patients with volume overload was analyzed.

Results: A total of 129 hemodialysis patients (74 men and 55 women; mean age: 59.4 ± 13.0 years) were recruited. The average hemodialysis duration was 55.5 (23.9–93.4) months, the NT-pro BNP level was 4992 (2,033–15,807) pg/mL, and the value of overhydration was 2.68 ± 0.19 (−1.9 to 12.2) L. The NT-pro BNP level was independently correlated with overhydration in both the LVEF ≥ 60% (β = 0.236, P = 0.044) and LVEF <60% (β = 0.516, P = 0.032) groups, even after adjustments for potentially confounding variables. In receiver operating characteristic curves of NT-pro BNP for predicting volume overload, the area under the curve was 0.783 [95% CI (0.688–0.879), P < 0.001) and 0.788 [95% CI (0.586–0.989), P < 0.001] in the LVEF ≥ 60% and LVEF < 60% groups, respectively.

Conclusions: NT-pro BNP is a predictive factor for volume overload in hemodialysis patients with or without EF declines.

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.

Volume Balance in Chronic Kidney Disease: Evaluation Methodologies and Innovation Opportunities

BACKGROUND

Patients affected by chronic kidney disease are at a risk of cardiovascular morbidity and mortality. Body fluids unbalance is one of the main characteristics of this condition, as fluid overload is highly prevalent in patients affected by the cardiorenal syndrome.

SUMMARY

We describe the state of the art and new insights into body volume evaluation. The mechanisms behind fluid balance are often complex, mainly because of the interplay of multiple regulatory systems. Consequently, its management may be challenging in clinical practice and even more so out-of-hospital. Availability of novel technologies offer new opportunities to improve the quality of care and patients' outcome. Development and validation of new technologies could provide new tools to reduce costs for the healthcare system, promote personalized medicine, and boost home care. Due to the current COVID-19 pandemic, a proper monitoring of chronic patients suffering from fluid unbalances is extremely relevant. Key Message: We discuss the main mechanisms responsible for fluid overload in different clinical contexts, including hemodialysis, peritoneal dialysis, and heart failure, emphasizing the potential impact provided by the implementation of the new technologies.

Implementation of a decision aid for recognition and correction of volume alterations (Recova®) in haemodialysis patients

BACKGROUND

Fluid overload is associated with mortality in haemodialysis patients, and 30% of patients remain fluid-overloaded after dialysis. The aim of this study was to evaluate if implementation of Recova^®, a decision aid combining clinical assessment with bioimpedance spectroscopy, facilitates individualization of target weight determination and thereby contributes to improved fluid status in maintenance haemodialysis patients.

METHODS

The impact of the implementation was measured as the proportion of participants at an adequate target weight at the end of the study, assessed as change in symptoms, hydration status, and N-terminal pro-brain natriuretic peptide (NT-proBNP). Nurses were instructed to use Recova every 2 weeks, and the process of the intervention was measured as frequencies of fluid status assessments, bioimpedance measurements, and target weight adjustments.

RESULTS

Forty-nine patients at two haemodialysis units were enrolled. In participants with fluid overload (n = 10), both overhydration and fluid overload symptom score decreased. In fluid-depleted participants (n = 20), target weight adjustment frequency and the estimated target weight increased. The post-dialytic negative overhydration was reduced, but NT-proBNP increased.

CONCLUSIONS

Implementation of Recova in haemodialysis care increased the monthly frequencies of bioimpedance measurements and target weight adjustments, and it contributed to symptom reduction.

TRIAL REGISTRATION

The Uppsala County Council Registry of Clinical Trials: FoU 2019-0001-15.

Do Natriuretic Peptide Measurements Provide Insights into Management of End-Stage Renal Disease Patients Undergoing Dialysis?

PURPOSE OF REVIEW

Impaired renal function may affect natriuretic peptide levels through a variety of factors and mechanisms, such as high prevalence of concomitant vascular and myocardial diseases, reduced clearance, increased risk of volume overload, and different types and solute removal techniques in the setting of dialysis. Nevertheless, accumulating evidence suggests that natriuretic peptide testing may provide insights into management of patients with chronic kidney disease (CKD) and end-stage kidney disease (ESRD) on dialysis, as they have been shown to be independently associated with morbidity and mortality.

RECENT FINDINGS

Rising natriuretic peptide levels over time may identify CKD patients more likely to approach ESRD and requiring dialysis initiation. Moreover, serial natriuretic peptide measurements may also be helpful in guiding fluid management in ESRD patients on dialysis. However, since patients with CKD usually have significantly higher and more variable baseline levels of natriuretic peptides than those without CKD, traditional cut-off values may not be applicable, and individualized trajectories should be applied and interpreted in the clinical context. Routine clinical use natriuretic peptide testing in the CKD and ESRD settings still needs to be refined and individualized, yet their diagnostic and prognostic values can provide valuable insights into clinical trajectories and potential treatment responses.

Pathophysiology and significance of natriuretic peptides in patients with end-stage kidney disease

Natriuretic peptides (NP), especially B type (BNP) and its N-terminal pro-B type natriuretic peptide (NT-proBNP), have long been regarded as biomarkers of volume overload and tools to exclude heart failure in the general population. However, their role in end-stage kidney disease (ESKD) is less certain given that BNP and NT-proBNP are excreted by the kidney and so serum concentrations of NPs are nearly universally elevated compared to controls. Nevertheless, the accumulated evidence suggests thatserum concentrations of NPs in patients with ESKD show moderate or strong positive relationships with underlying heart disease, abnormal cardiac structure or function and mortality. Limited evidence also supports the role of BNP including NT-proBNP, ANP in some studies, rather than CNP or DNP in risk stratification among ESKD patients as well as the utility of BNP samplings pre- and post- hemodialysis. However, studies of the cut-off values of NPs have yielded inconsistent results, such that further large-scale studies are needed to clarify these issues. This review summarizes the pathophysiology and significance of NPs in ESKD patients, especially their potential role as risk stratification biomarkers in clinical management.

Relationships among pulmonary capillary wedge pressure, dry weight and natriuretic peptide in patients undergoing hemodialysis: a three-dimensional speckle tracking echocardiography study

BACKGROUND

Although the evaluation of fluid status in hemodialysis (HD) patients is useful, relationship among pulmonary capillary wedge pressure (PCWP), dry body weight (DW) and natriuretic peptide has not been elucidated. In addition, there has been no objective marker for instantaneously monitoring hemodynamic improvement in response to HD. We previously reported that PCWP and time constant of left ventricular pressure decline (Tau) can be noninvasively estimated (ePCWP and eTau) by speckle tracking echocardiography (STE). The aim of this study was to elucidate the relationship among ePCWP, eTau, DW and natriuretic peptide in patients undergoing HD.

METHODS

We measured ePCWP and body weight (BW) by STE in 81 patients and ANP and BNP by blood examination in 31 patients just before and after HD during sinus rhythm.

RESULTS

The ePCWP decreased after HD, and this was associated with reductions in ln ANP, eTau and BW (r = 0.523, 0.271 and 0.814, respectively, p < 0.05). The % change in ePCWP was not correlated with the % change in ln BNP (p = 0.47). The change in ePCWP had a stronger correlation with the % change in BW than the change in any other parameters.

CONCLUSIONS

The ePCWP is more sensitive to estimate the change in BW during HD than any other parameters such as ANP and BNP. These results indicated that a substantial amount of excess fluid can be assessed real-time by STE using ePCWP.

Relative Change of Protidemia Level Predicts Intradialytic Hypotension

Background

Hemodialysis patients are at risk of intradialytic hypotension (IDH), which is associated with mortality and cardiovascular and neurological events. The use of biomarkers of volemia such as relative change in protidemia and BNP (B‐natriuretic peptide) levels to predict IDH remains unknown.

Methods and Results

We conducted a prospective observational study, which enrolled 170 chronic hemodialysis patients in a single center from September 2015 to March 2016. BNP and the relative change of protidemia level (Δprotidemia=postdialysis protidemia−predialysis protidemia) were measured monthly over 6 months. A logistic mixed regression model was used to define the best biomarkers that predict the 30‐day risk of IDH. Receiver operating characteristic analysis area under the curve was used to define the cutoff values of Δprotidemia that predict IDH A logistic mixed model reveals that Δprotidemia predicts the 30‐day risk of IDH but not BNP or age; odds ratio=1.12, 95% CI 1.08‐1.17), odds ratio=0.81, 95% CI (0.64; 1.07) and odds ratio =0.015 95% CI (0.99; 1.03), respectively. Adding the ultrafiltration rate did not improve the model. A receiver operating characteristic curve analysis showed that Δprotidemia of 10 g/L allowed for discrimination of the patients with IDH (area under the curve= 0.67; 95% CI 0.62‐0.72, P<0.05). There was an increase in area under the curve to 0.71 (95% CI 0.63‐0.76) in a subgroup of hemodialysis with BNP <300 ng/L, for a cutoff value of 11 g/L, especially for the nondiabetic patients.

Conclusions

Relative change in protidemia level (Δprotidemia) outperforms BNP and ultrafiltration rate as a predictor for 30‐day risk of IDH. These results should be confirmed by a prospective study.

Sodium and water handling during hemodialysis: new pathophysiologic insights and management approaches for improving outcomes in end-stage kidney disease

Space medicine and new technology such as magnetic resonance imaging of tissue sodium stores (²³NaMRI) have changed our understanding of human sodium homeostasis and pathophysiology. It has become evident that body sodium comprises 3 main components. Two compartments have been traditionally recognized, namely one that is circulating and systemically active via its osmotic action, and one slowly exchangeable pool located in the bones. The third, recently described pool represents sodium stored in skin and muscle interstitium, and it is implicated in cell and biologic activities via local hypertonicity and sodium clearance mechanisms. This in-depth review provides a comprehensive view on the pathophysiology and existing knowledge gaps of systemic hemodynamic and tissue sodium accumulation in dialysis patients. Furthermore, we discuss how the combination of novel technologies to quantitate tissue salt accumulation (e.g., ²³NaMRI) with devices to facilitate the precise attainment of a prescribed hemodialytic sodium mass balance (e.g., sodium and water balancing modules) will improve our therapeutic approach to sodium management in dialysis patients. While prospective studies are required, we think that these new diagnostic and sodium balancing tools will enhance our ability to pursue more personalized therapeutic interventions on sodium and water management, with the eventual goal of improving dialysis patient outcomes.

Mathematical model to predict B-type natriuretic peptide levels in haemodialysis patients

AIM

Clinical interpretation of B-type natriuretic peptide (BNP) levels in haemodialysis (HD) patients for fluid management remains elusive.

METHODS

We conducted a retrospective observational monocentric study. We built a mathematical model to predict BNP levels, using multiple linear regressions. Fifteen clinical/biological characteristics associated with BNP variation were selected. A first cohort of 150 prevalent HD (from September 2015 to March 2016) was used to build several models. The best model proposed was internally validated in an independent cohort of 75 incidents HD (from March 2016 to December 2017).

RESULTS

In cohort 1, mean BNP level was 630 ± 717 ng/mL. Cardiac disease (CD - stable coronary artery disease and/or atrial fibrillation) was present in 45% of patients. The final model includes age, systolic blood pressure, albumin, CD, normo-hydrated weight (NHW) and the fluid overload (FO) assessed by bio-impedancemetry. The correlation between the measured and the predicted log-BNP was 0.567 and 0.543 in cohorts 1 and 2, respectively. Age (β = 3.175e^-2 , P < 0.001), CD (β = 5.243e^-1 , P < 0.001) and FO (β = 1.227e^-1 , P < 0.001) contribute most significantly to the BNP level, respectively, but within a certain range. We observed a logistic relationship between BNP and age between 30 and 60 years, after which this relationship was lost. BNP level was inversely correlated with NHW independently of CD. Finally, our model allows us to predict the BNP level according to the FO.

CONCLUSION

We developed a mathematical model capable of predicting the BNP level in HD. Our results show the complex contribution of age, CD and FO on BNP level.

Brain natriuretic peptide reflects individual variation in hydration status in hemodialysis patients

Introduction: Fluid management in hemodialysis patients is a controversial topic. Brain natriuretic peptide (BNP) is secreted from the heart in response to volume overload, and may be a marker of overhydration in hemodialysis patients. Our aim was to investigate the correlation between BNP and overhydration in a cohort of hemodialysis patients, and to find out whether BNP and overhydration correlate in repeated measurements within individuals with elevated BNP.

Methods: The study was prospective, observational, and had a cross‐sectional part and a longitudinal follow‐up. The distribution of BNP was investigated in a cohort of 64 hemodialysis patients. Blood samples and bioimpedance spectroscopy measurements were performed before midweek dialysis. Subsequently, 11 study participants with elevated BNP concentrations (>500 pg/mL) were assessed in another nine dialysis sessions each. These individuals also had their cardiac function and heart rate variability (HRV) examined.

Findings: BNP was above 500 pg/mL in 38% of the participants, and correlated positively with overhydration (r_s = 0.381), inflammation and malnutrition, but not with systolic blood pressure. In comparison to participants with BNP below 500 pg/mL, participants with elevated BNP were older, had lower muscle strength, lower bodyweight and lower levels of hemoglobin and albumin. Echocardiography revealed cardiac anomalies in all 11 participants in the longitudinal follow‐up, and HRV, as measured by SDNN, was pathologically low. In repeated measurements, the between‐individuals variation of BNP in relation to overhydration was greater (SD = 0.581) than the within‐person variation (SD = 0.285).

Discussion: BNP correlates positively to overhydration, malnutrition, and inflammation. In a subgroup of patients with elevated BNP, who are mainly elderly and frail, BNP reflects individual variation in hydration status, and hence seems to be a modifiable marker of overhydration. These data suggest that BNP is best applied for measuring changes in hydration status within an individual over time.

Use of body composition measurements to guide the assessment of dry weight in anuric dialysis patients: improvements in blood pressure control

PURPOSE

Fluid management using a body composition monitor (BCM) based on bioimpedance spectroscopy has been found to be beneficial for maintenance hemodialysis (MHD) patients. Our purpose was to provide a management procedure for the adjustment of post-dialysis overhydration (OHpost) and to evaluate whether this approach could improve blood pressure.

METHODS

Post-dialysis fluid status was assessed weekly using the BCM. The reference value of OHpost and the flow procedure for post-dialysis target weight (PDTW) adjustment were established via measurements of OHpost in 60 normotensive MHD patients. In the interventional study, we adjusted the PDTW of hypertensive patients to the optimal OHpost range, with a 0.2-0.5 kg change in PDTW per week.

RESULTS

This observational study included 130 anuric MHD patients, of whom 60 were in the pre-dialysis systolic blood pressure (sBPpre) < 140 mmHg group. On multivariate logistic regression analysis, we found that only OHpost was significantly associated with sBPpre ≥ 140 mmHg (odds ratio = 2.293, p = 0.000). Patients in the OHpost < -1.8 L group were mainly male and younger, and had higher post-dialysis diastolic blood pressure, ultrafiltration volume, levels of nutrition markers (serum albumin and creatinine), body mass index, and lean tissue index (LTI). On multiple stepwise regression analysis, only the change in LTI was found to be an independent predictor of OHpost [R2 0.208, β = -0.196, 95% CI (-0.296, -0.095), p < 0.001]. The reference value of OHpost was found to deviate by - 2.5-0.5 L from that of normotensive patients. At the end of the study, the systolic blood pressure of 38 patients was less than 140 mmHg after PDTW adjustment. The changes in OHpost from the initial to last adjustment were significant (t = 5.431, p <  0.001), with a substantial decrease in the sBPpre (t = 11.208, p <  0.001).

CONCLUSIONS

Assessment of OHpost and LTI using a BCM with a patient-specific optimal PDTW adjustment flow can lead to significantly better control of hypertension in anuric MHD patients.

Patient-Centered Approach for Hypertension Management in End-Stage Kidney Disease: Art or Science?

Hypertension is present in most patients with end-stage kidney disease initiating dialysis and management of hypertension is a routine but challenging task in everyday dialysis care. End-stage kidney disease patients are uniquely heterogeneous individuals with significant variations in demographic characteristics, functional capacity, and presence of concomitant comorbid conditions and their severity. Therefore, these patients require personalized approaches in addressing not only hypertension but related illnesses, while also accounting for overall prognosis and projected longevity. There are only limited clinical trial data to guide individualized blood pressure management and current guidelines are based predominantly on observational evidence and expert opinions. Inthis review, we reflect on the shortcomings of peridialytic blood pressure recordings and discuss an important paradigm shift toward using out-of-dialysis blood pressure for evaluating hypertension control and for making treatment decisions. In addition, we provide our personal view on blood pressure goals and summarize nonpharmacologic and pharmacologic treatment options for individualized management of hypertension in end-stage kidney disease.

Predictive abilities of baseline measurements of fluid overload, assessed by bioimpedance spectroscopy and serum N-terminal pro-B-type natriuretic peptide, for mortality in hemodialysis patients

INTRODUCTION

Fluid overload is one of the most important, yet modifiable, risk factors associated with worse outcomes in hemodialysis (HD) patients. However, its precise assessment in clinical practice is still under investigation.

MATERIAL AND METHODS

This is an observational prospective study which included 285 stable patients with end-stage renal disease on standard thrice-weekly HD therapy. Overhydration was assessed by the combination of relative fluid overload (RFO), using bioimpedance spectroscopy, and N-terminal pro-B-type natriuretic peptide (NT-proBNP). The outcome of interest was all-cause mortality.

RESULTS

The median values for NT-proBNP and RFO were 4595 pg/ml and 6.9%, respectively. We divided the study population into four groups according to these median levels: group 1 - low NT-proBNP and low RFO; group 2 - high NT-proBNP and low RFO; group 3 - low NT-proBNP and high RFO; group 4 - high NT-proBNP and high RFO. During the follow-up (mean: 41.1, median: 48.7 months), 89 (31.2%) patients died. In the univariable Cox survival analysis only patients in group 4, and not those from group 2 or 3, had significantly higher HRs as compared to those in group 1 (HR = 1.5, 95% CI: 0.8-2.8, HR = 1.6, 95% CI: 0.8-2.9 and HR = 2.4, 95% CI: 1.3-4.2, for group 2, 3 and 4, respectively). Furthermore, these results were maintained in the multivariable Cox analysis.

CONCLUSIONS

Including both bioimpedance and NT-proBNP monitoring in a more comprehensive fluid status assessment could improve the diagnosis of fluid overload with a final improvement in patients' outcome.

Brain Natriuretic Peptide Is a Marker of Fluid Overload in Incident Hemodialysis Patients

BACKGROUND/AIMS

Brain natriuretic peptide (BNP) is secreted by cardiomyocytes under stretch condition. High blood levels are associated with decreased patient survival in heart failure patients and in hemodialysis (HD) patients. We report the monthly BNP change in the first months of HD therapy in incident patients and its relationship with fluid removal and cardiac history (CH).

METHODS

All patients starting HD therapy in our unit from May 2008 to December 2012 were retrospectively analyzed. Every month (M1 to M6), BNP was assessed before a midweek dialysis session. CH, monthly pre- and postdialysis blood pressure, and postdialysis body weight were collected.

RESULTS

A total of 236 patients were included in the analysis. The median BNP at HD start was 593 (175-1,433) pg/mL, with a significant difference between CH- and CH+ patients (291 vs. 731 pg/mL, p < 0.0001). Mortality was significantly higher in patients in the higher BNP tertile. BNP decreased significantly between M1 and M2 and then plateaued. The BNP change between M1 and M2 and between M1 and M6 was significantly correlated with the initial fluid removal. Applying stepwise multiple regression, the BNP change between M1 and M2 was significantly and independently related to fluid removal. The BNP level at M6 was also related to patient survival.

CONCLUSIONS

We confirm that in incident HD patients, BNP level is related to fluid excess and cardiac status. The BNP decrease in the first months of HD therapy is related to fluid excess correction. BNP appears as an important tool to evaluate hydration status correction after HD onset.

Pre-dialysis and post-dialysis hydration status and N-terminal pro-brain natriuretic peptide and survival in haemodialysis patients

PURPOSE

Many dialysis centres have no formal program for assessing and adjusting post-haemodialysis (HD) target weight. Apart from clinical assessment, there are bioimpedance devices and natriuretic peptides that could potentially aid clinical management. We wished to determine whether pre- or post-HD bioimpedance assessment of extracellular water (ECW) or N terminal probrain natriuretic peptide (NT-proBNP) affected patient outcomes.

METHODS

Multi-frequency bioimpedance assessments (MFBIA) were made before and after the midweek dialysis session, along with a post-dialysis NT-proBNP measurement.

RESULTS

Data from 362 patients, median age of 63 (50-76) years, 59.7% male, 41.2% Caucasoid, with a median dialysis vintage of 31.4 (13.5-61.7) months were available for review. During a median follow-up of 49.6 (21.9-50.2) months there were 110 (30.4%) deaths. Patients who died had significantly increased ECW, as % over-hydrated both pre-HD 6.6 (5.8-7.6)% vs. survivors 5.1 (4-6.6)%, and post-HD 5.1 (4-6.6)% vs. 0.5 (-1-2.2.0, p&lt;0.001, respectively. They also had higher NT-proBNP 325 (122-791) vs. 102 (48-342) pmol/l, p = 0.002. Using an adjusted Cox model, pre-HD ECW overhydration remained an independent factor associated with mortality (overhydration %: hazard ratio 1.15, 95% limits 1.03-1.28, p = 0.013), with a receiver operator curve (ROC) value of 0.7.

CONCLUSIONS

ECW excess is associated with increased mortality for HD patients, with ECW excess pre-dialysis being the strongest association, although these patients also had increased ECW post dialysis. Future trials are required to determine whether achieving euvolaemia as determined by bioimpedance improves patient survival.

Comparison of hydration and nutritional status between young and elderly hemodialysis patients through bioimpedance analysis

Background

The number of elderly people on dialysis is increasing rapidly. Fluid overload and malnutrition status are serious problems in elderly dialysis patients. We aimed to compare the hydration and nutritional status through bioimpedance analysis (BIA) between young and elderly hemodialysis (HD) patients and to analyze risk factors related to fluid overload and malnutrition status in these patients.

Method

We conducted a cross-sectional study, in which 82 HD (males 42, mean age 58.7±12.9 years) patients were enrolled. We collected different types of data: laboratory data, such as serum creatinine, albumin, total iron-binding capacity, hemoglobin, total cholesterol; anthropometric data, such as hand grip strength (HGS); BIA data, such as intracellular water, skeletal muscle mass, body cell mass, bone mineral content, phase angle (PhA), extra cellular water (ECW)/total body water (TBW) ratio; and malnutrition-inflammation score (MIS), which is a traditional nutritional parameter for dialysis patients. All patients were stratified into two groups according to their age: young (<65 years [n=54]) and elderly (≥65 years [n=28]).

Results

Total iron-binding capacity and HGS were significantly lower in elderly HD patients than in young HD patients (198.9±35.6 vs 221.4±52.1 mcg/dL; and 22.4±10.3 vs 36.4±23.2 kg, respectively) (P<0.05). Also, intracellular water and PhA measured by BIA were significantly lower (18.3±4.0 vs 20.3±4.2 L [P=0.043]; and 4.0±1.0 vs 4.9±1.2° [P=0.002], respectively), and ECW/TBW were higher in elderly HD patients (0.40±0.01 vs 0.39±0.01 [P=0.001]). ECW/TBW was positively associated with age (P<0.001) and the presence of diabetes (P<0.001) and was negatively associated with sex (P=0.001), albumin (P<0.001), urine volume (P=0.042), HGS (P<0.001), and PhA by BIA (P<0.001). MIS was negatively related to sex (P=0.001), albumin (P<0.001), HGS (P=0.001), and PhA (P<0.001) in HD patients. On multivariate analysis, older age (P=0.031), the presence of diabetes (P=0.035), and decreased PhA (P<0.001) were independent risk factors for increased ECW/TBW, representative of fluid overload status, whereas only decreased PhA (P=0.008) was a significant factor for MIS, representative of malnutrition status in these HD patients.

Conclusion

We found that fluid overload and malnutrition status were more common in elderly HD patients compared with young HD patients. PhA was a significant independent factor in fluid overload status and malnutrition in these HD patients. Thus, our results indicated that PhA assessed by BIA might be a clinically useful method for assessing nutritional and hydration status in elderly HD patients.

Fluid overload at start of continuous renal replacement therapy is associated with poorer clinical condition and outcome: a prospective observational study on the combined use of bioimpedance vector analysis and serum N-terminal pro-B-type natriuretic peptide measurement

Introduction

It is unclear whether the fluid status, as determined by bioimpedance vector analysis (BIVA) combined with serum N-terminal pro-B-type natriuretic peptides (NT-pro-BNP) measurement, is associated with treatment outcome among patients receiving continuous renal replacement therapy (CRRT). Our objective was to answer this question.

Methods

Patients who were in the intensive care units of a university teaching hospital and who required CRRT were screened for enrollment. For the enrolled patients, BIVA and serum NT-pro BNP measurement were performed just before the start of CRRT and 3 days afterward. According to the BIVA and NT-pro BNP measurement results, the patients were divided into four groups according to fluid status type: type 1, both normal; type 2, normal BIVA results and abnormal NT-pro BNP levels; type 3, abnormal BIVA results and normal NT-pro BNP levels; and type 4, both abnormal. The associations between fluid status and outcome were analyzed.

Results

Eighty-nine patients were enrolled, 58 were males, and the mean age was 49.0 ± 17.2 years. The mean score of Acute Physiology and Chronic Health Evaluation II (APACHE II) was 18.8 ± 8.6. The fluid status before CRRT start was as follows: type 1, 21.3% (19 out of 89); type 2, 16.9% (15 out of 89); type 3, 11.2% (10 out of 89); and type 4, 50.6% (45 out of 89). There were significant differences between fluid status types before starting CRRT on baseline values for APACHE II scores, serum creatinine, hemoglobin, platelet count, urine volume, and incidences of oliguria and acute kidney injury (P <0.05). There were significant differences between patients with different fluid status before CRRT start on hospital mortality—type 1, 26.3% (5 out of 19); type 2, 33.3% (5 out of 15); type 3, 40% (4 out of 10); and type 4, 64.4% (29 out of 45) (P = 0.019)—as well as renal function recovery rates: type 1, 57.1% (4 out of 7); type 2, 67.7% (6 out of 9); type 3, 50% (3 out of 6); and type 4, 23.7% (9 out of 38) (P = 0.051).

Conclusions

Fluid status abnormalities were common among patients receiving CRRT. Different types of fluid status distinguished by BIVA combined with serum NT-pro BNP measurements corresponded to different clinical conditions and treatment outcomes, which implies a value of this method for evaluation of fluid status among patients receiving CRRT.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-0871-3) contains supplementary material, which is available to authorized users.

Practical aspects of volume control in chronic kidney disease using whole body bioimpedance

BACKGROUND

Fluid status is an independent predictor of mortality in dialysis patients. Current methods of fluid assessment have several limitations.

SUMMARY

An ideal method should be cheap, portable, easy to perform without extensive training, reproducible and determines patients' excess or deficit of total body water. Bioimpedance analysis (BIA) fulfils many of these criteria and can give additional information on fat and lean tissue composition. The accuracy and precision of BIA has been shown to be equivalent to the 'gold standard' direct estimation techniques.

KEY MESSAGES

Although there remains some concern about its validity in dialysis patients, fluid overload determined by BIA has been shown to predict mortality. BIA-guided fluid management appears superior to conventional fluid management in achieving clinically important outcomes such as reduction in blood pressure, left ventricular mass index, and arterial stiffness. Accurate setting of dry weight might also help preserve residual renal function by limiting episodes of dehydration. Nevertheless, as with all new technologies, there are issues that still need to be resolved. This will be achieved only with larger prospective interventional studies to explore its specific roles in dialysis cohorts.

Predialysis NTproBNP predicts magnitude of extracellular volume overload in haemodialysis patients

INTRODUCTION

Increased natriuretic peptides are associated with increased cardiovascular and all-cause mortality for haemodialysis (HD) patients. However, debate continues whether these biomarkers are increased by extracellular water (ECW) excess and can be used to aid clinical assessment of volume status and help determine target weight.

METHODS

We measured N terminal probrain natriuretic peptide (NT-proBNP) predialysis in 375 stable haemodialysis outpatients with corresponding pre and postdialysis multifrequency bioelectrical impedance assessments (MFBIA) of (ECW)/total body water (TBW).

RESULTS

Median age 64 (51-75), 63.9% male, 42.9% diabetic, 43.2% Caucasoid, 14.4% with a history of myocardial infarction, 8.4% coronary artery bypass surgery, dialysis vintage 28.2 (12.3-55.5) months. Median predialysis NT-proBNP 283 (123-989) pmol/l, and predialysis ECW/TBW ratio 0.397 ± 0.029. On multivariate analysis, predialysis log NT-proBNP was associated with predialysis systolic blood pressure (β 0.007, p = 0.000), weight (β -0.008, p = 0.001), valvular heart disease (β 0.342, p = 0.015, ECW/TBW (β 1.3, p = 0.019) and log CRP (β 0.145, p = 0.037). Dividing patients into NTproBNP quartiles, %ECW/TBW and relative ECW overhydration were significantly greater for the highest quartile vs. lowest (40.5 ± 4.1 vs. 39.0 ± 1.1, and 1.51 ± 1.24 vs. 0.61 ± 0.69 l, respectively, p < 0.001).

CONCLUSION

In this study, predialysis NTproBNP values were associated with direct assessments of the extracellular volume excess measured by MFBIA and systolic arterial blood pressure. This suggests that predialysis NTproBNP values can potentially be used to aid clinical assessment of volume status in dialysis patients to determine target weight.

Effect of pioglitazone on sciatic nerve ischemia/reperfusion injury in rats

OBJECTIVE

Evaluation of the effect of pioglitazone on sciatic nerve ischemia/reperfusion (I/R) injury in rat.

METHOD

Sixty rats were divided into 10 groups (n = 6). Treatment groups received 15 mg/kg pioglitazone intraperitoneally 1 h before induction of I/R by clamping the right common iliac and femoral arteries for 3 h. After certain time intervals of reperfusion (0 h, 3 h, 1, 4, and 7 days), the function of the hind limb was assessed using behavioral scores based on gait, grasp, paw position, and pinch sensitivity. The sciatic nerve was removed for light microscopy studies and graded for ischemic fiber degeneration (IFD) and edema. Plasma malondialdehyde (MDA) level was measured as an indicator of lipid peroxidation at the end of reperfusion intervals.

RESULT

Behavioral scores were improved in the pioglitazone groups just on the 4th and 7th days of reperfusion (p < 0.05). Comparison of the pioglitazone with the control groups showed significant differences in edema at 4 and 7 days. Although IFD decreased in the pioglitazone group at 7 days of reperfusion, it was not statistically significant. In addition, the MDA level was significantly lower in pioglitazone-treated groups.

CONCLUSION

Our results show the protective effect of pioglitazone on sciatic nerve I/R injury.