Hyperkalemia: An adaptive response in chronic renal insufficiency

Impaired aldosterone response to potassium and hyperkalemia in patients receiving a renin-angiotensin-aldosterone system inhibitor

BACKGROUND/AIMS

Angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II receptor blockers (ARBs) are associated with the development of hyperkalemia. We evaluated the relationship between the serum aldosterone-to-potassium ratio (APR) and the risk of developing hyperkalemia in patients with chronic kidney disease (CKD) receiving ACEIs or ARBs.

METHODS

One hundred eighty-six patients with stage 3-4 CKD receiving an ACEI or ARB for at least 3 months were evaluated. Serum aldosterone and potassium concentrations were measured simultaneously, and serum APR was calculated (ng/mL per mmol/L). Patients were divided into two groups for comparison according to the median value above or below 2.42. The primary outcome was the difference between the two groups in the development of hyperkalemia (defined as a serum potassium level > 5.5 mmol/L). Incidence rates and risk factors of hyperkalemia were assessed.

RESULTS

During the follow-up period, 144 hyperkalemic events in 81 patients (43.5%) were identified, yielding an incidence rate of 24.6 events/100 person-years. The incidence rate was significantly higher in patients with a low serum APR than in patients with a high APR (35.8 events/100 patient-years vs. 12.9 events/100 patient-years, p < 0.001). In addition, diabetes mellitus, history of hyperkalemia, CKD progression during the follow-up period, and low serum APR were predictors of the development of hyperkalemia.

CONCLUSION

Low serum APR was associated with the occurrence of hyperkalemia in patients with CKD receiving ACEIs or ARBs, suggesting that the identification of patients administered these drugs who are at high risk for hyperkalemia may be achieved using this index.

Hyperkalemia and maintenance of renin-angiotensin system inhibitor therapy after initiating SGLT-2 or DPP-4 inhibitors

BACKGROUND

Post hoc analyses of clinical trials suggest that sodium-glucose cotransporter-2 inhibitors (SGLT-2i) lower the risk of hyperkalemia and facilitate the use of renin-angiotensin system inhibitors (RASi) in people with type 2 diabetes. Whether this is also observed in routine care is unclear. We investigated whether SGLT-2i lowered the risk of hyperkalemia and RASi discontinuation as compared to dipeptidyl peptidase 4 inhibitors (DPP-4i).

METHODS

Using the target trial emulation framework, we studied adults with type 2 diabetes (T2D) who started SGLT-2i or DPP-4i in Stockholm, Sweden (2014-2021). The outcomes were incident hyperkalemia (potassium >5.0 mmol/l), mild hyperkalemia (potassium >5-≤5.5 mmol/l), and moderate to severe hyperkalemia (potassium >5.5 mmol/l). Among RASi users, we studied time to RASi discontinuation through evaluation of pharmacy fills. Cox regression with inverse probability of treatment weighting was used to estimate per-protocol hazard ratios (HRs).

RESULTS

In total, 29 849 individuals (15 326 SGLT-2i and 14 523 DPP-4i initiators) were included (mean age 66 years, 37% women). About one-third of participants in each arm discontinued treatment within 1 year. Compared with DPP-4i, SGLT-2i use was associated with a lower rate of hyperkalemia (HR 0.77; 95% CI: 0.64-0.93), including both mild (0.76; 0.62-0.93) and moderate/severe (0.53; 0.40-0.69) hyperkalemia events. Of 19 116 participants who used RASi at baseline, 7% discontinued therapy. Initiation of SGLT-2i vs. DPP-4i was not associated with the rate of RASi discontinuation (0.97; 0.83-1.14). Results were consistent in intention-to-treat analysis and across strata of sex, cardiovascular disease, use of MRA, and use of RASi.

CONCLUSIONS

In patients with diabetes managed in routine clinical care, the use of SGLT-2i was associated with lower rates of hyperkalemia compared with DPP-4i. Possibly because of a relatively high rate of treatment discontinuations, this was not accompanied by higher persistence on RASi therapy.

Kinetic Modeling of In Vivo K+ Distribution and Fluxes with Stable K+ Isotopes: Effects of Dietary K+ Restriction

Maintaining extracellular potassium (K+) within narrow limits, critical for membrane potential and excitability, is accomplished through the internal redistribution of K+ between extracellular fluid (ECF) and intracellular fluid (ICF) in concert with the regulation of renal K+ output to balance K+ intake. Here we present evidence from high-precision analyses of stable K+ isotopes in rats maintained on a control diet that the tissues and organs involved in the internal redistribution of K+ differ in their speed of K+ exchange with ECF and can be grouped into those that exchange K+ with ECF either rapidly or more slowly ("fast" and "slow" pools). After 10 days of K+ restriction, a compartmental analysis indicates that the sizes of the ICF K+ pools decreased but that this decrease in ICF K+ pools was not homogeneous, rather occurring only in the slow pool (15% decrease, p < 0.01), representing skeletal muscles, not in the fast pool. Furthermore, we find that the dietary K+ restriction is associated with a decline in the rate constants for K+ effluxes from both the "fast" and "slow" ICF pools (p < 0.05 for both). These results suggest that changes in unidentified transport pathways responsible for K+ efflux from ICF to ECF play an important role in buffering the internal redistribution of K+ between ICF and ECF during K+ restriction. Thus, the present study introduces novel stable isotope approaches to separately characterize heterogenous ICF K+ pools in vivo and assess K+ uptake by individual tissues, methods that provide key new tools to elucidate K+ homeostatic mechanisms in vivo.

Management of Hyperkalemia in Patients with Chronic Kidney Disease Using Renin Angiotensin Aldosterone System Inhibitors

PURPOSE OF REVIEW

Use of renin-angiotensin-aldosterone system (RAAS) inhibiting medications is critical in the prevention of cardiovascular disease and kidney function decline in patients with chronic kidney disease (CKD); however, these agents can lead to hyperkalemia, an electrolyte disorder associated with risk of arrythmia, conduction disorders, and increased overall mortality. Discontinuation, or reduction of dose, of RAAS inhibitor therapy in hyperkalemic patients with CKD can lead to loss of kidney and cardiovascular protection afforded by these medications. Given the high prevalence of hyperkalemia among patients with CKD utilizing RAAS inhibitors, clear management principles are critical to minimize risk and maximize benefit when facing this clinical dilemma.

RECENT FINDINGS

Strategies to mitigate hyperkalemia that do not interfere with optimal RAAS inhibitor therapy should be prioritized when managing potassium elevation in patients with CKD. These strategies include discontinuing non-RAAS inhibitor medications known to cause hyperkalemia, correction of metabolic acidosis, and maximization of medication therapies that lower serum potassium, including diuretics and sodium-glucose cotransporter-2 (SGLT-2) inhibitors. Initiation of potassium exchange resins should also be considered to allow for sustained RAAS inhibitor utilization. An approach which employs multiple strategies concurrently is important to mitigate hyperkalemia and maintain long-term use of RAAS-inhibitors. Persistence of RAAS inhibitor use in patients with CKD is important to slow kidney function decline, delay onset of dialysis or the need for kidney transplant, and prevent adverse cardiovascular outcomes. When hyperkalemia develops among patients with CKD utilizing a RAAS inhibitor, a deliberate effort to reduce serum potassium levels using an approach that allows for continuation of maximally dosed RAAS inhibitor therapy is important. Patient education and engagement in the potassium management process is important for sustained success.

Pathophysiology and clinical management of hyperkalemia in chronic kidney disease

Adaptive increases in kidney and gastrointestinal excretion of K+ help to prevent hyperkalemia in patients with chronic kidney disease (CKD) as long as the glomerular filtration rate (GFR) remains >15-20 mL/min. K+ balance is maintained by increased secretion per functioning nephron, which is mediated by elevated plasma K+ concentration, aldosterone, increased flow rate, and enhanced Na+-K+-ATPase activity. Fecal losses of potassium also increase in CKD. These mechanisms are effective in preventing hyperkalemia if urine output is in excess of 600 mL/day and the GFR exceeds 15 mL/min. Development of hyperkalemia with only mild to moderate reductions in GFR should prompt a search for intrinsic disease of the collecting duct, disturbances in mineralocorticoid activity, and/or decreased delivery of sodium to the distal nephron. The initial approach to treatment is to review the patient's medication profile and whenever possible discontinue drugs that impair kidney K+ excretion. Patients should be educated on sources of K+ in the diet and should be strongly encouraged to avoid the use of K+ containing salt substitutes as well as herbal remedies since herbs may be a hidden source of dietary K+. Effective diuretic therapy and correction of metabolic acidosis are effective strategies to minimize the potential for hyperkalemia. Discontinuation or use of submaximal doses of renin-angiotensin blockers should be discouraged given the cardiovascular protective effect these drugs provide. Potassium binding drugs can be useful to enable use of these drugs and potentially allow liberalization of the diet in CKD patients.

Compared effectiveness of sodium zirconium cyclosilicate and calcium polystyrene sulfonate on hyperkalemia in patients with chronic kidney disease

Hyperkalemia is a well-recognized electrolyte abnormality in patients with chronic kidney disease (CKD). Potassium binders are often used to prevent and treat hyperkalemia. However, few studies have evaluated the difference in serum potassium (K⁺) level-lowering effect during the post-acute phase between the novel potassium binder, sodium zirconium cyclosilicate (ZSC), and conventional agents. This retrospective study included patients who received potassium binders (either ZSC or calcium polystyrene sulfonate [CPS]) in our hospital between May 2020 and July 2022. The patients were divided into the ZSC and CPS groups. After propensity score matching, we compared changes from baseline to the first follow-up point, at least 4 weeks after initiating potassium binders, in electrolytes including K⁺ level between the two groups. Of the 132 patients, ZSC and CPS were administered in 48 and 84 patients, respectively. After matching, 38 patients were allocated to each group. The ZSC group showed greater reduction in K⁺ levels than did the CPS group (P < 0.05). Moreover, a significant increase in serum sodium minus chloride levels, a surrogate marker for metabolic acidosis, was observed in the ZSC group (P < 0.05). Our results demonstrated that ZSC could potentially improve hyperkalemia and metabolic acidosis in patients with CKD.

[What is confirmed in the treatment of chronic kidney disease?]

Chronic kidney disease (CKD) is defined as a relevant excretion of albumin into the urine or a reduction of the glomerular filtration rate (GFR) over a longer time period of ≥ 3 months. The causes of CKD are manifold, whereby the association with diabetes mellitus is the most frequent cause. Early stages of CKD affect approximately 10% of the total population. The frequency of cardiovascular events, the risk of dependency on dialysis and the all-cause mortality increase exponentially with a decrease in the GFR and an increase in albuminuria. The guidelines of the German College of General Practitioners and Family Physicians (DEGAM) and the organization Kidney Disease: Improving Global Outcomes (KDIGO) recommend referral to a nephrologist with a GFR of ≤ 30 or ≤ 60 ml/min/1.73 m² in the presence of various cofactors. This means that the majority of CKD patients are treated by general internists or general practitioners. This article gives a concise summary of current data on the treatment of CKD and its associated complications in clinical practice. It refers to the current guidelines and also new study results which could perspectively expand the therapeutic repertoire.

Potassium Derangements: A Pathophysiological Review, Diagnostic Approach, and Clinical Management

Potassium is an essential cation critical in fluid and electrolyte balance, acid–base regulation, and neuromuscular functions. The normal serum potassium is kept within a narrow range of 3.5–5.2 meq/L while the intracellular concentration is approximately 140–150 meq/L. The total body potassium is about 45–55 mmol/kg; thus, a 70 kg male has an estimated ~136 g and 60 kg female has ~117 g of potassium. In total, 98% of the total body potassium is intracellular. Skeletal muscle contains ~80% of body potassium stores. The ratio of intracellular to extracellular potassium concentration (Ki/Ke) maintained by Na+/K+ ATPase determines the resting membrane potential. Disturbances of potassium homeostasis lead to hypo- and hyperkalemia, which if severe, can be life-threatening. Prompt diagnosis and management of these problems are important.

Estimating in vivo potassium distribution and fluxes with stable potassium isotopes

Extracellular potassium (K⁺) homeostasis is achieved by a concerted effort of multiple organs and tissues. A limitation in studies of K⁺ homeostasis is inadequate techniques to quantify K⁺ fluxes into and out of organs and tissues in vivo. The goal of the present study was to test the feasibility of a novel approach to estimate K⁺ distribution and fluxes in vivo using stable K⁺ isotopes. ⁴¹K was infused as KCl into rats consuming control or K⁺-deficient chow (n = 4 each), ⁴¹K-to-³⁹K ratios in plasma and red blood cells (RBCs) were measured by inductively coupled plasma mass spectrometry, and results were subjected to compartmental modeling. The plasma ⁴¹K/³⁹K increased during ⁴¹K infusion and decreased upon infusion cessation, without altering plasma total K⁺ concentration ([K⁺], i.e., ⁴¹K + ³⁹K). The time course of changes was analyzed with a two-compartmental model of K⁺ distribution and elimination. Model parameters, representing transport into and out of the intracellular pool and renal excretion, were identified in each rat, accurately predicting decreased renal K⁺ excretion in rats fed K⁺-deficient vs. control diet (P < 0.05). To estimate rate constants of K⁺ transport into and out of RBCs, ⁴¹K/³⁹K were subjected to a simple model, indicating no effects of the K⁺-deficient diet. The findings support the feasibility of the novel stable isotope approach to quantify K⁺ fluxes in vivo and sets a foundation for experimental protocols using more complex models to identify heterogeneous intracellular K⁺ pools and to answer questions pertaining to K⁺ homeostatic mechanisms in vivo.

Mesenchymal stem cells: A new therapeutic tool for chronic kidney disease

Chronic kidney disease (CKD) has a major impact on public health, which could progress to end-stage kidney disease (ESRD) and consume many medical resources. Currently, the treatment for CKD has many flaws, so more effective treatment tools are urgently required for CKD. Mesenchymal stem cells (MSCs) are primitive cells with self-renewal and proliferation capacity and differentiation potential. Extensive preclinical and clinical data has shown that cell-based therapies using MSCs can modulate immunity, inhibit inflammatory factors, and improve renal function in CKD, suggesting that MSCs have the potential to be a new, effective therapeutic tool for CKD. In this review, we will describe different kinds of MSCs and MSCs products for the treatment of CKD in experimental models and clinical trials, potential signaling pathways, therapeutic efficacy, and critical issues that need to be addressed before therapeutic application in humans.

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.

Hydroelectrolytic Disorder in COVID-19 patients: Evidence Supporting the Involvement of Subfornical Organ and Paraventricular Nucleus of the Hypothalamus

Multiple neurological problems have been reported in coronavirus disease-2019 (COVID-19) patients because severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) likely spreads to the central nervous system (CNS) via olfactory nerves or through the subarachnoid space along olfactory nerves into the brain's cerebrospinal fluid and then into the brain's interstitial space. We hypothesize that SARS-CoV-2 enters the subfornical organ (SFO) through the above routes and the circulating blood since circumventricular organs (CVOs) such as the SFO lack the blood-brain barrier, and infection of the SFO causes dysfunction of the hypothalamic paraventricular nucleus (PVN) and supraoptic nucleus (SON), leading to hydroelectrolytic disorder. SARS-CoV-2 can readily enter SFO-PVN-SON neurons because these neurons express angiotensin-converting enzyme-2 receptors and proteolytic viral activators, which likely leads to neurodegeneration or neuroinflammation in these regions. Considering the pivotal role of SFO-PVN-SON circuitry in modulating hydroelectrolyte balance, SARS-CoV-2 infection in these regions could disrupt the neuroendocrine control of hydromineral homeostasis. This review proposes mechanisms by which SARS-CoV-2 infection of the SFO-PVN-SON pathway leads to hydroelectrolytic disorder in COVID-19 patients.

Cardiovascular and Renal Outcomes Associated With Hyperkalemia in Chronic Kidney Disease: A Hospital-Based Cohort Study

Objective

To examine the association between hyperkalemia and long-term cardiovascular and renal outcomes in patients with chronic kidney disease.

Patients and Methods

An observational retrospective cohort study was performed using a Japanese hospital claims registry, Medical Data Vision (April 1, 2008, to September 30, 2018). Of 1,208,894 patients with at least 1 potassium measurement, 167,465 patients with chronic kidney disease were selected based on International Classification of Diseases, Tenth Revision codes or estimated glomerular filtration rate (eGFR) less than 60 mL/min/1.73 m². Hyperkalemia was defined as at least 2 potassium measurements of 5.1 mmol/L or greater within 12 months. Normokalemic controls were patients without a record of potassium levels of 5.1 mmol/L or greater and 3.5 mmol/L or less. Changes in eGFRs and hazard ratios of death, hospitalization for cardiac events, heart failure, and renal replacement therapy introduction were assessed between propensity score–matched hyperkalemic patients and normokalemic controls.

Results

Of 16,133 hyperkalemic patients and 11,898 normokalemic controls eligible for analyses, 5859 (36.3%) patients and 5859 (49.2%) controls were selected after propensity score matching. The mean follow-up period was 3.5 years. The 3-year eGFR change in patients and controls was −5.75 and −1.79 mL/min/1.73 m², respectively. Overall, hyperkalemic patients had higher risks for death, hospitalization for cardiac events, heart failure, and renal replacement therapy introduction than controls, with hazard ratios of 4.40 (95% CI, 3.74 to 5.18), 1.95 (95% CI, 1.59 to 2.39), 5.09 (95% CI, 4.17 to 6.21), and 7.54 (95% CI, 5.73 to 9.91), respectively.

Conclusion

Hyperkalemia was associated with significant risks for mortality and adverse clinical outcomes, with more rapid decline of renal function. These findings underscore the significance of hyperkalemia as a predisposition to future adverse events in patients with chronic kidney disease.

Unsuspecting Dietary Factors in Hyperkalemia: A Case Report on Why History Matters

Introduction

We present a case of hyperkalemia secondary to excessive dietary intake of hard caramel candies.

Case Report

An 88-year-old male who presented with acute abdominal pain and vomiting was found to have hyperkalemia of 6.9 milliequivalents per liter. He was stabilized, treated, and discharged the following day after resolution. The cause was identified as his daily consumption of 200 hard caramel candies.

Discussion

The patient had been consuming sugar-free candies, which induced a chronic diarrhea. This led to potassium wasting and augmentation of his home medications. When he transitioned to eating regular caramel candies, he retained too much potassium leading to his presentation.

Conclusion

While often overlooked, dietary history is a crucial part of history-taking to ensure that the underlying cause for illness is discovered and addressed.

Plasma potassium ranges associated with mortality across stages of chronic kidney disease: the Stockholm CREAtinine Measurements (SCREAM) project

Background

Small-scale studies suggest that hyperkalaemia is a less threatening condition in chronic kidney disease (CKD), arguing adaptation/tolerance to potassium (K⁺) retention. This study formally evaluates this hypothesis by estimating the distribution of plasma K⁺ and its association with mortality across CKD stages.

Methods

This observational study included all patients undergoing plasma K⁺ testing in Stockholm during 2006–11. We randomly selected one K⁺ measurement per patient and constructed a cross-sectional cohort with mortality follow-up. Covariates included demographics, comorbidities, medications and estimated glomerular filtration rate (eGFR). We estimated K⁺ distribution and defined K⁺ ranges associated with 90-, 180- and 365-day mortality.

Results

Included were 831 760 participants, of which 70 403 (8.5%) had CKD G3 (eGFR <60–30 mL/min) and 8594 (1.1%) had CKD G4–G5 (eGFR <30 mL/min). About 66 317 deaths occurred within a year. Adjusted plasma K⁺ increased across worse CKD stages: from median 3.98 (95% confidence interval 3.49–4.59) for eGFR >90 to 4.43 (3.22–5.65) mmol/L for eGFR ≤15 mL/min/1.73 m². The association between K⁺ and mortality was U-shaped, but it flattened at lower eGFR strata and shifted upwards. For instance, the range where the 90-day mortality risk increased by no more than 100% was 3.45–4.94 mmol/L in eGFR >60 mL/min, but was 3.36–5.18  in G3 and 3.26–5.53 mmol/L in G4–G5. In conclusion, CKD stage modifies K⁺ distribution and the ranges that predict mortality in the community.

Conclusion

Although this study supports the view that hyperkalaemia is better tolerated with worse CKD, it challenges the current use of a single optimal K⁺ range for all patients.

Association of Dietary Potassium Intake with the Development of Chronic Kidney Disease and Renal Function in Patients with Mildly Decreased Kidney Function: The Korean Multi-Rural Communities Cohort Study

Background

Dietary potassium has negative outcomes in patients with mildly impaired kidney function, while having positive outcomes in patients with hypertension. The association of dietary potassium intake with chronic kidney disease (CKD) development, with presence of hypertension, was studied in the Korean rural population with mildly impaired kidney function.

Material/Methods

From 3 rural areas of Korea, 5064 participants age ≥40 with CKD stage 2 at baseline were recruited. Patients were classified according to the quartile of dietary potassium intake. Newly developed CKD, defined as estimated glomerular filtration rate (eGFR) of <60 mL/min/1.73 m² at the time of follow-up, and eGFR decline, defined as eGFR decrease >15% at follow-up, were studied. The effect of dietary potassium on CKD development and eGFR decline were studied by Cox proportional hazard models. The association of potassium with blood pressures and C-reactive protein was also studied to examine the underlying mechanisms.

Results

Compared to 8.6% in normotensives, 15.7% of hypertensives developed CKD. The hazard ratio (HR) (95% confidence interval) of CKD was lower in high potassium diet only in hypertensives, with 0.60 (0.37–0.99) in the highest quartile. The eGFR decline was also lower in patients with higher potassium diet, with 0.70 (0.50–0.98) in Q3 and 0.54 (0.34–0.85) in Q4. Potassium intake has also been shown to decrease high diastolic blood pressure development (>90 mmHg) in hypertensives at 0.45 (0.25–0.83).

Conclusions

Dietary potassium was associated with lower risk of CKD development and eGFR decline, and this association was observed only in hypertensives.

A Case of Nonfatal Non-Collapsed Patient with Extreme Hyperkalaemia

This is a report of a non-collapsed patient with nonfatal, extreme hyperkalaemia of 10.7 mmol/L. The patient's hyperkalaemia was initially treated in the Emergency Department and then transferred to the Department of Renal Medicine of another hospital for further stabilisation. There have only been a few reported cases of successful management of extreme hyperkalaemia in excess of 10.0 mmol/L.

How Dangerous Is Hyperkalemia?

Hyperkalemia is a potentially life-threatening electrolyte disorder appreciated with greater frequency in patients with renal disease, heart failure, and with use of certain medications such as renin angiotensin aldosterone inhibitors. The traditional views that hyperkalemia can be reliably diagnosed by electrocardiogram and that particular levels of hyperkalemia confer cardiotoxic risk have been challenged by several reports of patients with atypic presentations. Epidemiologic data demonstrate strong associations of morbidity and mortality in patients with hyperkalemia but these associations appear disconnected in certain patient populations and in differing clinical presentations. Physiologic adaptation, structural cardiac disease, medication use, and degree of concurrent illness might predispose certain patients presenting with hyperkalemia to a lower or higher threshold for toxicity. These factors are often overlooked; yet data suggest that the clinical context in which hyperkalemia develops is at least as important as the degree of hyperkalemia is in determining patient outcome. This review summarizes the clinical data linking hyperkalemia with poor outcomes and discusses how the efficacy of certain treatments might depend on the clinical presentation.

Computer-assisted image processing 12 lead ECG model to diagnose hyperkalemia

BACKGROUND

We sought to develop an improved 12 lead ECG model to diagnose hyperkalemia by use of traditional and novel parameters.

METHODS

We retrospectively analyzed ECGs in consecutive hyperkalemic patients (serum potassium (K)>5.3mEq/L) by blinded investigators with normokalemic ECGs as internal controls. Potassium levels were modeled using general linear mixed models followed by refit with standardized variables. Optimum sensitivity and specificity were determined using cut point analysis of ROC-AUC.

RESULTS

The training set included 236 ECGs (84 patients) and validation set 97 ECGs (23 patients). Predicted K=(5.2354)+(0.03434*descending T slope)+(-0.2329*T width)+(-0.9652*reciprocal of new QRS width>100msec). ROC-AUC in the validation set was 0.78 (95% CI 0.69-0.88). Maximum specificity of the model was 84% for K>5.91 with sensitivity of 63%.

CONCLUSION

ECG model incorporating T-wave width, descending T-wave slope and new QRS prolongation improved hyperkalemia diagnosis over traditional ECG analysis.

Changes in urinary potassium excretion in patients with chronic kidney disease

BACKGROUND

Hyperkalemia is one of the more serious complications of chronic kidney disease (CKD), and the cause of potassium retention is a reduction in urinary potassium excretion. However, few studies have examined the extent of the decrease of urinary potassium excretion in detail with respect to decreased renal function.

METHODS

Nine hundred eighty-nine patients with CKD (CKD stages G1 and G2 combined: 135; G3a: 107; G3b: 170; G4: 289; and G5: 288) were evaluated retrospectively. Values for urinary potassium excretion were compared between CKD stages, and the associations between urinary potassium excretion and clinical parameters, including diabetes mellitus status and use of renin-angiotensin-aldosterone system inhibitors, were analyzed using a multivariable linear regression analysis.

RESULTS

Urinary potassium excretion gradually decreased with worsening of CKD (G5: 24.8 ± 0.8 mEq/d, P < 0.001 vs. earlier CKD stages). In contrast, the value of fractional excretion of potassium at CKD G5 was significantly higher than that at the other stages (30.63 ± 0.93%, P < 0.001). Multivariable linear regression analysis revealed that urinary potassium excretion was independently associated with urinary sodium excretion (standardized coefficient, 0.499), the estimated glomerular filtration rate (0.281), and serum chloride concentration (-0.086).

CONCLUSION

This study demonstrated that urinary potassium excretion decreased with reductions in renal function. Furthermore, urinary potassium excretion was mainly affected by urinary sodium excretion and estimated glomerular filtration rate in patients with CKD, whereas the presence of diabetes mellitus and use of renin-angiotensin-aldosterone system inhibitors were not associated with urinary potassium excretion in this study.

Potassium: From Physiology to Clinical Implications

BACKGROUND

Potassium (K(+)) is the major intracellular cation, with 98% of the total pool being located in the cells at a concentration of 140-150 mmol/l, and only 2% in the extracellular fluid, where it ranges between 3.5 and 5 mmol/l. A fine regulation of the intracellular-extracellular gradient is crucial for life, as it is the main determinant of membrane voltage; in fact, acute changes of K(+) plasma levels may have fatal consequences.

SUMMARY

An integrated system including an 'internal' and 'external' control prevents significant fluctuations of plasma levels in conditions of K(+) loading and depletion. The internal control regulates the intra-extracellular shift, a temporary mechanism able to maintain a constant K(+) plasma concentration without changing the total amount of body K(+). The external control is responsible for the excretion of the ingested K(+), and it has the kidney as the major player. The kidney excretes nearly 90% of the daily intake. Along the proximal tubule and the thick ascending limb on Henle's loop, the amount of K(+) reabsorption is quite fixed (about 80-90%); conversely, the distal nephron has the ability to adjust K(+) excretion in accordance with homeostatic needs. The present review analyzes: (1) the main molecular mechanisms mediating K(+) reabsorption and secretion along the nephron; (2) the pathophysiology of the principal K(+) derangements due to renal dysfunction, and (3) the effect of ingested K(+) on blood pressure and renal electrolyte handling.

KEY MESSAGES

Maintaining plasma K(+) levels in a tight range is crucial for life; thus, multiple factors are implicated in K(+) homeostasis, including kidney function. Recent studies have suggested that K(+) plasma levels, in turn, affect renal salt absorption in animal models; this effect may underlie the reduction of blood pressure observed in hypertensive subjects under K(+) supplementation.

Risk profiles of referred chronic kidney disease patients in a tertiary nephrology centre

Objective:

To determine the risk profile of chronic kidney disease (CKD) patients.

Methods:

This is an observational cross sectional study involving 130 patients for which data was collected prospectively.. Sixty five subjects with an estimated glomerular filtration rate (eGFR) below 120 ml/min/1.73 m² were recruited via random sampling technique from nephrology clinic in a tertiary nephrology referral center. Medical history, demographic data, urinary and serum biochemistry tests were obtained.

Results:

Most of the CKD patients who were referred to the nephrology clinic were asymptomatic. The most common laboratory abnormalities noted among CKD patients were proteinuria, anaemia and hyperkalaemia. Advancing age, pre-existing morbidities such as diabetes mellitus, hypertension and overweight are characteristics that are strongly associated with the referred CKD patients.

Conclusions:

Most of the referred CKD patients are in advanced age with diabetes, hypertension and overweight. Majority of the CKD remained asymptomatic despite in the advance stage of CKD. This strongly calls for cost effective screening for population at risk.

Serum Potassium Levels and Short-Term Outcomes in Patients With ST-Segment Elevation Myocardial Infarction

Current guidelines recommend maintaining serum potassium levels between 4.0 and 5.0 mEq/L (1 mEq/L = mmol/L) in patients with acute myocardial infarction. However, these guidelines are based on studies conducted before the β blocker and reperfusion era. We retrospectively analyzed 6613 patients diagnosed with ST-segment elevation myocardial infarction (STEMI) who presented without renal insufficiency. Patients were categorized into 5 groups according to mean serum potassium levels: <3.5, 3.5 to <4.0, 4.0 to <4.5, 4.5 to <5.0, and ≥5.0 mEq/L. Patients with potassium levels of 4.0 to <4.5 mEq/L had the lowest predefined event rates, which were 6.4% for 7-day malignant arrhythmia, 3.7% for 7-day mortality, and 5.3% for 30-day mortality. Compared with the reference group (4.0 to <4.5 mEq/L), multivariate regression analysis revealed significantly higher 30-day mortality risk in patients with potassium level of 4.5 to <5.0 (hazard ratio [HR]: 1.52, 95% confidence interval [CI]: 1.17-1.98; P = .002) and even higher risk in patients with potassium level of ≥5.0 mEq/L (HR: 1.80, 95% CI: 1.22-2.66; P = .002). The lowest 30-day mortality was observed in patients with STEMI having potassium levels between 4.0 and 4.5 mEq/L, and a level >4.5 mEq/L significantly increased mortality risk.

Renal mineralocorticoid receptor and electrolyte homeostasis

The renal mineralocorticoid receptor (MR) is a steroid hormone receptor essential for maintaining electrolyte homeostasis. Its role in mediating effects of aldosterone was likely vital in enabling the evolution of terrestrial life. Dysregulated aldosterone-MR signaling has been identified as the cause of multiple clinical diseases, suggesting the physiological importance of the MR. While the physiology of this pathway has been studied for over 60 years, only more recently have genetic mouse models been available to dissect its function in vivo. This review will focus on recent advances in our knowledge of MR function with an emphasis on these models.

Patiromer induces rapid and sustained potassium lowering in patients with chronic kidney disease and hyperkalemia

Patients with chronic kidney disease (CKD) have a high risk of hyperkalemia, which increases mortality and can lead to renin–angiotensin–aldosterone system inhibitor (RAASi) dose reduction or discontinuation. Patiromer, a nonabsorbed potassium binder, has been shown to normalize serum potassium in patients with CKD and hyperkalemia on RAASi. Here, patiromer's onset of action was determined in patients with CKD and hyperkalemia taking at least one RAASi. After a 3-day potassium- and sodium-restricted diet in an inpatient research unit, those with sustained hyperkalemia (serum potassium 5.5 – under 6.5 mEq/l) received patiromer 8.4 g/dose with morning and evening meals for a total of four doses. Serum potassium was assessed at baseline (0 h), 4 h postdose, then every 2–4 h to 48 h, at 58 h, and during outpatient follow-up. Mean baseline serum potassium was 5.93 mEq/l and was significantly reduced by 7 h after the first dose and at all subsequent times through 48 h. Significantly, mean serum potassium under 5.5 mEq/l was achieved within 20 h. At 48 h (14 h after last dose), there was a significant mean reduction of 0.75 mEq/l. Serum potassium did not increase before the next dose or for 24 h after the last dose. Patiromer was well tolerated, without serious adverse events and no withdrawals. The most common gastrointestinal adverse event was mild constipation in two patients. No hypokalemia (serum potassium under 3.5 mEq/l) was observed. Thus, patiromer induced an early and sustained reduction in serum potassium and was well tolerated in patients with CKD and sustained hyperkalemia on RAASis.

Effect of potassium present in stratum corneum during non-invasive measurement of potassium in human subjects using reverse iontophoresis

PURPOSE

Reverse iontophoresis (RI) is one of the potential techniques used to monitor the concentration of various analytes in body fluids non-invasively. Transdermal extraction of potassium is investigated using RI. In the present work, the effect of potassium on stratum corneum (SC) during RI, feasibility of RI for continuous monitoring of potassium, and use of potassium as internal standard in RI, are investigated.

METHODS

Tape stripping experiment is carried out to find potassium concentration in SC. RI is carried out continuously for 180 min without passive diffusion and after passive diffusion for 60 min. Skin impedance measurements are done at 20 Hz and 20 kHz.

RESULTS

Potassium is found to be in the range 300-650 nmol/cm(2) on SC by tape stripping experiment. Correlation coefficient between blood potassium and extracted potassium through RI after passive diffusion (R(2) = 0.5870) is more than without passive diffusion (R(2) = 0.5117). The skin impedance measurement shows that RI has more effect on SC than superficial layer of SC during RI.

CONCLUSION

The present investigations conclude that it is possible to monitor potassium continuously through RI and using potassium as internal standard in RI.

Optimal predialysis care

Management of severe chronic kidney disease (CKD) involves dealing with medical, nursing and psychosocial problems and therefore warrants support from a multidisciplinary team. In the Kidney Disease Outcomes Quality Initiative (KDOQI) classification system of CKD, preparation for renal replacement therapy has been recommended in CKD stage 4, characterized by a reduction in the estimated glomerular filtration rate (GFR) of <30 ml/min. In this article we share our approach to perfecting predialysis care. Tools are given to make an estimation of the progression of kidney disease. Also the prevention and treatment of metabolic complications and cardiovascular risk management are summarized. Finally, the possibilities for dialysis but even more important, aiming for pre-emptive transplantation, are being discussed. Using a multidisciplinary integrated care approach predialysis care has come of age.

The effect of renin-angiotensin system blockade on renal protection in chronic kidney disease patients with hyperkalemia

HYPOTHESIS

The aim of this study was to determine the effects of renin-angiotensin system (RAS) blockade maintenance on renal protection in chronic kidney disease (CKD) patients with hyperkalemia occurring during treatment with RAS blockade.

MATERIALS AND METHODS

CKD III or IV patients, who were prescribed with RAS blockers and also had hyperkalemia, were included. The study population was divided into two groups based on maintenance or withdrawal of RAS blocker. Renal outcomes (doubling of creatinine or end-stage renal disease) and incidence of hyperkalemia were compared between the two groups.

RESULTS

Out of 258 subjects who developed hyperkalemia during treatment with RAS blockers, 150 (58.1%) patients continued on RAS blockades, while RAS blockades were discontinued for more than 3 months in the remaining 108 patients. Renal event-free survival was significantly higher in the maintenance group compared with the withdrawal group. Cox proportional hazard ratio for renal outcomes was 1.35 (95% CI: 1.08-1.92, p=0.04) in the withdrawal group compared with the maintenance group. However, the incidence of hyperkalemia and hyperkalemia-related hospitalization or mortality did not differ between the two groups.

CONCLUSIONS

This study demonstrated that the maintenance of RAS blockade is beneficial for the preservation of renal function and relatively tolerable in patients with CKD and hyperkalemia occurring during treatment with RAS blockade.

Prediction and management of hyperkalemia across the spectrum of chronic kidney disease

Hyperkalemia commonly limits optimizing treatment to slow stage 3 or higher chronic kidney disease (CKD) progression. The risk of hyperkalemia is linked to dietary potassium intake, level of kidney function, concomitant diseases that may affect potassium balance such as diabetes, and use of medications that influence potassium excretion. The risk predictors for developing hyperkalemia are an estimated glomerular filtration rate of less than 45 mL/min/1.73 m(2) and a serum potassium level greater than 4.5 mEq/L in the absence of blockers of the renin-angiotensin-aldosterone system (RAAS). Generally, monotherapy with RAAS blockers does not increase risk substantially unless hypotension or volume depletion occur. Dual RAAS blockade involving any combination of an angiotensin-converting enzyme inhibitor, angiotensin-receptor blocker, renin inhibition, or aldosterone-receptor blocker markedly increases the risk of hyperkalemia in patients with stage 3 or higher CKD. Moreover, dual RAAS blockade further reduces albuminuria by 25% to 30% compared with monotherapy, it has failed to show a benefit on CKD progression or cardiovascular outcome, and thus is not indicated in such patients because of its marked increase in hyperkalemia potential. Although sodium polystyrene resins exist to manage hyperkalemia in patients requiring therapy that increases serum potassium levels, they are not well tolerated. Newer, more predictable, better-tolerated polymers to bind potassium are on the horizon and may be approved within the next 1 to 2 years.

Chronic renal disease progression: treatment strategies and potassium intake

Disordered potassium homeostasis is a common complication of chronic kidney disease and traditional management focuses on restricting potassium intake to avoid hyperkalemia. Permissive potassium intake carries the risk of hyperkalemia and hyperphosphatemia, and possibly may contribute to the development of uremic neuropathy. Excessive potassium restriction and removal by dialysis carries the risk of worsened chronic hypertension, intradialytic hypotension, renal fibrosis and cyst formation, and ventricular arrhythmias. Cohort studies have associated both hypokalemia and hyperkalemia with increased mortality in CKD. A single study of potassium intake in hemodialysis patients found increased intake associated with increased mortality despite adjustment for serum potassium concentration. We recommend avoiding mandatory potassium restriction in early chronic kidney disease. We endorse routine potassium restriction in advanced chronic kidney disease requiring hemodialysis and close monitoring of serum potassium concentration in any patients receiving renin-angiotensin-aldosterone system blockers.

Gut sensing of potassium intake and its role in potassium homeostasis

Extracellular K(+) homeostasis has been explained by feedback mechanisms in which changes in extracellular K(+) concentration drive renal K(+) excretion directly or indirectly via stimulating aldosterone secretion. However, this cannot explain meal-induced kaliuresis, which often occurs without increases in plasma K(+) or aldosterone concentrations. Recent studies have produced evidence supporting a feedforward control in which gut sensing of dietary K(+) increases renal K(+) excretion (and extrarenal K(+) uptake) independent of plasma K(+) concentrations, namely, a gut factor. This review focuses on these new findings and discusses the role of gut factor in acute and chronic regulation of extracellular K(+) as well as in the beneficial effects of high K(+) intake on the cardiovascular system.

Aldosterone and glomerular filtration--observations in the general population

Background

Increasing evidence suggests that aldosterone promotes renal damage. Since data on the association between aldosterone and renal function in the general population are sparse, we chose to address this issue. We investigated the associations between the plasma aldosterone concentration (PAC) or the aldosterone-to-renin ratio (ARR) and the estimated glomerular filtration rate (eGFR) in a sample of adult men and women from Northeast Germany.

Methods

A study population of 1921 adult men and women who participated in the first follow-up of the Study of Health in Pomerania was selected. None of the subjects used drugs that alter PAC or ARR. The eGFR was calculated according to the four-variable Modification of Diet in Renal Disease formula. Chronic kidney disease (CKD) was defined as an eGFR <60 ml/min/1.73 m².

Results

Linear regression models, adjusted for sex, age, waist circumference, diabetes mellitus, smoking status, systolic and diastolic blood pressures, serum triglyceride concentrations and time of blood sampling revealed inverse associations of PAC or ARR with eGFR (ß-coefficient for log-transformed PAC −3.12, p < 0.001; ß-coefficient for log-transformed ARR −3.36, p < 0.001). Logistic regression models revealed increased odds for CKD with increasing PAC (odds ratio for a one standard deviation increase in PAC: 1.35, 95% confidence interval: 1.06-1.71). There was no statistically significant association between ARR and CKD.

Conclusion

Our study demonstrates that PAC and ARR are inversely associated with the glomerular filtration rate in the general population.

Activation of mTORC1 in collecting ducts causes hyperkalemia

Mutation of TSC (encoding tuberous sclerosis complex protein) and activation of mammalian target of rapamycin (mTOR) have been implicated in the pathogenesis of several renal diseases, such as diabetic nephropathy and polycystic kidney disease. However, the role of mTOR in renal potassium excretion and hyperkalemia is not known. We showed that mice with collecting-duct (CD)-specific ablation of TSC1 (CDTsc1KO) had greater mTOR complex 1 (mTORC1) activation in the CD and demonstrated features of pseudohypoaldosteronism, including hyperkalemia, hyperaldosteronism, and metabolic acidosis. mTORC1 activation caused endoplasmic reticulum stress, columnar cell lesions, and dedifferentiation of CD cells with loss of aquaporin-2 and epithelial-mesenchymal transition-like phenotypes. Of note, mTORC1 activation also reduced the expression of serum- and glucocorticoid-inducible kinase 1, a crucial regulator of potassium homeostasis in the kidney, and decreased the expression and/or activity of epithelial sodium channel-α, renal outer medullary potassium channel, and Na(+), K(+)-ATPase in the CD, which probably contributed to the aldosterone resistance and hyperkalemia in these mice. Rapamycin restored these phenotypic changes. Overall, this study identifies a novel function of mTORC1 in regulating potassium homeostasis and demonstrates that loss of TSC1 and activation of mTORC1 results in dedifferentiation and dysfunction of the CD and causes hyperkalemia. The CDTsc1KO mice provide a novel model for hyperkalemia induced exclusively by dysfunction of the CD.

Role of pituitary in K+ homeostasis: impaired renal responses to altered K+ intake in hypophysectomized rats

The kidneys maintain extracellular K⁺ homeostasis by altering K⁺ excretion to match K⁺ intake. Because this can occur without changes in plasma K⁺ concentrations ([K⁺]), how the kidneys sense K⁺ intake is unclear. We tested the hypothesis that the pituitary plays a critical role in signaling K⁺ intake to the kidneys. If this hypothesis is true, hypophysectomy would impair kidney responses to altered K⁺ intake. Hypophysectomized (Hypox) and sham-operated control rats (n = 8 each) were compared for their abilities to adjust K⁺ excretion during a transition from normal to reduced (to one-third of normal) K⁺ intake, followed by a reversal to normal K⁺ intake. Food was provided only at night, and renal K⁺ excretion was determined both for absorptive (night or feeding) and postabsorptive (day or nonfeeding) periods. In normal rats, both absorptive and postabsorptive renal K⁺ excretion were changed in parallel to the changes in K⁺ intake, indicating a rapid adaptation of normal kidneys to altered K⁺ intake. In Hypox rats, whereas absorptive renal K⁺ excretion was changed in response to changes in K⁺ intake, postabsorptive K⁺ excretion was not responsive (P < 0.001), indicating impaired renal responses to altered K⁺ intake. In addition, Hypox rats, compared with control rats, showed K⁺ intolerance (increases in plasma [K⁺]) upon feeding (i.e., K⁺ intake) at night or following an intravenous K⁺ infusion (P < 0.01), indicating an impairment of acute renal responses to K⁺ intake. These data support that the pituitary plays a key role in the signaling of K⁺ intake to the kidneys (and kidney responses to altered K⁺ intake).

Mineral concentrations in bottled water products: implications for Canadians' mineral intakes

PURPOSE

The popularity of bottled water products (BWPs) is growing in Canada. Concentrations of minerals with important implications for health were compared in different types of BWPs.

METHODS

One sample of each brand and type of plain BWP (purified, remineralized, spring, mineral, and artesian), flavoured BWP, and nutrient-enriched BWP sold in major stores in Ottawa, Ontario, was purchased to allow determination of mineral concentrations by flame atomic absorption or emission spectroscopy. A total of 124 BWPs representing 37 brands were analyzed.

RESULTS

In general, spring and mineral water contained higher amounts of magnesium and calcium than did purified, remineralized, artesian, flavoured, or nutrient-enriched water. Most plain BWPs contained little sodium and potassium, whereas 15% to 35% of flavoured and nutrient-enriched products had considerably higher concentrations. Only magnesium and calcium concentrations were highly correlated (r=0.76, p<0.001). Calculation of the percentage of Dietary Reference Intakes that could be supplied by each product revealed that, if they are consumed habitually, many products can contribute substantially to recommended intakes of these minerals.

CONCLUSIONS

Mineral concentrations in most types of BWP varied, but distinct differences between types of products were identified. Consumers should be aware of the mineral content of BWPs because some could influence intakes of certain minerals significantly.

[When the resting membrane potential becomes restless. Acute hyperkalemia in the perioperative phase]

Acute hyperkalemia is a life-threatening event and often occurs abruptly and without warning in the perioperative field. Risk factors are found on multiple levels as they can derive from a patients pre-existing condition or result from the surgical intervention or management of anesthesia. The therapy of hyperkalemia depends on the dimensions of electrolyte disturbance and a distinction can be made between therapeutic measures with a rapid and those with a long-term effect.

Hyperkalemia secondary to renal hypoperfusion in a dog with third-degree atrioventricular block

OBJECTIVE

To demonstrate a critical role of artificial cardiac pacing to normalize severe bradyarrhythmia-induced hyperkalemia in a dog with third-degree atrioventricular (AV) block.

CASE SUMMARY

A dog was presented for evaluation of severe hyperkalemia and bradyarrhythmia. ECG revealed third-degree AV block with heart rate of 10-20 min, which was lower than usual ventricular escape rate. The etiology of severe hyperkalemia was considered secondary to significantly decreased renal perfusion and potassium excretion as a result of poor cardiac output caused by the AV block. Since potassium disorders may lead to life-threatening conditions such as cardiopulmonary arrest, artificial cardiac pacing was immediately pursued. Within 1 hour, serum potassium concentration was normalized, which confirmed that severe hyperkalemia occurred primarily due to third-degree AV block. The dog was then treated with permanent pacemaker implantation. A recheck evaluation 3-month post pacemaker implantation showed normal serum potassium concentration and the dog was clinically healthy.

NEW OR UNIQUE INFORMATION PROVIDED

This report describes hyperkalemia secondary to significantly decreased cardiac output and renal hypoperfusion caused by third-degree AV block. The authors propose that artificial cardiac pacing must be considered as an emergency treatment for bradyarrhythmia-induced hyperkalemia, which ultimately restores cardiac output and renal perfusion and normalizes serum potassium concentration.

Prevalence and factors associated with hyperkalemia in predialysis patients followed in a low-clearance clinic

BACKGROUND AND OBJECTIVES

Recent studies evaluated the prevalence of hyperkalemia and related risk factors in patients with CKD of various stages, but there is limited relevant information in predialysis patients. This study aimed to examine the prevalence and factors associated with hyperkalemia in the structured environment of a low-clearance clinic.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In a cross-sectional fashion over a prespecified period of 4 months, information on serum potassium and relevant laboratory variables, comorbidities, medications, and dietician input in patients with advanced CKD under follow-up in the low-clearance clinic of our department was recorded. Univariate and multiple logistic regression analyses were used to identify factors associated with serum potassium ≥ 5.5 meq/L.

RESULTS

The study population consisted of 238 patients aged 66.2 ± 4.2 years with estimated GFR of 14.5 ± 4.8 ml/min per 1.73 m(2). The prevalence of hyperkalemia. defined as potassium > 5.0, ≥ 5.5, and ≥ 6.0 meq/L., was at 54.2%, 31.5%, and 8.4%, respectively. In univariate comparisons, patients with potassium ≥ 5.5 meq/L had significantly higher urea and lower estimated GFR and serum bicarbonate; also, they were more often using sodium bicarbonate and had received potassium education and attempts for dietary potassium lowering. Use of angiotensin-converting enzyme inhibitors or angiotensin receptor blockers was not associated with hyperkalemia. In multivariate analyses, estimated GFR<15 ml/min per 1.73 m(2) and sodium bicarbonate use were independently associated with hyperkalemia.

CONCLUSIONS

The prevalence of hyperkalemia in predialysis patients with CKD is high. Even at this range of renal function, low estimated GFR seems to be the most important factor associated with hyperkalemia among the wide range of demographic, clinical, and laboratory characteristics studied.

Treatment and pathogenesis of acute hyperkalemia

This article focuses on the pathogenesis, clinical manifestations, and various treatment modalities for acute hyperkalemia and presents a systematic approach to selecting a treatment strategy. Hyperkalemia, a life-threatening condition caused by extracellular potassium shift or decreased renal potassium excretion, usually presents with non-specific symptoms. Early recognition of moderate to severe hyperkalemia is vital in preventing fatal cardiac arrhythmias and muscle paralysis. Management of hyperkalemia includes the elimination of reversible causes (diet, medications), rapidly acting therapies that shift potassium into cells and block the cardiac membrane effects of hyperkalemia, and measures to facilitate removal of potassium from the body (saline diuresis, oral binding resins, and hemodialysis). Hyperkalemia with potassium level more than 6.5 mEq/L or EKG changes is a medical emergency and should be treated accordingly. Treatment should be started with calcium gluconate to stabilize cardiomyocyte membranes, followed by insulin injection, and b-agonists administration. Hemodialysis remains the most reliable method to remove potassium from the body and should be used in cases refractory to medical treatment. Prompt detection and proper treatment are crucial in preventing lethal outcomes.

Early pancreas graft failure is associated with inferior late clinical outcomes after simultaneous kidney-pancreas transplantation

BACKGROUND

Early pancreas graft failure after simultaneous pancreas and kidney (SPK) transplantation is common. We studied the impact of early pancreas graft failure on long-term kidney and patient survival.

METHODS

We included all primary SPK transplants performed in the United States between January 1, 2000, and December 31, 2007, who had maintained kidney graft function at 90 days posttransplantation. Kaplan-Meier and Cox multivariate analyses were performed. The causes of death between the two cohorts were compared.

RESULTS

A total of 6282 SPK recipients were included in the analyses. Of those, 470 had lost pancreas graft within the first 90 days largely related to pancreas graft thrombosis. Early pancreas graft failure was associated with lower subsequent kidney graft and patient survival (log-rank, P=0.02 and P<0.001, respectively). Multivariate regression analyses demonstrated a 70% higher risk of kidney graft failure after 3 years (adjusted hazard ratio 1.69; 95% CI 1.08, 2.66; P=0.022) and more than doubled the risk for death (adjusted hazard ratio 2.18; 95% CI 1.67, 2.85; P<0.001) among SPK recipients with early pancreas graft failure. The causes of death were similar between the two cohorts.

CONCLUSION

Early pancreas graft failure in SPK transplant recipients is associated with an increased risk for subsequent kidney failure and death. Optimization of therapeutic interventions after early pancreas graft failure is needed.

Gut sensing of dietary K⁺ intake increases renal K⁺excretion

Dietary K(+) intake may increase renal K(+) excretion via increasing plasma [K(+)] and/or activating a mechanism independent of plasma [K(+)]. We evaluated these mechanisms during normal dietary K(+) intake. After an overnight fast, [K(+)] and renal K(+) excretion were measured in rats fed either 0% K(+) or the normal 1% K(+) diet. In a third group, rats were fed with the 0% K(+) diet, and KCl was infused to match plasma [K(+)] profile to that of the 1% K(+) diet group. The 1% K(+) feeding significantly increased renal K(+) excretion, associated with slight increases in plasma [K(+)], whereas the 0% K(+) diet decreased K(+) excretion, associated with decreases in plasma [K(+)]. In the KCl-infused 0% K(+) diet group, renal K(+) excretion was significantly less than that of the 1% K(+) group, despite matched plasma [K(+)] profiles. We also examined whether dietary K(+) alters plasma profiles of gut peptides, such as guanylin, uroguanylin, glucagon-like peptide 1, and glucose-dependent insulinotropic polypeptide, pituitary peptides, such as AVP, α-MSH, and γ-MSH, or aldosterone. Our data do not support a role for these hormones in the stimulation of renal K(+) excretion during normal K(+) intake. In conclusion, postprandial increases in renal K(+) excretion cannot be fully accounted for by changes in plasma [K(+)] and that gut sensing of dietary K(+) is an important component of the regulation of renal K(+) excretion. Our studies on gut and pituitary peptide hormones suggest that there may be previously unknown humoral factors that stimulate renal K(+) excretion during dietary K(+) intake.

Elevated salivary potassium in paediatric CKD patients, a novel excretion pathway

BACKGROUND

Hyperkalaemia is one of the complications of chronic renal failure. Gastrointestinal excretion and cellular uptake are two adaptive mechanisms for extra-renal potassium (K) disposal in these patients. The salivary glands' secretion system can actively excrete K into the oral cavity.

METHODS

We examined salivary K levels in four groups of paediatric chronic kidney disease (CKD) patients: 25 pre-dialytic (PreD) patients, 18 patients on maintenance dialysis (D), and 31 transplanted patients with a functioning graft (T), compared with 32 healthy children (C).

RESULTS

Salivary K levels were significantly higher in the D and PreD groups than the C group (P = 0.03 and P = 0.0004, respectively). Interestingly, a significant negative correlation was found between glomerular filtration rate and salivary K in PreD and T patients.

CONCLUSIONS

We suggest an extension of the gastrointestinal adaptive K pathway via salivary gland secretion in patients suffering from hyperkalaemia.

Serum potassium and outcomes in CKD: insights from the RRI-CKD cohort study

BACKGROUND AND OBJECTIVES

The relationship between serum potassium (S(K)) and mortality in chronic kidney disease (CKD) has not been systematically investigated.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We examined the predictors and mortality association of S(K) in the Renal Research Institute CKD Study cohort, wherein 820 patients with CKD were prospectively followed at four US centers for an average of 2.6 years. Predictors of S(K) were investigated using linear and repeated measures regression models. Associations between S(K) and mortality, the outcomes of ESRD, and cardiovascular events in time-dependent Cox models were examined.

RESULTS

The mean age was 60.5 years, 80% were white, 90% had hypertension, 36% had diabetes, the average estimated GFR was 25.4 ml/min per 1.73 m(2), and mean baseline S(K) was 4.6 mmol/L. Higher S(K) was associated with male gender, lower estimated GFR and serum bicarbonate, absence of diuretic and calcium channel blocker use, diabetes, and use of angiotensin-converting enzyme inhibitors and/or statins. A U-shaped relationship between S(K) and mortality was observed, with mortality risk significantly greater at S(K) < or = 4.0 mmol/L compared with 4.0 to 5.5 mmol/L. Risk for ESRD was elevated at S(K) < or = 4 mmol/L in S(K) categorical models. Only the composite of cardiovascular events or death as an outcome was associated with higher S(K) (> or = 5.5).

CONCLUSIONS

Although clinical practice usually emphasizes greater attention to elevated S(K) in the setting of CKD, our results suggest that patients who have CKD and low or even low-normal S(K) are at higher risk for dying than those with mild to moderate hyperkalemia.