The relevance of dietary sodium in hemodialysis

Examining the Relationship between Dietary Intake, Socioeconomic Status, and Systolic Blood Pressure of Adults on Hemodialysis in Quito, Ecuador

Background

In Ecuador, the number of adults on hemodialysis (HD) continues to rise. Currently, the effect dietary habits and socioeconomic status (SES) have on blood pressure is not known for those on HD.

Objectives

The objectives of this study focused on adults on HD in Quito, Ecuador to 1) assess the relationship between dietary intake and SES; 2) compare dietary intake to the Kidney Disease Outcomes Quality Initiative (KDOQI) guidelines; and 3) explore the relationship between dietary intake and systolic blood pressure.

Methods

This cross-sectional study was conducted at the dialysis center within Eugenio Espejo Specialties Hospital in Quito, Ecuador between May and June 2022 among 50 adults on HD. Three 24-h recalls were used to determine average dietary intake and the 25-item Instituto Nacional de Estadística y Censos-Stratification of SES was used to determine SES. Electrolytes and 2 blood pressure readings were collected. Qualitative narrative data analysis was performed to identify themes using NVivo v12. T-tests of independence, simple, and multiple linear regressions using age and sex as confounders were conducted using R and a P < 0.05 was deemed as statistically significant.

Results

On an average, 76% of participants consumed <25 kcal/kg body weight energy and 64% consumed <1 g protein/kg body weight. Participants consumed less energy and protein compared with the KDOQI guidelines (P < 0.05). Positive relationships were observed with potassium and blood pressure (β = 0.020, P < 0.05) and SES with energy, protein, and phosphorus (P < 0.05). Themes that were identified as contributing to dietary intake were limited knowledge, lack of consistency with dietary information, and limited appetite.

Conclusions

Findings from this study indicate that the focus should be on improving energy and protein intake for this population.

Results of Salt Intake Restriction Monitored with the New Sodium Control Biosensor

INTRODUCTION

Adherence to a low-sodium (Na) diet is crucial in patients under hemodialysis, as it improves cardiovascular outcomes and reduces thirst and interdialytic weight gain. Recommended salt intake is lower than 5 g/day. The new 6008 CAREsystem monitors incorporate a Na module that offers the advantage of estimating patients' salt intake. The objective of this study was to evaluate the effect of dietary Na restriction for 1 week, monitored with the Na biosensor.

METHODS

A prospective study was conducted in 48 patients who maintained their usual dialysis parameters and were dialyzed with a 6008 CAREsystem monitor with activation of the Na module. Total Na balance, pre-/post-dialysis weight, serum Na (sNa), changes in pre- to post-dialysis sNa (ΔsNa), diffusive balance, and systolic and diastolic blood pressure were compared twice, once after 1 week of patients' usual Na diet and again after another week with more restricted Na intake.

RESULTS

Restricted Na intake increased the percentage of patients on a low-Na diet (<85 Na mmol/day) from 8% to 44%. Average daily Na intake decreased from 149 ± 54 to 95 ± 49 mmol, and interdialytic weight gain was reduced by 460 ± 484 g per session. More restricted Na intake also decreased pre-dialysis sNa and increased both intradialytic diffusive balance and ΔsNa. In hypertensive patients, reducing daily Na by more than 3 g Na/day lowered their systolic blood pressure.

CONCLUSIONS

The new Na module allowed objective monitoring of Na intake, which in turn could permit more precise personalized dietary recommendations in patients under hemodialysis.

Dextrose solution for priming and rinsing the extracorporeal circuit in hemodialysis patients: A prospective pilot study

INTRODUCTION

Excess sodium intake and consequent volume overload are major clinical problems in hemodialysis (HD) contributing to adverse outcomes. Saline used for priming and rinsing of the extracorporeal circuit is a potentially underappreciated source of intradialytic sodium gain. We aimed to examine the feasibility and clinical effects of replacing saline as the priming and rinsing fluid by a 5% dextrose solution.

MATERIALS AND METHODS

We enrolled non-diabetic and anuric stable HD patients. First, the extracorporeal circuit was primed and rinsed with approximately 200-250 mL of isotonic saline during 4 weeks (Phase 1), subsequently a similar volume of a 5% dextrose solution replaced the saline for another 4 weeks (Phase 2), followed by another 4 weeks of saline (Phase 3). We collected data on interdialytic weight gain (IDWG), pre- and post-dialysis blood pressure, intradialytic symptoms, and thirst.

RESULTS

Seventeen chronic HD patients (11 males, age 54.1 ± 18.7 years) completed the study. The average priming and rinsing volumes were 236.7 ± 77.5 and 245.0 ± 91.8 mL respectively. The mean IDWG did not significantly change (2.52 ± 0.88 kg in Phase 1; 2.28 ± 0.70 kg in Phase 2; and 2.51 ± 1.2 kg in Phase 3). No differences in blood pressures, intradialytic symptoms or thirst were observed.

CONCLUSIONS

Replacing saline by 5% dextrose for priming and rinsing is feasible in stable HD patients and may reduce intradialytic sodium loading. A non-significant trend toward a lower IDWG was observed when 5% dextrose was used. Prospective studies with a larger sample size and longer follow-up are needed to gain further insight into the possible effects of using alternate priming and rinsing solutions lowering intradialytic sodium loading.

TRIAL REGISTRATION

Identifier NCT01168947 (ClinicalTrials.gov).

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.

Prehemodialysis hyponatremia and extracellular water: Is it simply too much water?

Observational hemodialysis (HD) studies report an association between hyponatremia and increased mortality. As volume overload is also associated with mortality, we wished to determine whether hyponatremia is linked to increased extracellular water (ECW). We measured ECW, total body water (TBW) and body composition predialysis with multifrequency bioimpedance, arm strength with pinch gauge and hand grip strength (PS, HGS), standard biochemistry profiles, comorbidity and clinical frailty scores (CFS). We reviewed 324 patients, 195 (60.2%) male, mean age 62.3 ± 15.6 years. Thirty-eight (11.7%) patients were hyponatremic (sodium ≤135 mmol/L), ECW/height² was not different, but ECW/TBW (0.409 ± 0.016 vs. 0.402 ± 0.016, p < 0.01), C reactive protein (CRP) (9(4-6) vs. 5(2-12) g/L, p < 0.05), CFS (5(4-6) vs. 4(3-6), p < 0.05) were higher in hyponatremic patients, whereas appendicular lean mass index (8.6 ± 1.7 vs. 9.4 ± 1.8 kg/m2, p < 0.01), serum albumin (36.3 ± 5.5 vs. 38.8 ± 5.0 g/L, p < 0.01) and PS (3.7(2.7-4.7) vs. 4.7 (3.2-6.5) kg, p < 0.05)) were lower. Both serum sodium, and serum sodium after adjustment for glucose were associated with serum creatinine (β 4.26, (95% confidence limits [CL] 1.9-6.7), β 3.98 (CL 1.6-6.4), both p = 0.001, respectively) and negatively with CRP (β -0.76, [CL] -1.5 to -0.5), β -0.72 (CL -1.44 to -0.12), p = 0.036, p = 0.046, respectively) in a multivariable model. Hyponatremic HD patients did not simply have an increased ECW, as the increased ECW/TBW and ECW/ICW ratios were more likely secondary to loss of muscle mass and strength, associated with increased CRP and reduced albumin, suggesting that hyponatremia is associated with inflammation, loss of muscle mass and increasing frailty.

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

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

Impact of salt taste dysfunction on interdialytic weight gain for hemodialysis patients; a cross-sectional study

Background

Little is known about salt taste dysfunction among hemodialysis (HD) patients. This study aimed to elucidate the prevalence of salt taste dysfunction and its relationship with interdialytic weight gain (IDWG) among HD patients.

Methods

A single-center cross-sectional study involving 99 maintenance HD patients was conducted in September 2015. Salt taste threshold was measured using a salt-impregnated test strip. Salt taste dysfunction was defined as a recognition threshold of ≥0.8%. IDWG was calculated as the mean value of weight gain at the beginning of each week during a 1-month period before the taste test. We performed a multivariate analysis using the standard linear regression model to investigate the association between salt taste dysfunction and IDWG.

Results

Among the 99 participants, 42% had a recognition threshold of 0.6%, whereas 38% had a recognition threshold of ≥1.6%. Overall, the prevalence of salt taste dysfunction was 58%. The mean (±SD) IDWG was 4.9% (±1.7%), and there was no significant difference in IDWG between the two groups with (4.9%) and without (4.8%) salt taste dysfunction (P = 0.90). A multivariate analysis indicated that salt taste dysfunction is not significantly associated with IDWG (mean difference = 0.06; 95% confidence interval = − 0.27 to 0.40).

Conclusions

The prevalence of salt taste dysfunction was very high among HD patients who had a unique distribution of salt taste recognition thresholds with two peaks. We found no significant association between salt taste dysfunction and IDWG.

Complementary Biomarker Assessment of Components Absorbed from Diet and Creatinine Excretion Rate Reflecting Muscle Mass in Dialysis Patients

To prevent protein energy malnutrition (PEM) and accumulation of waste products, dialysis patients require diet adjustments. Dietary intake assessed by self-reported intakes often provides biased information and standard 24-h urinary excretion is inapplicable in dialysis patients. We aimed to assess dietary intake via a complementary, less biased biomarker method, and to compare this to dietary diaries. Additionally, we investigated the prospective association of creatinine excretion rate (CER) reflecting muscle mass with mortality. Complete intradialytic dialysate and interdialytic urinary collections were used to calculate 24-h excretion of protein, sodium, potassium, phosphate and creatinine in 42 chronic dialysis patients and compared with protein, sodium, potassium, and phosphate intake assessed by 5-day dietary diaries. Cox regression analyses were employed to investigate associations of CER with mortality. Mean age was 64 ± 13 years and 52% were male. Complementary biomarker assessed (CBA) and dietary assessed (DA) protein intake were significantly correlated (r = 0.610; p < 0.001), but there was a constant bias, as dietary diaries overestimated protein intake in most patients. Correlations were found between CBA and DA sodium intake (r = 0.297; p = 0.056), potassium intake (r = 0.312; p = 0.047) and phosphate uptake/intake (r = 0.409; p = 0.008). However, Bland-Altman analysis showed significant proportional bias. During a median follow-up of 26.6 (25.3–31.5) months, nine dialysis patients (23%) died. CER was independently and inversely associated with survival (HR: 0.59 (0.42–0.84); p = 0.003). Excretion measurements may be a more reliable assessment of dietary intake in dialysis patients, as this method is relatively free from biases known to exist for self-reported intakes. CER seems to be a promising tool for monitoring PEM.

Dietary Sodium and Other Nutrient Intakes among Patients Undergoing Hemodialysis in New Zealand

This study describes baseline intakes of sodium and other nutrients in a multi-ethnic sample of hemodialysis patients in New Zealand participating in the SoLID Trial between May/2013 to May/2016. Baseline 3-day weighed food record collections were analyzed using Foodworks 8 Professional food composition database, supplemented by other sources of nutrient information. Intakes of dietary sodium and other nutrients were compared with relevant guidelines and clinical recommendations. Eighty-five participants completed a 3-day weighed food record. The mean (SD) sodium intake was 2502 (957) mg/day at and more than half of the participants exceeded recommended intake levels. Sodium intake was positively associated with energy intake. Only 5% of participants met the recommended calorie density; nine percent of participants ate the recommended minimum of 1.2 g/kg of protein per day; 68% of participants were consuming inadequate fiber at baseline. A high proportion of dialysis patients in SoLID Trial did not meet current renal-specific dietary recommendations. The data show excess sodium intake. It is also evident that there was poor adherence to dietary guidelines for a range of other nutrients. A total diet approach is needed to lower sodium intake and improve total diet quality among hemodialysis patients in New Zealand.

Excess fluid volume: sociodemographic and clinical analysis in haemodialysis patients

ABSTRACT Objective: To analyse the defining characteristics and related factors in the nursing diagnosis Excess fluid volume and its relationship to sociodemographic and clinical variables in haemodialysis patients. Method: Cross-sectional study, conducted using a form and physical examination, with a sample of 100 patients, between December 2012 and April 2013 at a university hospital and a dialysis clinic. Results: It was found 10 significant statistical associations between the defining characteristics/ related factors of Excess fluid volume and the sociodemographic and clinical variables. Conclusion: The defining characteristics and related factors of Excess fluid volume could be influenced by sociodemographic and clinical variables in haemodialysis clientele.

Dialysis frequency versus dialysis time, that is the question

We reviewed a number of prospective randomized and multiple retrospective cohort studies of different dialysis prescriptions: longer dialysis time, at a frequency of at least three times a week, or a frequency of daily hemodialysis with a shorter dialysis time. Interestingly, the retrospective analyses have generally found significant survival benefits in the intensive dialysis groups, whereas more modest effects were observed in the prospective randomized controlled trials. The reason for this discrepancy may be related to the retrospective nature of the studies and possible selection bias; for example, the patients who were prescribed more frequent dialysis may have had more difficulties with volume control or high blood pressure. In contrast, the randomized controlled trials of increased dialysis frequency, which have shown indirect and modest benefits in complex coprimary end points, have small sample sizes and are plagued with difficulties in recruitment and compliance with the randomly allocated more frequent dialysis. This review, which attempts to balance the potential benefits of more frequent dialysis with the burden on the patient's lifestyle, an increased risk of access malfunction, as well as societal costs of such intensive dialysis prescriptions, concludes in favor of the conventional three times per week dialysis (at a minimum) but at longer dialysis times than is currently prescribed based on the Kt/Vurea metric alone.