European Journal of Cardiovascular Medicine

Hypertension is a prevalent and significant concern among patients undergoing hemodialysis, contributing to increased cardiovascular morbidity and mortality (1). A key factor influencing blood pressure in this population is sodium balance, which is intricately linked to both interdialytic weight gain (IDWG) and the sodium "setpoint" of individual patients (2).

The concept of a sodium "setpoint" refers to the body's intrinsic osmoregulatory mechanism that maintains sodium balance and extracellular fluid volume. In hemodialysis patients, this setpoint can be influenced by various factors, including dietary sodium intake, residual renal function, and the sodium concentration in the dialysate. When the dialysate sodium concentration exceeds the patient's setpoint, it may lead to increased sodium retention, resulting in elevated IDWG and subsequent hypertension (3).

Interdialytic weight gain serves as a surrogate marker for sodium and fluid overload. Excessive IDWG is associated with increased blood pressure and a higher risk of cardiovascular events in hemodialysis patients (4). Studies have demonstrated that individualized adjustment of dialysate sodium concentration to align with a patient's setpoint can mitigate IDWG and improve blood pressure control (5).

Understanding the interplay between sodium setpoint, IDWG, and blood pressure is crucial for optimizing dialysis prescriptions and enhancing patient outcomes. Further

research is needed to refine strategies for individualized sodium management in hemodialysis patients.

Present study has been conducted with following aim and objective,

Aim

To evaluate the correlation between sodium “setpoint,” interdialytic weight gain (IDWG), and blood pressure in patients undergoing maintenance hemodialysis.

Objectives

To determine the individual sodium “setpoint” in hemodialysis patients.

To assess the magnitude of interdialytic weight gain (IDWG) in these patients.

To evaluate pre- and post-dialysis blood pressure and its association with sodium setpoint and IDWG.

To analyze whether individualized dialysate sodium prescription can influence IDWG and blood pressure control.

Study Design: This was a prospective observational study conducted over August 2020 to January 2021, 6 months in the hemodialysis unit of hospital. Study Population: Patients aged ≥18 years undergoing maintenance hemodialysis thrice weekly for at least 3 months were included. Patients with acute infections, hospitalization within the last month, significant liver disease, or those on peritoneal dialysis were excluded. Sample Size: A total of 60 patients were enrolled using convenience sampling. Data Collection: Baseline demographic and clinical data were collected, including age, sex, duration of hemodialysis, comorbidities, and antihypertensive medications. Assessment of Sodium Setpoint: The sodium “setpoint” for each patient was estimated by measuring pre-dialysis plasma sodium concentration over three consecutive dialysis sessions. The average pre-dialysis plasma sodium was considered the patient’s setpoint (1,2). Interdialytic Weight Gain (IDWG): IDWG was calculated as the difference between pre-dialysis weight and post-dialysis weight from the previous session. It was expressed both in kilograms and as a percentage of dry weight: IDWG (%) =Pre-dialysis weight – post-dialysis weight /Dry weight ×100 Blood Pressure Measurement: Pre-dialysis and post-dialysis blood pressure (systolic and diastolic) were recorded using a calibrated sphygmomanometer according to standard protocols. Hypertension was defined based on KDOQI guidelines. Dialysate Sodium Prescription: Dialysate sodium concentration was recorded for each patient. Individualized dialysate sodium was considered when the dialysate sodium matched the patient’s estimated sodium setpoint. Data Analysis: Data were analyzed using [SPSS version 13]. Continuous variables were expressed as mean ± standard deviation (SD) or median (interquartile range) as appropriate. Categorical variables were expressed as frequencies and percentages. Correlation between sodium setpoint, IDWG, and blood pressure was assessed using Pearson or Spearman correlation coefficients. A p-value <0.05 was considered statistically significant. Ethical Considerations: The study was approved by the Institutional Ethics Committee . Written informed consent was obtained from all participants prior to enrollment.

Baseline Characteristics

A total of 60 patients undergoing maintenance hemodialysis were included in the study. The mean age was 52.4 ± 12.3 years, with 38 (63.3%) males and 22 (36.7%) females. The median duration of hemodialysis was 4 (2–6) years. Comorbidities included hypertension in 45 (75%) patients and diabetes mellitus in 22 (36.7%) patients (Table 1).

Table 1: Baseline Demographic and Clinical Characteristics

Sodium Setpoint, IDWG, and Blood Pressure

The mean pre-dialysis plasma sodium (“setpoint”) was 138.5 ± 2.1 mmol/L. The mean interdialytic weight gain was 2.6 ± 0.8 kg (3.2 ± 1.0% of dry weight). The mean pre-dialysis systolic and diastolic blood pressures were 146 ± 14 mmHg and 88 ± 9 mmHg, respectively.

Correlation Analysis

Correlation analysis showed:

Sodium setpoint and IDWG: r = 0.42, p = 0.001 (moderate positive correlation)

Sodium setpoint and pre-dialysis systolic BP: r = 0.38, p = 0.004 (moderate positive correlation)

Sodium setpoint and pre-dialysis diastolic BP: r = 0.31, p = 0.02 (mild positive correlation)

IDWG and pre-dialysis systolic BP: r = 0.45, p < 0.001

IDWG and pre-dialysis diastolic BP: r = 0.36, p = 0.006

Table 2: Correlation between Sodium Setpoint, IDWG, and Blood Pressure

Effect of Individualized Dialysate Sodium

In 30 patients with individualized dialysate sodium matching their sodium setpoint, mean IDWG decreased from 2.7 ± 0.9 kg to 2.1 ± 0.7 kg (p < 0.01), and pre-dialysis systolic BP decreased from 148 ± 15 mmHg to 138 ± 12 mmHg (p < 0.01).

Table :3  Key Findings and Summary

Hypertension and chronic fluid overload continue to be major determinants of adverse cardiovascular outcomes in patients receiving maintenance hemodialysis. In the present study, sodium setpoint showed a significant positive association with interdialytic weight gain (IDWG) and pre-dialysis blood pressure, suggesting that sodium balance plays a central role in extracellular volume expansion and hemodynamic instability in this population. These findings are consistent with prior evidence showing that greater IDWG is closely linked to higher pre-dialysis blood pressure among prevalent hemodialysis patients, supporting the concept that fluid accumulation between dialysis sessions is a clinically meaningful contributor to poor blood pressure control [6].

The mean sodium setpoint observed in our cohort was 138.5 ± 2.1 mmol/L, which falls within the range generally reported in hemodialysis populations. The moderate positive correlation between sodium setpoint and IDWG indicates that patients with a relatively higher physiologic sodium balance may be more prone to thirst, fluid intake, and subsequent interdialytic fluid accumulation. This interpretation is supported by studies demonstrating that higher dialysate sodium exposure or unfavorable sodium gradients are associated with greater IDWG and more difficult volume control [7,9]. Davenport et al. showed that dialysate sodium concentration significantly influences interdialytic weight gain in chronic hemodialysis patients, while Hecking et al. further demonstrated that dialysate sodium concentration is associated not only with IDWG but also with important clinical outcomes such as hospitalization and mortality [7,9].

A similar pattern was observed in relation to blood pressure. In our study, sodium setpoint correlated positively with both systolic and diastolic pre-dialysis blood pressure, and IDWG also showed a strong association with pre-dialysis blood pressure values. These observations reinforce the established relationship between sodium-mediated fluid retention and hypertension in hemodialysis patients. Inrig et al. reported a clear association between higher IDWG and elevated blood pressure, emphasizing that fluid overload remains one of the most important modifiable causes of hypertension in this setting [6]. In addition, changes in dialysate composition affecting sodium exposure have been shown to influence both weight gain and blood pressure control, further supporting the biologic plausibility of our findings [10].

An important finding of the present study was that individualizing dialysate sodium according to the patient’s sodium setpoint was associated with reduced IDWG and improved blood pressure control. This is in agreement with interventional studies showing that lowering or individualizing dialysate sodium can reduce interdialytic fluid gain and improve hemodynamic parameters. Mendoza et al. demonstrated that reducing dialysate sodium concentration led to favorable changes in IDWG and blood pressure in patients on nocturnal in-center hemodialysis [8]. Likewise, Elshahawy et al. reported beneficial effects of individualized dialysate sodium prescriptions on volume-related outcomes in hemodialysis patients [11]. More recently, Radhakrishnan et al. confirmed in a prospective interventional trial that individualized dialysate sodium prescription can improve fluid balance and blood pressure control, supporting a personalized approach to dialysis prescription rather than a uniform sodium concentration for all patients [12].

Taken together, these findings suggest that a fixed dialysate sodium prescription may inadvertently promote sodium loading in some patients, thereby increasing thirst, IDWG, and pre-dialysis hypertension. In contrast, matching dialysate sodium more closely to the patient’s physiologic sodium setpoint appears to be a practical and clinically relevant strategy for optimizing sodium balance. Such an approach may help minimize chronic volume overload, improve blood pressure control, and potentially reduce long-term cardiovascular risk. Therefore, assessment of patient-specific sodium setpoint may represent an important step toward more individualized and physiologically appropriate hemodialysis care [8,9,11,12].

Limitations

This study had several limitations. The sample size was relatively small, and data were collected from a single center, which may limit generalizability. Long-term cardiovascular outcomes were not assessed. Additionally, dietary sodium intake was not rigorously controlled, which could influence IDWG and BP measurements. Future multicenter studies with larger cohorts and long-term follow-up are warranted to validate these findings.

Our study demonstrates that sodium setpoint is positively correlated with interdialytic weight gain and blood pressure in hemodialysis patients. Individualized adjustment of dialysate sodium to match the patient’s setpoint effectively reduces IDWG and improves blood pressure control. These findings support the integration of personalized sodium management strategies into routine hemodialysis care to optimize fluid and blood pressure control and potentially reduce cardiovascular risk.

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