Potassium: From Physiology to Clinical Implications

Management of hyperkalemia during treatment with mineralocorticoid receptor blockers: findings from esaxerenone

The nonsteroidal mineralocorticoid receptor (MR) blocker esaxerenone has demonstrated good antihypertensive activity in a variety of patients, including those with uncomplicated grade I-III hypertension, hypertension with moderate renal dysfunction, hypertension with type 2 diabetes mellitus with albuminuria, and hypertension associated with primary aldosteronism. Hyperkalemia has long been recognized as a potential side effect occurring during treatment with MR blockers, but there is a lack of understanding and guidance about the appropriate management of hyperkalemia during antihypertensive therapy with MR blockers, especially in regard to the newer agent esaxerenone. In this article, we first highlight risk factors for hyperkalemia, including advanced chronic kidney disease, diabetes mellitus, cardiovascular disease, age, and use of renin-angiotensin-aldosterone system inhibitors. Next, we examine approaches to prevention and management, including potassium monitoring, diet, and the use of appropriate therapeutic techniques. Finally, we summarize the currently available data for esaxerenone and hyperkalemia. Proper management of serum potassium is required to ensure safe clinical use of MR blockers, including awareness of at-risk patient groups, choosing appropriate dosages for therapy initiation and dosage titration, and monitoring of serum potassium during therapy. It is critical that physicians take such factors into consideration to optimize MR blocker therapy in patients with hypertension.

Abundant Monovalent Ions as Environmental Signposts for Pathogens during Host Colonization

Host colonization by a pathogen requires proper sensing and response to local environmental cues, to ensure adaptation and continued survival within the host. The ionic milieu represents a critical potential source of environmental cues, and indeed, there has been extensive study of the interplay between host and pathogen in the context of metals such as iron, zinc, and manganese, vital ions that are actively sequestered by the host. The inherent non-uniformity of the ionic milieu also extends, however, to "abundant" ions such as chloride and potassium, whose concentrations vary greatly between tissue and cellular locations, and with the immune response. Despite this, the concept of abundant ions as environmental cues and key players in host-pathogen interactions is only just emerging. Focusing on chloride and potassium, this review brings together studies across multiple bacterial and parasitic species that have begun to define both how these abundant ions are exploited as cues during host infection, and how they can be actively manipulated by pathogens during host colonization. The close links between ion homeostasis and sensing/response to different ionic signals, and the importance of studying pathogen response to cues in combination, are also discussed, while considering the fundamental insight still to be uncovered from further studies in this nascent area of inquiry.

Mineralocorticoid Receptor Antagonist Use in Heart Failure With Reduced Ejection Fraction and End-Stage Renal Disease Patients on Dialysis: A Literature Review

Mineralocorticoid receptor antagonists (MRAs) are known to have a proven mortality benefit in heart failure with reduced ejection fraction (HFrEF) without kidney disease. As patients with end-stage renal disease (ESRD) requiring either peritoneal dialysis or hemodialysis were excluded in clinical trials of HFrEF, the data are scant on the appropriate use of MRAs in this population. The unknown efficacy, along with concerns of adverse effects such as hyperkalemia, has limited the willingness of clinicians to consider using MRAs in these patients. However, it is unclear whether the risk of hyperkalemia is present if a patient is oliguric or anuric. Current guidelines recommend against the use of MRAs in patients with chronic kidney disease, but do not address the use of MRAs in patients requiring dialysis. This article will review the epidemiology of heart failure in ESRD, the pathophysiological derangements of the renin-angiotensin-aldosterone system in patients with kidney disease, and the results from case series and trials of the use of MRAs in ESRD with HFrEF. Although limited to several small trials using MRAs in peritoneal and hemodialysis patients with or without HFrEF, the current literature appears to show the potential for clinical benefits with little risk.

Contributions and competition of Mg2+ and K+ in folding and stabilization of the Twister ribozyme

Native folded and compact intermediate states of RNA typically involve tertiary structures in the presence of divalent ions such as Mg²⁺ in a background of monovalent ions. In a recent study, we have shown how the presence of Mg²⁺ impacts the transition from partially unfolded to folded states through a "push-pull" mechanism where the ion both favors and disfavors the sampling of specific phosphate-phosphate interactions. To further understand the ion atmosphere of RNA in folded and partially folded states results from atomistic umbrella sampling and oscillating chemical potential grand canonical Monte Carlo/molecular dynamics (GCMC/MD) simulations are used to obtain atomic-level details of the distributions of Mg²⁺ and K⁺ ions around Twister RNA. Results show the presence of 100 mM Mg²⁺ to lead to increased charge neutralization over that predicted by counterion condensation theory. Upon going from partially unfolded to folded states, overall charge neutralization increases at all studied ion concentrations that, while associated with an increase in the number of direct ion-phosphate interactions, is fully accounted for by the monovalent K⁺ ions. Furthermore, K⁺ preferentially interacts with purine N7 atoms of helical regions in partially unfolded states, thereby potentially stabilizing the helical regions. Thus, both secondary helical structures and formation of tertiary structures leads to increased counterion condensation, thereby stabilizing those structural features of Twister. Notably, it is shown that K⁺ can act as a surrogate for Mg²⁺ by participating in specific interactions with nonsequential phosphate pairs that occur in the folded state, explaining the ability of Twister to self-cleave at submillimolar Mg²⁺ concentrations.

Tuning intermediate filament mechanics by variation of pH and ion charges

The cytoskeleton is formed by three types of filamentous proteins - microtubules, actin filaments, and intermediate filaments (IFs) - and enables cells to withstand external and internal forces. Vimentin is the most abundant IF protein in humans and assembles into 10 nm diameter filaments with remarkable mechanical properties, such as high extensibility and stability. It is, however, unclear to which extent these properties are influenced by the electrostatic environment. Here, we study the mechanical properties of single vimentin filaments by employing optical trapping combined with microfluidics. Force-strain curves, recorded at varying ion concentrations and pH values, reveal that the mechanical properties of single vimentin IFs are influenced by pH and ion concentration. By combination with Monte Carlo simulations, we relate these altered mechanics to electrostatic interactions of subunits within the filaments. We thus suggest possible mechanisms that allow cells to locally tune their stiffness without remodeling the entire cytoskeleton.

The Associations of Diuretics and Laxatives Use with Cardiovascular Mortality. An Individual Patient-Data Meta-analysis of Two Large Cohort Studies

Purpose

To investigate the associations of diuretics overall, non-potassium-sparing diuretics in specific, and laxative use with cardiovascular mortality (CVM) in subjects with antihypertensive treatment.

Methods

Analyses included 4253 participants, aged 50 to 75 years, from the German ESTHER cohort and 105,359 participants, aged 50 to 69 years, from the UK Biobank. Cox proportional hazard regression models were applied in both studies, and then results were pooled using random-effects model meta-analyses.

Results

During 14 and 7 years of follow-up, 476 and 1616 CVM cases were observed in the ESTHER study and the UK Biobank, respectively. Compared to non-users, a 1.6-fold (hazard ratio [95% confidence interval] 1.57 [1.29; 1.90]), a 1.4-fold (1.39 [1.26; 1.53]), and no statistically significantly increased (1.13 [0.94; 1.36]) CVM were observed in users of diuretics overall, non-potassium-sparing diuretics in specific, and laxatives, respectively. Concurrent use of non-potassium-sparing diuretics and laxatives was associated with a 2-fold increased CVM (2.05 [1.55; 2.71]) when compared to users of neither diuretics nor laxatives. However, a test for interaction slightly missed statistical significance (p = 0.075).

Conclusions

These consistent results from two large cohort studies imply that more research is needed on the safety of diuretics in routine care. Although not statistically significant in this study, a drug-drug interaction of non-potassium-sparing diuretics and laxatives appears plausible. Physicians and pharmacists are advised to clarify additional laxative use in users of non-potassium-sparing diuretics and inform about the risk of concurrent use. Moreover, closer potassium monitoring intervals (e.g., every 3 months) might be indicated in concurrent users to prevent fatal cardiovascular events.

Electronic supplementary material

The online version of this article (10.1007/s10557-019-06894-w) contains supplementary material, which is available to authorized users.

Current Management of Hyperkalemia in Patients on Dialysis

Patients with end-stage renal disease (ESRD) on maintenance dialysis have a high risk of developing hyperkalemia, generally defined as serum potassium (K⁺) concentrations of >5.0 mmol/l, particularly those undergoing maintenance hemodialysis. Currently, the key approaches to the management of hyperkalemia in patients with ESRD are dialysis, dietary K⁺ restriction, and avoidance of medications that increase hyperkalemia risk. In this review, we highlight the issues and challenges associated with effective management of hyperkalemia in patients undergoing maintenance dialysis using an illustrative case presentation. In addition, we examine the potential nondialysis options for the management of these patients, including use of the newer K⁺ binder agents patiromer and sodium zirconium cyclosilicate, which may reduce the need for the highly restrictive dialysis diet, with its own implication on nutritional status in patients with ESRD, as well as reducing the risk of potentially life-threatening hyperkalemia.

Kidney Is Essential for Blood Pressure Modulation by Dietary Potassium

Eating more potassium may reduce blood pressure and the occurrence of other cardiovascular diseases by actions on various systems, including the vasculature, the sympathetic nervous system, systemic metabolism, and body fluid volume. Among these, the kidney plays a major role in the potassium-rich diet-mediated blood pressure reduction. PURPOSE OF REVIEW: To provide an overview of recent discoveries about the mechanisms by which a potassium-rich diet leads to natriuresis. RECENT FINDINGS: Although the distal convoluted tubule (DCT) is a short part of the nephron that reabsorbs salt, via the sodium-chloride cotransporter (NCC), it is highly sensitive to changes in plasma potassium concentration. Activation or inhibition of NCC raises or lowers blood pressure. Recent work suggests that extracellular potassium concentration is sensed by the DCT via intracellular chloride concentration which regulates WNK kinases in the DCT. High-potassium diet targets NCC in the DCT, resulting in natriuresis and fluid volume reduction, which are protective from hypertension and other cardiovascular problems.

Development, calibration, and validation of a novel human ventricular myocyte model in health, disease, and drug block

Human-based modelling and simulations are becoming ubiquitous in biomedical science due to their ability to augment experimental and clinical investigations. Cardiac electrophysiology is one of the most advanced areas, with cardiac modelling and simulation being considered for virtual testing of pharmacological therapies and medical devices. Current models present inconsistencies with experimental data, which limit further progress. In this study, we present the design, development, calibration and independent validation of a human-based ventricular model (ToR-ORd) for simulations of electrophysiology and excitation-contraction coupling, from ionic to whole-organ dynamics, including the electrocardiogram. Validation based on substantial multiscale simulations supports the credibility of the ToR-ORd model under healthy and key disease conditions, as well as drug blockade. In addition, the process uncovers new theoretical insights into the biophysical properties of the L-type calcium current, which are critical for sodium and calcium dynamics. These insights enable the reformulation of L-type calcium current, as well as replacement of the hERG current model.

Food Sources of Potassium in the Average Polish Diet

The aim of this study was to identify the food sources of potassium in the average Polish diet based on the data from the 2016 Household Budget Survey conducted on the representative sample of the Polish population (36,886 households, n = 99,230). This survey is organized by the Central Statistical Office and is related to the expenditures, quantitative consumption and revenues in households. We analyzed 91 sub-groups (i.e., milk, red meat) from 13 food categories (i.e., milk and dairy products, meat and products). Our findings indicated that the daily supply of potassium in the average Polish diet was 2617.9 mg, which meant covering the average allowance in 83%. Vegetables provided 32.5% of potassium, of which potatoes accounted for 16.2% of supply, and other vegetables for 16.2%. Tomatoes as well as other vegetables and mushrooms provided a total of 8.2% of potassium among vegetables. The next position was taken by the meat and meat products category (17.7%), with the largest share of meat products (6.7%) and red meat (5.2%). Cereal products supplied 16.64% of potassium, of which bread, rolls and bread products (12.2%) were of the greatest importance. Milk and dairy products turned out to be the fourth product category as a source of potassium (11.9%), with the highest share of milk (6.8%) and yoghurts and milk drinks (3.9%).

Lateral Subunit Coupling Determines Intermediate Filament Mechanics

The cytoskeleton is a composite network of three types of protein filaments, among which intermediate filaments (IFs) are the most extensible ones. Two very important IFs are keratin and vimentin, which have similar molecular architectures but different mechanical behaviors. Here we compare the mechanical response of single keratin and vimentin filaments using optical tweezers. We show that the mechanics of vimentin strongly depends on the ionic strength of the buffer and that its force-strain curve suggests a high degree of cooperativity between subunits. Indeed, a computational model indicates that in contrast to keratin, vimentin is characterized by strong lateral subunit coupling of its charged monomers during unfolding of α helices. We conclude that cells can tune their mechanics by differential use of keratin versus vimentin.

ERK1,2 Signalling Pathway along the Nephron and Its Role in Acid-base and Electrolytes Balance

Mitogen-activated protein kinases (MAPKs) are intracellular molecules regulating a wide range of cellular functions, including proliferation, differentiation, apoptosis, cytoskeleton remodeling and cytokine production. MAPK activity has been shown in normal kidney, and its over-activation has been demonstrated in several renal diseases. The extracellular signal-regulated protein kinases (ERK 1,2) signalling pathway is the first described MAPK signaling. Intensive investigations have demonstrated that it participates in the regulation of ureteric bud branching, a fundamental process in establishing final nephron number; in addition, it is also involved in the differentiation of the nephrogenic mesenchyme, indicating a key role in mammalian kidney embryonic development. In the present manuscript, we show that ERK1,2 signalling mediates several cellular functions also in mature kidney, describing its role along the nephron and demonstrating whether it contributes to the regulation of ion channels and transporters implicated in acid-base and electrolytes homeostasis.

Pharmacologic Treatment of Chronic Hyperkalemia in Patients with Chronic Kidney Disease

Hyperkalemia is frequently complicated in patients with advanced chronic kidney disease (CKD) because kidney is the major route of potassium excretion. Urinary potassium excretion is reduced according to the decline in glomerular filtration rate, and the risk of hyperkalemia is increased in patients with high potassium intake, advanced age, diabetes mellitus, congestive heart failure, and medications such as renin-angiotensin-aldosterone system(RAAS) blockades. On the other hand, the benefits of RAAS blockades and a high-potassium diet should be considered in CKD patients. To overcome these contradictory treatment strategies, potassium binders have emerged as new options to enhance fecal potassium excretion. In different regions of the world, four types of potassium binders are preferentially used. Whereas sodium polystyrene sulfonate (SPS) exchanges sodium for potassium, calcium polystyrene sulfonate (CPS) has the advantage of avoiding hypervolemia because it exchanges calcium for potassium. SPS was first introduced in the 1950s and used for a long time in western countries, and CPS is currently prescribed in Asia including South Korea. In contrast with the paucity of clinical studies using SPS or CPS, the recent randomized, controlled trials reported that two newer potassium binders, patiromer and sodium zirconium cyclosilicate (ZS-9), effectively and safely reduce serum potassium levels in CKD patients taking RAAS blockades. Our experiences showed that the long-term administration of a small dose of CPS was also effective and safe in treatment of chronic hyperkalemia. Further comparative trials among patiromer, ZS-9, and CPS are required to provide guides to cost-effective management of hyperkalemia in CKD patients.

DASH Dietary Pattern and Cardiometabolic Outcomes: An Umbrella Review of Systematic Reviews and Meta-Analyses

Background: The Dietary Approaches to Stop Hypertension (DASH) dietary pattern, which emphasizes fruit, vegetables, fat-free/low-fat dairy, whole grains, nuts and legumes, and limits saturated fat, cholesterol, red and processed meats, sweets, added sugars, salt and sugar-sweetened beverages, is widely recommended by international diabetes and heart association guidelines. Objective: To summarize the available evidence for the update of the European Association of the Study of Diabetes (EASD) guidelines, we conducted an umbrella review of existing systematic reviews and meta-analyses using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach of the relation of the DASH dietary pattern with cardiovascular disease and other cardiometabolic outcomes in prospective cohort studies and its effect on blood pressure and other cardiometabolic risk factors in controlled trials in individuals with and without diabetes. Methods: MEDLINE and EMBASE were searched through 3 January 2019. We included systematic reviews and meta-analyses assessing the relation of the DASH dietary pattern with cardiometabolic disease outcomes in prospective cohort studies and the effect on cardiometabolic risk factors in randomized and non-randomized controlled trials. Two independent reviewers extracted relevant data and assessed the risk of bias of individual studies. The primary outcome was incident cardiovascular disease (CVD) in the prospective cohort studies and systolic blood pressure in the controlled trials. Secondary outcomes included incident coronary heart disease, stroke, and diabetes in prospective cohort studies and other established cardiometabolic risk factors in controlled trials. If the search did not identify an existing systematic review and meta-analysis on a pre-specified outcome, then we conducted our own systematic review and meta-analysis. The evidence was summarized as risk ratios (RR) for disease incidence outcomes and mean differences (MDs) for risk factor outcomes with 95% confidence intervals (95% CIs). The certainty of the evidence was assessed using GRADE. Results: We identified three systematic reviews and meta-analyses of 15 unique prospective cohort studies (n = 942,140) and four systematic reviews and meta-analyses of 31 unique controlled trials (n = 4,414) across outcomes. We conducted our own systematic review and meta-analysis of 2 controlled trials (n = 65) for HbA1c. The DASH dietary pattern was associated with decreased incident cardiovascular disease (RR, 0.80 (0.76–0.85)), coronary heart disease (0.79 (0.71–0.88)), stroke (0.81 (0.72–0.92)), and diabetes (0.82 (0.74–0.92)) in prospective cohort studies and decreased systolic (MD, −5.2 mmHg (95% CI, −7.0 to −3.4)) and diastolic (−2.60 mmHg (−3.50 to −1.70)) blood pressure, Total-C (−0.20 mmol/L (−0.31 to −0.10)), LDL-C (−0.10 mmol/L (−0.20 to −0.01)), HbA1c (−0.53% (−0.62, −0.43)), fasting blood insulin (−0.15 μU/mL (−0.22 to −0.08)), and body weight (−1.42 kg (−2.03 to −0.82)) in controlled trials. There was no effect on HDL-C, triglycerides, fasting blood glucose, HOMA-IR, or CRP. The certainty of the evidence was moderate for SBP and low for CVD incidence and ranged from very low to moderate for the secondary outcomes. Conclusions: Current evidence allows for the conclusion that the DASH dietary pattern is associated with decreased incidence of cardiovascular disease and improves blood pressure with evidence of other cardiometabolic advantages in people with and without diabetes. More research is needed to improve the certainty of the estimates.

Potassium response and homeostasis in Mycobacterium tuberculosis modulates environmental adaptation and is important for host colonization

Successful host colonization by bacteria requires sensing and response to the local ionic milieu, and coordination of responses with the maintenance of ionic homeostasis in the face of changing conditions. We previously discovered that Mycobacterium tuberculosis (Mtb) responds synergistically to chloride (Cl-) and pH, as cues to the immune status of its host. This raised the intriguing concept of abundant ions as important environmental signals, and we have now uncovered potassium (K+) as an ion that can significantly impact colonization by Mtb. The bacterium has a unique transcriptional response to changes in environmental K+ levels, with both distinct and shared regulatory mechanisms controlling Mtb response to the ionic signals of K+, Cl-, and pH. We demonstrate that intraphagosomal K+ levels increase during macrophage phagosome maturation, and find using a novel fluorescent K+-responsive reporter Mtb strain that K+ is not limiting during macrophage infection. Disruption of Mtb K+ homeostasis by deletion of the Trk K+ uptake system results in dampening of the bacterial response to pH and Cl-, and attenuation in host colonization, both in primary murine bone marrow-derived macrophages and in vivo in a murine model of Mtb infection. Our study reveals how bacterial ionic homeostasis can impact environmental ionic responses, and highlights the important role that abundant ions can play during host colonization by Mtb.

The Influence of Sodium and Potassium Intake and Insulin Resistance on Blood Pressure in Normotensive Individuals Is More Evident in Women

BACKGROUND

Considering sex differences, salt sensitivity, and insulin resistance (IR), the effect of sodium restriction and increased potassium intake on blood pressure remains unclear in normotensive Asian individuals, compared to that in hypertensive patients.

METHODS

To assess the influence of sodium and potassium intake in normotensive individuals, we evaluated the estimated 24-hour urinary sodium and potassium excretion rate in 3,392 drug-naïve normotensive Japanese individuals (average age: 48.4 years) and analyzed its relation to blood pressure using multivariate regression analysis.

RESULTS

Multivariate regression analysis revealed that a 10-mmol/day increment in urinary sodium excretion related to an elevation in systolic blood pressure of 0.16 mm Hg in men and 0.37 mm Hg in women, after adjusting for known risk factors to salt sensitivity, including age, body mass index, serum creatinine, homeostasis model assessment of IR, and urinary potassium excretion. For urinary potassium excretion, a 10-mmol/day increment was associated with a decrease in systolic blood pressure, -0.54 mm Hg in men and -1.49 mm Hg in women, respectively. Furthermore, involvement of IR on blood pressure was observed only in women.

CONCLUSIONS

In drug-naïve normotensive individuals, the effects of a lower-salt and higher-potassium diet, and IR on blood pressure, were more evident in women. These results suggest that to prevent the new onset of hypertension and its complications, the balances of a sodium restriction and an increased potassium intake are important even in normotensive individuals, independent of known risk factors for salt sensitivity, especially in women.

Hypokalemia: a clinical update

Hypokalemia is a common electrolyte disturbance, especially in hospitalized patients. It can have various causes, including endocrine ones. Sometimes, hypokalemia requires urgent medical attention. The aim of this review is to present updated information regarding: (1) the definition and prevalence of hypokalemia, (2) the physiology of potassium homeostasis, (3) the various causes leading to hypokalemia, (4) the diagnostic steps for the assessment of hypokalemia and (5) the appropriate treatment of hypokalemia depending on the cause. Practical algorithms for the optimal diagnostic, treatment and follow-up strategy are presented, while an individualized approach is emphasized.

The importance of the thick ascending limb of Henle's loop in renal physiology and pathophysiology

The thick ascending limb (TAL) of Henle’s loop is a crucial segment for many tasks of the nephron. Indeed, the TAL is not only a mainstay for reabsorption of sodium (Na⁺), potassium (K⁺), and divalent cations such as calcium (Ca²⁺) and magnesium (Mg²⁺) from the luminal fluid, but also has an important role in urine concentration, overall acid–base homeostasis, and ammonia cycle. Transcellular Na⁺ transport along the TAL is a prerequisite for Na⁺, K⁺, Ca²⁺, Mg²⁺ homeostasis, and water reabsorption, the latter through its contribution in the generation of the cortico-medullar osmotic gradient. The role of this nephron site in acid–base balance, via bicarbonate reabsorption and acid secretion, is sometimes misunderstood by clinicians. This review describes in detail these functions, reporting in addition to the well-known molecular mechanisms, some novel findings from the current literature; moreover, the pathophysiology and the clinical relevance of primary or acquired conditions caused by TAL dysfunction are discussed. Knowing the physiology of the TAL is fundamental for clinicians, for a better understanding and management of rare and common conditions, such as tubulopathies, hypertension, and loop diuretics abuse.

Organotin Compounds Toxicity: Focus on Kidney

Organotin compounds (OTs) are synthetic persistent organometallic xenobiotics widely used in several commercial applications. They exert well-described harmful effects in brain, liver, adipose tissue, and reproductive organs, as they are endocrine-disrupting chemicals (EDCs), but the effects in the kidneys are less known. The kidneys are especially vulnerable to environmental contaminants because they are a metabolizing site of xenobiotics, therefore, pollutants can accumulate in renal tissue, leading to impaired renal function and to several renal abnormalities. Individuals chronically exposed to OTs present a threefold increase in the prevalence of kidney stones. These compounds can directly inhibit H⁺/K⁺-ATPase in renal intercalated cells, resulting in hypokalemia, renal tubular acidity, and increased urinary pH, which is a known risk factor for kidney stones formation. OTs effects are not only limited to induce nephrolithiasis, its nephrotoxicity is also due to increased reactive oxygen species (ROS). This increase leads to lipid peroxidation, abnormal cellular function, and cell death. Combined, the enzymatic and non-enzymatic antioxidant defense systems become deficient and there is a consequent uncontrolled generation of ROS that culminates in renal tissue damage. Still, few epidemiological and experimental studies have reported renal impact correlated to OTs exposure. This lack of investigation of the complete effect of OTs in renal function and structure led us to perform this review reporting the main researches about this subject.

Development of hyperkalemia following treatment with dapagliflozin (DAPA) in a patient with type 2 diabetes after bilateral adrenalectomy

Dapagliflozin (DAPA), a sodium-glucose co-transporter 2 (SGLT2) inhibitor, is known to have a beneficial diuretic effect, in addition to a glucose-lowering effect. Although SGLT2 inhibitor has been reported, the increase of hyperkalemia in patients treated with renin-angiotensin-aldosterone system (RAAS) inhibitors, their mechanism of action is unclear. We report the first case of a type 2 diabetes (T2DM) patient with potential mineralocorticoid deficiency who developed hyperkalemia after administration of DAPA. A 79-year-old woman underwent bilateral adrenalectomy for uncontrolled hypercortisolism due to an inoperable recurrence of Cushing's disease, and she was subsequently maintained on replacement therapy with glucocorticoid. She was diagnosed as having T2DM at 71 years of age and was treated with sitagliptin and miglitol. Since she presented with weight gain of about 5 kg over 6 months and her HbAlc level increased over 12%, 5 mg/day DAPA was added to her daily regimen. After the start of DAPA treatment, she developed hyperkalemia (6.5 mEq/L) with increased plasma renin activity of 53.1 ng/mL/h. She was diagnosed with aldosterone deficiency and started on fludrocortisone 0.1 mg daily, after which the hyperkalemia improved immediately. In this case, DAPA treatment could potentially increase the requirement for mineralocorticoid replacement, directly suggesting that the SGLT2 inhibition-induced natriuretic effect is accompanied by compensatory activation of the RAAS axis, which is essential to keep the serum potassium level within the normal range. Therefore, physicians should be careful about the development of hyperkalemia in patients when SGLT2 and RAAS inhibitors are used in combination.

Severe hyperkalaemia complicating parathyroidectomy in patients with end-stage renal disease

We evaluated the incidence of perioperative hyperkalaemia in end-stage renal disease (ESRD) patients undergoing parathyroidectomy and investigated possible contributors to this phenomenon. This was a retrospective cohort study looking at patients who had undergone parathyroidectomy for chronic kidney disease-associated mineral bone disease (CKD-MBD) at The Alfred Hospital, Melbourne, since 2001. Baseline demographics including age, gender, aetiology of renal failure and mode of renal replacement therapy as well as anaesthetic technique and duration of surgery were studied as possible contributors. Perioperative potassium values were compared to preoperative baseline. Following stratification into normokalaemic and hyperkalaemic groups, demographic and operative data were compared. Twenty-two patients met the inclusion criteria with a median (interquartile range, IQR) age of 48.5 (42-59) years. There was a male predominance of 68%. The median (IQR) surgical time was 131 (115-164) minutes. Potassium levels rose perioperatively, with a 27.3% incidence of perioperative hyperkalaemia. Median duration of surgery was longer in the hyperkalaemic patients (167 minutes versus 125 minutes). Following the withdrawal of cinacalcet, parathyroidectomy is increasingly required in ESRD patients with CKD-MBD. Potentially life-threatening hyperkalaemia poses a significant risk in the perioperative period. Serial electrolyte monitoring is crucial to safety in this patient group. A multidisciplinary approach to perioperative management is required to ensure optimal timing of renal replacement therapy and appropriate means of serial blood sampling.