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

Prevention of Intradialytic Hypotension in Hemodialysis Patients: Current Challenges and Future Prospects

Intradialytic hypotension, defined as rapid decrease in systolic blood pressure of greater than or equal to 20 mmHg or in mean arterial pressure of greater than or equal to 10 mmHg that results in end-organ ischemia and requires countermeasures such as ultrafiltration reduction or saline infusion to increase blood pressure to improve patient's symptoms, is a known complication of hemodialysis and is associated with several potential adverse outcomes. Its pathogenesis is complex and involves both patient-related factors such as age and comorbidities, as well as factors related to the dialysis prescription itself. Key factors include the need for volume removal during hemodialysis and a suboptimal vascular response which compromises the ability to compensate for acute intravascular volume loss. Inadequate vascular refill, incorrect assessment or unaccounted changes of target weight, acute illnesses and medication interference are further potential contributors. Intradialytic hypotension can lead to compromised tissue perfusion and end-organ damage, both acutely and over time, resulting in repetitive injuries. To address these problems, a careful assessment of subjective symptoms, minimizing interdialytic weight gains, individualizing dialysis prescription and adjusting the dialysis procedure based on patients' risk factors can mitigate negative outcomes.

Water - A life-giving toxin - A nephrological oxymoron. Health consequences of water and sodium balance disorders. A review article

BACKGROUND

This article aims to reveal misconceptions about methods of assessment of hydration status and impact of the water disorders on the progression of kidney disease or renal dysfunction.

MATERIALS AND METHODS

The PubMed database was searched for reviews, meta-analyses and original articles on hydration, volume depletion, fluid overload and diagnostic methods of hydration status, which were published in English.

RESULTS

Based on the results of available literature the relationship between the amount of fluid consumed, and the rate of progression of chronic kidney disease, autosomal dominant polycystic kidney disease, and kidney stones disease was discussed. Selected aspects of the assessment of the hydration level in clinical practice based on physical examination, laboratory tests, and imaging are presented. The subject of in-hospital fluid therapy is discussed. Based on available randomized studies, an attempt was made to assess, which fluids should be selected for intravenous treatment.

CONCLUSIONS

There is some evidence for the beneficial effect of increased water intake in preventing recurrent cystitis and kidney stones, but there are still no convincing data for chronic kidney disease and autosomal dominant polycystic kidney disease. Further studies are needed to clarify the aforementioned issues and establish a reliable way to assess the volemia and perform suitable fluid therapy.

B-type natriuretic peptide levels and volume status in twice-weekly hemodialysis patients

Background

Twice-weekly hemodialysis (HD) could be regarded as an important part of incremental hemodialysis, volume status of this treatment model remains to be elucidated.

Methods

Patients undergoing regular twice-weekly or thrice-weekly hemodialysis in our unit on June 2015 were enrolled into the cohort study with an average of 2.02 years follow-up. Volume status of the subjects was evaluated by clinical characteristics, plasma B-type natriuretic peptide (BNP) levels and bioimpedance assessments with body composition monitor (BCM). Cox proportional hazards models and Kaplan–Meier analysis were used to compare patient survival between the two groups.

Results

Compared with patients on thrice-weekly HD, twice-weekly HD patients had significantly higher log-transformed BNP levels (2.54 ± 0.41 vs. 2.33 ± 0.49 pg/ml, p = 0.010). Overhydration (OH) and the ratio of overhydration to extracellular water (OH/ECW) in twice-weekly HD group were significantly higher than that of thrice-weekly HD (OH, 2.54 ± 1.42 vs. 1.88 ± 1.46, p = 0.033; OH/ECW, 0.17 ± 0.07 vs. 0.12 ± 0.08, p = 0.015). However, subgroup analysis of patients within 6 years HD vintage indicated that the two groups had similar hydration status. Multivariate Cox regression analysis showed that log-transformed BNP levels, serum albumin and diabetes status were predictors of mortality in hemodialysis patients. Kaplan–Meier survival analysis indicated that patients with BNP levels higher than 500 pg/ml had significantly worse survival compared with those with lower BNP levels (p = 0.014).

Conclusions

Twice-weekly hemodialysis patients had worse volume status than that of thrice-weekly HD patients especially for those with long-term dialysis vintage, BNP level was a powerful predictor of mortality in HD patients.

Lung Ultrasound: A "Biomarker" for Fluid Overload?

Fluid overload is associated with poor outcomes in patients with acute kidney injury as well as end-stage kidney disease. Lung ultrasound (LUS) has been used in many different settings and specialties including the emergency department, intensive care unit, trauma, cardiology, and nephrology. Although LUS has been a valuable tool in assessing pulmonary congestion, LUS findings may not always be pathognomonic for pulmonary congestion. Furthermore, the feasibility of doing an extensive LUS examination as has been done in research studies may be hard to implement within the clinical setting. This review will go over the use of LUS to evaluate for fluid overload, compare LUS with other markers of fluid overload, review limitations of LUS, and suggest potential future directions in the use of LUS in nephrology.

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.

Range of plasma brain natriuretic peptide (BNP) levels in hemodialysis patients at a high risk of 1-year mortality and their relationship with the nutritional status: a retrospective cohort study in one institute

Background

Brain natriuretic peptide (BNP) levels are used as a marker of heart failure, which is the leading cause of morbidity and mortality in dialysis patients. BNP levels increase as renal function declines. The range of BNP levels associated with satisfactory longevity in dialysis patients currently remains unknown.

Methods

In total, 660 patients receiving maintenance hemodialysis were enrolled. BNP levels were measured at the end of the year and in a follow-up to assess 1-year mortality between 2008 and 2012. Patients were divided into six groups according to BNP levels: < 50 (reference), 50 to < 100, 100 to < 300, 300 to < 500, 500 to < 1000, and ≥ 1000 pg/mL. One-year mortality at each BNP level was analyzed using Cox’s proportional hazards model after adjustments for confounding factors.

Results

During the follow-up period, 78 (11.8%) deaths were recorded. After adjustments for confounding factors, such as gender, age, hemodialysis vintage, and primary disease, the risk of 1-year mortality was significantly high with BNP levels of 500 to < 1000 (hazard ratio [HR] 3.010; 95% confidence interval [CI] 1.065–10.729; P = 0.037) and more than 1000 pg/mL (HR 5.291; 95%CI 2.014–18.170; P = 0.0003). After adjustments for Kt/V, the risk of 1-year mortality was also significantly high with BNP levels of 500 to < 1000 (HR 3.045; 95%CI 1.065–10.929; P = 0.037) and more than 1000 pg/mL (HR 5.221; 95%CI 1.943–18.165; P = 0.0006). Following further adjustments for nutritional factors, such as albumin levels, total cholesterol levels, the normalized protein catabolic rate (nPCR), body mass index (BMI), and percent creatinine generation rate (%CGR), BNP levels of 500–1000 (HR 1.990; 95%CI 0.639–7.570; P = 0.244), and more than 1000 pg/mL (HR 2.100; 95%CI 0.663–8.105; P = 0.213) were no longer risk factors.

Conclusion

In dialysis patients, a BNP level ≥ 500 pg/mL is a risk factor for 1-year mortality. The risk associated with high BNP levels is reduced by nutritional factors, which suggests a relationship between high BNP levels and the nutritional status. In conclusion, efforts are needed to maintain BNP levels at lower than 500 pg/mL and improve the nutritional status.

Ultrafiltration volume by once-weekly hemodialysis is a predictor of technique survival of combination therapy with peritoneal dialysis and hemodialysis

Overhydration is a major cause of technique failure of peritoneal dialysis (PD). Hence, we investigated the impact of ultrafiltration (UF) volume by once-weekly hemodialysis (HD), excess volume beyond their dry weight, on technique survival of PD and HD combination therapy (PD+HD). Forty-six anuric PD+HD patients were divided into three groups according to baseline UF volume by HD: low-UF (<mean - 1SD), middle-UF (≥mean - 1SD and <mean + 1SD), and high-UF (≥mean + 1SD). High-UF group showed larger extracellular water normalized to height (P = .038) and longer HD sessions (P < .001) compared with low-UF group, whereas low-UF group was older than middle-UF group (P = .001). Technique survival rate was significantly lower in high-UF group than in low and middle-UF groups (P < .001), and the rates at 44 months were 80%, 90%, 20% in low, middle, and high-UF groups, respectively. Chronic overhydration was the leading cause of technique failure for all. This study suggests that fluid overload remains a major cause of technique failure of PD even after once-weekly HD is added.

[Natriuretic peptides in dialysis: From theory to clinical practice]

Cardiologists and emergency-wards physicians are used to check natriuretic peptides serum level, mainly B-type natriuretic peptide and N-terminal pro-Brain natriuretic peptide for acute cardiac failure diagnosis. Due to their accumulation in chronic kidney disease and their elimination by dialysis, natriuretic peptides sampling remains debatable in chronic kidney disease patients. In dialysis patients, high natriuretic peptides values are associated with mortality, left ventricular hypertrophy and cardiac failure. However, a single value cannot provide a reliable diagnosis. Our clinical practice is as follows: First, we prefer B-type natriuretic peptide to N-terminal pro-Brain natriuretic peptide because of its shorter half-life, with less impact of renal function and dialysis, making its interpretation easier in case of advanced chronic kidney disease or in dialysis patients; second, we define a reference value of B-type natriuretic peptide at dry weight from serial measurements; third, the B-type natriuretic peptide changes are interpreted according to extracellular fluid and cardiac status, but also from the arteriovenous fistula blood flow. In stable dialysis patients, B-type natriuretic peptide is sampled monthly and weekly in unstable patients. We illustrate our experience using clinical cases of overhydration, new cardiac disease onset, hypovolemia and arteriovenous fistula with high blood flow. Longitudinal follow-up of B-type natriuretic peptide is an important advance in dialysis patients in order to detect and treat extracellular fluid variations and cardiac disease status early, both important factors associated with hard outcomes.

Weight-Based Assessment of Fluid Overload in Patients with Acute Kidney Injury

INTRODUCTION

Acute kidney injury (AKI) with fluid overload is associated with poor outcomes. While percentage fluid overload (PFO) using intake/output charts (PFOi/o) has been validated as a marker of overload, accurate PFOi/o measurements may not be possible in a general ward. We propose an alternative weight-based PFO calculation: PFOw = [(maximum weight - baseline weight) ÷ baseline weight] × 100%.

METHODS

This is a prospective, observational pilot study on general ward inpatients with AKI who were referred for nephrology consult. PFOw was compared with PFOi/o, and both were evaluated for associations with dialysis requirement, AKI stage 2 or 3, and 90-day mortality.

RESULTS

Fifty-eight patients with a median age of 67.5 years (interquartile range 18.0) were recruited. Of which, 33 (56.9%) were males and 41 (70.7%) had preexisting CKD 3 or higher. We found no correlation between PFOi/o and PFOw (R2 = 0.015, p = 0.531). A higher PFOw was observed in AKI stage 2 or 3 (p = 0.005) and in patients requiring dialysis (p = 0.001). On multivariate analysis, each percentage increase in PFOw was associated with increased odds of AKI stage 2 or 3 (odds ratio 1.37 [95% CI 1.05-1.78], p = 0.020) and dialysis need (odds ratio 1.69 [95% CI 1.20-2.39], p = 0.003). Twenty-nine patients had complete quantitative data to calculate PFOi/o. Multivariate analysis of these 29 patients showed that PFOw correlated with AKI stage 2 or 3 and dialysis requirement, while PFOi/o had no correlation with these events. The area under the curve receiver operating characteristics of PFOw was 0.706 for AKI stage 2 or 3 and 0.819 for AKI requiring dialysis. The optimal PFOw cutoff was determined at ≥1%. Three deaths occurred within 90 days, and all had PFOw ≥ 1%, although the log-rank test did not achieve statistical significance (p = 0.050).

CONCLUSION

The proposed PFOw is a potential prognostic indicator for general ward patients with AKI. PFOw ≥ 1% is associated with poor renal outcomes.

Reinterpreting Renal Hemodynamics: The Importance of Venous Congestion and Effective Organ Perfusion in Acute Kidney Injury

The significance of effective renal perfusion is relatively underemphasized in the current literature. From a renal standpoint, besides optimizing cardiac output, renal perfusion should be maximized as well. Among the several additional variables of the critically ill, such as intra-abdominal pressure, the presence of venous congestion and elevated central venous pressures, airway pressures generated by mechanical ventilation do affect net renal perfusion. These forces represent both a potential danger and an ongoing opportunity to improve renal outcomes in the critically ill and an opportunity to move beyond the simplified viewpoint of optimizing volume status. Therefore, to optimize nephron-protective therapies, nephrologists and intensive care physicians should be familiar with the concept of net renal perfusion pressure. This review appraises the background literature on renal perfusion pressure, including the initial animal data and historical human studies up to the most current developments in the field, exploring potential avenues to assess and improve renal blood supply.

The association of overhydration with megafistulas in hemodialysis patients

Objectives: Diffuse enlargements of arteriovenous dialysis fistulas customarily attributed to either excessive arterial inflow or central outflow stenosis. The relationship between volume status and clinically enlarged (arteriovenous) fistula (CEF) formation in end-stage renal disease (ESRD) patients is not well understood.

Methods: We assessed the pre-dialysis bioimpedance spectroscopy-measured percentage of overhydration (OH%) in 13 prevalent dialysis patients with CEF development and negative angiography and compared the results with those of 52 control dialysis patients (CONTR). All patients were prevalent ESRD patients receiving thrice-weekly maintenance hemodiafiltration at an academic outpatient dialysis unit.

Results: 10/13 CEF patients had OH% ≥15% as compared to 20/52 control patients (Chi square p: .02). The degree of OH% was 20.2 ± 7.4% among the CEF vs. 14.4 ± 7.1% in the control group (Student’s t-test p: .01), representing 4.2 ± 3.2 vs. 2.8 ± 1.6 L of excess fluid pre-dialysis (p: .03). Patients with CEF development took an average of 1.7 ± 1.4 vs. 0.8 ± 0.8 (p: .002) antihypertensive medications compared to the CONTR patients, yet their blood pressure was higher: 156/91 vs. 141/78 mmHg (systolic/diastolic p: .03<.0001). We found no difference in fistula vintage, body mass index, age, diabetes status, or diuretic use. The odds ratio of having a CEF in patients with ≥15% OH status was 5.3 (95% CI: 1.3–21.7; p: .01), the Number Needed to Harm with overhydration was 4.

Conclusions: There is an association between bioimpedance spectroscopy-measured overhydrated clinical state and the presence of CEF; either as an increased volume capacitance or as a potential cause.

Soluble CD146 and B-type natriuretic peptide dissect overhydration into functional components of prognostic relevance in haemodialysis patients

Background

Accurate volume status evaluation and differentiation of cardiac and non-cardiac components of overhydration (OH) are fundaments of optimal haemodialysis (HD) management.

Methods

This study, by combining bioimpedance measurements, cardiovascular biomarkers and echocardiography, aimed at dissecting OH into its major functional components, and prospectively tested the association between cardiac and non-cardiac components of OH with mortality. In the first part, we validated soluble CD146 (sCD146) as a non-cardiac biomarker of systemic congestion in a cohort of 30 HD patients. In the second part, we performed a prospective 1-year follow-up study in an independent cohort of 144 HD patients.

Results

sCD146 incrementally increased after the short and long intervals after HD (+53 ng/mL, P = 0.006 and  +91 ng/mL, P < 0.001), correlated with OH as determined by bioimpedance and well-diagnosed OH (area under the receiver operating characteristics curve 0.72, P = 0.005). The prevalence of OH was lower for low-sCD146 and low-BNP patients (B-type natriuretic peptide, 29%) compared with subjects with either one or both biomarkers elevated (65-74%, P < 0.001). Notably, most low-BNP but high-sCD146 subjects were overhydrated. Systolic dysfunction was 2- to 3-fold more prevalent among high-BNP compared with low-BNP patients (44-68% versus 21-23%, chi-square P < 0.001), regardless of sCD146. One-year all-cause mortality was markedly higher in patients with high-BNP (P = 0.001) but not with high-sCD146. In multivariate analysis, systolic dysfunction and BNP, but not OH, were associated with lower survival.

Conclusions

The combination of BNP and sCD146 dissects OH into functional components of prognostic value. OH in HD patients is associated with higher mortality only if resulting from cardiac dysfunction.

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.

Acute Kidney Injury in Subjects With Chronic Kidney Disease Undergoing Total Joint Arthroplasty

BACKGROUND

Chronic kidney disease (CKD) has been associated with higher incidence of complications after total joint arthroplasty (TJA) but the incidence, risk factors and outcomes of acute kidney injury (AKI) in this setting remains insufficiently understood.

METHODS

We assessed the impact of baseline CKD on the risk of developing AKI after TJA performed between 1/2012 and 12/2016 in a single-center, retrospective cohort study. CKD was defined by estimated glomerular filtration rate <60 mL/min/1.73 m² on 2 separate occasions within 3 months prior TJA. AKI was defined using a modified Kidney Disease: Improving Global Outcomes criteria based on serum creatinine (sCr) only to assess the severity of AKI. Complete AKI recovery was defined as the lowest post-AKI sCr within 20% of pre-AKI sCr values and partial recovery if within 30%, all within 90 days after TJA.

RESULTS

Twenty-four percent of the 1,212 subjects undergoing TJA had pre-existing CKD. The overall incidence of AKI in the CKD subjects was 30%; of these, 55% had stage-1 AKI, 1% had stage-2 AKI and 44% had stage-3 AKI. AKI was more common in African Americans, those with diabetes or heart failure, requiring perioperative transfusions or receiving diuretics before surgery. While 82% of the AKI subjects achieved complete recovery of kidney function, 4% had only partial recovery and 14% did not reach a post-AKI sCr level within 30% of pre-AKI values. The incidence (P < 0.001) but not the severity (P = 0.202) of AKI correlated with stages of baseline CKD.

CONCLUSIONS

The presence of CKD was associated with a high incidence of AKI after TJA. In these subjects, more than half the cases of AKI were of mild degree and had a favorable outcome. However, 18% of them did not have complete recovery of kidney function. Stages of baseline CKD were associated with increased incidence but not severity of AKI after TJA.

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.

The association of overhydration with chronic inflammation in chronic maintenance hemodiafiltration patients

INTRODUCTION

Achieving euvolemia is one of the major challenges when treating end-stage renal disease (ESRD) patients receiving maintenance renal replacement therapy. Fluid overload is recognized as an independent predictor of mortality in ESRD, but its association with chronic inflammation is less well explored especially in chronic maintenance hemodiafiltration.

METHODS

We performed a cross-sectional study of 87 prevalent ESRD patients receiving chronic maintenance hemodiafiltration (vintage 66.5 ± 57.1 months) with bioimpedance analysis to characterize the degree of percent overhydration (OH%). We also compared the levels of inflammatory markers, including C-reactive protein (CRP), serum albumin, neutrophil/lymphocyte ratio (NLR), and hemoglobin red cell distribution width (RDW) for the overhydrated (OH% ≥ 15%) versus euvolemic (OH% < 15%) groups. Linear regression analysis was performed to explore relationships between the degree of OH and inflammatory indicators.

FINDINGS

The cohort represented an all-European population with a mean age of 60.9 ± 14.7 years and prevalence of diabetes mellitus of 27%. The entire cohort's OH% was 14.9% ± 5.1% (range -11.1% to 39.0%); further, the <15% group of patients' OH% was 8.0% ± 8.5% versus 20.9% ± 5.1% in the OH% ≥ 15% group (P < 0.0001). Forty-seven patients (53%) were overhydrated by traditional criteria (OH% ≥15%) and 20 patients (23%) were severely overhydrated (OH% > 20%). The euvolemic (OH% <15%) versus severely overhydrated (OH% > 20%) groups had significant differences in markers of inflammation: CRP (9.8 ± 10.6 vs. 21.5 ± 21.6 mg/L, P < 0.006), serum albumin (37.6 ± 02.9 vs. 34.5 ± 5.3 g/L, P < 0.004), and NLR (3.06 ± 1.25 vs. 3.92 ± 2.04; P < 0.004). On linear regression, significant correlations were found between OH% and CRP (r = 0.2899, P < 0.006), serum albumin (r = -0.3670; P < 0.0005), RDW (r = 0.2992; P < 0.005), and NLR (r = 0.2900; P < 0.006).

DISCUSSION

In a prevalent hemodiafiltration cohort, OH was common and correlated with several inflammatory markers.

Serum nitric oxide level correlates with serum brain natriuretic peptide and whole blood viscosity in hemodialysis patients

BACKGROUND

Nitric oxide (NO) is tonically synthesized by the vascular endothelium and known as a marker of vasodilatation and blood flow. As NO has a critical role in hemodynamics, NO may be associated with other hemodynamics-related factors including atrial natriuretic peptide (ANP), B-type natriuretic peptide (BNP) and whole blood viscosity (WBV). It has been reported that serum NO level increased in patients undergoing hemodialysis. However, there are few reports about the relationship between NO and hemodynamic parameters in hemodialysis patients.

OBJECTIVE

We investigated the associations between serum levels of NO and other hemodynamics-related factors such as ANP, BNP and WBV in patients with hemodialysis.

METHODS

NO, ANP, and BNP levels before hemodialysis were measured using ELISA method. We measured WBV in pre- and post-dialysis.

RESULTS

Mean serum levels of NO, ANP, and BNP were 13.97 ± 10.34 μg/mL, 198.85 ± 61.56 pg/mL, and 1233.32 ± 280.81 pg/mL, respectively in patients with hemodialysis. The mean WBV values at shear rates of 1, 5, and 300 s^-1 for pre-dialyses were 168.5 ± 62.5, 76.9 ± 20.6, and 33.3 ± 3.8 mP, respectively. Serum NO level was positively correlated with WBV at shear rates of 1, 5, and 300 s^-1 at pre- and post-hemodialysis. There is a correlation between serum nitrite levels and the change of SBV during hemodialysis. Serum nitrite levels correlated with the serum BNP levels. ANP levels have a negative correlation with pre-dialytic WBV. However, BNP levels did not correlate with WBV during hemodialysis.

CONCLUSIONS

WBV is linked to an imbalance in serum vasoactive substances in hemodialysis patients and can cause significant hemodynamic disturbance.

Successful Practice Transitioning Between Hemodialysis and Hemodiafiltration in Outpatient Units: Ten Key Issues for Physicians to Remember

Hemodiafiltration (HDF) during chronic renal replacement therapy (RRT) is a relatively new practice phenomenon, emerging over the last two decades. While the technological platforms utilized during chronic RRT are in many cases similar or effectively identical to conventional hemodialysis (HD), significant differences may emerge in daily practice. Several authors of this review moved practice site between the United States and the European Union and transitioned from an HD-based practice to predominantly HDF-practicing networks. In doing so, we became keenly aware of the potential pitfalls nephrologists may be facing during such transitions. This brief review is intended to provide a succinct overview of several practical concerns and complications nephrologists may encounter in daily practice of end-stage renal disease care, including but not limited to management of electrolytes, renal anemia and treatment goals and settings during HDF.

Peritoneal dialysis: The unique features by compartmental delivery of renal replacement therapy

Despite decades of research, the clinical efficacy of peritoneal dialysis (PD) remains enigmatic. We may wonder why the modality fail in some patients but perhaps the more proper question would be, why it works in so many? We know that the contribution of residual renal function (RRF), more so than in hemodialysis, is critically important to the well-being of many of the patients. Unique features of the modality include the relatively low volume of dialysate fluid needed to provide effective uremic control and the disproportionate tendency for both hypokalemia and hypoalbuminemia, when compared to hemodialysis. It is currently believed that most uremic toxins are generated on the interface of human and bacterial structures in the gastrointestinal tract, the intestinal biota. PD offers disproportionate removal of these toxins upon "first-pass", i.e., via PD fluid exchanges before reaching the systemic circulation beyond the gastrointestinal compartment. Studies examining the net removal gradient of protein-bound uremic toxins during PD are scarce, whereas RRF receives considerably more attention without effective interventions being developed to preserve it. We propose an alternative view on PD, emphasizing the modality's compartmental nature, both for its benefits and the limitations.

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.

Outcomes of diuretic use in pre-dialysis CKD patients with moderate renal deterioration attending tertiary care referral center

INTRODUCTION

Diuretic therapy has been the mainstay of treatment in chronic kidney disease (CKD) patients, primarily for hypertension and fluid overload. Apart from their beneficial effects, diuretic use is associated with adverse renal outcomes. The current study is aimed to determine the outcomes of diuretic therapy.

METHODOLOGY

A prospective observational study was conducted by inviting pre-dialysis CKD patients. Fluid overload was assessed by Bioimpedance analysis (BIA).

RESULTS

A total 312 patients (mean age 64.5 ± 6.43) were enrolled. Among 144 (46.1%) diuretic users, furosemide and hydrochlorothiazide (HCTZ) were prescribed in 69 (48%) and 39 (27%) patients, respectively, while 36 (25%) were prescribed with combination therapy (furosemide plus HCTZ). Changes in BP, fluid compartments, eGFR decline and progression to RRT were assessed over a follow-up period of 1 year. Maximum BP control was observed with combination therapy (-19.3 mmHg, p < 0.001) followed by furosemide [-10.6 mmHg with 80 mg thrice daily (p < 0.001)], -9.3 mmHg with 40-60 mg (p < 0.001) and -5.9 mmHg with 20-40 mg (p = 0.02) while HCTZ offered minimal SBP control [-3.7 mmHg with 12.5-25 mg (p = 0.04)]. Decline in extracellular water (ECW) ranged from -1.5 L(p = 0.01) with thiazide diuretics to -3.8 L(p < 0.001) with combination diuretics. Decline in eGFR was maximum (-3.4 ml/min/1.73 m², p = 0.01) with combination diuretics and least with thiazide diuretics (-1.6 ml/min/1.73 m², p = 0.04). Progression to RRT was observed in 36 patients.

CONCLUSION

It is cautiously suggested to discourage the use of diuretic combination therapy and high doses of single diuretic therapy. Prescribing of diuretics should be done by keeping in view benefit versus harm for each patient.

Volume-related weight gain as an independent indication for renal replacement therapy in the intensive care units

Attempts to identify specific therapies to reverse acute kidney injury (AKI) have been unsuccessful in the past; only modifying risk profile or addressing the underlying disease processes leading to AKI proved efficacious. The current thinking on recognizing AKI is compromised by a "kidney function percent-centered" viewpoint, a paradigm further reinforced by the emergence of serum creatinine-based automated glomerular filtration reporting over the last two decades. Such thinking is, however, grossly corrupted for AKI and poorly applicable in critically ill patients in general. Conventional indications for renal replacement therapy (RRT) may have limited applicability in critically ill patients and there has been a relative lack of progress on RRT modalities in these patients. AKI in critically ill patients is a highly complex syndrome and it may be counterproductive to produce complex clinical practice guidelines, which are labor and resource-intensive to maintain, difficult to memorize or may not be immediately available in all settings all over the world. Additionally, despite attempts to develop reliable and reproducible biomarkers to replace serum creatinine as a guide to therapy such biomarkers failed to materialize. Under such circumstances, there is an ongoing need to reassess the practical value of simple measures, such as volume-related weight gain (VRWG) and urine output, both for prognostic markers and clinical indicators for the need for RRT. This current paper reviews the practical utility of VRWG as an independent indication for RRT in face of reduced urine output and hemodynamic instability.

Brain Natriuretic Peptide and Body Fluid Composition in Patients with Chronic Kidney Disease: A Cross-Sectional Study to Evaluate the Relationship between Volume Overload and Malnutrition

BACKGROUND/AIM

Fluid volume overload occurs in chronic kidney disease (CKD), leading to the compensatory release of natriuretic peptides. However, the elevated cardiac peptides may also be associated with malnutrition as well as volume overload.

METHODS

Body fluid composition was measured in 147 patients with CKD between 2009 and 2015, and its relationship to brain natriuretic peptide (BNP) levels was examined. Body fluid composition was separated into three components: (a) a water-free mass consisting of muscle, fat, and minerals; (b) intracellular water (ICW) content, and (c) extracellular water (ECW) content. Excess fluid mass was calculated using Chamney's formula.

RESULTS

The measured BNP levels in the tertile groups were 10.9 ± 5.4, 36.3 ± 12.5, and 393 ± 542 pg/ml, respectively. Patients in a higher log-transformed BNP level tertile were more likely to be older, to have a higher frequency of cardiac comorbidities, pulse pressure, C-reactive protein levels, and proteinuria, and to have lower serum sodium, kidney function, and serum albumin (p < 0.05). In body fluid composition, decreased body mass was significantly associated with the ECW-to-ICW ratio in relation to the downward ICW slope (r = -0.235, p = 0.004) and was strongly correlated with excess fluid mass (r = -0.701, p < 0.001). The ECW-to-ICW ratio and excess fluid mass was independently associated with the BNP levels.

CONCLUSION

Fluid volume imbalance between intra- and extracellular water regulated by decreased cell mass was independently associated with BNP levels, which may explain the reserve capacity for fluid accumulation in patients with CKD.

The role of natriuretic peptides in volume assessment and mortality prediction in Haemodialysis patients

Background

Maintaining optimal fluid balance is essential in haemodialysis (HD) patients but clinical evaluation remains problematic. Other technologies such as bioimpedance are emerging as valuable adjuncts. This study was undertaken to explore the potential utility of the natriuretic peptides – atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) in the assessment of fluid status and cardiovascular risk in this setting.

Methods

This was a cross-sectional study carried out in an unselected cohort of 170 prevalent HD patients. Volume status was assessed by clinical parameters – the presence or absence of peripheral oedema, raised jugular venous pressure and basal lung crepitations; by extracellular fluid volume (ECFV) status determined by whole body bioimpedance; and by serum levels of BNP and ANP (pre- and post –dialysis). The relationships of ANP and BNP levels to clinical and bioimpedance parameters of volume status was determined. Patients were followed up for 5 years to assess the relationship of natriuretic peptide levels to mortality.

Results

Bioimpedance estimates of ECFV expansion (>105 % of ideal ECFV) was present in 52 % of patients pre-dialysis. A significant proportion (21 %) of pre-dialysis patients had a depleted ECFV (<95 % of ideal ECFV) pre-dialysis. The situation was reversed post-dialysis. A raised JVP >3 cm was the most reliable clinical sign of ECFV expansion inferred from bioimpedance measurements and natriuretic peptide levels. The vast majority of patients with this sign also had lung crepitations or peripheral oedema or both. BNP was a stronger predictor of ECFV expansion than either pre- or post-dialysis ANP. BNP was also a stronger predictor of five-year survival.

Conclusion

Serum levels of BNP have a strong relationship to both volume status and survival in HD patients. We found no clear role for measurement of ANP, though changes in blood levels may be a sensitive indicator of acute changes in volume status. Whether monitoring levels of these peptides has a role in the management of volume status and cardiovascular risk requires further study.

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.

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.