Hyponatraemia, mortality and haemodialysis: An unexplained association

Correlation of plasmatic sodium determined by the laboratory and that determined by the dialysis machine

INTRODUCTION

Changes in plasma sodium concentration (pNa, expressed in mEq/L) are common in hemodialysis (HD) patients. Hemodialysis monitors can estimate pNa by using an internal algorithm based on ion dialysance measurements. The present study studies the accuracy of the correlation between the pNa estimated by the dialysis monitor and that measured by the biochemistry laboratory at our center.

MATERIAL AND METHODS

A single-centre prospective observational study in patients on a chronic HD program with the 6008 CAREsystem monitor and standard sodium (138mmol/L) and bicarbonate (32mmol/L) prescriptions. Venous blood samples were drawn from each patient before and after each HD session to ensure inter- and intra-individual validity. The pNa was measured in the biochemistry laboratory using indirect potentiometry and simultaneously the estimated pNa by the HD monitor was recorded at the beginning and at the end of the HD session. For statistical analysis, a scatterplot was made, and Spearman's correlation quotient was calculated. In addition, the differences between both methods were represented as Bland-Altman diagrams.

RESULTS

The pre-dialysis pNa measured in the laboratory was 137.49±3.3, and that of the monitor, 137.96±2.91, with a correlation with R2 value of 0.683 (p<0.001). The post-dialysis pNa measured in the laboratory was 137.08±2.23, and that of the monitor was 138.87±1.88, with an R2 of 0.442 (p<0.001). On the Bland-Altman plots, the pre-dialysis pNa has a systematic error of 0.49, in favor of the monitor-estimated pNa, with a 95% confidence interval (CI) of (-3.24 to a 4.22). In the post-dialysis pNa, a systematic error of 1.79 with a 95% CI of (-1.64 to 5.22) was obtained.

CONCLUSION

The correlation between the pNa estimated by Fresnius 6008 CAREsystem HD monitor and that measured by the laboratory is good, especially pre-dialysis measurements. Further studies should verify the external validity of these results.

Conductivity variations and changes in serum sodium concentration during dialysis related to monitor switching

INTRODUCTION

The sodium gradient during hemodialysis sessions is one of the key factors in sodium balance in patients with dialysis-dependent chronic kidney disease; however, until the appearance of the new monitors with sodium modules, the differences between prescribed and measured sodium have been understudied. The present study aimed to compare the impact on the measured conductivity and the initial and final plasma sodium after changing the 5008 Cordiax to the new 6008 Cordiax monitor.

MATERIAL AND METHODS

106 patients on hemodialysis were included. Each patient underwent 2 dialysis sessions in which only the monitor was varied. The variables collected were dialysate, sodium and bicarbonate prescribed, real conductivity, initial and final plasma sodium measured, and the calculated sodium gradient (ΔPNa).

RESULTS

The change of dialysis monitor showed small but statistically significant differences in the initial (138.14mmol/L with 5008 vs. 138.81mmol/L with 6008) and final plasma sodium (139.58mmol/L vs. 140.97mmol/L), as well as in the actual conductivity obtained (13.97 vs. 14.1mS/cm). The ΔPNa also increased significantly.

CONCLUSION

The change from 5008 to 6008 monitor is associated with increased conductivity, leading the patient to end the sessions with higher plasma sodium and ΔPNa. Knowing and confirming this change will allow us to individualize the sodium prescription and avoid possible undesirable effects. It could be the preliminary study to explore the new sodium biosensor incorporated into the new generation of monitors.

Hyponatremia and mortality in patients undergoing maintenance hemodialysis: Systematic review and meta-analysis

INTRODUCTION

This systematic review and meta-analysis examined the relationship between hyponatremia and worse outcomes in patients undergoing maintenance hemodialysis.

METHODS

The MEDLINE, EMBASE, CENTRAL, and Web of Science databases were used to search for relevant articles. The target population was patients on maintenance hemodialysis (those undergoing hemodialysis for ≥60 days). The defined outcomes were death, cardiovascular disease, cognitive decline, and falls. Meta-analysis was performed with a random-effects model of pairwise comparisons of normonatremia and hyponatremia defined for each study, 1-mmol/L increment of sodium analysis, and dose-response analysis using the sodium concentration defined for each study. This study was registered with PROSPERO (registration number CRD42018087667).

RESULTS

Thirteen articles were included. The pairwise analysis revealed that the hazard ratio for all-cause mortality was 1.45 (95% confidence interval, 1.31-1.61). The analysis of 1-mmol/L increment of sodium included six studies with a hazard ratio for all-cause mortality of 0.94 (95% confidence interval, 0.91-0.97) for each 1-mmol/L increase in the serum sodium concentration. In the dose-response analysis, assuming a linear relationship, a sodium increment of 1 mmol/L revealed a hazard ratio for all-cause mortality of 0.97 (95% confidence interval, 0.96-0.98). Other outcomes could not be integrated.

CONCLUSIONS

Hyponatremia is associated with all-cause mortality in patients undergoing maintenance hemodialysis. Healthcare providers should pay special attention to even the slightest indication of hyponatremia.

Practical implementation and clinical benefits of the new automated dialysate sodium control biosensor

Background

A key feature of dialysis treatment is the prescription of dialysate sodium (Na). This study aimed to describe the practical implementation of a new automated dialysate Na control biosensor and to assess its tolerance and the beneficial clinical effects of isonatraemic dialysis.

Methods

A prospective study was carried out in 86 patients who, along with their usual parameters, received the following five consecutive phases of treatment for 3 weeks each: phase 0: baseline 5008 machine; phases 1 and 2: 6008 machine without activation of the Na control biosensor and the same fixed individualized Na dialysate prescription or adjusted to obtain similar conductivity to phase 0; phases 3 and 4: activated Na control to isonatraemic dialysis (Na dialysate margins 135-141 or 134-142 mmol/L).

Results

When the Na control was activated, the few episodes of cramps or hypotension disappeared when the lower dialysate Na margin was increased by 1 or 2 mmol/L. The activated Na control module showed significant differences compared with baseline and the non-activated Na module in final serum Na values, diffusive Na balance, and changes in pre- to postdialysis plasma Na values. The mean predialysis systolic blood pressure value was significantly lower in phase 4 than in phase 1. There were no significant differences in total Na balance in the four 6008 phases evaluated.

Conclusions

The implementation of the automated dialysate Na control module is a useful new tool, which reduced the diffusive load of Na with good tolerance. The module had the advantages of reducing thirst, interdialytic weight gain and intradialytic plasma Na changes.

Novel Algorithm for the Differential Diagnosis of Hyponatraemia in Anuric Patients Undergoing Maintenance Haemodialysis

INTRODUCTION

Hyponatraemia is associated with increased mortality in patients undergoing maintenance haemodialysis. In anuric patients, hyponatraemia development depends on the water-sodium ratio in retained fluid within the interdialysis interval (IDI).

OBJECTIVE

This study aimed to calculate the retained sodium-retained water ratio in patients on maintenance haemodialysis and make a differential diagnosis of hyponatraemia according to these data.

METHODS

The amount of retained water was determined as body weight gain (ΔBW) within the IDI. Sodium retention was calculated using our formula: eRNa+ = ΔBW × (SNa+)t2 - total body water (TBW)t1 × ([SNa+]t1 - [SNa+]t2), where TBW represents the calculated volume of the total body water and (SNa+)t1 and (SNa+)t2 represent the sodium concentration at the beginning and at the end of the IDI, respectively. We performed 89 measurements in 32 anuric patients on maintenance haemodialysis.

RESULTS

Hyponatraemia was detected in 13 measurements at the end of the IDI. The ΔBW had no statistically significant difference between normonatraemic and hyponatraemic patients. Hyponatraemic patients had significantly lower levels of retained sodium. The retained water--retained sodium ratio facilitated in differentiating dilution hyponatraemia, nutritional hyponatraemia, depletion hyponatraemia, and dilution hyponatraemia associated with sodium wasting or malnutrition.

CONCLUSION

The composition of retained fluid during the IDI may be hypotonic, hypertonic, or isotonic in relation to the extracellular fluid. Most of the hyponatraemic patients had hypotonic fluid retained during the IDI because of dilution as well as gastrointestinal sodium loss and/or malnutrition.

The Association Between Handgrip Strength and Predialysis Serum Sodium Level in Patients With Chronic Kidney Disease Stage 5D

Purpose: Handgrip strength (HGS) is a useful tool for the systematic assessment of muscle function related to nutritional status. Reduced HGS has been associated with adverse clinical outcomes in chronic kidney disease (CKD) stage 5D patients. In the same patients, predialysis low serum sodium (sNa) has been associated with malnutrition and mortality. Here, we investigated the role of predialysis sNa on muscle function in CKD-5D patients.

Methods: We evaluated 45 patients on hemodialysis (HD) and 28 patients on peritoneal dialysis (PD) with HGS measurement, bioimpedance analysis, anthropometric measures, and malnutrition inflammation score (MIS). According to established diagnostic criteria, reduced HGS was defined as strength below 30 and 20 Kg in men and women, respectively. Predialysis sNa values were defined as the mean of all predialysis measurements during the preceding 6 months. Data analysis was performed separately for each of the HD and PD groups.

Results: The proportions of reduced HGS did not differ between the HD (66%) and PD (54%) groups, respectively. Patients in the HD group as compared to those in the PD group had higher serum albumin and potassium and mid-arm muscle circumference and lower residual renal function (RRF) and residual urine volume. Multivariate logistic analysis, after controlling for muscle mass, nutritional biomarkers, MIS, fluid overload and RRF, showed that for every 1 mmol/l increase of sNa the odds of reduced HGS was decreased by 60% (OR = 0.40, 95% CI: 0.16–0.99) and 42% (OR = 0.58, 95% CI: 0.36–0.93) in HD and PD patients, respectively. However, stratified analysis indicated that lower sNa levels predicted reduced HGS in individuals with a background of malnutrition, inflammation, overhydration and less preserved RRF, representing unfavorable conditions strongly related to muscle wasting in the dialysis setting.

Conclusions: Predialysis sNa is a strong and independent determinant of HGS, a reliable nutritional marker in CKD-5D stage patients. However, according to our findings, lower sNa levels appear to be a marker of underlying unfavorable conditions that are heavily associated with reduced HGS, rather than a causal determinant of reduced HGS. Whether optimizing sNa levels improves patient muscle performance requires further investigations.

Haemodialysis patients have worse postural balance with an associated risk of falls

INTRODUCTION

Postural balance is the result of a complex interaction of sensory input which keeps us upright. Haemodialysis patients have alterations which can lead to postural instability and a risk of falls. Our objective was to analyse postural stability and its relationship with the risk of falls in haemodialysis patients using a force platform.

MATERIAL AND METHODS

This was a prospective cross-sectional study. Postural balance was recorded using a force platform in prevalent haemodialysis patients. We collected epidemiological, dialysis, analytical and treatment data. The incidence of falls was recorded over the 6 months following the tests. The postural stability analysis was performed with a portable strain gauge platform (AMTI AccuGait®) and a specific software unit for stabilometry (Balance Trainer® program). We measured 31 balance parameters; the balance variables used were: Area95; AreaEffect; VyMax; Xrange and Yrange. The stabilometry studies were performed in 3 situations: with eyes open; with eyes closed; and with the patient performing a simultaneous task. We performed one study at the start of the dialysis session, and a second study at the end. Stabilometry was measured in a control group under similar conditions.

RESULTS

We studied 32 patients with a mean age of 68 years old; of this group, 20 subjects were male and 12 were female. Their mean weight was 74kg, with a mean BMI of 27.6kg/m². In the controls, there were no significant differences in the stabilometry between the 3 situations studied. Both pre- and post-haemodialysis, patients with closed eyes showed greater imbalance, and there were significant differences with the other situations and controls. We found a significant increase in instability after the haemodialysis session, and greater instability in the 13 patients with diabetes (P<.05). The 4 patients with hyponatraemia (Na<136mmol/l) had worse balance in the simultaneous task situation (P=.038). Various drugs, such as insulin (P=.022), antiplatelet agents (P=.036) and beta-blockers (P=.029), were associated with imbalance. The 10 patients who suffered falls had greater imbalance, Yrange, Xrange, Area95 and AreaEffect, both pre- and post-haemodialysis (P<.05) than those without falls.

CONCLUSIONS

Haemodialysis patients have alterations which can lead to postural instability and a risk of falls. Prevention programmes which include specific exercises to improve balance could be beneficial in reducing the risk of falls in this population.

High dose haemodialysis and haemodiafiltration parameters and the relationship with advanced vascular calcification

Background

Vascular calcification (VC) is a risk factor for cardiovascular disease in end-stage renal disease (ESRD) patients undergoing maintenance haemodialysis (MHD). However, evidence is still insufficient about the association between dialysis parameters and VC. Thus, this study was to evaluate association of dialysis parameters with VC.

Methods

We enrolled 297 ESRD patients undergoing MHD at six distinct centers in Korea. Study participants were categorized into 3 groups by the scoring system of abdominal aortic calcification based on lateral lumbar radiography (no VC group: 0, mild VC group: 1–7 and advanced VC group: 8–24). We compared the features of dialysis parameters according to the severity of VC. Multivariate logistic regression analysis was used to calculate adjusted odd ratios (ORs) and 95% confidence interval (CI) for mild and advanced VC in each haemodialysis parameter (adjusted OR [95% CI]).

Results

Pooled Kt/V (spKt/V), equilibrated Kt/V (eKt/V), standard Kt/V (stdKt/V) and the proportion of haemodiafiltration were increased along with the severity of VC. Multivariate regression analysis indicated that advanced VC was positively associated with spKt/V (5.27 [1.51–18.41]), eKt/V (6.16 [1.45–26.10]), stdKt/V (10.67 [1.74–65.52]) and haemodiafiltration (3.27 [1.74 to 6.16]).

Conclusion

High dose dialysis and haemodiafiltration were significantly associated with advanced VC.

Unlike Kt, high Kt/V is associated with greater mortality: The importance of low V

INTRODUCTION

Kt/V has been used as a synonym for haemodialysis dose. Patient survival improved with a Kt/V>1; this target was subsequently increased to 1.2 and 1.3. The HEMO study revealed no significant relationship between Kt/V and mortality. The relationship between Kt/V and mortality often shows a J-shaped curve. Is V the confounding factor in this relationship? The objective of this study is to determine the relationship between mortality and Kt/V, Kt and body water content (V) and lean mass (bioimpedance).

METHODS

We studied a cohort of 127 prevalent haemodialysis patients, who we followed-up for an average of 36 months. Kt was determined by ionic dialysance, and V and nutrition parameters by bioimpedance. Kt/V, Kt corrected for body surface area (Kt/BSA) and target Kt/BSA were calculated. The mean data from 18,998 sessions were used as haemodialysis parameters, with a mean of 155 sessions per patient.

RESULTS

Mean age was 70.4±15.3 years and 61% were male; 76 were dialysed via an arteriovenous fistula and 65 were on online haemodiafiltration. Weight was 70.6 (16.8)kg; BSA 1.8 (0.25) m²; total body water (V) 32.2 (7.41) l and lean mass index (LMI) 11.1 (2.7)kg/m². Mean Kt/V was 1.84 (0.44); Kt 56.1 (7)l and Kt/BSA 52.8 (10.4)l. The mean target Kt/BSA was 49.7 (4.5)l. Mean Kt/BSA-target Kt/BSA +6.4 (7.0)l. Patients with a higher Kt/V had worse survival rates than others; with Kt this is not the case. Higher Kt/V values are due to a lower V, with poorer nutrition parameters. LMI and serum albumin were the parameters that best independently predicted the risk of death and are lower in patients with a higher Kt/V and lower V.

CONCLUSION

Kt/V is not useful for determining dialysis doses in patients with low or reduced body water. Kt or the Kt/BSA are proposed as an alternative.

Xerostomia, thirst, sodium gradient and inter-dialytic weight gain in hemodialysis diabetic vs. non-diabetic patients

Background

In hemodialysis (HD) patients, xerostomia and hyposalivation may intensify sensations of thirst, and contribute to the intake of fluids and excessive inter-dialytic weight gain (IWG). Since IWG is regarded to be higher in diabetic patients than in non-diabetics HD enhancing their mortality, it is crucial to define plausible underlying causes. Therefore, the study investigates factors contributing to the increased IWG in diabetic HD patients.

Material and Methods

The study included 97 HD patients (38 diabetics) receiving hemodialysis. All participants completed surveys comprising the Dialysis Thirst Inventory (DTI) and Xerostomia Inventory. Unstimulated whole saliva flow rate (USWFR) was measured, with USWFR below 0.1 mL/min being regarded as hyposalivation. Additionally, pre- and post-dialysis serum sodium concentration, sodium gradient and IWG were assessed. In diabetic HD patients, hemoglobin A1c (HbA1c) level was measured.

Results

Significantly higher scores were found in diabetic than non-diabetic HD patients with regard to DTI (21.2±7.7 vs. 17.1±6.2: Z=2.44, p=0.03) and xerostomia (40.5±6.1 vs. 29.9±14.4: Z=4.15, p=0.003). Hyposalivation was observed more often in diabetic HD patients (Z=2.23, p=0.04). IGW was significantly higher in participants with diabetes (Z=2.44, p=0.03), as was the pre-dialysis sodium serum (Z=3.4, p=0.008). High levels of HbA1c were associated with lower levels of serum sodium (r=-0.67 p<0.05). HbA1c positively correlated with pre-dialysis sodium gradient (r=0.66 p<0.05). However, multiple regression analysis found that the only predictors of increased IWG (>4.8 IWG%) in diabetic patients remained saliva flow rate and pre-dialysis sodium gradient.

Conclusions

Concomitant diabetes in hemodialysis patients appears to intensify subjective xerostomia and thirst sensation. It also leads to excessive IWG by the increase of pre-dialysis serum sodium gradient.

Key words:Diabetes mellitus, hemodialysis, hyposalivation, inter-dialytic weight gain, sodium gradient.

Association of serum sodium and risk of all-cause mortality in patients with chronic kidney disease: A meta-analysis and sysematic review

Studies on the association of dysnatraemia with all-cause mortality risk in chronic kidney disease (CKD) patients have yielded inconsistent results. This meta-analysis aimed to evaluate the association of hyponatremia or hypernatremia with all-cause mortality risk in CKD patients. An electronic literature search was performed in Web of Science, Pubmed and Embase databases from inception to March 2017 for available observational studies evaluating the association of dysnatraemia with all-cause mortality risk in CKD patients. Pooled hazard risk (HR) with 95% confidence interval (CI) was calculated for hyponatremia or hypernatremia vs. normonatremia. Seven studies that enrolled 742,979 CKD patients were identified. Baseline hyponatremia (HR 1.34; 95% CI: 1.15-1.57), and not hypernatremia (HR 1.12; 95%: CI 0.93-1.34), was independently associated with increased risk of all-cause mortality, when compared than the normonatremia category. In time-dependent analyses, both time-averaged hyponatremia (HR 1.65; 95% CI: 1.27-2.15) and hypernatremia (HR 1.41; 95% CI: 1.20-1.65) had a higher independent risk of all-cause mortality. Furthermore, subgroup analyses by type of patients, study design, sample size and follow-up duration revealed similar results across most of these analyses. Baseline hyponatremia and time-dependent hyponatremia or hypernatremia were independently associated with increased all-cause mortality risk in CKD patients.