Serum-to-dialysate potassium gradient and its association with short-term outcomes in hemodialysis patients

Point-of-Care Chemistry-Guided Dialysate Adjustment to Reduce Arrhythmias: A Pilot Trial

Introduction

Excessive dialytic potassium (K) and acid removal are risk factors for arrhythmias; however, treatment-to-treatment dialysate modification is rarely performed. We conducted a multicenter, pilot randomized study to test the safety, feasibility, and efficacy of 4 point-of-care (POC) chemistry-guided protocols to adjust dialysate K and bicarbonate (HCO3) in outpatient hemodialysis (HD) clinics.

Methods

Participants received implantable cardiac loop monitors and crossed over to four 4-week periods with adjustment of dialysate K or HCO3 at each treatment according to pre-HD POC values: (i) K-removal minimization, (ii) K-removal maximization, (iii) Acidosis avoidance, and (iv) Alkalosis avoidance. The primary end point was percentage of treatments adhering to the intervention algorithm. Secondary endpoints included pre-HD K and HCO variability, adverse events, and rates of clinically significant arrhythmias (CSAs).

Results

Nineteen subjects were enrolled in the study. HD staff completed POC testing and correctly adjusted the dialysate in 604 of 708 (85%) of available HD treatments. There was 1 K ≤3, 29 HCO3 <20 and 2 HCO3 >32 mEq/l and no serious adverse events related to study interventions. Although there were no significant differences between POC results and conventional laboratory measures drawn concurrently, intertreatment K and HCO3 variability was high. There were 45 CSA events; most were transient atrial fibrillation (AF), with numerically fewer events during the alkalosis avoidance period (8) and K-removal maximization period (3) compared to other intervention periods (17). There were no significant differences in CSA duration among interventions.

Conclusion

Algorithm-guided K/HCO3 adjustment based on POC testing is feasible. The variability of intertreatment K and HCO3 suggests that a POC-laboratory-guided algorithm could markedly alter dialysate-serum chemistry gradients. Definitive end point-powered trials should be considered.

Hyperkalaemia prevalence and dialysis patterns in Chinese patients on haemodialysis: an interim analysis of a prospective cohort study (PRECEDE-K)

BACKGROUND

Hyperkalaemia is a known risk factor for cardiac arrhythmia and mortality in patients on haemodialysis. Despite standard adequate haemodialysis, hyperkalaemia is common in patients with end-stage renal disease (ESRD) at interdialytic intervals. Data on hyperkalaemia burden and its effects on dialysis patterns and serum potassium (sK) fluctuations in patients on haemodialysis in China remain limited. The prospective, observational cohort study (PRECEDE-K; NCT04799067) investigated the prevalence, recurrence, and treatment patterns of hyperkalaemia in Chinese patients with ESRD on haemodialysis.

METHODS

Six hundred adult patients were consecutively enrolled from 15 secondary and tertiary hospitals in China. In this interim analysis, we report the baseline characteristics of the cohort, the prevalence of predialysis hyperkalaemia (sK > 5.0 mmol/L), and the trends in serum-dialysate potassium gradient and intradialytic sK shift at Visit 1 (following a long interdialytic interval [LIDI]).

RESULTS

At baseline, most patients (85.6%) received three-times weekly dialysis; mean duration was 4.0 h. Mean urea reduction ratio was 68.0% and Kt/V was 1.45; 60.0% of patients had prior hyperkalaemia (previous 6 months). At Visit 1, mean predialysis sK was 4.83 mmol/L, and 39.6% of patients had hyperkalaemia. Most patients (97.7%) received a dialysate potassium concentration of 2.0 mmol/L. The serum-dialysate potassium gradient was greater than 3 mmol/L for over 40% of the cohort (1- < 2, 2- < 3, 3- < 4, and ≥ 4 mmol/L in 13.6%, 45.1%, 35.7%, and 5.2% of patients, respectively; mean: 2.8 mmol/L). The intradialytic sK reduction was 1- < 3 mmol/L for most patients (0- < 1, 1- < 2, 2- < 3, and ≥ 3 mmol/L in 24.2%, 62.2%, 12.8%, and 0.9% of patients, respectively; mean: 1.4 mmol/L).

CONCLUSIONS

Hyperkalaemia after a LIDI was common in this real-world cohort of Chinese patients despite standard adequate haemodialysis, and led to large serum-dialysate potassium gradients and intradialytic sK shifts. Previous studies have shown hyperkalaemia and sK fluctuations are highly correlated with poor prognosis. Effective potassium-lowering treatments should be evaluated for the improvement of long-term prognosis through the control of hyperkalaemia and sK fluctuations.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT04799067.

Adverse Gastrointestinal Events With Sodium Polystyrene Sulfonate Use in Patients on Maintenance Hemodialysis: An International Cohort Study

Background

There are concerns regarding the gastrointestinal (GI) safety of sodium polystyrene sulfonate (SPS), a medication commonly used in the management of hyperkalemia.

Objective

To compare the risk of GI adverse events among users versus non-users of SPS in patients on maintenance hemodialysis.

Design

International prospective cohort study.

Setting

Seventeen countries (Dialysis Outcomes and Practice Patterns Study [DOPPS] phase 2-6 from 2002 to 2018).

Patients

50 147 adults on maintenance hemodialysis.

Measurements

An adverse GI event defined by a GI hospitalization or GI fatality with SPS prescription compared with no SPS prescription.

Methods

Overlap propensity score-weighted Cox models.

Results

Sodium polystyrene sulfonate prescription was present in 13.4% of patients and ranged from 0.42% (Turkey) to 20.6% (Sweden) with 12.5% use in Canada. A total of 935 (1.9%) adverse GI events (140 [2.1%] with SPS, 795 [1.9%] with no SPS; absolute risk difference 0.2%) occurred. The weighted hazard ratio (HR) of a GI event was not elevated with SPS use compared with non-use (HR = 0.93, 95% confidence interval = 0.83-1.6). The results were consistent when examining fatal GI events and/or GI hospitalization separately.

Limitations

Sodium polystyrene sulfonate dose and duration were unknown.

Conclusions

Sodium polystyrene sulfonate use in patients on hemodialysis was not associated with a higher risk of an adverse GI event. Our findings suggest that SPS use is safe in an international cohort of maintenance hemodialysis patients.

Digital health technology to support care and improve outcomes of chronic kidney disease patients: as a case illustration, the Withings toolkit health sensing tools

Cardiovascular disease (CVD) is a major burden in dialysis-dependent chronic kidney disease (CKD5D) patients. Several factors contribute to this vulnerability including traditional risk factors such as age, gender, life style and comorbidities, and non-traditional ones as part of dialysis-induced systemic stress. In this context, it appears of utmost importance to bring a closer attention to CVD monitoring in caring for CKD5D patients to ensure early and appropriate intervention for improving their outcomes. Interestingly, new home-used, self-operated, connected medical devices offer convenient and new tools for monitoring in a fully automated and ambulatory mode CKD5D patients during the interdialytic period. Sensoring devices are installed with WiFi or Bluetooth. Some devices are also available in a cellular version such as the Withings Remote Patient Monitoring (RPM) solution. These devices analyze the data and upload the results to Withings HDS (Hybrid data security) platform servers. Data visualization can be viewed by the patient using the Withings Health Mate application on a smartphone, or with a web interface. Health Care Professionals (HCP) can also visualize patient data via the Withings web-based RPM interface. In this narrative essay, we analyze the clinical potential of pervasive wearable sensors for monitoring ambulatory dialysis patients and provide an assessment of such toolkit digital medical health devices currently available on the market. These devices offer a fully automated, unobtrusive and remote monitoring of main vital functions in ambulatory subjects. These unique features provide a multidimensional assessment of ambulatory CKD5D patients covering most physiologic functionalities, detecting unexpected disorders (i.e., volume overload, arrhythmias, sleep disorders) and allowing physicians to judge patient's response to treatment and recommendations. In the future, the wider availability of such pervasive health sensing and digital technology to monitor patients at an affordable cost price will improve the personalized management of CKD5D patients, so potentially resulting in improvements in patient quality of life and survival.

Serum potassium in elderly heart failure patients as a predictor of readmission within 1 year

Blood potassium levels are associated with adverse outcomes in patients with congestive heart failure (HF). However, it is unclear whether there are differences in outcome events in elderly patients with different blood potassium levels at the time of emergency readmission within 1 year. This study used data from patients hospitalized with HF, integrating electronic medical records from the PhysioNet restricted health data database and external outcome data. We conducted a retrospective study of HF patients aged 60 years and older, using baseline data, comorbidities, laboratory tests, and medication use as covariates to analyze the effect of serum potassium levels on outcome events, with the primary outcome being readmission within 1 year. A priori was used to calculate the sample size, and this retrospective cohort study included a total of 788 elderly HF patients, of whom 20.3% had hypokalaemia (K⁺  < 3.5 mmol/L) and 14.7% had hyperkalemia (K⁺  > 4.7 mmol/L). According to a multivariate Cox regression model, patients with hyperkalemia had a shorter time interval between readmissions within 1 year, with a hazard ratio (HR) and its 95% CI of 1.134 (1.006-1.279). Three models were used to analyze patients with different blood potassium levels and, after correction, the high potassium group was at high risk relative to the low and normal groups, with significant differences in outcome events, with HRs and their 95% CI of 1.266 (1.03-1.557), 1.245 (1.01-1.534), and 1.439 (1.142-1.812), respectively. The robustness of the model was also demonstrated by competing risk models with subgroup analysis, showing that blood potassium levels had a stable effect on outcome events and were not altered by covariates (age, sex, diabetes, chronic kidney disease, NT-proBNP, high-sensitivity troponin, and glomerular filtration rate). The results show that high blood potassium levels are associated with the outcome event of readmission within 1 year in elderly patients with HF. Blood potassium levels at the time of the first hospitalization may therefore be a valuable predictor.

Association of Hyperkalemia and Hypokalemia with Patient Characteristics and Clinical Outcomes in Japanese Hemodialysis (HD) Patients

This study aimed to examine the characteristics and clinical outcomes of Japanese hemodialysis patients with dyskalemia. A retrospective study was conducted using a large Japanese hospital group database. Outpatients undergoing thrice-a-week maintenance hemodialysis were stratified into hyperkalemia, hypokalemia, and normokalemia groups based on their pre-dialysis serum potassium (sK) levels during the three-month baseline period. Baseline characteristics of the three groups were described and compared for the following outcomes during follow-up: all-cause mortality, all-cause hospitalization, major adverse cardiovascular events (MACE), cardiac arrest, fatal arrythmia, and death related to arrhythmia. The study included 2846 eligible patients, of which 67% were men with a mean age of 65.65 (SD: 12.63) years. When compared with the normokalemia group (n = 1624, 57.06%), patients in the hypokalemia group (n = 313, 11.00%) were older and suffered from malnutrition, whereas patients in the hyperkalemia group (n = 909, 31.94%) had longer dialysis vintage. The hazard ratios for all-cause mortality and MACE in the hypokalemia group were 1.47 (95% confidence interval [CI], 1.13–1.92) and 1.48 (95% CI, 1.17–1.86), respectively, whereas that of death related to arrhythmia in the hyperkalemia group was 3.11 (95% CI, 1.03–9.33). Thus, dyskalemia in maintenance hemodialysis patients was associated with adverse outcomes, suggesting the importance of optimized sK levels.

QT-Prolonging Antibiotics, Serum-to-Dialysate Potassium Gradient, and Risk of Sudden Cardiac Death Among Patients Receiving Maintenance Hemodialysis

Rationale & Objective

Treatment with certain QT interval-prolonging antibiotics is associated with a higher risk of sudden cardiac death among individuals with hemodialysis-dependent kidney failure. Concurrent exposure to large serum-to-dialysate potassium gradients, which promote large potassium shifts, may augment the proarrhythmic effects of these medications. The primary objective of this study was to examine whether the serum-to-dialysate gradient modifies the cardiac safety of azithromycin, and separately, levofloxacin/moxifloxacin.

Study Design

Retrospective observational cohort study using a new-user study design.

Setting & Population

Adult in-center hemodialysis patients with Medicare coverage in the US Renal Data System (2007-2017).

Exposure

Initiation of azithromycin (or levofloxacin/moxifloxacin) as compared to amoxicillin-based antibiotics (exposure). Serum-to-dialysate potassium gradient (effect modifier). Individual patients could contribute multiple study antibiotic treatment episodes to the analyses.

Outcomes

Sudden cardiac death (14 days).

Analytical Approach

Inverse probability of treatment-weighted survival models to estimate HRs and robust 95% CIs.

Results

The azithromycin versus amoxicillin-based antibiotic cohort included 89,379 unique patients with 113,516 azithromycin and 103,493 amoxicillin-based treatment episodes. Azithromycin versus amoxicillin-based antibiotic treatment was associated with a higher risk of sudden cardiac death overall, HR, 1.68; 95% CI, 1.31-2.16. The risk was numerically higher when the baseline serum-to-dialysate potassium gradient was ≥3 mEq/L compared with <3 mEq/L (HR, 2.22; 95% CI, 1.46-3.40 vs HR, 1.43; 95% CI. 1.04-1.96, P _interaction = 0.07). Analogous analyses in a respiratory fluoroquinolone (levofloxacin/moxifloxacin) versus amoxicillin-based antibiotic cohort with 79,449 unique patients and 65,959 respiratory fluoroquinolone and 103,776 amoxicillin-based treatment episodes yielded similar results.

Limitations

Residual confounding.

Conclusions

Although treatment with azithromycin and, separately, respiratory fluoroquinolones were each associated with a heightened risk of sudden cardiac death, this risk was augmented in the setting of larger serum-to-dialysate potassium gradients. Minimizing the potassium gradient may be an approach to reduce the cardiac risk of these antibiotics.

Association of Bradycardia and Asystole Episodes with Dialytic Parameters: An Analysis of the Monitoring in Dialysis (MiD) Study

Background

Bradycardia and asystole events are common among patients treated with maintenance hemodialysis. However, triggers of these events in patients on maintenance hemodialysis (HD), particularly during the long interdialytic period when these events cluster, are uncertain.

Methods

The Monitoring in Dialysis Study (MiD) enrolled 66 patients on maintenance HD who were implanted with loop recorders and followed for 6 months. We analyzed associations of predialysis laboratory values with clinically significant bradyarrhythmia or asystole (CSBA) during the 12 hours before an HD session. Associations with CSBA were analyzed with mixed-effect models. Adjusted negative binomial mixed-effect regression was used to estimate incidence rate ratios (IRR) for CSBA. We additionally evaluated associations of CSBA at any time during follow-up with time-averaged dialytic and laboratory parameters and associations of peridialytic parameters with occurrence of CSBA from the start of one HD session to the beginning of the next.

Results

There were 551 CSBA that occurred in the last 12 hours of the interdialytic interval preceding 100 HD sessions in 12% of patients and 1475 CSBA events in 23% of patients overall. We did not identify significant associations between dialytic parameters or serum electrolytes and CSBA in the last 12 hours of the interdialytic interval in adjusted analyses. Median time-averaged ultrafiltration rate was significantly higher in individuals without CSBA (9.8 versus 8, P=0.04). Use of dialysate sodium concentrations ≤135 (versus 140) mEq/L was associated with a reduced risk of CSBA from the start of one session to the beginning of next.

Conclusions

Although a few factors had modest associations with CSBA in some analyses, we did not identify any robust associations of modifiable parameters with CSBA in the MiD Study. Further investigation is needed to understand the high rates of arrhythmia in the hemodialysis population.

Associations of Serum and Dialysate Potassium Concentrations With Incident Atrial Fibrillation in a Cohort Study of Older US Persons Initiating Hemodialysis for Kidney Failure

Introduction

Atrial fibrillation (AF) disproportionally affects persons on maintenance hemodialysis (HD). Associations of serum and dialysate potassium concentrations [K⁺] with AF incidence are poorly understood.

Methods

We conducted a cohort study using Medicare claims merged with clinical data from a dialysis provider to determine whether serum-[K⁺] and/or dialysate-[K⁺] independently associated with AF incidence. Persons insured by fee-for-service Medicare aged ≥67 years at dialysis initiation and free from diagnosed AF prior to day 120 of dialysis were eligible. Serum-[K⁺] and dialysate-[K⁺] were assessed in 30-day intervals and patients were followed-up with for AF incidence in subsequent 30-day intervals.

Results

During 2006 to 2011, 15,190 persons (mean age = 76.3 years) initiating HD had no prior AF diagnosis. Mean serum-[K⁺] was 4.5 mEq/l; dialysate-[K⁺] was 3 mEq/l in 34% and 2 mEq/l in 52% of patients. Followed-up over 21,907 person-years, 2869 persons had incident AF (incidence/100 person-years, 13.1 [95% confidence interval [CI], 12.6-13.6]). The multivariable-adjusted association of serum-[K⁺] with incident AF was J-shaped as follows: relative to a serum-[K⁺] of 4.5 mEq/l, lower serum-[K⁺] associated with increased AF risk, whereas confidence bands for higher serum-[K⁺] indicated no association. Dialysis against a dialysate-[K+] of 3 mEq/l versus 2 mEq/l independently associated with a 14% (95% CI, 5%-24%) lower incidence of AF. No effect modification between serum-[K⁺] and dialysate-[K⁺] was detected (P = 0.34).

Conclusion

Lower serum-[K⁺] was independently associated with incident AF whereas elevated serum-[K+] was not. The findings support adoption of dialysate solutions with a dialysate-[K⁺] of 3 mEq/l, regardless of patients' serum-[K+], and elimination of lower dialysate-[K+] solutions from practice. Clinical trials randomizing patients to different dialysate-[K⁺] are warranted to establish causality.

The modifying effect of the serum-to-dialysate potassium gradient on the cardiovascular safety of SSRIs in the hemodialysis population: a pharmacoepidemiologic study

BACKGROUND

Hypokalemia is a risk factor for drug-induced QT-prolongation. Larger serum-to-dialysate potassium gradients during hemodialysis may augment the proarrhythmic risks of selective serotonin reuptake inhibitors (SSRIs).

METHODS

We conducted a cohort study using 2007-2017 data from the United States Renal Data System and a large dialysis provider to examine if the serum-to-dialysate potassium gradient modifies SSRI cardiac safety. Using a new-user design, we compared 1-year sudden cardiac death (SCD) risk among hemodialysis patients newly treated with higher (citalopram, escitalopram) vs. lower (fluoxetine, fluvoxamine, paroxetine, sertraline) QT-prolonging potential SSRIs, overall and stratified by baseline potassium gradient (≥4 vs. <4 mEq/L). We used inverse probability of treatment weighted survival models to estimate weighted hazard ratios (HRs) and 95% confidence intervals (CIs), and conducted a confirmatory nested case-control study.

RESULTS

The study included 25,099 patients: 11,107 (44.3%) higher QT-prolonging potential SSRI new-users and 13,992 (55.7%) lower QT-prolonging potential SSRI new-users. Overall, higher vs. lower QT-prolonging potential SSRI use was not associated with SCD, weighted HR of 1.03 (95% CI, 0.86-1.24). However, a greater risk of SCD was associated with higher vs. lower QT-prolonging potential SSRI use among patients with baseline potassium gradients ≥4 mEq/L, but not among those with gradients <4 mEq/L, weighted HR of 2.17 (95% CI, 1.16-4.03) vs. 0.95 (0.78-1.16). Nested case-control analyses yielded analogous results.

CONCLUSIONS

The serum-to-dialysate potassium gradient may modify the association between higher vs. lower QT-prolonging SSRI use and SCD among people receiving hemodialysis. Minimizing the potassium gradient in the setting of QT-prolonging medication use may be warranted.

Chronic Hyperkaliemia in Chronic Kidney Disease: An Old Concern with New Answers

Increasing potassium intake ameliorates blood pressure (BP) and cardiovascular (CV) prognoses in the general population; therefore the World Health Organization recommends a high-potassium diet (90–120 mEq/day). Hyperkalaemia is a rare condition in healthy individuals due to the ability of the kidneys to effectively excrete dietary potassium load in urine, while an increase in serum K⁺ is prevalent in patients with chronic kidney disease (CKD). Hyperkalaemia prevalence increases in more advanced CKD stages, and is associated with a poor prognosis. This scenario generates controversy on the correct nutritional approach to hyperkalaemia in CKD patients, considering the unproven link between potassium intake and serum K⁺ levels. Another concern is that drug-induced hyperkalaemia leads to the down-titration or withdrawal of renin-angiotensin system inhibitors (RASI) and mineralocorticoids receptors antagonists (MRA) in patients with CKD, depriving these patients of central therapeutic interventions aimed at delaying CKD progression and decreasing CV mortality. The new K⁺-binder drugs (Patiromer and Sodium-Zirconium Cyclosilicate) have proven to be adequate and safe therapeutic options to control serum K⁺ in CKD patients, enabling RASI and MRA therapy, and possibly, a more liberal intake of fruit and vegetables.

Lethal ventricular arrhythmia can be prevented by adjusting the dialysate potassium concentration and the use of anti-arrhythmic agents: a case report and literature review

Background

Hypokalemia is common in patients with malnutrition undergoing hemodialysis and is often involved in the development of lethal arrhythmia. Moreover, hemodialysis therapy decreases the serum potassium concentration due to potassium removal to the dialysate. However, it is difficult to adjust the dialysate potassium concentration owing to the use of the central dialysate delivery system in Japan. Here, we have presented a case undergoing hemodialysis with dialysate potassium concentration adjustment to prevent ventricular arrhythmia.

Case presentation

A 56-year-old man with Emery-Dreifuss muscular dystrophy and chronic heart failure was admitted to our hospital and needed subsequent hemodialysis therapy due to renal dysfunction. During hemodialysis, the cardiac resynchronization therapy defibrillator was activated to the treatment of his lethal ventricular arrhythmia. Decreases in serum potassium concentration after hemodialysis and changes in serum potassium concentration during HD were considered the causes of lethal ventricular arrythmia. Therefore, along with using anti-arrhythmic agents, the dialysate potassium concentration was increased from 2.0 to 3.5 mEq/L to minimize changes in the serum potassium concentration during hemodialysis. Post-dialysis hypokalemia disappeared and these changes during hemodialysis were minimized, and no lethal ventricular arrhythmia occurred thereafter.

Conclusions

In this case, we prevented lethal arrhythmia by maintaining the serum potassium concentration by increasing the dialysate potassium concentration, in addition to the use of anti-arrhythmic agents. In the acute phase of patients with frequent lethal arrhythmia undergoing hemodialysis, an increase in dialysate potassium concentration may be an effective method for preventing arrhythmogenic complications.

Hidden risks associated with conventional short intermittent hemodialysis: A call for action to mitigate cardiovascular risk and morbidity

The development of maintenance hemodialysis (HD) for end stage kidney disease patients is a success story that continues to save many lives. Nevertheless, intermittent renal replacement therapy is also a source of recurrent stress for patients. Conventional thrice weekly short HD is an imperfect treatment that only partially corrects uremic abnormalities, increases cardiovascular risk, and exacerbates disease burden. Altering cycles of fluid loading associated with cardiac stretching (interdialytic phase) and then fluid unloading (intradialytic phase) likely contribute to cardiac and vascular damage. This unphysiologic treatment profile combined with cyclic disturbances including osmotic and electrolytic shifts may contribute to morbidity in dialysis patients and augment the health burden of treatment. As such, HD patients are exposed to multiple stressors including cardiocirculatory, inflammatory, biologic, hypoxemic, and nutritional. This cascade of events can be termed the dialysis stress storm and sickness syndrome. Mitigating cardiovascular risk and morbidity associated with conventional intermittent HD appears to be a priority for improving patient experience and reducing disease burden. In this in-depth review, we summarize the hidden effects of intermittent HD therapy, and call for action to improve delivered HD and develop treatment schedules that are better tolerated and associated with fewer adverse effects.

Potassium responses to sodium zirconium cyclosilicate in hyperkalemic hemodialysis patients: post-hoc analysis of DIALIZE

BACKGROUND

Sodium zirconium cyclosilicate (SZC) is an effective and well-tolerated treatment for hyperkalemia in maintenance hemodialysis patients. In post-hoc analyses of the phase 3b DIALIZE study, we examined the spectrum of potassium responses to SZC.

METHODS

Post-hoc analyses with SZC and placebo included: the number of long interdialytic interval (LIDI) visits during the 4-week evaluation period where patients attained pre-dialysis serum potassium (sK⁺) concentrations of 4.0-5.0 and 4.0-5.5 mmol/L; potassium gradient (the difference between pre-dialysis sK⁺ and dialysate potassium) at days 36, 43, 50, and 57, and change from baseline to the end of treatment (EOT) using categories of potassium gradient (1 to < 2, 2 to < 3, 3 to < 4, and ≥ 4 mmol/L).

RESULTS

A greater proportion of patients achieved the ranges of pre-dialysis sK⁺ concentration with SZC versus placebo for ≥1, ≥ 2, ≥ 3, and 4 LIDI visits over 4 weeks; 23.7 and 48.5% of patients in the SZC group achieved pre-dialysis sK⁺ concentrations of 4.0-5.0 and 4.0-5.5 mmol/L, respectively, at all 4 LIDI visits. Baseline mean potassium gradient was similar with SZC and placebo. At day 57, mean (standard deviation) potassium gradient was 2.78 (0.08) mmol/L with SZC and 3.52 (0.08) mmol/L with placebo; mean difference (95% confidence interval) was - 0.74 mmol/L (- 0.97 to - 0.52). A greater reduction in potassium gradient category from baseline towards lower-risk categories at EOT was observed with SZC versus placebo.

CONCLUSIONS

These analyses expand our knowledge of the spectrum of potassium responses with SZC in hyperkalemic hemodialysis patients.

TRIAL REGISTRATION

NCT03303521 .

Multitargeted interventions to reduce dialysis-induced systemic stress

Hemodialysis (HD) is a life-sustaining therapy as well as an intermittent and repetitive stress condition for the patient. In ridding the blood of unwanted substances and excess fluid from the blood, the extracorporeal procedure simultaneously induces persistent physiological changes that adversely affect several organs. Dialysis patients experience this systemic stress condition usually thrice weekly and sometimes more frequently depending on the treatment schedule. Dialysis-induced systemic stress results from multifactorial components that include treatment schedule (i.e. modality, treatment time), hemodynamic management (i.e. ultrafiltration, weight loss), intensity of solute fluxes, osmotic and electrolytic shifts and interaction of blood with components of the extracorporeal circuit. Intradialytic morbidity (i.e. hypovolemia, intradialytic hypotension, hypoxia) is the clinical expression of this systemic stress that may act as a disease modifier, resulting in multiorgan injury and long-term morbidity. Thus, while lifesaving, HD exposes the patient to several systemic stressors, both hemodynamic and non-hemodynamic in origin. In addition, a combination of cardiocirculatory stress, greatly conditioned by the switch from hypervolemia to hypovolemia, hypoxemia and electrolyte changes may create pro-arrhythmogenic conditions. Moreover, contact of blood with components of the extracorporeal circuit directly activate circulating cells (i.e. macrophages-monocytes or platelets) and protein systems (i.e. coagulation, complement, contact phase kallikrein-kinin system), leading to induction of pro-inflammatory cytokines and resulting in chronic low-grade inflammation, further contributing to poor outcomes. The multifactorial, repetitive HD-induced stress that globally reduces tissue perfusion and oxygenation could have deleterious long-term consequences on the functionality of vital organs such as heart, brain, liver and kidney. In this article, we summarize the multisystemic pathophysiological consequences of the main circulatory stress factors. Strategies to mitigate their effects to provide more cardioprotective and personalized dialytic therapies are proposed to reduce the systemic burden of HD.

Association between serum potassium and risk of all-cause mortality among chronic kidney diseases patients: A systematic review and dose-response meta-analysis of more than one million participants

We aimed to perform a meta-analysis, using prospective cohort studies, to test the association between serum potassium and all-cause mortality among chronic kidney diseases (CKD) patients. A systematic search was performed using PubMed-MEDLINE and Scopus, up to July 2020. Prospective cohort studies which reported risk estimates of all-cause mortality in CKD patients with different serum potassium levels were included in the present meta-analysis. Thirteen studies were included in the analysis. A nonlinear dose-response meta-analysis suggested that there is a J-shaped association between serum potassium levels and the risk of all-cause mortality, with a nadir at serum potassium of 4.5 mmol/L. Subgroup analyses indicated that the strength and shape of the association between serum potassium and all-cause mortality may be influenced by age. Our meta-analysis provides supportive evidence that there is a J-shape association between serum potassium and all-cause mortality among CKD patients.

Hyperkalemia in patients undergoing hemodialysis: its pathophysiology and management

Potassium is a major intracellular cation in the body, regulating membrane potential of excitable cells, such as cardiomyocytes and skeletal muscle cells. Because the kidney plays a critical role in controlling potassium balance, the elevation in serum potassium levels is one of the most common complications in patients with maintenance hemodialysis (MHD). In addition to reduced renal potassium excretion, the alteration in body potassium distribution owing to comorbid conditions may also contribute to dyskalemia. Besides potassium elimination through hemodialysis in MHD patients, accumulating data indicate the potential importance of extra‐renal elimination involving the gastrointestinal system, which can be affected by the inhibitors of the renin‐angiotensin‐aldosterone system. In this article, the literature on potassium physiology in MHD patients is reviewed with an emphasis on the changes from individuals with normal kidney function. This article also summarizes the findings of recent studies on dietary control, dialysate prescription, and pharmacological therapy.

Sudden cardiac death in dialysis patients: different causes and management strategies

Sudden cardiac death (SCD) represents a major cause of death in end-stage kidney disease (ESKD). The precise estimate of its incidence is difficult to establish because studies on the incidence of SCD in ESKD are often combined with those related to sudden cardiac arrest (SCA) occurring during a haemodialysis (HD) session. The aim of the European Dialysis Working Group of ERA-EDTA was to critically review the current literature examining the causes of extradialysis SCD and intradialysis SCA in ESKD patients and potential management strategies to reduce the incidence of such events. Extradialysis SCD and intradialysis SCA represent different clinical situations and should be kept distinct. Regarding the problem, numerically less relevant, of patients affected by intradialysis SCA, some modifiable risk factors have been identified, such as a low concentration of potassium and calcium in the dialysate, and some advantages linked to the presence of automated external defibrillators in dialysis units have been documented. The problem of extra-dialysis SCD is more complex. A reduced left ventricular ejection fraction associated with SCD is present only in a minority of cases occurring in HD patients. This is the proof that SCD occurring in ESKD has different characteristics compared with SCD occurring in patients with ischaemic heart disease and/or heart failure and not affected by ESKD. Recent evidence suggests that the fatal arrhythmia in this population may be due more frequently to bradyarrhythmias than to tachyarrhythmias. This fact may partly explain why several studies could not demonstrate an advantage of implantable cardioverter defibrillators in preventing SCD in ESKD patients. Electrolyte imbalances, frequently present in HD patients, could explain part of the arrhythmic phenomena, as suggested by the relationship between SCD and timing of the HD session. However, the high incidence of SCD in patients on peritoneal dialysis suggests that other risk factors due to cardiac comorbidities and uraemia per se may contribute to sudden mortality in ESKD patients.

A Uremic Goat Model Created by Subtotal Renal Artery Embolization and Gentamicin

A large animal model of (end-stage) kidney disease (ESKD) is needed for the preclinical testing of novel renal replacement therapies. This study aimed to create stable uremia via subtotal renal artery embolization in goats and induce a temporary further decline in kidney function by administration of gentamicin. Renal artery embolization was performed in five Dutch white goats by infusing polyvinyl alcohol particles in branches of the renal artery, aiming for the embolization of ~80% of one kidney and complete embolization of the contralateral kidney. Gentamicin was administered to temporarily further increase the plasma concentrations of uremic toxins. After initial acute kidney injury, urea and creatinine plasma concentrations stabilized 1.5 ± 0.7 months post-embolization and remained elevated (12 ± 1.4 vs. 5.6 ± 0.8 mmol/L and 174 ± 45 vs. 65 ± 5.6 µmol/L, resp.) during follow-up (16 ± 6 months). Gentamicin induced temporary acute-on-chronic kidney injury with a variable increase in plasma concentrations of small solutes (urea 29 ± 15 mmol/L, creatinine 841 ± 584 µmol/L, phosphate 2.2 ± 0.3 mmol/L and potassium 5.0 ± 0.6 mmol/L) and protein-bound uremic toxins representative of patients with ESKD. A uremic goat model characterized by stable moderate uremia was established via subtotal renal artery embolization with the induction of temporary severe acute-on-chronic kidney injury by the administration of gentamicin, allowing preclinical in vivo validation of novel renal replacement technologies.

Prescription patterns of dialysate potassium and potassium binders and survival on haemodialysis-the French Renal Epidemiology and Information Network registry

BACKGROUND

Management of potassium disorders in patients on haemodialysis (HD) is complex. We studied prescription patterns of dialysate potassium and potassium binders, and their associations with patient survival.

METHODS

This national registry-based study included 25 629 incident adult patients alive after 3 months of HD from 2010 through 2013 and followed-up through 31 December 2014. We used Cox proportional hazard models to estimate multiadjusted mortality hazard ratios (HRs) associated with time-dependent exposure to facility-level dialysate potassium concentrations and patient-level potassium binder exposure.

RESULTS

Almost all dialysis units used, and generally most often, dialysate potassium concentrations of 2 mmol/L. During this period, use of concentrations <2 mmol/L tended to decrease and those ≥3 mmol/L to increase. In 2014, 9% of units used a single dialysate formula, 41% used two and 50% three or more. The most frequent combinations were 2 and 3 mmol/L (40%), and <2, 2 and 3 mmol/L (37%). Compared with patients on HD in units using only one dialysate formula, those in units using two or three had adjusted mortality HRs of 0.91 [95% confidence interval (CI) 0.82-1.01] and 0.84 (0.75-0.93), respectively. Potassium binders were prescribed for 37% of all patients at baseline. Adjusted mortality HRs associated with doses <4, 4-8 and ≥8 g/day versus none were 1.22 (95% CI 1.04-1.51), 0.6 (0.54-0.66) and 0.25 (0.24-0.33), respectively.

CONCLUSIONS

Diversity in facility-level use of dialysate potassium concentrations and potassium binder use at an appropriate dose appear to be associated with better survival in HD patients.

Cardiac arrhythmia during early-week and mid-week dialysis in hemodialysis patients

Data on cardiac arrhythmia and electrolyte changes during the dialysis cycle have been limited. Fifty-two hemodialysis (HD) patients underwent 48-h Holter monitoring during early-week and mid-week HD sessions. Pre-HD and post-HD blood samples were collected in both HD sessions. The 48-h Holter data were divided into five phases: (1) 4-h during the early-week HD (HD1), (2) 12-h post-HD1, (3) 16-h period between Phases 2 and 4 (used as the patient's baseline electrocardiography [ECG]), (4) 12-h pre-HD2 phase, and (5) 4-h during the mid-week HD (HD2). The patients' mean age was 68.54 ± 13.37 years. We found that the dialysate-to-serum[K] gradient and changes of S[K] were significantly higher in HD1 than in HD2, as well as changes of S[Mg]. There were no significant ECG changes during the 4-h HD1 and HD2 when compared with the baseline ECG. Phase 2 of Holter ECG was the most common phase that showed significant changes (increased QT interval dispersion (QTD), increased ventricular events, increased number of premature ventricular contractions, ST elevation and ST depression), which was contributed from the dialysate[K] 2 mmol/L subgroup, but not the dialysate[K] 3 mmol/L subgroup. In the subgroup of patients with a high ultrafiltration rate (UFR; mean UFR ≥10 mL/kg/h), there were significantly increased ventricular events and ST-segment changes in Phase 2. In conclusion, ECG changes were associated with the dialysis cycle, significantly in the 12-h after early-week HD sessions. These may be associated with low dialysate[K] or high dialysate-to-S[K] gradient, high ultrafiltration rate and duration of the interdialytic interval.

Dialysis-Induced Cardiovascular and Multiorgan Morbidity

Hemodialysis has saved many lives, albeit with significant residual mortality. Although poor outcomes may reflect advanced age and comorbid conditions, hemodialysis per se may harm patients, contributing to morbidity and perhaps mortality. Systemic circulatory "stress" resulting from hemodialysis treatment schedule may act as a disease modifier, resulting in a multiorgan injury superimposed on preexistent comorbidities. New functional intradialytic imaging (i.e., echocardiography, cardiac magnetic resonance imaging [MRI]) and kinetic of specific cardiac biomarkers (i.e., Troponin I) have clearly documented this additional source of end-organ damage. In this context, several factors resulting from patient-hemodialysis interaction and/or patient management have been identified. Intradialytic hypovolemia, hypotensive episodes, hypoxemia, solutes, and electrolyte fluxes as well as cardiac arrhythmias are among the contributing factors to systemic circulatory stress that are induced by hemodialysis. Additionally, these factors contribute to patients' symptom burden, impair cognitive function, and finally have a negative impact on patients' perception and quality of life. In this review, we summarize the adverse systemic effects of current intermittent hemodialysis therapy, their pathophysiologic consequences, review the evidence for interventions that are cardioprotective, and explore new approaches that may further reduce the systemic burden of hemodialysis. These include improved biocompatible materials, smart dialysis machines that automatically may control the fluxes of solutes and electrolytes, volume and hemodynamic control, health trackers, and potentially disruptive technologies facilitating a more personalized medicine approach.

Fluctuations in plasma potassium in patients on dialysis

Plasma potassium concentration is maintained in a narrow range to avoid deleterious electrophysiologic consequences of both abnormally low and high levels. This is achieved by redundant physiologic mechanisms, with the kidneys playing a central role in maintaining both short-term plasma potassium stability and long-term total body potassium balance. In patients with end-stage renal disease, the lack of kidney function reduces the body’s ability to maintain normal physiologic potassium balance. Routine thrice-weekly dialysis therapy achieves long-term total body potassium mass balance, but the intermittent nature of dialytic therapy can result in wide fluctuations in plasma potassium concentration and consequently contribute to an increased risk of arrhythmogenicity. Various dialytic and nondialytic interventions can reduce the magnitude of these fluctuations, but the impact of such interventions on clinical outcomes remains unclear.

A simple modification of dialysate potassium: its impact on plasma potassium concentrations and the electrocardiogram

Background

Sudden death is frequent in haemodialysis (HD) patients. Both hyperkalaemia and change of plasma potassium (K) concentrations induced by HD could explain this. The impact of increasing dialysate K by 1 mEq/L on plasma K concentrations and electrocardiogram (ECG) results before and after HD sessions was studied.

Methods

Patients with pre-dialysis K >5.5 mEq/L were excluded. ECG and K measurements were obtained before and after the first session of the week for 2 weeks. Then, K in the dialysate was increased (from 1 or 3 to 2 or 4 mEq/L, respectively). Blood and ECG measurements were repeated after 2 weeks of this change.

Results

Twenty-seven prevalent HD patients were included. As expected, a significant decrease in K concentrations was observed after the dialysis session, but this decrease was significantly lower after the switch to an increased dialysate K. The pre-dialysis K concentrations were not different after changing, but post-dialysis K concentrations were higher after switching (P < 0.0001), with a lower incidence of post-dialysis hypokalaemia. Regarding ECG, before switching, the QT interval (QT) dispersion increased during the session, whereas no difference was observed after switching. One week after switching, post-dialysis QT dispersion [38 (34-42) ms] was lower than post-dialysis QT dispersion 2 weeks and 1 week before switching [42 (38-57) ms, P = 0.0004; and 40 (35-50) ms, P = 0.0002].

Conclusions

A simple increase of 1 mEq/L of K in the dialysate is associated with a lower risk of hypokalaemia and a lower QT dispersion after the dialysis session. Further study is needed to determine if such a strategy is associated with a lower risk of sudden death.

Melatonin receptor activation protects against low potassium-induced ventricular fibrillation by preserving action potentials and connexin-43 topology in isolated rat hearts

Hypokalemia prolongs the QRS and QT intervals, deteriorates intercellular coupling, and increases the risk for arrhythmia. Melatonin preserves gap junctions and shortens action potential as potential antiarrhythmic mechanisms, but its properties under hypokalemia remain unknown. We hypothesized that melatonin protects against low potassium-induced arrhythmias through the activation of its receptors, resulting in action potential shortening and connexin-43 preservation. After stabilization in Krebs-Henseleit solution (4.5 mEq/L K⁺ ), isolated hearts from Wistar rats underwent perfusion with low-potassium (1 mEq/L) solution and melatonin (100 μmol/L), a melatonin receptor blocker (luzindole, 5 μmol/L), melatonin + luzindole or vehicle. The primary endpoint of the study was the prevention of ventricular fibrillation. Electrocardiography was used, and epicardial action potentials and heart function were measured and analyzed. The ventricular expression, dephosphorylation, and distribution of connexin-43 were examined. Melatonin reduced the incidence of low potassium-induced ventricular fibrillation from 100% to 59%, delayed the occurrence of ventricular fibrillation and induced a faster recovery of sinus rhythm during potassium restitution. Melatonin prevented QRS widening, action potential activation delay, and the prolongation of action potential duration at 50% of repolarization. Other ECG and action potential parameters, the left ventricular developed pressure, and nonsustained ventricular arrhythmias did not differ among groups. Melatonin prevented connexin-43 dephosphorylation and its abnormal topology (lateralization). Luzindole abrogated the protective effects of melatonin on electrophysiological properties and connexin-43 misdistribution. Our results indicate that melatonin receptor activation protects against low potassium-induced ventricular fibrillation, shortens action potential duration, preserves ventricular electrical activation, and prevents acute changes in connexin-43 distribution. All of these properties make melatonin a remarkable antifibrillatory agent.

Treating potassium disturbances: kill the killers but avoid overkill

OBJECTIVES

In this publication, we review the definitions, symptoms, causes, differential diagnoses and therapies of hypokalemia and hyperkalemia.

METHODS

Comprehensive tables and diagnostic algorithms are provided when appropriate.

RESULTS AND CONCLUSIONS

Although both hypokalemia and hyperkalemia may be life-threatening, this is essentially the case with severe changes (serum potassium < 2.5 or > 6.5 mmol/L), the presence of symptoms or electrocardiographic deviations, the association with aggravating factors (e.g. digitalis intake) and/or rapid acute changes. Only these truly need an emergency therapeutic approach. In all other cases, a careful consideration of the causes and their correction should prevail over additional approaches to modify serum potassium concentration. Although most therapeutic approaches to both hypokalemia and hyperkalemia have been well established since many years, recently two new intestinal potassium binders have been introduced on the market. It remains to be elucidated whether these drugs truly have an additional role on top of the existing treatments.

Management of hyperkalemia in patients with kidney disease: a position paper endorsed by the Italian Society of Nephrology

Hyperkalemia (HK) is the most common electrolyte disturbance observed in patients with kidney disease, particularly in those in whom diabetes and heart failure are present or are on treatment with renin-angiotensin-aldosterone system inhibitors (RAASIs). HK is recognised as a major risk of potentially life threatening cardiac arrhythmic complications. When an acute reduction of renal function manifests, both in patients with chronic kidney disease (CKD) and in those with previously normal renal function, HK is the main indication for the execution of urgent medical treatment and the recourse to extracorporeal replacement therapies. In patients with end-stage renal disease, the presence of HK not responsive to medical therapy is an indication at the beginning of chronic renal replacement therapy. HK can also be associated indirectly with the progression of CKD, because the finding of high potassium values leads to withdrawal of treatment with RAASIs, which constitute the first choice nephro-protective treatment. It is therefore essential to identify patients at risk of developing HK, and to implement therapeutic interventions aimed at preventing and treating this dangerous complication of kidney disease. Current strategies aimed at the prevention and treatment of HK are still unsatisfactory, as evidenced by the relatively high prevalence of HK also in patients under stable nephrology care, and even in the ideal setting of randomized clinical trials where optimal treatment and monitoring are mandatory. This position paper will review the main therapeutic interventions to be implemented for the prevention, detection and treatment of HK in patients with CKD on conservative care, in those on dialysis, in patients in whom renal disease is associated with diabetes, heart failure, resistant hypertension and who are on treatment with RAASIs, and finally in those presenting with severe acute HK.

A Phase 3b, Randomized, Double-Blind, Placebo-Controlled Study of Sodium Zirconium Cyclosilicate for Reducing the Incidence of Predialysis Hyperkalemia

BACKGROUND

Patients with ESRD have minimal renal potassium excretion and, despite hemodialysis, often have persistent predialysis hyperkalemia. The DIALIZE study (NCT03303521) evaluated sodium zirconium cyclosilicate (SZC) in the management of hyperkalemia in hemodialysis patients.

METHODS

In the DIALIZE study, a double-blind, placebo-controlled, phase 3b multicenter study, we randomized adults with ESRD who were managed by three-times weekly hemodialysis and had predialysis hyperkalemia to receive placebo or SZC 5 g once daily on non-dialysis days, and titrated towards maintaining normokalemia over 4 weeks, in 5 g increments to a maximum of 15 g. The primary efficacy outcome was proportion of patients during the 4-week stable-dose evaluation period who maintained predialysis serum potassium of 4.0-5.0 mmol/L during at least three of four hemodialysis treatments after the long interdialytic interval and did not require urgent rescue therapy to reduce serum potassium.

RESULTS

In total, 196 patients (mean [standard deviation (SD)] age =58.1 [13.7] years old) were randomized to sodium zirconium cyclosilicate or placebo. Of 97 patients receiving sodium zirconium cyclosilicate, 41.2% met the primary end point and were deemed treatment responders compared with 1.0% of 99 patients receiving placebo (P<0.001). Rescue therapy to reduce serum potassium during the treatment period was required by 2.1% of patients taking sodium zirconium cyclosilicate versus 5.1% taking placebo. Serious adverse events occurred in 7% and 8% of patients in sodium zirconium cyclosilicate and placebo groups, respectively. The two groups displayed comparable interdialytic weight gain. There were few episodes of hypokalemia.

CONCLUSIONS

Sodium zirconium cyclosilicate is an effective and well-tolerated treatment for predialysis hyperkalemia in patients with ESRD undergoing adequate hemodialysis.

Postdialysis Hypokalemia and All-Cause Mortality in Patients Undergoing Maintenance Hemodialysis

BACKGROUND AND OBJECTIVES

Almost half of patients on dialysis demonstrate a postdialysis serum potassium ≤3.5 mEq/L. We aimed to examine the relationship between postdialysis potassium levels and all-cause mortality.

DESIGN, SETTING, PATIENTS, & MEASUREMENTS

We conducted a cohort study of 3967 participants on maintenance hemodialysis from the Dialysis Outcomes and Practice Patterns Study in Japan (2009-2012 and 2012-2015). Postdialysis serum potassium was measured repeatedly at 4-month intervals and used as a time-varying variable. We estimated the hazard ratio of all-cause mortality rate using Cox hazard regression models, with and without adjusting for time-varying predialysis serum potassium. Models were adjusted for baseline characteristics and time-varying laboratory parameters. We also analyzed associations of combinations of pre- and postdialysis potassium with mortality.

RESULTS

The age of participants at baseline was 65±12 years (mean±SD), 2552 (64%) were men, and 96% were treated with a dialysate potassium level of 2.0 to <2.5 mEq/L. The median follow-up period was 2.6 (interquartile range, 1.3-2.8) years. During the follow-up period, 562 (14%) of 3967 participants died, and the overall mortality rate was 6.7 per 100 person-years. Compared with postdialysis potassium of 3.0 to <3.5 mEq/L, the hazard ratios of postdialysis hypokalemia (<3.0 mEq/L) were 1.84 (95% confidence interval, 1.44 to 2.34) in the unadjusted model, 1.44 (95% confidence interval, 1.14 to 1.82) in the model without adjusting for predialysis serum potassium, and 1.10 (95% confidence interval, 0.84 to 1.44) in the model adjusted for predialysis serum potassium. The combination of pre- and postdialysis hypokalemia was associated with the highest mortality risk (hazard ratio, 1.72; 95% confidence interval, 1.35 to 2.19, reference; pre- and postdialysis nonhypokalemia).

CONCLUSIONS

Postdialysis hypokalemia was associated with mortality, but this association was not independent of predialysis potassium.

Dialysis Prescription and Sudden Death

In the United States, end-stage renal disease patients receiving hemodialysis have an exceedingly high risk of sudden cardiac death (SCD), accounting for 29% of death events, likely relating to their uremic milieu, recurring exposure to fluid and electrolyte fluxes, and underlying cardiovascular pathology. Furthermore, epidemiologic studies have shown that SCD events, as well as mortality and hospitalizations, occur most frequently on the first dialysis day after the long interdialytic gap, suggesting that abrupt fluctuations in the accumulation and removal of electrolytes, fluid, and uremic toxins over the dialysis cycle may be contributory. Some population-based observational studies have suggested that lower dialysate potassium concentrations appear to be associated with a heightened risk of postdialysis cardiac arrest in hemodialysis patients, although the optimal serum-to-dialysate potassium gradient remains unclear. Some observational studies have suggested that low dialysate calcium concentrations and high serum-to-dialysate calcium gradients may predispose patients to SCD. There is ongoing controversy about an association between higher dialysate bicarbonate concentrations and higher risk of cardiac arrest, likely owing to confounding by indication. Some observational studies also have shown that large interdialytic weight gains, fluid retention, and high ultrafiltration rates are linked with higher risk of SCD and mortality. However, there remains considerable controversy regarding the pros and cons of designating a specific upper ultrafiltration limit with extended treatment times as a clinical practice measure, and further studies are needed to define the optimal tools, metrics, targets, and implementation measures for volume control in the hemodialysis population. In this review, we highlight the epidemiology and pathophysiology of how specific aspects of the hemodialysis procedure may relate to the risk of SCD, as well as preventative strategies and future research directions that can address this risk.

Dialysate potassium concentration: Should mass balance trump electrophysiology?

Nephrologists are faced with a difficult dilemma in choosing the ideal dialysis prescription to maintain neutral potassium mass balance. Should potassium mass balance goals prioritize the normalization of serum potassium levels using low potassium dialysate at the expense of provoking intradialytic arrhythmias, or should mass balance goals favor permissive hyperkalemia using higher dialysate potassium to avoid rapid intradialytic fluxes at the risk of more interdialytic arrhythmias? This review examines the factors that determine potassium mass balance among HD patients, the relationships between serum and dialysate potassium levels and outcomes, and concludes by examining currently available approaches to reducing risk of arrhythmias while managing potassium mass balance.

Dialysate Potassium and Mortality in a Prospective Hemodialysis Cohort

BACKGROUND

Studies examining the association of dialysate potassium concentration and mortality in hemodialysis patients show conflicting findings. We hypothesized that low dialysate potassium concentrations are associated with higher mortality, particularly in patients with high pre-dialysis serum potassium concentrations.

METHODS

We evaluated 624 hemodialysis patients from the prospective Malnutrition, Diet, and Racial Disparities in Kidney Disease study recruited from 16 outpatient dialysis facilities over 2011-2015 who underwent protocolized collection of dialysis treatment characteristics every 6 months. We examined the association of dialysate potassium concentration, categorized as 1, 2, and 3 mEq/L, with all-cause mortality risk in the -overall cohort, and stratified by pre-dialysis serum potassium (< 5 vs. ≥5 mEq/L) using case-mix adjusted Cox models.

RESULTS

In baseline analyses, dialysate potassium concentrations of 1 mEq/L were associated with higher mortality, whereas concentrations of 3 mEq/L were associated with similar mortality in the overall cohort (reference: 2 mEq/L): adjusted hazard ratios (aHRs; 95% CI) 1.70 (1.01-2.88) and 0.95 (0.64-1.39), respectively. In analyses stratified by serum potassium, baseline dialysate potassium concentrations of 1 mEq/L were associated with higher mortality in patients with serum potassium ≥5 mEq/L but not in those with serum potassium < 5 mEq/L: aHRs (95% CI) 2.87 (1.51-5.46) and 0.74 (0.27-2.07), respectively (p interaction = 0.04). These findings were robust with incremental adjustment for serum potassium, potassium-binding resins, and potassium-modifying medications.

CONCLUSION

Low (1 mEq/L) dialysate potassium -concentrations were associated with higher mortality, particularly in hemodialysis patients with high pre-dialysis serum potassium. Further studies are needed to identify therapeutic strategies that mitigate inter-dialytic serum potassium accumulation and subsequent high dialysate serum potassium gradients in this population.