Role of sodium in hemodialysis

The role of intra- and interdialytic sodium balance and restriction in dialysis therapies

The relationship between sodium, blood pressure and extracellular volume could not be more pronounced or complex than in a dialysis patient. We review the patients' sources of sodium exposure in the form of dietary salt intake, medication administration, and the dialysis treatment itself. In addition, the roles dialysis modalities, hemodialysis types, and dialysis fluid sodium concentration have on blood pressure, intradialytic symptoms, and interdialytic weight gain affect patient outcomes are discussed. We review whether sodium restriction (reduced salt intake), alteration in dialysis fluid sodium concentration and the different dialysis types have any impact on blood pressure, intradialytic symptoms, and interdialytic weight gain.

Hyponatraemia and fluid overload are associated with higher risk of mortality in dialysis patients

BACKGROUND

The 5-year mortality rate for haemodialysis patients is over 50%. Acute and chronic disturbances in salt and fluid homeostasis contribute to poor survival and are established as individual mortality risk factors. However, their interaction in relation to mortality is unclear.

METHODS

We used the European Clinical Database 5 to investigate in a retrospective cohort analysis the relationship between transient hypo- and hypernatremia, fluid status and mortality risk of 72 163 haemodialysis patients from 25 countries. Incident haemodialysis patients with at least one valid measurement of bioimpedance spectroscopy were followed until death or administrative censoring from 1 January 2010 to 4 December 2019. Fluid overload and depletion were defined as >2.5 L above, and -1.1 L below normal fluid status, respectively. N = 2 272 041 recorded plasma sodium and fluid status measurements were available over a monthly time grid and analysed in a Cox regression model for time-to-death.

RESULTS

Mortality risk of hyponatremia (plasma sodium <135 mmol/L) was slightly increased when fluid status was normal [hazard ratio (HR) 1.26, 95% confidence interval (CI) 1.18-1.35], increased by half when patients were fluid depleted (HR 1.56, 95% CI 1.27-1.93) and accelerated during fluid overload (HR 1.97, 95% CI 1.82-2.12).

CONCLUSIONS

Plasma sodium and fluid status act independently as risk factors on mortality. Patient surveillance of fluid status is especially important in the high-risk subpopulation of patients with hyponatremia. Prospective patient-level studies should examine the effects of chronic hypo- and hypernatremia, risk determinants, and their outcome risk.

Automated adjustment of dialysate sodium by the hemodialysis monitor: Rationale, implementation, and clinical benefits

Prescribing dialysate sodium is the responsibility of the physician, but there are currently no clear guidelines for this prescription. Furthermore, there is quite frequently a significant difference between prescribed and measured dialysate sodium. Several arguments, both theoretical and experimental, suggest that dialysate sodium should be adjusted individually in such a way as to result in a decreasing sodium profile that takes into account the patient's predialytic natremia. The generalization in clinical routine of this strategy requires the integration into the hemodialysis monitor of software making the machine capable to automatically adjust the dialysate sodium at each session. The only three such softwares that have been integrated into hemodialysis machines for routine clinical use are discussed. All three work with conductivity measurements as a surrogate for sodium concentrations. Although there are only a few publications on the use of these softwares in clinical practice, they appear to result in improved intradialytic tolerance to the dialysis treatment, better control of hypertension, and reduced thirst, leading to decreased interdialytic weight gain.

A first proof-of-concept for the non-invasive, time-efficient measurement of the plasma sodium concentration for individualized dialysis

Dialysis-induced changes in plasma sodium concentration may cause undesirable side effects. To prevent these, the sodium content in dialysis fluid has to be individualized based on the patient's plasma sodium concentration. In this paper, we describe a simple conductivity based method for measuring the plasma sodium concentration. The method is based on performing a bypass during which the residual volume on the dialysate side of the dialyzer at least partially adopts the sodium concentration on the blood side. The conductivity at dialysate outlet of the dialyzer after the end of bypass corresponds to the sodium concentration. We show that already 14 s of bypass are sufficient to subsequently measure a conductivity that correlates with the blood-side sodium concentration. Thus, the short bypass method allows a time saving of 88% compared to the long bypass of 120 s. In vitro experiments with bovine blood show that plasma sodium concentration can be non-invasively and time-efficiently measured during dialysis. Bland Altman analysis reveals a bias of 0.28 mmol/l and limits of agreement of -3.17 and 3.74 mmol/l for the long bypass. For the short bypass, bias is 0.09 mmol/l and limits are -3.90 and 4.08 mmol/l. Since the method presented is based on established conductivity cells, no additional sensors are required, so that the method could be easily implemented in dialysis machines. In future, performing a bypass at the beginning of a treatment may be used to adjust the composition of dialysis fluid individually for each patient.

Comparative Impact of Isolated Ultrafiltration and Hemodialysis on Fluid Distribution: A Bioimpedance Study

INTRODUCTION

Isolated ultrafiltration (IUF) is an alternative treatment for diuretic-resistant patients with fluid retention. Although hemodialysis (HD) predominantly decreases extracellular water (ECW), the impact of IUF on fluid distribution compared with HD remains unclear.

METHODS

We compared the effect of HD (n = 22) and IUF (n = 10) sessions on the body fluid status using a bioimpedance analysis device (InBody S10).

RESULTS

The total ultrafiltration volume was similar between HD and IUF (HD 2.5 ± 0.3 vs. ICF 2.1 ± 0.3 L/session, p = 0.196). The reduction rate of ECW was significantly higher than that of intracellular water (ICW) after HD (ECW -7.9% ± 0.8% vs. ICW -3.0% ± 0.9%, p < 0.001) and IUF (ECW -5.8% ± 0.9% vs. ICW -3.6% ± 0.8%, p = 0.048). However, the change in the ratio of ECW to total body water in HD was significantly larger than that in IUF (HD -3.2% ± 0.3% vs. ICF -1.1% ± 0.4%, p < 0.001). The reduction rates in serum tonicity (effective osmolality) were higher after HD than after IUF (HD -1.8% ± 0.5% vs. IUF -0.6% ± 0.2%, p = 0.052). Among the components of effective osmolality, the reduction rates of serum K+ and glucose levels after HD were significantly higher than those after IUF (serum K+: HD -30.5% ± 1.6% vs. IUF -0.5% ± 3.8%, p < 0.001; serum glucose: HD -15.4% ± 5.0% vs. IUF 0.7% ± 4.8%, p = 0.026), while the serum Na+ level was slightly and similarly reduced (HD -0.8% ± 0.4% vs. IUF -0.8% ± 0.4%, p = 0.500). The reduction in the osmolal gap value (measured osmolality-calculated osmolarity) was significantly greater after HD sessions than after IUF sessions (HD -12.4 ± 1.4 vs. IUF 2.0 ± 1.0 mOsm/kg, p = 0.001).

CONCLUSION

The extracellular fluid reduction effect of HD is stronger than that of IUF. The different changes in effective osmolality and osmolal gap after HD and IUF sessions may be related to the different effects of HD and IUF on fluid distribution.

Impact of dialysate sodium concentration on vascular refilling

BACKGROUND

Although relationship between dialysate sodium concentration and hemodynamic stability has been well studied over the years, outcomes of absolute blood volume (ABV) maintenance and vascular refilling volume (V_ref ) modifications were not included, as its analysis has not been easily accessible to direct investigation. However, recent studies report a simple and feasible methodology to assess ABV and V_ref during hemodialysis (HD) treatments. It is the aim of this study to analyze whether sodium concentration in dialysate modifies ABV drop and V_ref .

METHODS

The study was performed in 19 patients under HD. During three different sessions, sodium concentration in dialysate was randomized to three different profiles: low sodium concentration (LNa, 138 mEq/L), neutral sodium concentration (NNa, 140 mEq/L), and high sodium concentration (HNa, 143 mEq/L). ABV and V_ref were calculated using Kron et al methodology.

RESULTS

Predialysis values of the measured parameters showed similar results for the three profiles. Sodium concentration showed an effect on ABV drop, V_ref, and vascular refilling fraction (F_ref ). Pair-wise comparison revealed mean ABV decreased 0.21 L less when using HNa profile versus LNa profile (p = 0.027), a mean V_ref increase of 0.39 L (p = 0.038), and a mean F_ref increase of 9.94% (p = 0.048).

CONCLUSIONS

This study shows that the use of HNa profiles increases V_ref and F_ref and reduces ABV drop during dialysis treatments when compared to LNa profiles.

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).

Effect of low dialysate sodium in the management of intradialytic hypertension in maintenance hemodialysis patients: A single-center Indian experience

BACKGROUND

High dialysate sodium is a significant contributor to intradialytic hypertension (IDH) in maintenance hemodialysis patients. In this study, we aimed to study the effect of low dialysate sodium on IDH in Indian hemodialysis patients.

MATERIALS AND METHODS

Fifty patients on maintenance hemodialysis for atleast 3 months with episodes of IDH were enrolled in this study. The study was performed in two different stages. In the first phase, patients were dialyzed with standard dialysate sodium (140 mEq/L) for eight consecutive sessions and in the second phase, they were dialyzed with low sodium dialysate (136 mEq/L) for eight consecutive sessions. Differences in pre, intradialytic, and post-HD blood pressure, interdialytic weight gain, mean serum sodium, intradialytic adverse events, and number of IDH episodes requiring intervention between the two phases were assessed.

RESULTS

The mean age of the study population was 52 years (36 males,14 females). The mean post-HD systolic and diastolic BP was 163.26 ± 9.58 mmHg and 88.60 ± 5.27 mmHg in the standard dialysate phase and 142.38 ± 14.09 mmHg and 84.58 ± 4.276 mmHg, respectively, in the low dialysate phase (p < 0.01). Interdialytic weight gain was 3.34 ± 0.9 and 3.11 ± 0.86 in the standard and low sodium dialysate phases, respectively (p = 0.19).The mean pre-HD plasma sodium level was 138.48 ± 3.69 and 135.80 ± 1.35 mEq/dl, respectively, in standard and low dialysate phases (p = 0.01). There was significant reduction in number of IDH episodes requiring intervention. There was no difference in hypotensive episodes, adverse events between the two phases.

CONCLUSION

In patients with intradialytic hypertension, low dialysate sodium significantly reduces the post-HD blood pressure and intradialytic hypertensive episodes, when compared with standard sodium dialysate.

Dyselectrolytemia-management and implications in hemodialysis (Review)

Hemodialysis is a method for the renal replacement therapy followed by series of acute and chronic complications. Dyselectrolytemia appears in patients undergoing dialysis through mechanisms related to the chronic kidney disease and/or to the dialysis therapy and for this group of patients it is associated with an increase of morbidity and mortality. The dialysate has a standard composition, which can be modified according to the patient's characteristics. During hemodialysis patients are exposed to 18,000-36.000 litres of water/year, and the water purity along with the biochemical composition of the dialysate are essential. The individualization of the dialysis prescription is recommended for each patient and it has an important role in preventing the occurrence of dyselectrolyemia. The individualization of the treatment prescription according to the blood constants of each patient is the prerogative of the nephrologist and the association of the electrolyte imbalances with the patients cardiovascular mortality explains the importance of paying special attention to them.

Individualized dialysate sodium prescriptions using sodium gradients for high-risk hemodialysis patients lowered interdialytic weight gain and achieved target weights

INTRODUCTION

Large interdialytic weight gain (IDWG) is associated with increased morbidity and mortality in chronic hemodialysis patients. Over 50% of patients at our inner city tertiary academic center dialysis unit had IDWG and target weights (TW) above goal. We conducted an open-label nonrandomized study to explore the effects of an individualized dialysate sodium (DNa) prescription using Na gradients in patients at high risk for large IDWG. Thirty-three patients receiving chronic hemodialysis received individualized DNa prescriptions with a DNa bath of 0 to -2 meq/L below their serum Na level in the intervention group, while patients in the control group were prescribed the standard dialysate Na at 138 mmol/L. Serum Na level, predialysis SBP, symptomatic hypotensive episodes, and %hemodialysis treatments with large IDWG (%TxAIDWG) and above TW(%TxATW) were recorded before and three months after the intervention. We used student t tests to compare continuous variables and Chi-square tests to compare binary variables between the groups at baseline and after the intervention. Age- and sex-adjusted linear regression models were also constructed to assess the differences in each continuous outcome between the groups. Multivariable logistic regression models were conducted by modeling IDWG decrease and above estimated-dry-weight (EDW) decrease as binary dependent variables with adjustment for age, sex, and EDW change.

FINDINGS

Patients with individualized DNa concentrations had 3.6 times greater odds of having lower IDWG than those with standard dialysate Na concentration. This significant association remained after adjustment for age, sex, and changes in EDW (OR: 3.63; 95% CI, 1.03-12.9). There was no difference in predialysis BP or symptomatic hypotensive episodes between the two groups.

DISCUSSION

Individualized DNa prescriptions appeared to be well tolerated and may be effective for optimal fluid management in high-risk hemodialysis patients.

Effects of Individualized Dialysate Sodium Prescription in Hemodialysis - Results from a Prospective Interventional Trial

INTRODUCTION

Individualized dialysate sodium prescription does affect weight gain, blood pressure (BP), and intradialytic complications. A prospective interventional trial (Dialysate Individualised Sodium (DISO) trial) was conducted to study this issue in Indian patients.

METHODS

Forty patients on thrice-weekly maintenance hemodialysis (HD) for at least 6 weeks were enrolled. The study was performed in two different phases. In the first phase, 12 consecutive HD sessions were done with a standard dialysate sodium concentration of 140 mEq/L. In the second phase, 12 consecutive HD sessions were done with dialysate sodium concentration set to individualized value (mean of pre-HD sodium concentration multiplied by Donnan coefficient of 0.95). Differences in pre- and post-HD sodium, interdialytic weight gain (IDWG), pre- and post-HD BP, thirst scores, and intradialytic adverse events during both phases were assessed.

RESULTS

The mean age of patients was 45.65 years (24 males, 16 females). The mean serum pre-HD sodium level was 138.7 ± 1.7 meq/L in the standard phase and 138.2 ± 2.6meq/L in the individualized phase (P = 0.229). In the standard phase, the mean IDWG was 2.64 ± 1.56 kg and 2.13 ± 0.99 kg in the individualized phase (P = 0.008). The mean pre-HD systolic BP was 138 ± 18 mmHg and 134 ± 17 mmHg in the standard and individualized phases (P = 0.008). There was no difference in intradialytic symptoms, hypotensive episodes or requirement of interventions. Hypertension episodes occurred at a mean value of 2.2 and 1.2 in the standard and individualized phases, respectively (P = 0.010).

CONCLUSION

The use of individualized dialysate sodium level is safe and results in lower IDWG, pre-HD systolic BP, and intradialytic hypertension in patients on HD.

Automated individualization of dialysate sodium concentration reduces intradialytic plasma sodium changes in hemodialysis

In standard care, hemodialysis patients are often treated with a center‐specific fixed dialysate sodium concentration, potentially resulting in diffusive sodium changes for patients with plasma sodium concentrations below or above this level. While diffusive sodium load may be associated with thirst and higher interdialytic weight gain, excessive diffusive sodium removal may cause intradialytic symptoms. In contrast, the new hemodialysis machine option “Na control” provides automated individualization of dialysate sodium during treatment with the aim to reduce such intradialytic sodium changes without the need to determine the plasma sodium concentration. This proof‐of‐principle study on sodium control was designed as a monocentric randomized controlled crossover trial: 32 patients with residual diuresis of ≤1000 mL/day were enrolled to be treated by high‐volume post‐dilution hemodiafiltration (HDF) for 2 weeks each with “Na control” (individually and automatically adjusted dialysate sodium concentration) versus “standard fixed Na” (fixed dialysate sodium 138 mmol/L), in randomized order. Pre‐ and post‐dialytic plasma sodium concentrations were determined at bedside by direct potentiometry. The study hypothesis consisted of 2 components: the mean plasma sodium change between the start and end of the treatment being within ±1.0 mmol/L for sodium‐controlled treatments, and a lower variability of the plasma sodium changes for “Na control” than for “standard fixed Na” treatments. Three hundred seventy‐two treatments of 31 adult chronic hemodialysis patients (intention‐to‐treat population) were analyzed. The estimate for the mean plasma sodium change was −0.53 mmol/L (95% confidence interval: [−1.04; −0.02] mmol/L) for “Na control” treatments and −0.95 mmol/L (95% CI: [−1.76; −0.15] mmol/L) for “standard fixed Na” treatments. The standard deviation of the plasma sodium changes was 1.39 mmol/L for “Na control” versus 2.19 mmol/L for “standard fixed Na” treatments (P = 0.0004). Whereas the 95% CI for the estimate for the mean plasma sodium change during “Na control” treatments marginally overlapped the lower border of the predefined margin ±1.0 mmol/L, the variability of intradialytic plasma sodium changes was lower during “Na control” versus “standard fixed Na” treatments. Thus, automated dialysate sodium individualization by “Na control” approaches isonatremic dialysis in the clinical setting.

Effect of plasma sodium concentration on blood pressure regulators during hemodialysis: a randomized crossover study

Background

Intradialytic hypotension is a common complication of hemodialysis. The Hemocontrol biofeedback system, improving intradialytic hemodynamic stability, is associated with an initial transient increase in plasma sodium levels. Increases in sodium could affect blood pressure regulators.

Methods

We investigated whether Hemocontrol dialysis affects vasopressin and copeptin levels, endothelial function, and sympathetic activity in twenty-nine chronic hemodialysis patients. Each patient underwent one standard hemodialysis and one Hemocontrol hemodialysis. Plasma sodium, osmolality, nitrite and nitrate (NOx), endothelin-1, angiopoietins-1 and 2, and methemoglobin as measures of endothelial function, plasma catecholamines as indices of sympathetic activity and plasma vasopressin and copeptin levels were measured six times during each modality. Blood pressure, heart rate, blood volume, and heart rate variability were repeatedly monitored. Generalized Estimating Equations was used to compare the course of the parameters during the two treatment modalities.

Results

Plasma sodium and osmolality were significantly higher during the first two hours of Hemocontrol hemodialysis. Overall, mean arterial pressure (MAP) was higher during Hemocontrol dialysis. Neither the measures of endothelial function and sympathetic activity nor copeptin levels differed between the two dialysis modalities. In contrast, plasma vasopressin levels were significantly higher during the first half of Hemocontrol dialysis. The intradialytic course of vasopressin was associated with the course of MAP.

Conclusions

A transient intradialytic increase in plasma sodium did not affect indices of endothelial function or sympathetic activity compared with standard hemodialysis, but coincided with higher plasma vasopressin levels. The beneficial effect of higher intradialytic sodium levels on hemodynamic stability might be mediated by vasopressin.

Trial registration

ClinicalTrials.gov. Identifier: NCT03578510. Date of registration: July 5th, 2018. Retrospectively registered.

[The different modalities of isonatric hemodialysis]

Setting dialysate sodium allows to adequately adjust sodium balance and plasma sodium at the end of dialysis session. In accordance with the set-point theory based on the concept of restoring cellular hydration, an adequate target for plasma sodium at the end of the session could be the value of predialysis plasma sodium concentration (isonatric hemodialysis). Some recently available dialysis monitors provide an on-line value of plasma-water conductivity usually converted in on-line natremia. There are different modalities of isonatric hemodialysis depending on whether the online value of natremia is used or not. By reviewing the few studies concerning the isonatric hemodialysis, it seems logical to set a target of postdialysis on-line natremia (or plasma-water conductivity) slightly lower than its predialysis value. However this strategy requires specifically designed software not yet available in clinical routine.

Associations between dialysate sodium concentration and plasma sodium concentration of dogs receiving intermittent hemodialysis treatments

OBJECTIVE To compare dialysate sodium concentration and patient plasma sodium concentration of dogs during intermittent hemodialysis treatments. SAMPLE 211 intermittent hemodialysis treatments performed on 40 client-owned dogs for the management of dialysis-dependent uremia. PROCEDURES Medical records were reviewed to determine the plasma sodium concentration of each dog before and after routine hemodialysis treatments. Associations between detected changes in plasma sodium concentration and dialysate sodium concentration were evaluated by use of Spearman rank correlations and linear regression analysis. RESULTS Significant linear correlations were found between the dialysate sodium concentration and patient sodium concentration. The starting dialysate-to-patient sodium gradient was associated with the strongest correlation to the change in patient sodium concentration at the end of the dialysis session. Modest correlations existed between the dialysate sodium concentration and postdialysis patient sodium concentration as well as between the predialysis dialysate-to-patient sodium gradient and postdialysis dialysate-to-patient sodium gradient. CONCLUSIONS AND CLINICAL RELEVANCE The dialysate sodium concentration was correlated with the patient sodium concentration in dogs, and the dialysate-to-patient sodium gradient could be used to further refine this association to predict the postdialysis patient sodium concentration and potentially manage dysnatremia during hemodialysis. Prospective studies should be performed to determine how these associations can be used to correct aberrations as well as to avoid unwanted alterations in patient sodium concentrations.

The Importance of Dialysate Sodium Concentration in Determining Interdialytic Weight Gains in Chronic Hemodialysis Patients: The PanThames Renal Audit

Background and Objectives

There is controversy as to the optimum dialysate sodium to be used for hemodialysis patients, with reports of hypertension and increased interdialytic weight gains with high sodium dialysates and intradialytic hypotension and cramps with low sodium dialysates.

Methods

We analyzed the effect of different dialysate sodium concentrations during a one-week period in an audit of 2187 established patients regularly receiving dialysis three times a week. Patients were given general dietary advice to restrict dietary sodium intake, but no systematic assessment of dietary sodium intake was undertaken.

Results

The prescription of a dialysate sodium concentration of 140 mmol/L and >140 mmol/L, was associated with greater interdialytic weight gains, 3.5% and 4.1% respectively, compared to 2.8% and 2.7% for those using dialysate sodium concentrations of 137 and 136 mmol/L, respectively (p<0.05). The mean pulse pressure was greater patients dialyzing using a sodium of 140 mmol/L, compared to 136 mmol/L, 70 (13) vs 63 (15) mmHg (p<0.011). In addition, 13.5% of patients using the highest sodium dialysate suffered symptomatic intradialytic hypotension requiring intravenous fluid resuscitation, compared to 2.7% who used the lowest sodium concentrate (p<0.05).

Conclusions

This analysis would support the use of lower dialysate sodium concentrations to aid in reducing interdialytic weight gains and subsequent intradialytic hypotension.

Sodium Prescription in the Prevention of Intradialytic Hypotension: New Insights into an Old Concept

Background: Sodium prescription in patients with intradialytic hypotension remains a challenge for the attending nephrologist, as it increases dialysate conductivity in hypotension-prone patients, thereby adding to dietary sodium levels. Methods: New sodium prescription strategies are now available, including the use of a mathematical model to compute the sodium mass to be removed during dialysis as a physiological controller. Results: This review describes the sodium load of patients with end-stage renal disease on chronic hemodialysis (HD) and discusses 2 strategies to remove excess sodium in patients prone to intradialytic hypotension, namely, Profiled HD and the hemodiafiltration Aequilibrium System. Conclusion: The Profiled HD and Aequilibrium System trial both proved effective in counteracting intradialytic hypotension.

Plasma Calcium Concentration Modifies the Blood Sodium During Hemodialysis: Lessons from Hard Water Syndrome

Introduction. Extracellular sodium (Na+) concentration is maintained within a tight physiological range due to hormonal control, that mainly modulates thirst, Na+ and water renal excretion. Extra-renal regulation of Na+ and water homeostasis is only partially understood. Recently it has been debated whether the osmotically inactive Na+ storage is fixed or variable. Methods. In the present study, fourteen End-Stage Renal Disease (ESRD) patients treated by chronic hemodialysis underwent by accident to a sharp increase in plasmatic calcium (Ca+2) levels due to the failure of the water control system, leading to the so-called hard water syndrome. The levels of plasmatic Ca+2 after 1 hr of hemodialysis were correlated with urea, Na+, potassium (K+) and creatinine levels. Eleven ESRD patients treated with hemodialysis under similar conditions were used as controls. Results. The hard water syndrome resulted in hypercalcemia, while mean plasma levels of Na+, K+ and urea were not different compared to controls. Plasma creatinine levels were slightly but significantly higher that control. A correlation analysis on the measured variables has showed a positive correlation between plasma Ca+2 and Na+ levels (Pearson=0.428, p=0.032), and the absence of any correlation with K+, creatinine and urea concentration. Conclusions. Our study suggests that acute changes in plasmatic Ca+2 levels may affect Na+ concentration in the absence of renal function; it is possible that hypercalcemia may trigger Na+ release from the osmotically inactive storage. These data further support previous observations on the interplay of sodium and calcium at extrarenal sites.

Iatrogenic hypernatremia in hemodialysis patients: A result of erroneous online conductivity monitor and conductivity meter reading

Hyponatremia is common in chronic kidney disease and in end stage kidney disease (ESKD) but hypernatremia is infrequent in ESKD. The incidence of hypernatremia is higher in ambulatory peritoneal dialysis (PD) than in hemodialysis (HD) patients. In PD patients it is often a result of excessive ultrafiltration but in HD it is often a result of dialysate composition errors. Dialysate composition errors can inadvertently cause either hyponatremia or hypernatremia. We present two cases of symptomatic hypernatremia which manifested as increased thirst, excessive weight gain and worsening hypertension in HD patients. The hypernatremia was caused by a combination of errors in online conductivity reading and a faulty hand held conductivity meter. Symptoms were relieved in both patients after replacement of the dialysis machine.

The Dialysis Sodium Gradient: A Modifiable Risk Factor for Fluid Overload

Background

Fluid overload in patients on conventional hemodialysis is a frequent complication, associated with increased cardiovascular morbidity and mortality. The dialysate sodium prescription is a potential modifiable risk factor. Our primary objective was to describe associations between dialysate-to-serum sodium gradient and parameters of fluid status. A secondary objective was to evaluate the 6-month risk of hospitalization and mortality in relation to sodium gradient.

Methods

We performed a cross-sectional study of 110 prevalent conventional hemodialysis patients at a single center. The associations of sodium gradient with interdialytic weight gain index (IDWG%), ultrafiltration (UF) rate, and blood pressure (BP) were analyzed.

Results

The mean serum sodium gradient was 4.6 ± 3.6 mEq/L. There was a direct correlation between sodium gradient and IDWG% (r = 0.48, p < 0.01) as well as UF rate (r = 0.44, p < 0.01). In a logistic regression model, a 1 mEq/L higher sodium gradient was associated with increased risk of IDWG% >3% (OR 1.33, p < 0.01) and increased risk of UF rate >10 mL/kg/h (OR 1.16, p = 0.03), but there were no associations with intradialytic hypotension, intradialytic hypertension or BP. No significant differences were found with 6-month hospitalization or mortality risk in relation to sodium gradient.

Conclusion

A higher sodium gradient was associated with significant increases in IDWG and UF rates, known to be associated with poor outcomes, but was not associated with intradialytic hypotension. Individualizing the dialysate sodium prescription to minimize sodium gap may lead to less fluid overload in conventional hemodialysis patients.

Dialysate Sodium: Rationale for Evolution over Time

Oligo-anuric individuals receiving hemodialysis (HD) are dependent on the dialysis machine to regulate sodium and water balance. Interest in adjusting the dialysate sodium concentration to promote tolerance of the HD procedure dates back to the early years of dialysis therapy. Evolution of dialysis equipment technologies and clinical characteristics of the dialysis population have prompted clinicians to increase the dialysate sodium concentration over time. Higher dialysate sodium concentrations generally promote hemodynamic stabilization and reduce intradialytic symptoms but often do so at the expense of stimulating thirst and promoting volume expansion. The opposite may be true for lower dialysate sodium concentrations. Observational data suggest that the association between dialysate sodium and outcomes may differ by serum sodium levels, supporting the trend toward individualization of the dialysate sodium prescription. However, lack of randomized controlled clinical trial data, along with operational safety concerns related to individualized dialysate sodium prescriptions, have prevented expert consensus regarding the optimal approach to the dialysate sodium prescription.

Electrolytes and Fluid Management in Hemodialysis and Peritoneal Dialysis

The kidney is a complex and vital organ, regulating the electrolyte and fluid status of the human body. As hemodialysis (HD) and peritoneal dialysis (PD) are forms of renal replacement therapy and not an actual kidney, they do not possess the same physiologic regulation of both fluid and electrolytes. Precise regulation of fluid and electrolytes in the HD and PD population remains a constant challenge. In this review, fluid status of both HD and PD will be examined, as well as sodium, potassium, phosphorous, and calcium. Each electrolyte will be analyzed by its physiological significance, the complications that arise when a proper balance cannot be maintained, and methods to correct these imbalances. An overview of the fluid compartments and volume of distribution within the body will be discussed. Ultrafiltration, a modality used in both forms of renal replacement therapy, will be defined, along with its impact on fluid status. Fluid assessment will be addressed, along with proper maintenance of fluid homeostasis. By having an understanding of the pathophysiology behind the fluid and electrolyte abnormalities that occur in end-stage renal disease, one can direct proper management with medications, diet, and alterations in dialysis to provide patients with the most optimal form of renal replacement therapy available.

Finite-element modeling of time-dependent sodium exchange across the hollow fiber of a hemodialyzer by coupling with a blood pool model

INTRODUCTION

Hollow fiber models describe the exchange of solutes between blood and dialysate across the membrane of a single fiber of the hemodialysis filter (hemodialyzer). This work aims to develop a new approach to simulate the solute exchange in a hollow fiber in a dynamic and realistic way. Sodium was chosen as our solute of interest due to its importance in hemodialysis as an osmotic regulator.

METHODS

A 2-dimensional (2D) hollow fiber model based on the finite element method (FEM) is coupled to a simple blood pool model to dynamically update the concentration of the solute entering the dialyzer. The resulting coupled model maintains the geometrical detail of the 2D fiber representation and gains a dynamic, blood-side inlet solute concentration. In vitro dialysis sessions were carried out for model validation, by implementing a combination of blood volume loss and/or sodium concentration steps. Plasmatic sodium concentration was recorded by blood gas sampling. Dialysate inlet and outlet conductivities were continuously recorded.

RESULTS

Simulated plasmatic sodium concentration was compared with data from the blood gas samples. A mean error of 1.76 ± 1.03 mM was found for the complete dataset, along with a 3.87 mM maximum error. The simulated outlet dialysate sodium concentration was compared with the recorded outlet dialysate conductivity: a very high correlation was found on the whole dataset (R2 = 0.992).

CONCLUSIONS

Coupling our FEM hollow fiber model to a simple blood pool model proved to be an effective approach for dynamical analysis of the properties of the hemodialyzer.

Clinical Effects of Standard and Individualized Dialysate Sodium in Patients on Maintenance Hemodialysis

BACKGROUND:

The degree to which the dialysate prescription and, in particular, the dialysate sodium concentration influences blood pressure and interdialytic weight gain (IDWG) via changes in sodium flux, plasma volume or the other parameters is not well understood. The aim of the study was to investigate whether dialysis patients will have some beneficial effects of dialysate sodium set up according to serum sodium or sodium modeling.

MATERIAL AND METHODS:

Ninety-two nondiabetic subjects (52 men and 40 women) performed 12 consecutive hemodialysis (HD) sessions (4 weeks) with dialysate sodium concentration set up on 138 mmol/L (standard sodium – first phase), followed by 24 sessions (second phase) wherein dialysate sodium was set up according to individualized sodium. Variables of interest were: systolic, diastolic and mean blood pressure, pulse, IDWG, thirst score – (Xerostomia Inventory (XI) and Dialysis Thirst Inventory (DTI)) and side effects (occurrence of hypotension and muscle cramps). After the first phase, the subjects were divided into 3 groups: normotensive (N=76), hypertensive (N= 11) and hypotensive (N=5) based on the average pre-HD systolic BP during the whole period of the first phase.

RESULTS:

Sodium individualization resulted in significantly lower blood pressure (133.61 ± 11.88 versus 153.60 ± 14.26 mmHg; p=0.000) and IDWG (2.21 ± 0.93 versus 1.87 ± 0.92 kg; p=0.018) in hypertensive patients, whereas normotensive patients showed only significant decrease in IDWG (2.21 ± 0.72 versus 2.06 ± 0.65, p=0,004). Sodium profiling in hypotensive patients significantly increased IDWG (2.45 vs. 2.74, p= 0,006), and had no impact on blood pressure. Thirst score was significantly lower in normotensive patients with individualized-sodium HD and showed no change in the other two groups. During the second phase, hypotension occurred in only 1 case and muscle cramps in 10 normotensive patients.

CONCLUSION:

Individualized sodium resulted in clinical benefits in normotensive and hypertensive patients.

[Hemodynamic effects of succinate-containing dialyzing solution]

AIM

To assess the results of using an acetate-free succinate-containing dialyzing solution (SDS) against natremia and blood pressure (BP) in patients on chronic hemodialysis (HD).

SUBJECTS AND METHODS

Ninety-two patients were transferred from 3 Saint Petersburg HD centers to 3-month HD treatment using SDS. The investigators measured blood biochemical indicators immediately before and 1 and 3 months after the investigation, BP before and after a successive HD session, and the patients' weight and its gain in the period between HD sessions. Hypotensive and hypertensive episodes were recorded during HD sessions throughout the investigation.

RESULTS

Following 3-month treatment using SDS, there were statistically significant decreases in blood sodium levels and systolic BP (SBP) prior to a HD session. At the same time, patients with a baseline pre-HD SBP of less than 100 mm Hg were observed to have a statistically significant increase in this indicator by the end of the investigation. Pre-dialysis diastolic BP (DBP) and post- dialysis SBP and DBP substantially unchanged. After 3 months of SDS use, there was a statistically significant reduction in weight gain in the period between HD sessions. When SDS was administered, the frequency of hypertensive episodes tended to decline after a HD session.

CONCLUSION

The use of SDS causes a drop in pre-dialysis blood sodium levels, ensuring adequate dehydration in patients and improving hypertension control. In doing so, SDS prevents hypotension during a HD session.

A neglected issue in dialysis practice: haemodialysate

The intended function of dialysate fluid is to correct the composition of uraemic blood to physiologic levels, both by reducing the concentration of uraemic toxins and correcting electrolyte and acid-base abnormalities. This is accomplished principally by formulating a dialysate whose constituent concentrations are set to approximate normal values in the body. Sodium balance is the cornerstone of intradialysis cardiovascular stability and good interdialytic blood pressure control; plasma potassium concentration and its intradialytic kinetics certainly play a role in the genesis of cardiac arrhythmias; calcium is related to haemodynamic stability, mineral bone disease and also cardiac arrhythmias; the role of magnesium is still controversial; lastly, acid buffering by means of base supplementation is one of the major roles of dialysis. In conclusion, learning about the art and the science of fashioning haemodialysates is one of the best ways to further the understanding of the pathophysiologic processes underlying myriad acid-base, fluid, electrolyte as well as blood pressure abnormalities of the uraemic patient on maintenance haemodialysis.

Sodium gradient, xerostomia, thirst and inter-dialytic excessive weight gain: a possible relationship with hyposalivation in patients on maintenance hemodialysis

Purpose

The aim of the study was to assess whether hyposalivation is linked with increased thirst sensation and weight gain in hemodialysis (HD) patients and whether there is any connection between hyposalivation and sodium balance.

Methods

One hundred and eleven participants (64 males and 47 females) receiving maintenance hemodialysis, mean age 59.1 ± 13.6 years old, were involved in the study. All participants completed a survey evaluating thirst intensity (DTI) and xerostomia inventory (XI). In addition, pre-dialysis sodium concentration and inter-dialytic weight gain (IWG) were assessed. The division into no-hyposalivation and hyposalivation groups was based on an unstimulated whole saliva (UWS) flow rate.

Results

Hyposalivation, UWS below 0.1 mL/min, was reported in 28.8 % of HD patients. In these participants, IWG was higher than in patients with UWS > 0.1 mL/min (3.65 ± 1.78 vs 3.0 ± 1.4; p = 0.042), as well as the pre-dialysis sodium gradient (3.22 ± 2.1 vs 1.6 ± 2.8; p = 0.031). The mean XI and DTI scores did not differ between study groups. In the hyposalivation group, pre-dialysis sodium serum gradient negatively correlated with saliva outflow (ρ = −0.61, p = 0.019) and positively with IWG (ρ = 0.49, p = 0.022). IWG correlated with XI (ρ = 0.622, p = 0.016) in hyposalivation group and with DTI in no-hyposalivation group (ρ = 0.386, p = 0.033).

Conclusions

Hyposalivation significantly correlates with IWG; however, its influence on thirst and self-reported mouth dryness seems to be weaker than expected. Additionally, hyposalivation was found to be associated with an elevated pre-dialysis sodium gradient.

Rationale and design of the Sodium Lowering In Dialysate (SoLID) trial: a randomised controlled trial of low versus standard dialysate sodium concentration during hemodialysis for regression of left ventricular mass

BACKGROUND

The current literature recognises that left ventricular hypertrophy makes a key contribution to the high rate of premature cardiovascular mortality in dialysis patients. Determining how we might intervene to ameliorate left ventricular hypertrophy in dialysis populations has become a research priority. Reducing sodium exposure through lower dialysate sodium may be a promising intervention in this regard. However there is clinical equipoise around this intervention because the benefit has not yet been demonstrated in a robust prospective clinical trial, and several observational studies have suggested sodium lowering interventions may be deleterious in some dialysis patients.

METHODS/DESIGN

The Sodium Lowering in Dialysate (SoLID) study is funded by the Health Research Council of New Zealand. It is a multi-centre, prospective, randomised, single-blind (outcomes assessor), controlled parallel assignment 3-year clinical trial. The SoLID study is designed to study what impact low dialysate sodium has upon cardiovascular risk in dialysis patients. The study intends to enrol 118 home hemodialysis patients from 6 sites in New Zealand over 24 months and follow up each participant over 12 months. Key exclusion criteria are: patients who dialyse more frequently than 3.5 times per week, pre-dialysis serum sodium of <135 mM, and maintenance hemodiafiltration. In addition, some medical conditions, treatments or participation in other dialysis trials, which contraindicate the SoLID study intervention or confound its effects, will be exclusion criteria. The intervention and control groups will be dialysed using dialysate sodium 135 mM and 140 mM respectively, for 12 months. The primary outcome measure is left ventricular mass index, as measured by cardiac magnetic resonance imaging, after 12 months of intervention. Eleven or more secondary outcomes will be studied in an attempt to better understand the physiologic and clinical mechanisms by which lower dialysate sodium alters the primary end point.

DISCUSSION

The SoLID study is designed to clarify the effect of low dialysate sodium upon the cardiovascular outcomes of dialysis patients. The study results will provide much needed information about the efficacy of a cost effective, economically sustainable solution to a condition which is curtailing the lives of so many dialysis patients.

TRIAL REGISTRATION

Australian and New Zealand Clinical Trials Registry number: ACTRN12611000975998.

Altering plasma sodium concentration rapidly changes blood pressure during haemodialysis

BACKGROUND

Plasma sodium is increased following each meal containing salt. There is an increasing interest in the effects of plasma sodium concentration, and it has been suggested that it may have direct effects on blood pressure (BP) and possibly influences endothelial function. Experimental increases of plasma sodium concentration rapidly raise BP even when extracellular volume falls.

METHODS

Ten patients with end-stage renal failure established on haemodialysis were studied during the first 2 h of dialysis without fluid removal during this period. They were randomized to receive haemodialysis with (i) dialysate sodium concentration prescribed to 135 mmol/L and (ii) 145 mmol/L in random order in a prospective, single-blinded crossover study. BP measurements and blood samples were taken every 30 min.

RESULTS

Pre-dialysis sitting BP was 137/76 ± 7/3 mmHg. Lower dialysate sodium concentration (135 mmol/L) reduced plasma sodium concentration [139.49 ± 0.67 to 135.94 ± 0.52 mmol/L (P < 0.001)], whereas plasma sodium concentration was not altered by higher dialysate sodium (145 mmol/L) (140.17 ± 0.66 mmol/L at baseline to 140.72 ± 0.43 mmol/L at 120 min). Systolic BP was lower with dialysate sodium concentration 135 mmol/L [area under the curve (AUC) 15823.50 ± 777.15 (mmHg)min] compared with 145 mmol/L [AUC 17018.20 ± 1102.17 (mmHg)min], mean difference 1194.70 ± 488.41 (mmHg)min, P < 0.05. There was a significant positive relationship between change in plasma sodium concentration and change in systolic BP. This direct relationship suggests that a fall of 1 mmol/L in plasma sodium concentration would be associated with a 1.7 mmHg reduction in systolic BP (P < 0.05).

CONCLUSIONS

The potential mechanism for the increase in BP seen with salt intake may be through small but significant changes in plasma sodium concentration.

Blood pressure and blood volume: acute and chronic considerations in hemodialysis

Hypertension is highly prevalent yet poorly controlled in the majority of dialysis patients and represents a significant burden of disease, with rates of morbidity and mortality greater than those in the general population. In dialysis, blood volume plays a critical role in the pathogenesis of hypertension, with expansion of extracellular volume increasingly recognized as an independent risk factor for morbidity and mortality. Within the current paradigm of dialysis prescription the majority of patients remain chronically volume expanded. However, management of blood pressure and volume state is difficult for clinicians with a paucity of randomized evidence adding to the complexity of nonlinear morbidity and mortality associations. With dialysis itself as a significant cardiac stressor, control of volume state is critical to minimize intradialytic hemodynamic instability, aid in preservation of cardiac anatomy and prevent progression to cardiovascular morbidity and mortality. This review explores the relationship of blood volume to blood pressure and potential targets for management in this at risk population.

Does a reduction in dialysate sodium improve blood pressure control in haemodialysis patients?

INTRODUCTION

There has been debate as to the value of lower sodium dialysates to control blood pressure in haemodialysis patients, as sodium is predominantly removed by ultrafiltration.

METHODS

Re-audit of clinical practice following reduction in dialysate sodium concentration.

RESULTS

Overall dialysate sodium concentration decreased from 138.9 ± 1.7 to 137.8 ± 1.7 mmol/L (mean ± standard deviation), resulting in a reduction in pre- and post-dialysis mean arterial pressure (MAP) of 4 mmHg (from 100.6 ± 15.6 to 97.1 ± 15.6, P < 0.01 and from 91.7 ± 15.6 to 87.1 ± 14.6, P < 0.001 respectively), yet fewer patients were prescribed antihypertensives (49.6 vs 60.6%), and less antihypertensive medications/patient (mean 0.86 vs 1.05), ultrafiltration requirements (2.8% vs 3.2% body weight, P < 0.001), and symptomatic intradialytic hypotension (0.19 vs 0.28 episodes per week, P < 0.001). A multivariable model showed that for a dialysate sodium of 136 mmol/L, younger patients had higher MAP than older patients (0.35 mmHg lower MAP/year older; but with a dialysate sodium of 140 mmol/L, there was minimal association of MAP with age (0.07 mmHg higher MAP/year older).

CONCLUSION

Change in clinical practice, amounting to a modest reduction in dialysate sodium was associated with a reduction not only in pre- and post-dialysis blood pressures, but also ultrafiltration requirements and symptomatic intradialytic hypotension. However, this effect on blood pressure was most marked for older patients and women, within minimal effects for younger patients, and lesser effects for men, suggesting that dialysate sodium reduction alone may help improve blood pressure control, but requires additional factors such as dietary sodium restriction to be effective in younger male patients.

Survey of depression by Beck Depression Inventory in uremic patients undergoing hemodialysis and hemodiafiltration

High prevalence of depression has been reported in patients with end stage kidney disease and depression is associated with increased morbidity and mortality. We aimed to investigate the prevalence of depression in patients receiving standard hemodialysis (SHD) and hemodiafiltration (HDF) and compare the associated factors between these treatment modalities. The Beck Depression Inventory (BDI) was used to survey for major depressive symptoms. Demographic and biochemical data were reviewed and collected. Point prevalence of depression in HDF patients was significantly lower than SHD patients (23.9% vs. 43.1%, P < 0.05). The BDI score was also higher in SHD than HDF group (13.2 ± 11.6 vs. 8.7 ± 11.2, P < 0.05). SHD patients with major depressive symptoms had significantly lower levels of hemoglobin, albumin, creatinine, sodium and hand grip strength but had higher prevalence of diabetes and high sensitivity C-reactive protein (hs-CRP) levels. In HDF patients, phosphorus level was significantly lower in patients with major depressive symptoms. Logistic regression analysis revealed that hs-CRP, serum sodium and hand grip strength were significantly associated with major depressive symptoms in patients treated with SHD; while serum phosphorus was identified in HDF groups. We concluded that prevalence of depression was high in dialysis patients. Patients receiving HDF had a lower mean BDI score and a nearly 50% lower prevalence rate of major depressive symptoms than that of SHD. Factors associated with depression were different between two modalities.

Preservation of blood pressure stability with hypertonic mannitol during hemodialysis initiation

BACKGROUND

Intradialytic hypotensive events are common among hemodialysis patients and are associated with a variety of patient- and procedure-related factors, including intradialytic decline in plasma osmolality. Prior studies and practice have suggested that administration of osmotically active drugs may ameliorate blood pressure decline during chronic hemodialysis.

METHODS

Clinical and treatment data were collected for 102 consecutive patients requiring initiation of renal replacement therapy in 2 major teaching hospitals. Routine administration of mannitol differed according to institutional protocols, allowing its examination as the primary exposure of interest. Generalized linear models were fit to estimate associations of mannitol use during dialysis initiation with intradialytic blood pressure, as assessed by: (1) intradialytic blood pressure decline; (2) nadir intradialytic blood pressure; (3) absolute systolic blood pressure <90 mm Hg or decline >20 mm Hg.

RESULTS

Mean age was 62 years (±16), 70% were male and 44% were diabetic. Mean predialysis and nadir systolic blood pressure were 142 mm Hg (±29) and 121 mm Hg (±26), respectively. Mannitol administration was associated with a lesser decline in intradialytic blood pressure, a higher nadir blood pressure and fewer hypotensive events requiring intervention. No effect modification was evident according to diabetes or acuity of kidney disease (chronic vs. acute).

CONCLUSIONS

Mannitol administration appears to preserve hemodynamic stability during hemodialysis initiation. Randomized controlled trials are needed to confirm these findings and identify optimal management strategies to prevent intradialytic hypotension.

Individualized reduction in dialysate sodium in conventional in-center hemodialysis

Recent studies have focused on the association between dialysate sodium (Na(+)) prescriptions and interdialytic weight gain (IDWG). We report on a case series of 13 patients undergoing conventional, thrice-weekly in-center hemodialysis with an individualized dialysate Na(+) prescription. Individualized dialysate Na(+) was achieved in all patients through a stepwise weekly reduction of the standard dialysate Na(+) prescription (140 mEq/L) by 2-3 mEq/L until reaching a Na(+) gradient of -2 mEq/L (dialysate Na(+) minus average plasma Na(+) over the preceding 3 months). Interdialytic weight gain, with and without indexing to dry weight (IDWG%), blood pressure, and the proportion of treatments with cramps, intradialytic hypotension (drop in systolic blood pressure >30 mmHg) and intradialytic hypotension requiring an intervention were reviewed. At the beginning of the observation period, the pre-hemodialysis (HD) plasma Na(+) concentration ranged from 130 to 141 mEq/L. When switched from the standard to the individualized dialysate Na(+) concentration, IDWG% decreased from 3.4% ± 1.6% to 2.5% ± 1.0% (P = 0.003) with no change in pre- or post-HD systolic or diastolic blood pressures (all P > 0.05). We found no significant change in the proportion of treatments with cramps (6% vs. 13%), intradialytic hypotension (62% vs. 65%), or intradialytic hypotension requiring an intervention (29% vs. 33%). Individualized reduction of dialysate Na(+) reduces IDWG% without significantly increasing the frequency of cramps or hypotension.

How should we manage adverse intradialytic blood pressure changes?

Variations in intradialytic blood pressure (BP) are a common and predictable occurrence in ESRD patients. These are caused by a decrease in blood volume provoked by ultrafiltration, lack of normal compensatory responses to fluid removal, underlying cardiac disease, and electrolyte changes that may adversely affect cardiovascular function. Intradialytic hypotension is the most frequent complication of the hemodialysis (HD) procedure and is fundamentally a consequence of an ultrafiltration rate that surpasses mechanisms activated to avert a decline in BP. Intradialytic hypertension is a less well-understood problem that has been recently associated with increased mortality. Fundamental patient characteristics and components of the HD procedure are involved in the pathophysiology of intradialytic hypotension and intradialytic hypertension. Correction of patient factors, modulation of HD prescription, and management of pharmacologic agents are the strategies to deal with adverse intradialytic BP changes.

Are dialysate sodium levels too high?

Universal lower dialysate [Na+] is often advocated as a means of improving the dire cardiovascular plight of our dialysis patients. However, there is evidence associating lower dialysate [Na+] and increased morbidity and mortality especially in frailer patients, probably as a result of more frequent intra-dialytic hypotension. In this editorial, we summarize arguments for and against lower dialysate [Na+], and provide recommendations around selecting the most appropriate dialysate [Na+] for specific clinical subsets that may benefit from manipulation of salt and water balance. The lack of overall clarity on relative benefits and risks of lower dialysate [Na+] does not support the case for empirical "across the board" change, and experimental testing in clinical trials is required to determine safe and effective use.

Dialysate sodium concentration and the association with interdialytic weight gain, hospitalization, and mortality

BACKGROUND AND OBJECTIVES

Recommendations to decrease the dialysate sodium (DNa) prescription demand analyses of patient outcomes. We analyzed morbidity and mortality at various levels of DNa, simultaneously accounting for interdialytic weight gain (IDWG) and for the mortality risk associated with lower predialysis serum sodium (SNa) levels.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We used multiply-adjusted linear mixed models to evaluate the magnitude of IDWG and Cox proportional hazards models to assess hospitalizations and deaths in 29,593 patients from the Dialysis Outcomes and Practice Patterns Study with baseline DNa and SNa as predictors, categorized according to lowest to highest levels.

RESULTS

IDWG increased with higher DNa across all SNa categories, by 0.17% of body weight per 2 mEq/L higher DNa; however, higher DNa was not associated with higher mortality in a fully adjusted model (also adjusted for SNa; hazard ratio [HR]=0.98 per 2 mEq/L higher DNa, 95% confidence interval [CI] 0.95-1.02). Instead, higher DNa was associated with lower hospitalization risk (HR=0.97 per 2 mEq/L higher DNa, 95% CI 0.95-1.00, P=0.04). Additional adjustments for IDWG did not change these results. In sensitivity analyses restricted to study facilities, in which 90%-100% of patients have the same DNa (56%), the adjusted HR for mortality was 0.88 per 2 mEq/L higher DNa (95% CI 0.83-0.94). These analyses represented a pseudo-randomized experiment in which the association between DNa and mortality is unlikely to have been confounded by indication.

CONCLUSIONS

In the absence of randomized prospective studies, the benefit of reducing IDWG by decreasing DNa prescriptions should be carefully weighed against an increased risk for adverse outcomes.

Predialysis serum sodium level, dialysate sodium, and mortality in maintenance hemodialysis patients: the Dialysis Outcomes and Practice Patterns Study (DOPPS)

BACKGROUND

Predialysis serum sodium concentrations recently have been linked to patient characteristics and outcomes in hemodialysis patients and may have implications for the dialysate sodium prescription.

STUDY DESIGN

Prospective cohort study.

PARTICIPANTS

11,555 patients from 12 countries in the Dialysis Outcomes and Practice Patterns Study (DOPPS), phases I (1996-2001) and III (2005-2008).

PREDICTORS

Demographics, comorbid conditions, laboratory measurements (model 1); mean serum sodium level, dialysate sodium concentration (model 2).

OUTCOMES

Serum sodium level, using adjusted linear mixed models (model 1); all-cause mortality, using Cox proportional hazards models (model 2).

RESULTS

Median follow-up was 12 months, with 1,727 deaths (15%) occurring during the study period (12,274 patient-years). Mean serum sodium level in the DOPPS countries was 138.5 ± 2.8 mEq/L. Japan had the highest (139.1 ± 2.6 mEq/L) and Australia/New Zealand had the lowest mean serum sodium level (137.4 ± 2.8 mEq/L). Serum sodium level was associated positively with male sex, black race, body mass index, serum albumin level, and creatinine level and negatively with neurologic and psychiatric disease, white blood cell count, and intradialytic weight loss (0.16 mEq/L lower per 1% loss). Higher serum sodium level was associated with lower adjusted all-cause mortality in a continuous model (HR, 0.95 per 1 mEq/L higher; 95% CI, 0.93-0.97). Dialysate sodium prescription was not associated with serum sodium level. Mortality analyses restricted to the serum sodium tertile with the highest mortality (serum sodium <137 mEq/L) showed lower mortality risk in patients with dialysate sodium prescriptions >140 mEq/L.

LIMITATIONS

Causality cannot be established in this observational study, which does not consider potential effects of dialysate sodium level on postdialysis thirst, dietary salt and water intake, interdialytic weight gain, and cardiovascular stability.

CONCLUSIONS

Lower serum sodium levels are associated with certain hemodialysis patient characteristics and higher adjusted risk of death. The lower mortality observed in our adjusted analyses in patients with serum sodium levels <137 mEq/L dialyzed against dialysate sodium prescriptions >140 mEq/L is intriguing, may be related to intradialytic cardiovascular stability, and deserves further study.

Dialysate sodium, serum sodium and mortality in maintenance hemodialysis

BACKGROUND

Individuals with end-stage kidney disease appear to have stable pre-dialysis serum sodium concentrations over time, with lower values associating with increased mortality. Dialysate sodium concentrations have increased over many years in response to shorter treatments, but the relationship between serum sodium, dialysate sodium and outcomes in chronic hemodialysis patients has not yet been systematically examined.

METHODS

We studied a cohort of 2272 individuals receiving thrice-weekly hemodialysis treatment. Available data included demographics, laboratory and clinical measures, details of the dialysis prescription and 30-month follow-up. We examined the distribution of serum and dialysate sodium among subjects and compared mortality according to dialysate and serum sodium concentrations using Cox regression models.

RESULTS

Dialysate sodium concentration varied within and among dialysis centers. The pre-dialysis serum sodium concentration (mean 136.1 mmol/L) did not differ across dialysate sodium concentrations. There was evidence for effect modification for mortality according to differing serum sodium and dialysate sodium concentrations (P=0.05). For each 4 mmol/L increment in serum sodium, the hazard ratio for death was 0.72 [95% confidence interval (CI) 0.63-0.81] with lower dialysate sodium compared to 0.86 (95% CI 0.75-0.99) for higher dialysate sodium. Higher dialysate sodium concentration was associated with mortality at higher, but not lower, pre-dialysis serum sodium concentrations.

CONCLUSIONS

The pre-dialysis serum sodium concentration appears to be unaffected by the dialysate sodium concentration. The relationship between serum and dialysate sodium and mortality appears to be variable. Further research is warranted to determine the biological mechanisms of these associations and to re-examine total body sodium handling in hemodialysis.

Effect of lowering dialysate sodium concentration on interdialytic weight gain and blood pressure in patients undergoing thrice-weekly in-center nocturnal hemodialysis: a quality improvement study

BACKGROUND

Patients on in-center nocturnal hemodialysis therapy typically experience higher interdialytic weight gain (IDWG) than patients on conventional hemodialysis therapy. We determined the safety and effects of decreasing dialysate sodium concentration on IDWG and blood pressure in patients on thrice-weekly in-center nocturnal hemodialysis therapy.

STUDY DESIGN

Quality improvement, pre-post intervention.

SETTINGS & PARTICIPANTS

15 participants in a single facility.

QUALITY IMPROVEMENT PLAN

Participants underwent three 12-week treatment phases, each with different dialysate sodium concentrations, as follows: phase A, 140 mEq/L; phase B, 136 or 134 mEq/L; and phase A(+), 140 mEq/L. Participants were blinded to the exact timing of the intervention.

OUTCOMES

IDWG, IDWG/dry weight (IDWG%), and blood pressure.

MEASUREMENTS

Outcome data were obtained during the last 2 weeks of each phase and compared with mixed models. The fraction of sessions with adverse events (eg, cramping and hypotension) also was reported.

RESULTS

IDWG, IDWG%, and predialysis systolic blood pressure decreased significantly by 0.6 ± 0.6 kg, 0.6% ± 0.8%, and 8.3 ± 14.9 mm Hg, respectively, in phase B compared with phase A (P < 0.05 for all comparisons). No differences in predialysis diastolic and mean arterial or postdialysis blood pressures were found (P > 0.05 for all comparisons). The proportion of treatments with intradialytic hypotension was low and similar in each phase (P = 0.9). In phase B compared with phase A, predialysis plasma sodium concentration was unchanged (P > 0.05), whereas postdialysis plasma sodium concentration decreased by 3.7 ± 1.9 mEq/L (P < 0.05).

LIMITATIONS

Modest sample size.

CONCLUSION

Decreasing dialysate sodium concentrations in patients undergoing thrice-weekly in-center nocturnal hemodialysis resulted in a clinical and statistically significant decrease in IDWG, IDWG%, postdialysis plasma sodium concentration, and predialysis systolic blood pressure without increasing adverse events. Prolonged exposure to higher than required dialysate sodium concentrations may drive IDWG and counteract some of the purported benefits of "go-slow" (longer session length) hemodialysis.