Is there a role for N-terminal probrain-type natriuretic peptide in determining volume status in haemodialysis patients?

Extracellular water/total body water ratio as predictor of mortality in hemodialysis patients

BACKGROUND

Overhydration is a predictor of mortality in hemodialysis (HD) patients. Bioimpedance spectroscopy (BIS) is used to determine the body composition. Extracellular Water/Total Body Water (ECW/TBW) ratio has been proposed to predict mortality.

METHODS

Multicenter, prospective, observational, proof-of-concept study to estimate the impact of ECW/TBW in global and cardiovascular mortality and the relationship with cardiovascular biomarkers. The study included 60 patients (mean age, 71.8 ± 11.4 years; mean time on HD, 52.3 ± 30.8 months) with a median follow-up of 30.5 months (IQ range, 17.2-34 months).

RESULTS

Post-dialysis ECW/TBW was directly associated with NT-proBNP and cTnT. During the study 28 patients died, most of them (43%) due to cardiovascular events. Compared to the survivors, these subjects had a higher post-dialysis ECW/TBW ratio (p = 0.006), while for cardiovascular mortality the only significant difference was a higher pre-dialysis ECW/TBW. The ability of post-dialysis ECW/TBW ratio to predict all-cause mortality had an area under the ROC curve (AUC) of 0.71 (CI 95%, 0.57-0.81; p = 0.002), with a cutoff point of 0.5023. For cardiovascular mortality the AUC was 0.66 (CI 95%, 0.52-0.77; p = 0.045), with a cutoff point of 0.4713.

CONCLUSIONS

The post-dialysis ECW/TBW ratio measured by BIS can be a predictor of all-cause and cardiovascular mortality.

The Influence of Perioperative Fluid Therapy on N-terminal-pro-brain Natriuretic Peptide and the Association With Heart and Lung Complications in Patients Undergoing Colorectal Surgery: Secondary Results of a Clinical Randomized Assessor-blinded Multicenter Trial

OBJECTIVE

To investigate the influence of intravenous (iv) fluid volumes on the secretion of N-terminal-pro-brain natriuretic peptide (NT-Pro-BNP) in colorectal surgical patients and its association with cardiopulmonary complications (CPC). In addition, to examine if preoperative NT-Pro-BNP can predict the risk for postoperative CPC.

METHODS

Blood samples from patients enrolled in a previously published clinical randomized assessor-blinded multicenter trial were analyzed. Included were adult patients undergoing elective colorectal surgery with the American-Society-of-Anesthesiologists-scores of 1-3. Samples from 135 patients were available for analysis. Patients were allocated to either a restrictive (R-group) or a standard (S-group) iv-fluid regimen, commencing preoperatively and continuing until discharge. Blood was sampled every morning until the fourth postoperative day. The primary outcome for this study was NT-Pro-BNP changes and its association with fluid therapy and CPC.

RESULTS

The S-group received more iv-fluid than the R-group on the day-of-surgery [milliliter, median (range) 6485 (4401-10750) vs 3730 (2250-8510); P < 0.001] and on the first postoperative day. NT-Pro-BNP was elevated in the S-group compared with the R-group on all postoperative days [area under the curve: median (interquartile range) pg/mL: 3285 (1697-6179) vs 1290 (758-3719); P < 0.001 and in patients developing CPC vs no-CPC (area under the curve), median (interquartile range): 5196 (1823-9061) vs 1934 (831-5301); P = 0.005]. NT-pro-BNP increased with increasing fluid volumes all days (P < 0.003). Preoperative NT-Pro-BNP predicted CPC [odds ratio (confidence interval): 1.573 (0.973-2.541), P = 0.032; positive predictive value = 0.257, negative predictive value = 0.929].

CONCLUSIONS

NT-pro-BNP increases with iv-fluid volumes given to colorectal surgical patients, and the level of NT-Pro-BNP is associated with CPC. Preoperative NT-Pro-BNP is predictive for CPC, but the diagnostic value is low.Clinicaltrials.gov NCT03537989.

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.

Is N-terminal pro-brain natriuretic peptide a reliable marker for body fluid status in children with chronic kidney disease?

INTRODUCTION

Brain natriuretic peptides, released in response to left ventricular stress, have a strong prognostic value in dialysis patients. However, their role in detecting abnormalities of fluid status is under debate; the relationship between volume status and brain natriuretic peptides (BNPs) differs among various studies. The aim of our study was to evaluate the clinical utility of N-terminal proBNP in the assessment of fluid status and cardiovascular risk in this setting.

MATERIAL AND METHODS

The study included 65 children: 10 pre-dialysis, 13 hemodialysis, 12 peritoneal dialysis patients and 30 healthy controls. Volume status was determined by multifrequency bioimpedance and NT-pro-BNP, as well as echocardiography to estimate the left ventricle structure and function.

RESULTS

The median log NT-proBNP values of hemodialysis and peritoneal dialysis patients were 3.66 (2.05-4.90) and 3.57 (2.51-4.13) pg/ml, respectively, and significantly higher compared with the control group (p < 0.001, p < 0.001). On simple correlation, NT-proBNP was correlated with markers of volume overload and cardiac dysfunction. On multivariate regression analysis, only left ventricle mass index (β = 0.402, p = 0.003) and left atrium diameter (β = 0.263, p = 0.018) were independently associated with NT-proBNP (adjusted R 2 of the model: 0.707, p < 0.001).

CONCLUSIONS

Our research suggested that NT-proBNP, which was correlated with LV systolic and diastolic dysfunction and fluid overload as assessed by bioimpedance, can be used to evaluate cardiovascular states in a chronic kidney disease (CKD) population. From the early stages of CKD, periodic monitoring of NT-proBNP levels may be essential for early detection of patients with high risk of cardiovascular events, and for taking preventive intervention as soon as possible.

Nutritional status after conversion from conventional to in-centre nocturnal hemodialysis

INTRODUCTION

Recipients of conventional hemodialysis (CHD; 3-4 h/session, 3 times/week) experience volume expansion and nutritional impairment which may contribute to high mortality. Prolongation of sessions with in-centre nocturnal hemodialysis (INHD; 7-8 h/session, 3 times/week) may improve clinical outcomes by enhancement of ultrafiltration and uremic toxin removal.

MATERIALS AND METHODS

In this prospective cohort study, 56 adult patients who were receiving maintenance CHD for at least 90 days were assigned to CHD (patients who remained in CHD) and INHD (patients who switched to INHD) groups. Both groups were followed for 1 year divided into four 13-week quarters; post-dialysis weight and interdialytic weight gain (IDWG) were captured in each quarter. Repeated measures analysis of variance was used to calculate group main effect, time main effect or time-group interaction effect.

RESULTS

Conversion to INHD was associated with a mean (95% confidence interval) change in IDWG of 0.5 (0.08, 1.2) kg as compared to -0.3 (-0.9, 0.1) kg in the CHD group (p < 0.01). In the INHD group, post-dialysis weight (% of baseline pre-dialysis weight) decreased after conversion, reaching a nadir during the first 3 months (0.7%) and subsequently it gradually increased and returned to its baseline at the end of follow-up. A similar temporal trend was seen for serum creatinine but not serum N-terminal pro-brain natriuretic peptide (NT-proBNP) which is a marker of extracellular volume. The changes in serum albumin, prealbumin and hs-CRP were not different between the two groups.

CONCLUSIONS

Conversion to INHD was associated with greater IDWG and relatively stable body mass. We speculate that this gain in weight reflects an increase in lean body mass following the change in dialysis modality, which can be concluded from the parallel increase in serum creatinine and the lack of increase in NT-proBNP.

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.

Analysis of Clinically Relevant Factors for Pulmonary Hypertension in Maintenance Hemodialysis Patients

BACKGROUND Pulmonary hypertension (PH) is common in patients with maintenance hemodialysis (MHD) and is associated with high mortality. This study analyzed clinically relevant factors for pulmonary hypertension in MHD patients and the effect of serum pentraxin3 (PTX3) in the pathogenesis of PH to provide the basis for early diagnosis and treatment of MHD patients with PH. MATERIAL AND METHODS This study included 60 MHD patients (group A) and 30 healthy controls (group B). Group A was further divided into PH and non-PH groups. Clinical characteristics, auxiliary examination results and serum PTX3 level of the PH and non-PH groups were compared. Binary logistic regression was used to assess the risk factors for PH in MHD patients. ROC curve was applied to evaluate the diagnostic value of PTX3 in PH. RESULTS The incidence rate of PH in MHD patients was 50%, and most presented as mild to moderate. Compared with the non-PH group, patients in PH group presented significantly longer atrial diameter, right ventricular diameter and main pulmonary artery diameter (P<0.05), as well as higher PTX3 and NT-proBNP level. Atrial diameter and PTX3 level were the risk factors for PH in MHD patients. AUC of PTX3 was 0.721 (95%CI: 0.590-0.851, P=0.003). CONCLUSIONS The prevalence of PH was higher in MHD patients and mostly presented as mild to moderate. Such patients often developed heart structural changes and cardiac ultrasound was highly recommended. Serum PTX3 level was significantly elevated and could be used as a marker of PH in MHD patients.

Vasoactive Peptide Levels after Change of Dialysis Mode

Background/Aims

Plasma concentrations of the N-terminal fragment of pro-brain natriuretic peptide (NT-proBNP) are increased in end-stage renal disease. Improvement in hemodynamic stability has been reported when switching from hemodialysis (HD) to on-line hemodiafiltration (ol-HDF). The aim of this study was to investigate plasma concentrations of NT-proBNP, BNP and neuropeptide Y (NPY) during a 1-year follow-up, after a change from high-flux HD to postdilution ol-HDF. Additional variables were also studied, e.g. pulse wave velocity and ordinary clinical parameters.

Method

We conducted a prospective, single-center study including 35 patients who were switched from HD to HDF. Plasma concentrations of NT-proBNP, BNP and NPY before and after dialysis were measured at baseline (i.e. HD) and at 1, 2, 4, 6 and 12 months on HDF.

Results

All three peptide levels decreased significantly during HD and HDF when comparing concentrations before and after dialysis. Mean absolute value (before/after) and relative decrease (%) before versus after dialysis was 13.697/9.497 ng/l (31%) for NT-proBNP, 62/40 ng/ml (35%) for BNP and 664/364 pg/l (45%) for NPY. No significant differences were observed when comparing predialysis values over time. However, postdialysis NT-proBNP concentration showed a significant decrease of 48% over time after the switch to HDF.

Conclusion

The postdialysis plasma levels of NT-proBNP, BNP and NPY decreased significantly during both dialysis modes when compared to before dialysis. The postdialysis lowering of NT-proBNP increased further over time after the switch to ol-HDF; the predialysis levels were unchanged, suggesting no effect on its production in the ventricles of the heart.

The Associations of Malnutrition and Aging with Fluid Volume Imbalance between Intra- and Extracellular Water in Patients with Chronic Kidney Disease

OBJECTIVES

Fluid imbalance due to sodium retention and malnutrition can be characterized by the ratio of extracellular water (ECW) to intracellular water (ICW). We investigated whether the ECW/ICW ratio is a risk factor for adverse outcomes.

DESIGN

Retrospective cohort study.

SETTING AND PARTICIPANTS

149 patients with chronic kidney disease from 2005 to 2009, who were followed until August 2013.

MEASUREMENTS

Body fluid composition was measured by bioelectrical impedance analysis. Patients were categorized according to the ECW/ICW ratio tertile. Daily nutrient intake was estimated from 24-h dietary recall and analyzed using standard food composition tables. The main outcomes were adverse renal outcomes, as defined by a decline of 50% or more from the baseline glomerular filtration rate or initiation of renal replacement therapy, cardiovascular events, and all-cause mortality.

RESULTS

The ECW/ICW ratio increased with downward ICW slope with age and renal dysfunction besides ECW excess with massive proteinuria. Sodium intake, protein intake, and calorie intake were negatively correlated with the ECW/ICW ratios due to the steeper decreasing ICW content with the decreased dietary intake than the decreasing ECW content. During a median 4.9-year follow up, patients in the highest tertile had the worst adverse renal outcomes (15.9 vs. 5.1 per 100 patient-years, P < 0.001), cardiovascular events (4.1 vs. 0.3 per 100 patient-years, P = 0.002), and mortality (11.2 vs. 1.3 per 100 patient-years, P < 0.001). The adjusted hazard ratio (95% confidence intervals) for adverse renal outcomes, cardiovascular events, and mortality were 1.15 (1.03 - 1.26), 1.12 (0.93 - 1.31), and 1.29 (1.11 - 1.50), respectively.

CONCLUSIONS

Fluid imbalance between ICW and ECW occurring in malnourished and elderly patients with chronic kidney disease may explain the reserve capacity for volume overload and is associated with adverse renal outcomes and all-cause mortality.

Diagnostic value of B-type natriuretic peptide for estimating left atrial size and its usefulness for predicting all-cause mortality and cardiovascular events among chronic haemodialysis patients

AIM

Estimating fluid balance in haemodialysis patients is essential when determining dry weight, but limited methods are currently available. B-type natriuretic peptide (BNP) is a useful surrogate marker in patients with congestive heart failure (CHF), but whether its validity could be generalized to haemodialysis patients has not been studied well.

METHODS

A total of 457 haemodialysis patients at a dialysis centre were analyzed. Determinants of BNP were assessed in connection with ultrasound cardiography (UCG) records, Kt/V, ultrafiltration rate (UFR), and demographic factors. All-cause death and cardiovascular (CV) events were recorded as the main outcome.

RESULTS

Among the UCG records, left atrial diameter (LAD), left ventricular ejection fraction (LVEF), were determinants of log-transformed (ln) BNP; UFR, age and sex were also significant. There was a positive correlation between BNP and LAD (r = 0.285, P < 0.001). Receiver operating characteristic (ROC) analysis revealed that BNP had 90% and 80% sensitivity to predict the presence of LA enlargement of 77.9 pg/mL and 133.2 pg/mL, respectively. Higher BNP and lower LVEF were associated with higher risk for developing all-cause death and CVD. In the adjusted model, patients with BNP higher than 471 pg/mL had hazard ratio of 2.18 (95% confidence interval (CI) 1.20-3.96, P = 0.01), compared to those with BNP <109 pg/mL.

CONCLUSION

B-type natriuretic peptide was determined by LAD, LVEF, UFR, age and sex. BNP and LAD had positive correlation and BNP could become a useful tool for estimating the presence of LA enlargement. BNP and LVEF was a strong risk factor for predicting all-cause death and CV events among patients undergoing haemodialysis.

Association between ratio of measured extracellular volume to expected body fluid volume and renal outcomes in patients with chronic kidney disease: a retrospective single-center cohort study

Background

Excess extracellular volume is a major clinical problem in patients with chronic kidney disease (CKD). However, whether the extracellular volume status is associated with disease progression is unclear. We investigated the association between the extracellular volume status and renal outcomes.

Methods

We performed a retrospective cohort study of 149 patients with CKD who underwent bioelectrical impedance analysis (BIA) from 2005 to 2009. Patients were categorized according to tertiles of extracellular volume status. The extracellular volume status was assessed by examining the ratio of extracellular water measured by BIA (ECW_BIA) to the total body water calculated using the Watson formula (TBW_Watson). The main outcomes were adverse renal outcomes as defined by a decline of ≥50% from the baseline glomerular filtration rate or initiation of renal replacement therapy.

Results

A higher %ECW_BIA/TBW_Watson ratio tended to be associated with older age, male sex, diabetes mellitus, resistant hypertension, lower renal function, lower serum albumin levels, higher proteinuria levels, and a higher frequency of furosemide use. In the multivariate analysis, proteinuria remained independently associated with the %ECW_BIA/TBW_Watson ratio. Both the intracellular and extracellular water volumes decreased with age (correlation between ICW and age, r = -0.30, P < 0.001; correlation between ECW and age, r = -0.17, P = 0.03). Consequently, the %ECW_BIA in the body fluid composition increased with age. During a median follow-up of 4.9 years, patients in the highest tertile of the %ECW_BIA/TBW_Watson ratio were at greater risk of adverse renal outcomes (16.6 per 100.0 patient years) than were those in the lowest tertile (8.1 per 100.0 patient years) or second tertile (5.6 per 100.0 patient years) (log-rank P = 0.005). After adjustment for covariates, the %ECW_BIA/TBW_Watson ratio was significantly associated with adverse renal outcomes (hazard ratio, 1.21; 95 % confidence interval, 1.10–1.34; P < 0.001).

Conclusions

The ECW_BIA/TBW_Watson ratio was independently associated with adverse renal outcomes. Proteinuria was independently associated with the extracellular volume status. The balance between ICW and ECW changes with age in that the percentage of ECW content in the body fluid composition increases. Elderly patients with CKD may thus be susceptible to volume overload.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2369-15-189) contains supplementary material, which is available to authorized users.

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.

Indications and management of mechanical fluid removal in critical illness

BACKGROUND

The Acute Dialysis Quality Initiative (ADQI) dedicated its Twelfth Consensus Conference (2013) to all aspects of fluid therapy, including the management of fluid overload (FO). The aim of the working subgroup 'Mechanical fluid removal' was to review the indications, prescription, and management of mechanical fluid removal within the broad context of fluid management of critically ill patients.

METHODS

The working group developed a list of preliminary questions and objectives and performed a modified Delphi analysis of the existing literature. Relevant studies were identified through a literature search using the MEDLINE database and bibliographies of relevant research and review articles.

RESULTS

After review of the existing literature, the group agreed the following consensus statements: (i) in critically ill patients with FO and with failure of or inadequate response to pharmacological therapy, mechanical fluid removal should be considered as a therapy to optimize fluid balance. (ii) When using mechanical fluid removal or management, targets for rate of fluid removal and net fluid removal should be based upon the overall fluid balance of the patient and also physiological variables, individualized, and reassessed frequently. (iii) More research on the role and practice of mechanical fluid removal in critically ill patients not meeting fluid balance goals (including in children) is necessary.

CONCLUSION

Mechanical fluid removal should be considered as a therapy for FO, but more research is necessary to determine its exact role and clinical application.

Can non-invasive measurements aid clinical assessment of volume in patients with cirrhosis?

AIM: To evaluate the non-invasive assessments of volume status in patients with cirrhosis.

METHODS: Echocardiography and multifrequency bioimpedance analysis measurements and short synacthen tests were made in 20 stable and 25 acutely decompensated patients with cirrhosis.

RESULTS: Both groups had similar clinical assessments, cortisol response and total body water (TBW), however the ratio of extracellular water (ECW)/TBW was significantly greater in the trunk (0.420 ± 0.004 vs 0.404 ± 0.005), and limbs (R leg 0.41 ± 0.003 vs 0.398 ± 0.003, P < 0.05, and L leg 0.412 ± 0.003 vs 0.399 ± 0.003) with decompensated cirrhosis compared to stable cirrhotics, P < 0.05). Echocardiogram derived right atrial and ventricular filling and end diastolic pressures and presence of increased left ventricular end diastolic volume and diastolic dysfunction were similar in both groups. The decompensated group had lower systemic blood pressure, mean systolic 101.8 ± 4.3 vs 122.4 ± 5.3 and diastolic 58.4 ± 4.1 mmHg vs 68.8 ± 3.1 mmHg respectively, P < 0.01, and serum albumin 30 (27-33) vs 32 (31-40.5) g/L, P < 0.01.

CONCLUSION: Decompensated cirrhotics had greater leg and truncal ECW expansion with lower serum albumin levels consistent with intravascular volume depletion and increased vascular permeability.