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

Calculated plasma volume status in hemodialysis patients

BACKGROUND

Plasma volume (PV) calculated from hematocrit and body weight has applications in cardiovascular disease. The current study investigated the validity of the calculated PV for predicting volume overload and its prognostic utility in patients undergoing hemodialysis (HD).

PATIENTS AND METHODS

Fifty-four HD patients were prospectively enrolled, and their actual PV (aPV) and relative PV status (PVS) were calculated. Bioelectrical impedance analysis (BIA) with assessment of and total body water (TBW), intracellular water (ICW), extracellular water (ECW), and overhydration (OH) and routine blood examinations were performed before dialysis. A second cohort of 164 HD patients was retrospectively enrolled to evaluate the relationship between the calculated PVS and the outcome, with an endpoint of all-cause mortality.

RESULTS

aPV was significantly associated with TBW, ICW, ECW, OH, and ECW/TBW (all p < 0.001), and most strongly with ECW (r = 0.83). aPV predicted the extent of volume overload with an AUC of 0.770 (p < 0.001), but PVS did not (AUC = 0.617, p = 0.091). Median follow-up time was 53 months, during the course of which 60 (36.58%) patients died. Values for PVS (12.94 ± 10.87% vs. 7.45 ± 5.90%, p = 0.024) and time-averaged PVS (12.83 ± 11.20 vs. 6.78 ± 6.22%, p < 0.001) were significantly increased in patients who died relative to those who survived. A value of time-averaged PVS >8.72% was significantly associated with an increased incidence of all-cause mortality (HR = 2.48, p = 0.0023).

CONCLUSIONS

aPV was most strongly associated with ECW measured using BIA. HD patients with higher time-averaged PVS had a higher rate of all-cause mortality.

Comparison of hemodialysis urea clearance using spent dialysate and Kt/Vurea equations

INTRODUCTION

Dialysis adequacy is traditionally calculated from pre- and post-hemodialysis session serum urea concentrations and expressed as the urea reduction ratio, or Kt/Vurea. However, with increasing hemodiafiltration usage, we wished to determine whether there were any differences between standard Kt/Vurea equations and directly measured spent dialysate urea clearance.

METHODS

Urea clearance was measured from collected effluent dialysate and compared with various other methods of Kt/Vurea calculation, including change in total body urea from measuring pre- and post-total body water with bioimpedance and the Watson equation, by standard Kt/V equations, and online clearance measurements using effective ionic dialysance (OLC).

RESULTS

We compared urea clearance in 41 patients, 56.1% male, mean age 69.3 ± 12.6 years with 87.8% treated by hemodiafiltration. Reduction in total body urea was greater when estimating changes in total body urea, compared to measured dialysate losses of 58.4% (48.5-67.6) vs 71.6% (62.1-78), p < 0.01. Sessional urea clearance (Kt/Vurea) was greater using the online Solute-Solver program compared to OLC, median 1.45(1.13-1.75) vs 1.2 (0.93-1.4), and 2nd generation Kt/V equations 1.3 (1.02-1.66), p < 0.01, but not different from estimated total body urea clearance 1.36 (1.15-1.73) and dialysate clearance 1.36 (1.07-1.76). The mean bias compared to the Solute-Solver program was greatest with OLC (-0.25), compared to second-generation equations (-0.02), estimated total body clearance (-0.02) and measured dialysate clearance (-0.01).

CONCLUSION

This study demonstrated that the result from equations estimating urea clearance indirectly from pre- and postblood samples from hemo- and hemodiafiltration treatments was highly correlated with direct measurements of dialysate urea clearance.

Interrelationships between sarcopenia, bone turnover markers and low bone mineral density in patients on hemodialysis

BACKGROUND

Hemodialysis (HD) patients are at risk for sarcopenia (SP) and bone loss, which may impact falls and bone fragility and lead to poor prognosis. Patients with HD and those with osteoporosis (OP) are still underdiagnosed and untreated. The aims of the present study were to evaluate the factors that affect bone mineral density (BMD) loss in HD patients, and explore traditional and novel approaches to manage chronic kidney disease-mineral-bone disorder (CKD-MBD).

METHODS

Patients who underwent regular HD at the First Affiliated Hospital of Soochow University were retrospectively evaluated. According to the WHO osteoporosis criteria, patients were categorized into three groups: normal BMD, osteopenia, and osteoporosis. Demographic and clinical data, skeletal muscle mass, and bone turnover markers(BTM) were compared between the three groups. The correlation between bone density and muscle mass was calculated, and related risk factors were analyzed.

RESULTS

This study enrolled 130 HD patients, 36 patients were diagnosed with sarcopenia (27.7%), 44 patients were diagnosed with osteopenia (33.8%), 19 patients were diagnosed with osteoporosis (14.6%), and 23 patients were diagnosed with osteosarcopenia (17.7%). The SMI was positively correlated with the BMD of the lumbar spine (r = 0.23, p < 0.01) and femoral neck (r = 0.22, p < 0.05). In ordinal logistic regression analysis, the odds ratio (OR) for low BMD was high for patients with sarcopenia (OR = 5.894, 95% CI 1.592-21.830, p < 0.01), older age (OR = 1.095, 95% CI 1.041-1.153, p < 0.001), higher TRACP-5b levels (OR = 1.597, 95% CI 1.230-2.072, p < 0.01), and lower 25-OH vitamin D levels (OR = 0.631, 95% CI 0.544-0.733, p < 0.001).

CONCLUSION

The preservation of skeletal muscle mass could be important to prevent a BMD decrease in HD patients. Adequate intake of vitamin D and control of TRACP-5b levels will help reduce the occurrence and progression of osteopenia/sarcopenia in HD patients.

Effect of bioimpedance-defined overhydration parameters on mortality and cardiovascular events in patients undergoing dialysis: a systematic review and meta-analysis

OBJECTIVE

To evaluate the role of bioimpedance-defined overhydration (BI-OH) parameters in predicting the risk of mortality and cardiovascular (CV) events in patients undergoing dialysis.

METHODS

We searched multiple electronic databases for studies investigating BI-OH indicators in the prediction of mortality and CV events through 23 May 2020. We assessed the effect of BI-OH indexes using unadjusted hazard ratios (HRs) and 95% confidence intervals (CIs). Sensitivity analysis was used for each outcome.

RESULTS

We included 55 studies with 104,758 patients in the meta-analysis. Extracellular water/total body water (ECW/TBW) >0.4 (HR 5.912, 95% CI: 2.016-17.342), ECW/intracellular water (ICW) for every 0.01 increase (HR 1.041, 95% CI: 1.031-1.051), and OH/ECW >15% (HR 2.722, 95% CI: 2.005-3.439) increased the risk of mortality in patients receiving dialysis. ECW/TBW >0.4 (HR 2.679, 95% CI: 1.345-5.339) and ECW/ICW per increment of 10% (HR 1.032, 95% CI: 1.017-1.047) were associated with an increased risk of CV events in patients undergoing dialysis. A 1-degree increase in phase angle was a protective factor for both mortality (HR 0.676, 95% CI: 0.474-0.879) and CV events (HR 0.736, 95% CI: 0.589-0.920).

CONCLUSIONS

BI-OH parameters might be independent predictors for mortality and CV events in patients undergoing dialysis.

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.

Association of NT-proBNP and BNP With Future Clinical Outcomes in Patients With ESKD: A Systematic Review and Meta-analysis

RATIONALE & OBJECTIVE

Use of brain natriuretic peptide (BNP) and N-terminal pro-BNP (NT-proBNP) for cardiovascular (CV) risk assessment in patients with end-stage kidney disease (ESKD) remains unclear. We examined the associations between different threshold elevations of these peptide levels and clinical outcomes in patients with ESKD.

STUDY DESIGN

Systematic review and meta-analysis.

SETTING & STUDY POPULATIONS

We searched MEDLINE and EMBASE (through September 2019) for observational studies of adults with ESKD (estimated glomerular filtration rate≤15mL/min/1.73m² or receiving maintenance dialysis).

SELECTION CRITERIA FOR STUDIES

Studies that reported NT-proBNP or BNP levels and future CV events, CV mortality, or all-cause mortality.

DATA EXTRACTION

Cohort characteristics and measures of risk associated with study-specified peptide thresholds.

ANALYTICAL APPROACH

Hazard ratios (HRs) for clinical outcomes associated with different NT-proBNP and BNP ranges were categorized into common thresholds and pooled using random-effects meta-analysis.

RESULTS

We identified 61 studies for inclusion in our review (19,688 people). 49 provided sufficient detail for inclusion in meta-analysis. Pooled unadjusted HRs for CV mortality were progressively greater for greater thresholds of NT-proBNP, from 1.45 (95% CI, 0.91-2.32) for levels>2,000pg/mL to 5.95 (95% CI, 4.23-8.37) for levels>15,000pg/mL. Risk for all-cause mortality was significantly higher at all NT-proBNP thresholds ranging from> 1,000 to> 20,000pg/mL (HR range, 1.53-4.00). BNP levels>550pg/mL were associated with increased risk for CV mortality (HR, 2.54; 95% CI, 1.49-4.33), while the risks for all-cause mortality were 2.04 (95% CI, 0.82-5.12) at BNP levels>100pg/mL and 2.97 (95% CI, 2.21-3.98) at BNP levels>550pg/mL. Adjusted analyses demonstrated similarly greater risks for CV and all-cause mortality with greater NT-proBNP concentrations.

LIMITATIONS

Incomplete outcome reporting and risk for outcome reporting bias. Estimation of risk for CV events for specific thresholds of both peptides were limited by poor precision.

CONCLUSIONS

ESKD-specific NT-proBNP and BNP level thresholds of elevation are associated with increased risk for CV and all-cause mortality. This information may help guide interpretation of NT-proBNP and BNP levels in patients with ESKD.

Hemodialysis patients with less extracellular water overload and smaller cardiac atrial chamber sizes are at greater risk of a fall in blood pressure during dialysis

Intradialytic hypotension is the most common complication of hemodialysis (HD) treatments. Excessive ultrafiltration results in reduced cardiac preload. We aimed to determine whether a fall in systolic blood pressure during HD was greater in patients starting HD with (a) less overhydration measured by extracellular water (ECW) and (b) lower cardiac preload by cardiac magnetic resonance imaging (MRI). Pre-HD measurements of ECW and total body water (TBW) were performed using multifrequency bioimpedance (MFBIA). Cardiac chamber sizes and functions were determined by MRI. Twenty-six patients, 18 males (69.2%), 11 (42.3%) with diabetes, mean age 63.9 ± 15.9 years were studied. Systolic blood pressure (SBP) fell in 15 (57.7%) patients, and either did not change or increased in 9. There was no difference in demographics between groups. Patients with a fall in SBP had lower pre-HD ECW/TBW (0.400 ± 0.018 vs 0.418 ± 0.021), indexed right ventricular end-diastolic volume (81.2 ± 37.6 vs 100.8 ± 33.7 mL/m² ), and indexed left atrial size (13.7 ± 3.9 vs 18.3 ± 5.0 mL/m² ), all P < .05, respectively. There were univariate correlations between the change in SBP and pre-HD ECW/TBW for the trunk (r = .50, P = .009) and indexed left atrial volume (r = .54, P = .005). A fall in blood pressure occurred more commonly in patients starting HD with lower overhydration as measured by bioimpedance, and those with smaller cardiac chamber sizes. Patients with the lowest ECW/TBW and smallest cardiac chamber sizes had the greatest falls in SBP. This study reinforces the importance of determining physiological target weights and avoiding inappropriately low target weights for HD patients.

Pilot Study to Detect Changes in Blood Flow in the External Auditory Meatus During Hemodialysis

Blood flow to internal organs is reported to fall during hemodialysis (HD). As such, noninvasive monitoring devices are required to detect changes in perfusion, which could then be used for therapeutic interventions. We report on a pilot study monitoring blood flow in the outer auditory meatus. We measured the maximum pulse wave amplitude and indicators of blood flow by analyzing red and green color changes in the outer auditory meatus from video recordings made using an otoscope fitted with a digital camera during HD treatments. We studied 61 patients, 43 (71.5%) male, mean age 64.9 ± 12.7 years. Weight fell from 72.8 ± 22.5 kg predialysis to 71.5 ± 22.1 kg postdialysis (P < 0.001). BP did not significantly change (predialysis 142 ± 29/67 ± 18 to 143 ± 25/68 ± 17 mm Hg postdialysis). The maximum pulse wave amplitude in the external auditory meatus fell from 0.21 (0.1-0.55) to 0.14 (0.04-0.4) after 90 min, P < 0.001, and remained low thereafter, and the change at the end of the dialysis session was associated with percentage weight loss (r = -0.37, P = 0.003). Green and red pixel values did not change (predialysis 0.339 [0.333-0.345] to 0.302 [0.291-0.33] post, and 0.301 [0.293-0.328] predialysis to 0.339 [0.334-0.347] post, respectively). This pilot study showed that the maximum pulse wave amplitude measured in the external auditory meatus fell during the dialysis session, and that the fall was associated with fluid removal. This could potentially lead to the development of a monitoring device, which could fit in the ear and record during the dialysis session.

Monitoring Volume Status Using Bioelectrical Impedance Analysis in Chronic Hemodialysis Patients

Fluid overload can be an independent risk factor of cardiovascular events and all-cause death in end-stage renal disease (ESRD) patients on chronic hemodialysis. We performed a retrospective study to investigate whether intermittent control of fluid status decreases the rate of these complications using bioelectrical impedance analysis (BIA). In ESRD patients on chronic hemodialysis, we identified the ratio of extracellular water to total body water (ECW/TBW) every 6 months using InBody S10 (Biospace, Seoul, Korea), which was measured within 30 minutes after dialysis initiation on the first dialysis day of the week. The uncontrolled group included 57 (40.1%) patients with all ECW/TBW measurements ≥0.40; in contrast, the controlled group included 85 (59.9%) with any measured ECW/TBW <0.40. Included patients were followed for 29 (12-42) months. The risk of cardiovascular events was higher in the uncontrolled group (hazard ratio [HR], 2.4; 95% confidence interval [CI], 1.2-5.1; p < 0.05) than it was in the controlled group; however, this difference disappeared after adjusting for age, sex, and Charlson comorbidity index (not significant). On the other hand, the patients in the uncontrolled group had a higher risk of all-cause death than did those in the controlled group, independent of age, sex, and Charlson comorbidity index (HR, 4.7; 95% CI, 1.4-16.1; p < 0.05). In conclusion, monitoring volume status using BIA may help to predict all-cause death in chronic hemodialysis patients. Further controlled studies are needed to confirm that strict volume control could reduce the rates of cardiovascular events and mortality in this population.

Bioimpedance-defined overhydration predicts survival in end stage kidney failure (ESKF): systematic review and subgroup meta-analysis

Both overhydration and comorbidity predict mortality in end-stage kidney failure (ESKF) but it is not clear whether these are independent of one another. We undertook a systematic review of studies reporting outcomes in adult dialysis patients in which comorbidity and overhydration, quantified by whole body bioimpedance (BI), were reported. PubMed, EMBASE, PsychInfo and the Cochrane trial database were searched (1990-2017). Independent reviewers appraised studies including methodological quality (assessed using QUIPS). Primary outcome was mortality, with secondary outcomes including hospitalisation and cardiovascular events. Of 4028 citations identified, 46 matched inclusion criteria (42 cohorts; 60790 patients; 8187 deaths; 95% haemodialysis/5% peritoneal dialysis). BI measures included phase angle/BI vector (41%), overhydration index (39%) and extra:intracellular water ratio (20%). 38 of 42 cohorts had multivariable survival analyses (MVSA) adjusting for age (92%), gender (66%), diabetes (63%), albumin (58%), inflammation (CRP/IL6-37%), non-BI nutritional markers (24%) and echocardiographic data (8%). BI-defined overhydration (BI-OH) independently predicted mortality in 32 observational cohorts. Meta-analysis revealed overhydration >15% (HR 2.28, 95% CI 1.56-3.34, P < 0.001) and a 1-degree decrease in phase angle (HR 1.74, 95% CI 1.37-2.21, P < 0.001) predicted mortality. BI-OH predicts mortality in dialysis patients independent of the influence of comorbidity.

Addition of Novel Biomarkers for Predicting All-Cause and Cardiovascular Mortality in Prevalent Hemodialysis Patients

Novel biomarkers might improve the prediction of mortality in hemodialysis (HD) patients. We simultaneously measured the levels of conventional and novel biomarkers [serum N-terminal pro-brain natriuretic peptide (NT-proBNP), intact fibroblast growth factor-23 (FGF23), β2-microglobulin (β2MG), cystatin C, and high-sensitivity C-reactive protein (hsCRP)] in 307 prevalent Japanese HD patients. There were 66 all-cause deaths, and 25 cardiovascular (CV) deaths during 2 years, which were assessed using Cox models and concordance (C)-statistics. The addition of NT-proBNP alone (P < 0.05) or NT-proBNP, hsCRP, and β2MG as a panel (C-statistics: 0.834 vs. 0.776, P < 0.01) to a conventional risk model composed of age, diabetes, and the serum albumin level significantly improved the prediction of 2-year all-cause mortality, and the addition of NT-proBNP and hsCRP as a panel to a conventional risk model composed of age significantly improved the prediction of 2-year CV mortality (P < 0.05) in Japanese prevalent HD patients. Neither FGF23 nor cystatin C improved mortality prediction.

Estimated dietary sodium intake in haemodialysis patients using food frequency questionnaires

BACKGROUND

In clinical practice, dietary sodium assessment requires reliable and rapid screening tools. We wished to evaluate the usefulness of food frequency questionnaires (FFQ) in estimating dietary sodium intakes in haemodialysis patients.

METHODS

We used the Derby Salt Questionnaire (DSQ), and Scored Sodium Questionnaire (SSQ) to estimate sodium intake. Body composition was determined by bioimpedance.

RESULTS

In total, 139 haemodialysis patients (95 men) completed the FFQs, with mean ± standard deviation age 67 ± 15 years. The mean FFQ scores were DSQ 3.5 ± 2.0 and SSQ 68.4 ± 24.5. Men had higher estimated dietary sodium intakes [DSQ median (range) 3.6 (0.6-10.1) versus female 2.2 (0.5-9.1), P = 0.007)]. Younger patients and those aged >75 years had the higher SSQ dietary sodium scores; 70.7 ± 27.8 and 76.8 ± 24.6 versus those aged 55-75 years, 61.8 ± 22.3, P = 0.04. Patients with greater estimated sodium intake had higher extracellular water (ECW) to intracellular water (ICW) ratios pre-dialysis [75.1 ±12.5 versus 67.7 ± 4.8, P < 0.001] and ECW excess pre-dialysis [1.8 (1.5-2.6) versus 1.3 (0.8-2.0) L, P < 0.05]. Mean arterial pressure (MAP) and inter-dialytic weight gains did not differ; however, the fall in MAP during dialysis was lower in the higher estimated dietary sodium group (0.9 ± 13.7% versus 6.5 ± 14.1%, P = 0.04).

CONCLUSIONS

Both questionnaires were acceptable to patients and identified higher estimated dietary sodium intake for men, those with greater ECW and, somewhat surprisingly, we found that older patients had a greater dietary sodium intake than expected.