An Integrated View of Potassium Homeostasis

Simple methods for estimating the maximum 24-hour urinary potassium excretion in kidney failure without replacement therapy patients

BACKGROUND

Adjusting dietary potassium intake based on 24-hour urinary potassium excretion is the primary method of preventing hyperkalemia. Currently, there is no accurate and convenient method for calculating maximum 24-hour urinary potassium excretion in kidney failure without replacement therapy patients. We developed and validated two new models to assess the upper limit of dietary potassium consumption in this high-risk cohort, using the maximum 24-hour urinary potassium excretion as a proxy.

METHODS

The data of 145 kidney failure without replacement therapy patients with hyperkalemia was gathered. The prediction models were developed using multilayer perceptron and stepwise multiple linear regression utilizing a stochastic sample of 102 (70%) patients. Within the rest 43 (30%), the performance of various models was independently verified.

RESULTS

The two new models had low bias (-0.02 and -0.57 mmol/24h vs 66.74 and 79.91 mmol/24h, mean absolute error = 5.57 and 5.22 vs 68.95 and 81.37), high accuracy (percentage of calculated values within_±30% of measured values = 83.45% and 84.14% vs 0.00% and 0.00%), high correlation with measured values (Spearman correlation coefficient = 0.72 and 0.72 vs 0.46 and 0.45, intraclass correlation coefficient = 0.67 and 0.70 vs 0.03 and 0.03) and high agreement with 24-hour urine potassium measurements (95% limits of agreement of Bland-Altman plot = 13.70 and 13.20 mmol/24h vs 113.8 and 191.3 mmol/24h).

CONCLUSION

These new models show high clinical application value for the calculation of maximum 24-hour urinary potassium excretion in kidney failure without replacement therapy patients with hyperkalemia.

Metal Ion Signaling in Biomedicine

Complex multicellular organisms are composed of distinct tissues involving specialized cells that can perform specific functions, making such life forms possible. Species are defined by their genomes, and differences between individuals within a given species directly result from variations in their genetic codes. While genetic alterations can give rise to disease-causing acquisitions of distinct cell identities, it is now well-established that biochemical imbalances within a cell can also lead to cellular dysfunction and diseases. Specifically, nongenetic chemical events orchestrate cell metabolism and transcriptional programs that govern functional cell identity. Thus, imbalances in cell signaling, which broadly defines the conversion of extracellular signals into intracellular biochemical changes, can also contribute to the acquisition of diseased cell states. Metal ions exhibit unique chemical properties that can be exploited by the cell. For instance, metal ions maintain the ionic balance within the cell, coordinate amino acid residues or nucleobases altering folding and function of biomolecules, or directly catalyze specific chemical reactions. Thus, metals are essential cell signaling effectors in normal physiology and disease. Deciphering metal ion signaling is a challenging endeavor that can illuminate pathways to be targeted for therapeutic intervention. Here, we review key cellular processes where metal ions play essential roles and describe how targeting metal ion signaling pathways has been instrumental to dissecting the biochemistry of the cell and how this has led to the development of effective therapeutic strategies.

Serum potassium levels as an independent predictor of unplanned enteral nutrition discontinuation in older adults with gastroesophageal reflux disease

BACKGROUND & AIMS

Enteral nutrition in older adults is often associated with intolerance, a phenomenon not well-understood in the context of gastroesophageal reflux disease (GERD). This observational study aimed to evaluate serum potassium levels as an independent prognostic factor for unplanned enteral nutrition discontinuation in older adults with GERD.

METHODS

We conducted a retrospective analysis of 213 consecutive patients with GERD who received enteral nutrition at our institution from April 2018 to March 2023. The dietary assessment involved extracting relevant nutritional information from the patients' medical records. The incidence of enteral nutrition discontinuation due to complications was monitored over a 30-day period after initiation.

RESULTS

Patients were categorized into three groups based on initial serum potassium levels: low (<4.0 mmol/L), intermediate (4.0-4.5 mmol/L), and high (≥4.5 mmol/L). During the follow-up, 35 % of patients experienced events leading to the discontinuation of enteral nutrition. Higher potassium levels correlated with an increased risk of unplanned discontinuation of enteral nutrition (log-rank P = 0.002). Multivariate Cox proportional hazards analysis identified serum potassium level as an independent predictor of unplanned discontinuation (hazard ratio: 1.700 [95 % confidence interval: 1.100-2.627] per 1 mmol/L, P = 0.017).

CONCLUSIONS

Serum potassium level is a robust independent predictor of unplanned enteral nutrition discontinuation in older adults with GERD. Our findings suggest that monitoring and adjusting potassium levels may be essential for improving outcomes in this vulnerable population.

Translating evidence into practice: Managing electrolyte imbalances and iron deficiency in heart failure

Mineral abnormalities are a common complication of heart failure (HF). In particular, dyskalaemia, hyponatraemia, and hypomagnesaemia are prevalent, with hypo- and hyperkalaemia observed in over 40 % of HF patients, hyponatraemia in 18-27 %, hypomagnesaemia in 7-52 %, and phosphate imbalance in 13 %. These abnormalities serve as indicators of the severity of HF and are strongly associated with an increased risk of morbidity and mortality. The neurohumoral activation, including the renin-angiotensin-aldosterone system (RAAS), the sympathetic nervous system, and vasopressin, HF medications such as diuretics and RAAS inhibitors, amd concomitant diseases such as chronic kidney disease, can disrupt mineral homeostasis. Iron deficiency (ID) is another of the most common mineral abnormalities, affecting up to 60 % of HF patients. ID is significantly associated with adverse clinical outcomes such as reduced quality of life and exercise capacity, HF re-hospitalization, and all-cause mortality. Various pathways contribute to the development of ID in HF, including reduced iron intake due to anorexia, increased hepcidin levels associated with chronic inflammation and hepatic congestion, and occult gastrointestinal bleeding due to the concomitant use of antithrombotic agents. The efficacy of iron replacement therapy has been demonstrated in clinical trials, particularly in heart failure with reduced ejection fraction (HFrEF), whilst more recently, it has also been shown to improve exercise capacity in patients with heart failure with preserved ejection fraction (HFpEF). This review focuses on potassium and phosphate abnormalities, hyponatraemia, hypomagnesaemia, and ID in HF, providing a comprehensive overview of the mechanisms, clinical significance, and intervention strategies with the latest findings.

Functional and biotechnological cues of potassium homeostasis for stress tolerance and plant development

Potassium (K+) is indispensable for the regulation of a plethora of functions like plant metabolism, growth, development, and abiotic stress responses. K+ is associated with protein synthesis and entangled in the activation of scores of enzymes, stomatal regulation, and photosynthesis. It has multiple transporters and channels that assist in the uptake, efflux, transport within the cell as well as from soil to different tissues, and the grain filling sites. While it is implicated in ion homeostasis during salt stress, it acts as a modulator of stomatal movements during water deficit conditions. K+ is reported to abate the effects of chilling and photooxidative stresses. K+ has been found to ameliorate effectively the co-occurrence of drought and high-temperature stresses. Nutrient deficiency of K+ makes leaves necrotic, leads to diminished photosynthesis, and decreased assimilate utilization highlighting the role it plays in photosynthesis. Notably, K+ is associated with the detoxification of reactive oxygen species (ROS) when plants are exposed to diverse abiotic stress conditions. It is irrefutable now that K+ reduces the activity of NADPH oxidases and at the same time maintains electron transport activity, which helps in mitigating the oxidative stress. K+ as a macronutrient in plant growth, the role of K+ during abiotic stress and the protein phosphatases involved in K+ transport have been reviewed. This review presents a holistic view of the biological functions of K+, its uptake, translocation, signaling, and the critical roles it plays under abiotic stress conditions, plant growth, and development that are being unraveled in recent times.

The impact of serum potassium ion variability on 28-day mortality in ICU patients

OBJECTIVE

Potassium ion disorders are prevalent among patients in Intensive Care Units (ICUs), yet there is a notable deficiency in established protocols and supplemental plans for potassium management. This retrospective study conducted at a single center aims to explore the relationship between potassium levels, their variability, and the 28-day mortality rate in ICU patients.

METHODS

This study analyzed data from patients admitted to the ICU of the First Affiliated Hospital of Guangxi Medical University between October 2022 and October 2023. We assessed serum potassium variability using the coefficient of variation and categorized it into four quartile groups (Q1, Q2, Q3, Q4). Additionally, patients were classified into six groups based on serum potassium concentrations. The associations between these categories and the 28-day mortality rate were evaluated using binary logistic regression, adjusting for potential confounders.

RESULTS

A total of 506 patients and 12,099 potassium measurements were analyzed. The group with the lowest potassium variability (Q1) exhibited the lowest mortality rate at 21% (P<0.01). It is noteworthy that within 28 days in the intensive care unit (ICU), the coefficient of variation (CV) of potassium levels significantly increased among deceased patients compared to surviving patients (P < 0.01).

CONCLUSION

Significant variability in potassium levels is associated with an increased risk of 28-day mortality among ICU patients, underscoring the need for stringent monitoring and management of potassium levels in this population.

Potassium Homeostasis

Potassium homeostasis is essential for maintaining the normal resting membrane potential of excitable cells. Yet daily dietary potassium typically far exceeds total extracellular potassium, thus the body has elegant strategies to shift potassium into cells promptly after a meal and then the kidneys efficiently excrete potassium. Potassium excretion depends on adequate kidney perfusion and filtration, sodium delivery to the distal nephron and aldosterone action on the distal nephron. Both hypokalemia and hyperkalemia have been associated with an increase in mortality. In this piece, we share 5 challenging cases to explore normal potassium homeostasis and disorders that can lead to derangements in potassium balance or excretion.

Downregulation of TASK-3 Channel Induces Senescence in Granulosa Cells of Bovine Cystic Ovarian Follicles

Ovarian cysts are linked to hormone imbalances and altered gene expressions, but the connection between cysts and ion channel expression is understudied. This study explored the role of TWIK-related acid-sensitive K+ (TASK) channels in bovine ovarian cyst formation. The ovarian follicles were split into small (5 to 10 mm in diameter) and large (>25 mm in diameter) groups. Among the measured K+, Na+, and Cl- concentrations in follicular fluid (FF) obtained from small-sized follicles (SFs) and large-sized follicles (LFs), the K+ concentration was significantly lower in LFFF. Quantitative PCR, Western blot, and immunocytochemistry data revealed that TASK-3 expression levels significantly decreased by approximately 50% in LFs and granulosa cells obtained from LFs (LFGCs) compared to the corresponding controls. The TASK-3 protein was localized to the plasma membranes of GCs. The diameters of LFGCs were larger than those of SFGCs. The cell swelling response to exposure to a hypotonic solution (200 mOsm/L) was highly reduced in TASK-3-overexpressing cells compared to vector-transfected cells. TASK-3-knockdown cells showed arrested growth. Senescence markers were detected in LFGCs and TASK-3-knockdown cells. These findings suggest that reduced TASK-3 expression in LFs is associated with the inhibition of GC growth, leading to senescence and cyst formation.

Dietary Strategies in the Prevention and Treatment of Hypertension in Children and Adolescents: A Narrative Review

This study aims to gather information on effective dietary strategies for the prevention and treatment of hypertension (HTN) in children and adolescents. It discusses specific nutritional models such as the Diet Approaches to Stop Hypertension (DASH diet), traditional Asian diets, plant-based diets, the Southern European traditional Atlantic diet, and the Mediterranean diet, highlighting the benefits of these approaches. The manuscript also addresses dehydration resulting from insufficient fluid intake among children, as well as the consumption of inappropriate beverages, like soft drinks and energy drinks, which contributes to the development of HTN. Additionally, it examines the role of oxidative stress in the pathomechanism of HTN in children, particularly in relation to the antioxidant potential of food components such as selenium, magnesium, and selected vitamins. The relationship between sodium and potassium intake from food and the development of HTN in children is also explored. Finally, this study discusses public health strategies for the prevention of HTN in children. A comprehensive search was performed across multiple databases, such as PubMed/MEDLINE, the Cochrane Library, Science Direct, and EBSCO. This search focused on locating English-language meta-analyses, systematic reviews, randomized clinical trials, and observational studies from around the globe.

Development of Optical Nanosensors for Detection of Potassium Ions and Assessment of Their Biocompatibility with Corneal Epithelial Cells

Imbalance of potassium-ion levels in the body can lead to physiological dysfunctions, which can adversely impact cardiovascular, neurological, and ocular health. Thus, quantitative measurement of potassium ions in a biological system is crucial for personal health monitoring. Nanomaterials can be used to aid in disease diagnosis and monitoring therapies. Optical detection technologies along with molecular probes emitting within the near-infrared (NIR) spectral range are advantageous for biological measurements due to minimal interference from light scattering and autofluorescence within this spectral window. Herein, we report the development of NIR fluorescent nanosensors, which can quantitatively detect potassium ions under biologically relevant conditions. The optical nanosensors were developed by using photoluminescent single-walled carbon nanotubes (SWCNTs) encapsulated in polymers that contain potassium chelating moieties. The nanosensors, polystyrene sulfonate [PSS-SWCNTs, nanosensor 1 (NS1)] or polystyrene-co-polystyrene sulfonate [PS-co-PSS-SWCNTs, nanosensor 2 (NS2)], exhibited dose-dependent optical responses to potassium ion level. The nanosensors demonstrated their biocompatibility via the evaluation of cellular viability, proliferation assays, and expression of cytokeratin 12 in corneal epithelial cells (CEpiCs). Interestingly, the nanosensors' optical characteristics and their responses toward CEpiCs were influenced by encapsulating polymers. NS2 exhibited a 10 times higher fluorescence intensity along with a higher signal-to-noise ratio as compared to NS1. NS2 showed an optical response to potassium ion level in solution within 5 min of addition and a limit of detection of 0.39 mM. Thus, NS2 was used for detailed investigations including potassium ion level detection in serum. NS2 showed a consistent response to potassium ions at the lower millimolar range in serum. These results on optical sensing along with biocompatibility show a great potential for nanotube sensors in biomedical research.

Sodium and potassium excretion and its association with cardiovascular disorders in Mexican adults

Worldwide, as well as in Mexico, the leading cause of death is cardiovascular disease (CVD). Hypertension is the main risk factor for CVD; about 50% of the adult population suffers from this condition. High sodium (Na) intake combined with low potassium (K) intake can trigger cardiovascular disorders such as high blood pressure (BP). The aim of this study was to estimate the mean excretion of Na and K in Mexican adults using a spot urine sample, and its association with cardiovascular disorders. Information on 2,778 adults, 20-59 years of age, who participated in ENSANUT-2016 was analyzed. Na and K were estimated using Tanaka formulae. Biomarkers such as glucose, total cholesterol, triglycerides, HDL cholesterol and LDL cholesterol, and anthropometry were measured. Mean Na was 3,354 mg/day (95%CI: 3,278, 3,429), 1,440 mg/day of K (95%CI: 1,412, 1,469), and the Na-K ratio was 2.4. The excretion of Na was greater in adults with high BP (3,542 mg/day) compared to those with normal BP (3,296 mg/day). In adults with hypertension, excretion of K was 10% greater (1,534 mg/day) than in adults with normal BP (1,357 mg/day). In adults with moderate reduction of renal function, Na excretion was 22% less (2,772 mg/day) than in adults with normal kidney function (3,382 mg/day). The results of this study show that the cardiovascular health of Mexican adults is at risk, as they showed high Na excretion and low K excretion.

Maximum serum K+ concentration within 1 hour with enteral replacement in severe hypokalemia

Introduction

Introduction: we report two cases with severe hypokalemia. Patients and methods: a 68-year-old woman was admitted with lower limb swelling and urinary symptoms; on the fourth day serum K+ concentration (s[K+]) was 2.3 mmol/L. A 64-year-old woman was admitted with pain in the lumbosacral spine, she was diagnosed with multiple myeloma. After receiving specific therapy she showed s[K+] at 2.4 mmol/L. A KCl solution containing 26.8 mEq of K+ was administered enterally, which increased s[K+] by 0.7 mmol/L within 1 h. Results and conclusion: these cases reveal that peak s[K+] may be achieved within 1 hour after KCl intake in severe hypokalemia, which is probably faster than IV administration.

Artificial DNA Framework Channel Modulates Antiapoptotic Behavior in Ischemia-Stressed Cells via Destabilizing Promoter G-Quadruplex

Regulating folding/unfolding of gene promoter G-quadruplexes (G4s) is important for understanding the topological changes in genomic DNAs and the biological effects of such changes on important cellular events. Although many G4-stabilizing ligands have been screened out, effective G4-destabilizing ligands are extremely rare, posing a great challenge for illustrating how G4 destabilization affects gene function in living cells under stress, a long-standing question in neuroscience. Herein, we report a distinct methodology able to destabilize gene promoter G4s in ischemia-stressed neural cells by mitigating the ischemia-induced accumulation of intracellular K+ with an artificial membrane-spanning DNA framework channel (DFC). We also show that ischemia-triggered K+ influx is positively correlated to anomalous stabilization of promoter G4s and downregulation of Bcl-2, an antiapoptotic gene with neuroprotective effects against ischemic injury. Intriguingly, the DFC enables rapid transmembrane transport of excessive K+ mediated by the internal G4 filter, leading to the destabilization of endogenous promoter G4 in Bcl-2 and subsequent turnover of gene expression at both transcription and translation levels under ischemia. Consequently, this work enriches our understanding of the biological roles of endogenous G4s and may offer important clues to study the cellular behaviors in response to stress.

Potassium homeostasis and therapeutic intervention with sodium zirconium cyclosilicate: A model-informed drug development case study

Potassium (K+ ) is the main intracellular cation in the body. Elevated K+ levels (hyperkalemia) increase the risk of life-threatening arrhythmias and sudden cardiac death. However, the details of K+ homeostasis and the effects of orally administered K+ binders, such as sodium zirconium cyclosilicate (SZC), on K+ redistribution and excretion in patients remain incompletely understood. We built a fit-for-purpose systems pharmacology model to describe K+ homeostasis in hyperkalemic subjects and capture serum K+ (sK+ ) dynamics in response to acute and chronic administration of SZC. The resulting model describes K+ distribution in the gastrointestinal (GI) tract, blood, and extracellular and intracellular spaces of tissue, renal clearance of K+ , and K+ -SZC binding and excretion in the GI tract. The model, which was fit to time-course sK+ data for individual patients from two clinical trials, accounts for bolus delivery of K+ in meals and oral doses of SZC. The virtual population of patients derived from fitting the model to these trials was then modified to predict the SZC dose-response and inform clinical trial design in two new applications: emergency lowering of sK+ in severe hyperkalemia and prevention of hyperkalemia between dialysis sessions in patients with end-stage chronic kidney disease. In both cases, the model provided novel and useful insight that was borne out by the now completed clinical trials, providing a concrete case study of fit-for-purpose, model-informed drug development after initial approval of a drug.

Impact of salinity stress on cotton and opportunities for improvement through conventional and biotechnological approaches

Excess salinity can affect the growth and development of all plants. Salinization jeopardizes agroecosystems, induces oxidative reactions in most cultivated plants and reduces biomass which affects crop yield. Some plants are affected more than others, depending upon their ability to endure the effects of salt stress. Cotton is moderately tolerant to salt stress among cultivated crops. The fundamental tenet of plant breeding is genetic heterogeneity in available germplasm for acquired characteristics. Variation for salinity tolerance enhancing parameters (morphological, physiological and biochemical) is a pre-requisite for the development of salt tolerant cotton germplasm followed by indirect selection or hybridization programs. There has been a limited success in the development of salt tolerant genotypes because this trait depends on several factors, and these factors as well as their interactions are not completely understood. However, advances in biochemical and molecular techniques have made it possible to explore the complexity of salt tolerance through transcriptomic profiling. The focus of this article is to discuss the issue of salt stress in crop plants, how it alters the physiology and morphology of the cotton crop, and breeding strategies for the development of salinity tolerance in cotton germplasm.

Effect of low sodium and high potassium diet on lowering blood pressure and cardiovascular events

Incorporating aggressive lifestyle modifications along with antihypertensive medication therapy is a crucial treatment strategy to enhance the control rate of hypertension. Dietary modification is one of the important lifestyle interventions for hypertension, and it has been proven to have a clear effect. Among food ingredients, sodium and potassium have been found to have the strongest association with blood pressure. The blood pressure-lowering effect of a low sodium diet and a high potassium diet has been well established, especially in hypertensive population. A high intake of potassium, a key component of the Dietary Approaches to Stop Hypertension (DASH) diet, has also shown a favorable impact on the risk of cardiovascular events. Additionally, research conducted with robust measurement methods has shown cardiovascular benefits of low-sodium intake. In this review, we aim to discuss the evidence regarding the relationship between the low sodium and high potassium diet and blood pressure and cardiovascular events.

Oral potassium poisoning: a retrospective review of the National Poison Data System 2010-2021

INTRODUCTION

Oral potassium poisoning can be life-threatening. The study aimed to describe patterns of oral potassium poisoning in adult and pediatric populations and characterize its clinical presentation and management as reported by United States poison centers.

METHODS

This is a retrospective review of the National Poison Data System from 1 January 2010 through 30 June 2021. We descriptively analyzed cases involving single substance, oral potassium salts. In a second step, we requested a subset of case-specific narratives for cases that resulted in major outcome or death, as well as cases where patients received any of the following therapies: whole bowel irrigation, sodium bicarbonate, calcium, insulin or hemodialysis. We classified hyperkalemia by expected toxicity: mild (peak potassium concentration <6.5 mEq/L), moderate (peak potassium concentration 6.5 to <8 mEq/L) or severe (peak potassium concentration ≥ 8mEq/L).

RESULTS

The National Poison Data System included 1,820 cases, 52.3 percent being adults. Among adult cases, 20% (n = 189) resulted in a moderate effect, major effect or death. Among pediatric cases aged <10 years, all exposures were unintentional. Analysis of 49 case narratives showed a median peak potassium concentration of 7.1 mEq/L (interquartile range 5.4-8.6) and a moderate correlation with the dose ingested (r = 0.66). Severe hyperkalemia was associated with QRS complex widening (P < 0.001), peaked T-waves (P = 0.001), and neurological symptoms (P = 0.04). Whole bowel irrigation was associated with mild hyperkalemia (P = 0.011), and hemodialysis was associated with severe hyperkalemia (P < 0.001).

DISCUSSION

Analysis of data showed that therapy to promote intracellular shift of potassium is the mainstay of management of oral potassium poisoning, followed by hemodialysis.

LIMITATIONS

Poison center data are susceptible to reporting bias. National Poison Data System data are affected by completeness and accuracy of reporting from health care providers and the lay public.

CONCLUSIONS

Single substance, oral potassium poisoning, reported to United States poison centers, is mostly unintentional and rarely results in hyperkalemia.

Acute Hyperkalemia Management in the Emergency Department

Acute hyperkalemia is characterized by high concentrations of potassium in the blood that can potentially lead to life-threatening arrhythmias that require emergent treatment. Therapy involves the utilization of a constellation of different agents, all targeting different goals of care. The first, and most important step in the treatment of severe hyperkalemia with electrocardiographic (ECG) changes, is to stabilize the myocardium with calcium in order to resolve or mitigate the development of arrythmias. Next, it is vital to target the underlying etiology of any ECG changes by redistributing potassium from the extracellular space with the use of intravenous regular insulin and inhaled beta-2 agonists. Finally, the focus should shift to the elimination of excess potassium from the body through the use of intravenous furosemide, oral potassium-binding agents, or renal replacement therapy. Multiple nuances and controversies exist with these therapies, and it is important to have a robust understanding of the underlying support and recommendations for each of these agents to ensure optimal efficacy and minimize the potential for adverse effects and medication errors.

Diet, cellular, and systemic homeostasis control the cycling of potassium stable isotopes in endothermic vertebrates

The naturally occurring stable isotopes of potassium (41K/39K, expressed as δ41K) have the potential to make significant contributions to vertebrate and human biology. The utility of K stable isotopes is, however, conditioned by the understanding of the dietary and biological factors controlling natural variability of δ41K. This paper reports a systematic study of K isotopes in extant terrestrial endothermic vertebrates. δ41K has been measured in 158 samples of tissues, biofluids, and excreta from 40 individuals of four vertebrate species (rat, guinea pig, pig and quail) reared in two controlled feeding experiments. We show that biological processing of K by endothermic vertebrates produces remarkable intra-organism δ41K variations of ca. 1.6‰. Dietary δ41K is the primary control of interindividual variability and δ41K of bodily K is +0.5-0.6‰ higher than diet. Such a trophic isotope effect is expected to propagate throughout trophic chains, opening promising use for reconstructing dietary behaviors in vertebrate ecosystems. In individuals, cellular δ41K is related to the intensity of K cycling and effectors of K homeostasis, including plasma membrane permeability and electrical potential. Renal and intestinal transepithelial transports also control fractionation of K isotopes. Using a box-modeling approach, we establish a first model of K isotope homeostasis. We predict a strong sensitivity of δ41K to variations of intracellular and renal K cycling in normal and pathological contexts. Thus, K isotopes constitute a promising tool for the study of K dyshomeostasis.

Practical patient care appraisals with use of new potassium binders in heart failure and chronic kidney diseases

Hyperkalaemia is a life-threatening condition leading to significant morbidity and mortality. It is common in heart failure and in chronic kidney disease (CKD) patients due to the diseases themselves, which often coexist, the high co-presence of diabetes, the fluctuations in renal function, and the use of some drugs [i.e. renin-angiotensin-aldosterone system (RAAS) inhibitors]. Hyperkalaemia limits their administration or uptitration, thus impacting on mortality. New K + binders, namely patiromer and sodium zirconium cyclosilicate (ZS-9), are an intriguing option to manage hyperkalaemia in heart failure and/or CKD patients, both to reduce its fatal effects and to let clinicians uptitrate RAAS inhibition. Even if their real impact on strong outcomes is still to be determined, we hereby provide a practical approach to favour their use in routine clinical practice in order to gain the correct confidence and provide an additive tool to heart failure and CKD patients' wellbeing. New trials are welcome to fill the gap in knowledge.

Consensus document on the management of hyperkalemia

Hyperkalaemia is a common electrolyte imbalance with potentially serious short-, medium- and long-term consequences on morbidity and mortality rates and the use of national health service resources. The fact that different medical specialities can manage hyperkalaemia makes it important to have a unified approach, and the recent availability of new specific drug treatments means that the approach needs to be updated. This consensus document from the scientific societies most directly involved in the management of hyperkalaemia (Sociedad Española de Cardiología [Spanish Society of Cardiology], Sociedad Española de Endocrinología y Nutrición [Spanish Society of Endocrinology and Nutrition], Sociedad Española de Medicina Interna [Spanish Society of Internal Medicine], Sociedad Española de Medicina de Urgencias y Emergencias [Spanish Society of Accident and Emergency Medicine] and Sociedad Española de Nefrología [Spanish Society of Nephrology]) first of all reviews basic aspects of potassium balance and blood potassium. Then it goes on to focus on the concept, epidemiology, pathophysiology and diagnostic and therapeutic approaches to hyperkalaemia. The available evidence and the main published studies have been reviewed with the aim of providing a useful tool in the multidisciplinary approach to patients with hyperkalaemia.

Association between annual variability of potassium levels and prognosis in patients undergoing hemodialysis

BACKGROUND

Hyperkalemia and hypokalemia are associated with mortality in patients undergoing hemodialysis. However, there are few reports on the association between potassium level fluctuations and mortality. We retrospectively investigated the association between serum potassium level variability and mortality in patients undergoing hemodialysis.

METHODS

This study was conducted at a single center. Variability in serum potassium levels was evaluated using the standard deviation of potassium level from July 2011 to June 2012, and its association with prognosis was examined by following up the patients for 5 years. Serum potassium variability was assessed as the coefficient of variation, and the statistical analysis was performed after log transformation.

RESULTS

Among 302 patients (mean age 64.9 ± 13.3; 57.9% male; and median dialysis vintage 70.5 months [interquartile range, IQR 34-138.3]), 135 died during the observation period (median observation period 5.0 years [2.3-5.0]). Although the mean potassium level was not associated with prognosis, serum potassium level variability was associated with prognosis, even after adjustments for confounding factors such as age and dialysis time (hazard ratio: 6.93, 95% confidence interval [Cl] 1.98-25.00, p = 0.001). After the adjustments, the coefficient of variation of potassium level in the highest tertile (T3) showed a higher relative risk for prognosis than that in T1 (relative risk: 1.98, 95% CI 1.19-3.29, p = 0.01).

CONCLUSIONS

Variability in serum potassium levels was associated with mortality in patients undergoing hemodialysis. Careful monitoring of potassium levels and their fluctuations is necessary for this patient population.

Dietary anions control potassium excretion: it is more than a poorly absorbable anion effect

The urinary potassium (K+) excretion machinery is upregulated with increasing dietary K+, but the role of accompanying dietary anions remains inadequately characterized. Poorly absorbable anions, including [Formula: see text], are thought to increase K+ secretion through a transepithelial voltage effect. Here, we tested if they also influence the K+ secretion machinery. Wild-type mice, aldosterone synthase (AS) knockout (KO) mice, or pendrin KO mice were randomized to control, high-KCl, or high-KHCO3 diets. The K+ secretory capacity was assessed in balance experiments. Protein abundance, modification, and localization of K+-secretory transporters were evaluated by Western blot analysis and confocal microscopy. Feeding the high-KHCO3 diet increased urinary K+ excretion and the transtubular K+ gradient significantly more than the high-KCl diet, coincident with more pronounced upregulation of epithelial Na+ channels (ENaC) and renal outer medullary K+ (ROMK) channels and apical localization in the distal nephron. Experiments in AS KO mice revealed that the enhanced effects of [Formula: see text] were aldosterone independent. The high-KHCO3 diet also uniquely increased the large-conductance Ca2+-activated K+ (BK) channel β4-subunit, stabilizing BKα on the apical membrane, the Cl-/[Formula: see text] exchanger, pendrin, and the apical KCl cotransporter (KCC3a), all of which are expressed specifically in pendrin-positive intercalated cells. Experiments in pendrin KO mice revealed that pendrin was required to increase K+ excretion with the high-KHCO3 diet. In summary, [Formula: see text] stimulates K+ excretion beyond a poorly absorbable anion effect, upregulating ENaC and ROMK in principal cells and BK, pendrin, and KCC3a in pendrin-positive intercalated cells. The adaptive mechanism prevents hyperkalemia and alkalosis with the consumption of alkaline ash-rich diets but may drive K+ wasting and hypokalemia in alkalosis.NEW & NOTEWORTHY Dietary anions profoundly impact K+ homeostasis. Here, we found that a K+-rich diet, containing [Formula: see text] as the counteranion, enhances the electrogenic K+ excretory machinery, epithelial Na+ channels, and renal outer medullary K+ channels, much more than a high-KCl diet. It also uniquely induces KCC3a and pendrin, in B-intercalated cells, providing an electroneutral KHCO3 secretion pathway. These findings reveal new K+ balance mechanisms that drive adaption to alkaline and K+-rich foods, which should guide new treatment strategies for K+ disorders.

Impact of chronic potassium binder treatment on the clinical outcomes in patients with hyperkalemia: Results of a nationwide hospital-based cohort study

Introduction: Hyperkalemia (HK) is a common disorder in patients with heart failure or chronic kidney disease, and potassium binders (PBs) are recommended to control serum potassium (S-K) levels. Although HK is often a chronic condition, short-term and intermittent PBs treatment has been largely applied to control S-K levels, and little is known about the impact of long-term and chronic PBs treatment on clinical outcomes. Method: This retrospective cohort study was conducted using a Japanese claims database (April 2008-September 2018). HK was defined as at least two S-K ≥5.1 mmol/L within a 12-month(M) interval. The index date was defined as the initial PB prescription date, and the S-K values were examined at 3M, 6M, and 12M after the index. The medication possession ratio (MPR) was used to evaluate the length of the prescribed period of PB, as prescription refill was not allowed in Japan. Clinical outcomes were analyzed by comparing MPR <80% to MPR ≥80% using Cox proportional hazards regression. Results: We found 4,321 patients with HK and were on initial PB treatments, and 993 and 3,328 patients were categorized in the MPR <80% and MPR ≥80% groups, respectively. The mean prescription days ±SD in the MPR <80% and MPR ≥80% groups were 114.7 ± 9.1 and 1151.2 ± 22.5, respectively. S-K value with adjustment by covariates in MPR <80% and MPR ≥80% groups were 5.62 (95% CI: 5.57-5.68) and 5.72 (95% CI: 5.68-5.76) at index followed by 4.65 (95% CI: 4.58-4.71) and 4.57 (95% CI: 4.51-4.62) at 3M, respectively. The hazard ratios of incidence rates in hospitalization was 1.41 (p < 0.001), introduction of renal replacement therapy was 1.25 (p < 0.003), recurrent HK was 1.67 (p < 0.001), and decreased eGFR was 1.41 (p < 0.001), respectively. Conclusion: These results indicate a higher risk of adverse outcomes when PBs were not prescribed chronically, whereas S-K levels were similarly controlled. Chronic control with continued PBs rather than temporary treatment may be associated with the reduction of adverse clinical outcomes in patients with HK.

Aldosterone: Renal Action and Physiological Effects

Aldosterone exerts profound effects on renal and cardiovascular physiology. In the kidney, aldosterone acts to preserve electrolyte and acid-base balance in response to changes in dietary sodium (Na+ ) or potassium (K+ ) intake. These physiological actions, principally through activation of mineralocorticoid receptors (MRs), have important effects particularly in patients with renal and cardiovascular disease as demonstrated by multiple clinical trials. Multiple factors, be they genetic, humoral, dietary, or otherwise, can play a role in influencing the rate of aldosterone synthesis and secretion from the adrenal cortex. Normally, aldosterone secretion and action respond to dietary Na+ intake. In the kidney, the distal nephron and collecting duct are the main targets of aldosterone and MR action, which stimulates Na+ absorption in part via the epithelial Na+ channel (ENaC), the principal channel responsible for the fine-tuning of Na+ balance. Our understanding of the regulatory factors that allow aldosterone, via multiple signaling pathways, to function properly clearly implicates this hormone as central to many pathophysiological effects that become dysfunctional in disease states. Numerous pathologies that affect blood pressure (BP), electrolyte balance, and overall cardiovascular health are due to abnormal secretion of aldosterone, mutations in MR, ENaC, or effectors and modulators of their action. Study of the mechanisms of these pathologies has allowed researchers and clinicians to create novel dietary and pharmacological targets to improve human health. This article covers the regulation of aldosterone synthesis and secretion, receptors, effector molecules, and signaling pathways that modulate its action in the kidney. We also consider the role of aldosterone in disease and the benefit of mineralocorticoid antagonists. © 2023 American Physiological Society. Compr Physiol 13:4409-4491, 2023.

Evaluation of safety, effectiveness and treatment patterns of sodium zirconium cyclosilicate in management of hyperkalaemia in China: a real-world study protocol

INTRODUCTION

Hyperkalaemia (HK) is a potentially life-threatening electrolyte imbalance associated with several adverse clinical outcomes. The efficacy and negative effects of currently existing treatment options have made HK management questionable. Sodium zirconium cyclosilicate (SZC), a novel highly selective potassium binder, is approved for the treatment of HK. The present study will be aimed to assess the safety, effectiveness and treatment patterns of SZC in Chinese patients with HK in a real-world clinical setting as it is required by China's drug review and approval process.

METHODS AND ANALYSIS

This is a multicentre, prospective cohort study which plans to enrol 1000 patients taking SZC or willing to take SZC from approximately 40 sites in China. Patients ≥18 years of age at the time of signing the written informed consent and with documented serum potassium levels ≥5.0 mmol/L within 1 year before study enrolment day will be included. Eligible patients will receive SZC treatment and will be followed up for 6 months from enrolment day. The primary objective will be to evaluate the safety of SZC for the management of HK in Chinese patients in terms of adverse events (AEs), serious AEs as well as discontinuation of SZC. The secondary objectives will include understanding the SZC dosage information in terms of its effectiveness and treatment patterns under real-world clinical practice and assessing effectiveness of SZC during the observational period.

ETHICS AND DISSEMINATION

This study protocol was approved by the Ethics Committee of the First Affiliated Hospital of Dalian Medical University (approval number: YJ-JG-YW-2020). All the participating sites have received the ethics approval. Results will be disseminated through national and international presentations and peer-reviewed publications.

TRIAL REGISTRATION NUMBER

NCT05271266.

Emergency room presentations of people with anorexia nervosa

People with anorexia nervosa (AN) tend to shy away from engaging in typical primary care provider relationships in order to avoid detection. Therefore, they may seek care for their medical concerns through a local emergency department (ED). Inherently, AN is associated with a litany of medical complications, which become more prevalent as the severity of their eating disorder increases. Notwithstanding the typical young age at the onset of AN, no body system is immune to these medical complications. Thus, ED providers may need to pursue a medical diagnosis in order to explain presenting symptoms in people with AN. In addition to the medical issues, AN is also a serious mental illness with high mortality rates, including deaths by suicide. Therefore, ED providers also need to be familiar with relevant mental health issues for these people.

The role of residual renal function on potassium intake and excretion in patients on peritoneal dialysis

BACKGROUND

Patients on chronic dialysis are at increased risk of developing disorders in potassium balance. The preservation of residual renal function (RRF), frequently observed in patients on peritoneal dialysis (PD), may contribute to better control of serum potassium. This study aimed to investigate the role residual renal function on potassium intake and excretion in PD patients.

METHODS

In this cross-sectional study, dietary potassium was evaluated by the 3-day food record. Potassium concentration was determined in serum, 24 h dialysate, stool ample, and 24 h urine of patients with diuresis > 200 mL/day, who were considered non-anuric.

RESULTS

Fifty-two patients, 50% men, 52.6 ± 14.0 years, and PD vintage 19.5 [7.0-44.2] months, were enrolled. Compared to the anuric group (n = 17, 33%), the non-anuric group (n = 35, 67%) had lower dialysate potassium excretion (24.8 ± 5.3 vs 30.9 ± 5.9 mEq/d; p = 0.001), higher total potassium intake (44.5 ± 16.7 vs 35.1 ± 8.1 mEq/d; p = 0.009) and potassium intake from fruit (6.2 [2.4-14.7] vs 2.9 [0.0-6.0]mEq/d; p = 0.018), and no difference in serum potassium (4.8 ± 0.6 vs 4.8 ± 0.9 mEq/L; p = 0.799) and fecal potassium (2.2 ± 0.5 vs 2.1 ± 0.7 mEq/L; p = 0.712). In non-anuric patients, potassium intake correlated directly with urinary potassium (r = 0.40; p = 0.017), but not with serum, dialysate, or fecal potassium. In the anuric group, potassium intake tended to correlate positively with serum potassium (r = 0.48; p = 0.051) and there was no correlation with dialysate or fecal potassium.

CONCLUSION

The presence of residual renal function constitutes an important factor in the excretion of potassium, which may allow the adoption of a less-restrictive diet.

Pathophysiologic approach in genetic hypokalemia: An update

The pathophysiology of genetic hypokalemia is close to that of non-genetic hypokalemia. New molecular pathways physiologically involved in renal and extrarenal potassium homeostasis have been highlighted. A physiological approach to diagnosis is illustrated here, with 6 cases. Mechanisms generating and sustaining of hypokalemia are discussed. After excluding acute shift of extracellular potassium to the intracellular compartment, related to hypokalemic periodic paralysis, inappropriate kaliuresis (>40mmol/24h) concomitant to hypokalemia indicates renal potassium wasting. Clinical analysis distinguishes hypertension-associated hypokalemia, due to hypermineralocorticism or related disorders. Genetic hypertensive hypokalemia is rare. It includes familial hyperaldosteronism, Liddle syndrome, apparent mineralocorticoid excess,11beta hydroxylase deficiency and Geller syndrome. In case of normo- or hypo-tensive hypokalemia, two etiologies are to be considered: chloride depletion or salt-wasting tubulopathy. Diarrhea chlorea is a rare disease responsible for intestinal chloride depletion. Due to the severity of hypokalemic metabolic alkalosis, this disease can be misdiagnosed as pseudo-Bartter syndrome. Gitelman syndrome is the most frequent cause of genetic hypokalemia. It typically associates renal sodium and potassium wasting, hypomagnesemia, conserved chloride excretion (>40mmol/24h), and low-range calcium excretion (urinary Ca/creatinine ratio<0.20mmol/mmol). Systematic analysis of hydroelectrolytic disorder and dynamic hormonal investigation optimizes indications for and orientation of genotyping of hereditary salt-losing tubulopathy.

Lysosomal Potassium Channels

Lysosomes are acidic membrane-bound organelles that use hydrolytic enzymes to break down material through pathways such as endocytosis, phagocytosis, mitophagy, and autophagy. To function properly, intralysosomal environments are strictly controlled by a set of integral membrane proteins such as ion channels and transporters. Potassium ion (K⁺) channels are a large and diverse family of membrane proteins that control K⁺ flux across both the plasma membrane and intracellular membranes. In the plasma membrane, they are essential in both excitable and non-excitable cells for the control of membrane potential and cell signaling. However, our understanding of intracellular K⁺ channels is very limited. In this review, we summarize the recent development in studies of K⁺ channels in the lysosome. We focus on their characterization, potential roles in maintaining lysosomal membrane potential and lysosomal function, and pathological implications.

A mathematical model of potassium homeostasis: Effect of feedforward and feedback controls

Maintaining normal potassium (K+) concentrations in the extra- and intracellular fluid is critical for cell function. K+ homeostasis is achieved by ensuring proper distribution between extra- and intracellular fluid compartments and by matching K+ excretion with intake. The Na+-K+-ATPase pump facilitates K+ uptake into the skeletal muscle, where most K+ is stored. Na+-K+-ATPase activity is stimulated by insulin and aldosterone. The kidneys regulate long term K+ homeostasis by controlling the amount of K+ excreted through urine. Renal handling of K+ is mediated by a number of regulatory mechanisms, including an aldosterone-mediated feedback control, in which high extracellular K+ concentration stimulates aldosterone secretion, which enhances urine K+ excretion, and a gastrointestinal feedforward control mechanism, in which dietary K+ intake increases K+ excretion. Recently, a muscle-kidney cross talk signal has been hypothesized, where the K+ concentration in skeletal muscle cells directly affects urine K+ excretion without changes in extracellular K+ concentration. To understand how these mechanisms coordinate under different K+ challenges, we have developed a compartmental model of whole-body K+ regulation. The model represents the intra- and extracellular fluid compartments in a human (male) as well as a detailed kidney compartment. We included (i) the gastrointestinal feedforward control mechanism, (ii) the effect of insulin and (iii) aldosterone on Na+-K+-ATPase K+ uptake, and (iv) aldosterone stimulation of renal K+ secretion. We used this model to investigate the impact of regulatory mechanisms on K+ homeostasis. Model predictions showed how the regulatory mechanisms synthesize to ensure that the extra- and intracelluller fluid K+ concentrations remain in normal range in times of K+ loading and fasting. Additionally, we predict that without the hypothesized muscle-kidney cross talk signal, the model was unable to predict a return to normal extracellular K+ concentration after a period of high K+ loading or depletion.

High K+ intake alleviates experimental autoimmune encephalomyelitis (EAE) and increases T regulatory cells

Multiple sclerosis is believed to be triggered by the interplay between the environmental and genetic factors. In contrast to the Paleolithic diet, the modern Western diet is high in Na⁺ and low in K⁺. The present study was undertaken to determine whether high K⁺ intake alleviated experimental autoimmune encephalomyelitis (EAE), a model of multiple sclerosis. Treatment of C57BL/6 or SJL mice for 7 days with a 5 % K⁺ diet prior to induction of EAE and maintaining mice on the diet until the end of experiments delayed the onset, reduced the peak, and accelerated the recovery of EAE in both strains compared with mice on a control diet (0.7 % K⁺), whereas feeding C57BL/6 mice with a 0.1 % K⁺ diet did the opposite. High K⁺ intake increased the splenic Treg cell frequency in the pretreatment and peak EAE. Thus, high K⁺ intake attenuates EAE, possibly by increasing the Treg cells.

Thyrotoxic Periodic Paralysis: The Peril of Potassium Replacement

Hypokalemic periodic paralysis (HPP) is a clinical condition of sudden-onset, recurrent transient episodes of weakness caused by severe hypokalemia. Thyrotoxic periodic paralysis (TPP) is a specific subgroup of the HPP spectrum, where hypokalemia occurs in the setting of thyrotoxicosis, and the repletion of potassium must be performed with caution. A male in his second decade of life with hyperthyroidism non-adherent to methimazole presented with acute-onset bilateral lower extremity weakness. On physical examination, the patient had diffuse thyromegaly and tremors on outstretched hands. Bilateral lower extremity weakness and decreased reflexes were also noted, with preserved muscle tone and normal passive range of motion. Labs demonstrated hyperactive thyroid function and severe hypokalemia at 1.7 mEq/L, with U waves present on the electrocardiogram. In the intensive care unit, the patient received methimazole and propranolol for thyrotoxicosis and a total dose of 60 mEq/L of potassium replacement therapy. Despite the expected correction by 0.6 mEq/L, his follow-up potassium level dramatically increased to 5.7 mEq/L, resulting in the actual correction of 4.0 mEq/L. Within a few hours, the patient regained his baseline strength with a significant improvement in tremors. Patients with TPP present with acute-onset extremity weakness and severe hypokalemia, which reverses quickly with potassium repletion. Clinicians should not only treat thyrotoxicosis but also avoid overly aggressive repletion of potassium as this may lead to rebound hyperkalemia when the initial transcellular potassium shift is reversed.

Dietary Potassium Intake and Risk of Diabetes: A Systematic Review and Meta-Analysis of Prospective Studies

(1) Background: Dietary potassium intake is positively associated with reduction of cardiovascular risk. Several data are available on the relationship between dietary potassium intake, diabetes risk and glucose metabolism, but with inconsistent results. Therefore, we performed a meta-analysis of the prospective studies that explored the effect of dietary potassium intake on the risk of diabetes to overcome these limitations. (2) Methods: A random-effects dose-response meta-analysis was carried out for prospective studies. A potential non-linear relation was investigated using restricted cubic splines. (3) Results: A total of seven prospective studies met the inclusion criteria. Dose-response analysis detected a non-linear relationship between dietary potassium intake and diabetes risk, with significant inverse association starting from 2900 mg/day by questionnaire and between 2000 and 5000 mg/day by urinary excretion. There was high heterogeneity among studies, but no evidence of publication bias was found. (4) Conclusions: The results of this meta-analysis indicate that habitual dietary potassium consumption is associated with risk of diabetes by a non-linear dose-response relationship. The beneficial threshold found supports the campaigns in favour of an increase in dietary potassium intake to reduce the risk of morbidity and mortality. Further studies should be carried out to explore this topic.

Machine Learning Models Predicting Cardiovascular and Renal Outcomes and Mortality in Patients with Hyperkalemia

Hyperkalemia is associated with increased risks of mortality and adverse clinical outcomes. The treatment of hyperkalemia often leads to the discontinuation or restriction of beneficial but potassium-increasing therapy such as renin-angiotensin-aldosterone inhibitors (RAASi) and high-potassium diet including fruits and vegetables. To date, limited evidence is available for personalized risk evaluation in this heterogeneous and multifactorial pathophysiological condition. We developed risk prediction models using extreme gradient boosting (XGB), multiple logistic regression (LR), and deep neural network. Models were derived from a retrospective cohort of hyperkalemic patients with either heart failure or chronic kidney disease stage ≥3a from a Japanese nationwide database (1 April 2008−30 September 2018). Studied outcomes included all-cause death, renal replacement therapy introduction (RRT), hospitalization for heart failure (HHF), and cardiovascular events within three years after hyperkalemic episodes. The best performing model was further validated using an external cohort. A total of 24,949 adult hyperkalemic patients were selected for model derivation and internal validation. A total of 1452 deaths (16.6%), 887 RRT (10.1%), 1,345 HHF (15.4%), and 621 cardiovascular events (7.1%) were observed. XGB outperformed other models. The area under receiver operator characteristic curves (AUROCs) of XGB vs. LR (95% CIs) for death, RRT, HHF, and cardiovascular events were 0.823 (0.805−0.841) vs. 0.809 (0.791−0.828), 0.957 (0.947−0.967) vs. 0.947 (0.936−0.959), 0.863 (0.846−0.880) vs. 0.838 (0.820−0.856), and 0.809 (0.784−0.834) vs. 0.798 (0.772−0.823), respectively. In the external dataset including 86,279 patients, AUROCs (95% CIs) for XGB were: death, 0.747 (0.742−0.753); RRT, 0.888 (0.882−0.894); HHF, 0.673 (0.666−0.679); and cardiovascular events, 0.585 (0.578−0.591). Kaplan−Meier curves of the high-risk predicted group showed a statistically significant difference from that of the low-risk predicted groups for all outcomes (p < 0.005; log-rank test). These findings suggest possible use of machine learning models for real-world risk assessment as a guide for observation and/or treatment decision making that may potentially lead to improved outcomes in hyperkalemic patients while retaining the benefit of life-saving therapies.

Fifteen-minute consultation: Emergency management of children presenting with hyperkalaemia

Hyperkalaemia can lead to life-threatening cardiac arrhythmias. A good understanding of the physiological basis of management can help us rationalise treatment and reduce plasma potassium levels efficiently and effectively. Management focuses on avoidance of arrythmias, rapid intracellular movement of potassium and finally reduction of total body potassium. Fluid management in hyperkalaemia should be carefully considered, with balanced solutions providing theoretical benefits compared to 0.9% saline in certain situations.

Assessing potassium levels in critically ill patients with heart failure: application of a group-based trajectory model

AIMS

Abnormalities in potassium homeostasis are frequently seen in hospitalized patients. A poor outcome in heart failure (HF) has been linked to both hypokalaemia and hyperkalaemia. The studies on the connection between variations in potassium levels and all-cause mortality remain scarce. We delineated trajectories of potassium levels and investigated the association of these trajectories with all-cause mortality of critically ill patients with HF.

METHODS AND RESULTS

A retrospective analysis of blood potassium levels (9 times) in patients with HF after being admitted to the intensive care unit (ICU). Potassium levels were divided into three groups according to the first serum potassium level in ICU and thereafter categorized as follows: hypokalaemia group (n = 336) (<3.5 mmol/L), normal blood potassium-level group (n = 3322) (3.5-5.0 mmol/L), and hyperkalaemia group (n = 395) (>5.0 mmol/L). According to the group-based trajectory modelling (GBTM), the hyperkalaemia group and the normal blood potassium-level group can be divided into three trajectory groups: the low-level stable group, the medium-level stable group, and the high-level decline group. The hypokalaemia group can be divided into two trajectory groups: the low-level rise group and the high-level rise group. A total of 4053 HF patients were included (mean age 71.81 ± 13.12 years, 54.90% males, 45.10% females). After adjusting for possible confounding variables, in the hyperkalaemia group, the low-level stable group had lower 28 day [high-level decline group vs. low-level stable group hazard ratio (HR), 95% confidence interval (CI): 2.917, 1.555-5.473; P < 0.05] and 365 day (high-level decline group vs. low-level stable group HR, 95% CI: 2.854, 1.820-4.475; P < 0.05) all-cause mortality. In the normal blood potassium-level group, the medium-level stable group had lower 28 day (medium-level stable group vs. low-level stable group HR, 95% CI: 0.776, 0.657-0.918; P < 0.05) and 365 day (medium-level stable group vs. low-level stable group HR, 95% CI: 0.827, 0.733-0.934; P < 0.05) all-cause mortality. In the hypokalaemia group, the cumulative survival of the high-level rise group and the low-level rise group did not differ significantly.

CONCLUSIONS

Critically ill patients with HF have blood potassium trajectories. And the trajectories are associated with all-cause mortality for hyperkalaemia and normal blood potassium-level patients. GBTM is a granular method to describe the evolution of blood potassium, which may increase the current knowledge of blood potassium-level adjustment.

Potassium homeostasis: sensors, mediators, and targets

Transmembrane potassium (K) gradients are key determinants of membrane potential that can modulate action potentials, control muscle contractility, and influence ion channel and transporter activity. Daily K intake is normally equal to the amount of K in the entire extracellular fluid (ECF) creating a critical challenge - how to maintain ECF [K] and membrane potential in a narrow range during feast and famine. Adaptations to maintain ECF [K] include sensing the K intake, sensing ECF [K] vs. desired set-point and activating mediators that regulate K distribution between ECF and ICF, and regulate renal K excretion. In this focused review, we discuss the basis of these adaptions, including (1) potential mechanisms for rapid feedforward signaling to kidney and muscle after a meal (before a rise in ECF [K]), (2) how skeletal muscles sense and respond to changes in ECF [K], (3) effects of K on aldosterone biosynthesis, and (4) how the kidney responds to changes in ECF [K] to modify K excretion. The concepts of sexual dimorphisms in renal K handling adaptation are introduced, and the molecular mechanisms that can account for the benefits of a K-rich diet to maintain cardiovascular health are discussed. Although the big picture of K homeostasis is becoming more clear, we also highlight significant pieces of the puzzle that remain to be solved, including knowledge gaps in our understanding of initiating signals, sensors and their connection to homeostatic adjustments of ECF [K].

Hyperkalemia in Chronic Kidney Disease: Links, Risks and Management

Hyperkalemia is a common clinical problem with potentially fatal consequences. The prevalence of hyperkalemia is increasing, partially due to wide-scale utilization of prognostically beneficial medications that inhibit the renin-angiotensin-aldosterone-system (RAASi). Chronic kidney disease (CKD) is one of the multitude of risk factors for and associations with hyperkalemia. Reductions in urinary potassium excretion that occur in CKD can lead to an inability to maintain potassium homeostasis. In CKD patients, there are a variety of strategies to tackle acute and chronic hyperkalemia, including protecting myocardium from arrhythmias, shifting potassium into cells, increasing potassium excretion from the body, addressing dietary intake and treating associated conditions, which may exacerbate problems such as metabolic acidosis. The evidence base is variable but has recently been supplemented with the discovery of novel oral potassium binders, which have shown promise and efficacy in studies. Their use is likely to become widespread and offers another tool to the clinician treating hyperkalemia. Our review article provides an overview of hyperkalemia in CKD patients, including an exploration of relevant guidelines and nuances around management.

Adding eosinophil count to EMERALD rules predicts subarachnoid haemorrhage better in emergency department

BACKGROUND

Subarachnoid haemorrhage (SAH) clinical decision rules can provide successful results in the differential diagnosis of non-traumatic headache.

AIM

The aim of this study is to investigate whether a laboratory parameter that can be added to clinical decision-making rules can better predict subarachnoid haemorrhages in patients presenting to the emergency department with headache.

METHODS

We conducted a retrospective cohort study between March 2017 and March 2019. Patients over the age of 18 who admitted to the emergency department with non-traumatic, acute headache last 14 days before admission and evaluated by imaging and laboratory studies were included in the study.

RESULTS

A total of 867 patients were included and 141 of them had SAH. In detecting the SAH, Ottawa SAH rule sensitivity (85.1%), specificity (47.1%), positive predictive value (PPV) (23.8%) and negative predictive value (NPV) (94.2%), and for EMERALD SAH, rule sensitivity (96.4%), specificity (43.2%), PPV (24.8%) and NPV (98.4%). In the regression analysis, statistically significant result was obtained to exclude the diagnosis of SAH with the decrease in the eosinophil value (cutoff < 0.085 10^3/µL, OR: 0.011, 95% CI: 0.001-0.213, p = 0.003). When eosinophil value was added to EMERALD SAH rule, it provided a 100% of sensitivity, a 38.4% of specificity, a 24% of PPV and a 100% of NPV in detecting the SAH.

CONCLUSIONS

EMERALD SAH rule plus eosinophil, which offers 100% sensitivity and NPV for predicting SAH in adult non-traumatic headaches, may be recommended as a successful and practical decision rule for clinical use according to the Ottawa and EMERALD SAH rule.

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

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

Dysnatremia in Gastrointestinal Disorders

The primary solute of the milieu intérieur is sodium and accompanying anions. The solvent is water. The kidneys acutely regulate homeostasis in filtration, secretion, and resorption of electrolytes, non-electrolytes, and minerals while balancing water retention and clearance. The gastrointestinal absorptive and secretory functions enable food digestion and water absorption needed to sustain life. Gastrointestinal perturbations including vomiting and diarrhea can lead to significant volume and electrolyte losses, overwhelming the renal homeostatic compensatory mechanisms. Dysnatremia, potassium and acid-base disturbances can result from gastrointestinal pathophysiologic processes. Understanding the renal and gastrointestinal contributions to homeostatis are important for the clinical evaluation of perturbed volume disturbances.

Perimortem dynamics of blood potassium concentration in patients dying in intensive care unit: A prospective nested cohort study

To enable diagnosis of hyperkalemia from the perimortem blood sample, we aim to describe the natural dynamics of blood potassium [K⁺ ] in patients dying after withdrawal of care while in an intensive care unit. In a nested sub-study of international Death Prediction and Physiology after Removal of Therapy (DePPaRT) project, we obtained serial whole-blood samples and analyzed ions and acid-base parameters in 23 patients just before life-sustaining treatment withdrawal, at the time of death, and after 5 and 30 min after death. Of the 631 patients in the DePPaRT study, we obtained consent and enrolled 23 subjects in the [K⁺ ] sub-study (12 M, 11F, aged 73 ± 14 years), mostly dying from irreversible brain damage or multi-organ failure. Blood [K⁺ ] rose from the median 4.3 (IQR 3.9; 4.8) mEq/L at treatment withdrawal to 5.2 (IQR 5.0; 6.8) mEq/L at death and then to 5.85 (IQR 5.2; 6.8) mEq/L after 30 min (mean rise of +0.64 mEq.L^-1 .h^-1 ). These changes were associated with progressive lactic and hypercapnic acidemia. After correcting the measured [K+] for pH by subtracting 0.6 mEq/L from [K+] for every 0.1 pH decrease from 7.40, the calculated [K+] remained normal or decreased from that measured at treatment withdrawal. In contrast to the late autolysis phase, the early changes of blood [K⁺ ] after death are slow and can be fully explained by progressive acidemia. Our data suggest that the diagnosis of hyperkalemia at death from a blood sample obtained within 30 min after death can be made by adjusting the [K+] concentration to a pH 7.40.

Yield and Compositional Profile of Eggplant Fruits as Affected by Phosphorus Supply, Genotype and Grafting

The present experiment addressed the effects of two phosphorus regimes (30 and 90 kg ha−1, hereafter P30 and P90) on yield and composition of eggplant fruits in ‘Birgah’ and ‘Dalia’, whether or not these cultivars were grafted onto Solanum torvum ‘Espina’. The P30 regime did not reduce yield, and promoted fruits’ dry matter and total phenols content, along with their concentrations of macronutrients, mesonutrients (S and Na) and micronutrients (mostly Cu, B, Zn); however, their Fe concentrations were depressed. The rootstock ‘Espina’ increased fruit yield, dry matter content, epicarp chroma (in ‘Birgah’) and Ca content, together with their concentrations of B and Zn (especially at P30), but reduced their Fe content, mostly under P30. Thus, the reduced P supply and grafting proved to be effective tools to enhance fruit yield, carpometric and almost all nutritional traits in eggplant, in a framework of more sustainable crop management. However, the reduced fruit concentration of Fe suggests that the affinity of the rootstock with specific micro minerals should be taken into account, along with the option to adopt complementary practices (e.g., targeted micronutrient fertilizations) to manage the micro mineral composition of eggplants.

Correlation between Hyperkalemia and the Duration of Several Hospitalizations in Patients with Chronic Kidney Disease

(1) Background: This observational study aimed to verify the association between serum potassium levels and hospitalization days in patients with chronic kidney disease in a follow up of nine months. (2) Methods: Patients with chronic kidney disease were divided into group A (180 patients, potassium ≤ 5.1 mEq/L) and B (90 patients, potassium > 5.1 mEq/L). Student's t-test, Mann-Whitney test, Pearson's Chi-Square test, Pearson/Spearman's correlation test and linear regression test were performed in the entire sample and in stage-G4/5 subsample. (3) Results: Groups A and B differed for estimated glomerular filtration rate (eGFR) (34.89 (IQR, 16.24-57.98) vs. 19.8 (IQR, 10.50-32.50) mL/min/1.73 m2; p < 0.0001), hemoglobin (11.64 ± 2.20 vs. 10.97 ± 2.19 g/dL, p = 0.048), sum of hospitalization days (8 (IQR, 6-10) vs. 11 (IQR, 7-15) days; p < 0.0001) and use of angiotensin II receptor blockers (40.2% vs. 53.3%; p = 0.010). Considering patients with eGFR 6-30 mL/min/1.73 m2, differences in the sum of hospitalization days were confirmed. Multivariable regression analysis showed that hyperkalemia is an independent risk factor of increased hospital length. In stage G4-G5, regression analysis showed that hyperkalemia is the only independent risk factor (β = 2.93, 95% confidence interval, 0.077-5.794, p = 0.044). (4) Conclusions: We observed significantly greater odds of increased length of hospital stay among patients with higher potassium, mostly in stages G4-G5 chronic kidney disease.

Effect of drying, blanching, pickling and maceration on the fate of 40K, total K and 137Cs in bolete mushrooms and dietary intake

The effects of blanching, blanching and pickling and maceration on the leaching of ¹³⁷Cs and ⁴⁰K from the flesh of three edible bolete mushroom species-Boletus edulis, Leccinum scabrum and Leccinum versipelle-were investigated. Significant (p < 0.05) decreases in activity were observed but varied depending on the treatment. Relative to fresh mushrooms, blanching decreased the activity concentration of ¹³⁷Cs by 15 ± 13%, and of ⁴⁰K, by 16 ± 7%, but blanching and pickling (vinegar) reduced activity more effectively, by 55 ± 8% and 40 ± 20% respectively. The corresponding losses of ¹³⁷Cs and ⁴⁰K through maceration of dried, powdered mushrooms were 38 ± 11% and 35 ± 14% ww, respectively. These results indicate that traditional domestic processing methods may not be as efficient at excluding ¹³⁷Cs radioactivity as shown in some other studies. The activity concentration of ¹³⁷Cs in a typically sized (100 g) portion of a processed mushroom (sourced from nearshore regions of the southern Baltic Sea coast near Gdańsk in 2015) meal was projected to be low, i.e. in the range of 0.51 to 12 Bq kg^-1 ww. The corresponding effective dose of ¹³⁷Cs from blanched, blanched and pickled and macerated mushrooms per capita was also assessed to be low, from 0.001 to 0.010 μSv. Nutritionally, the median concentration of potassium (330 mg) in 100 g portions of blanched or pickled mushrooms would account for around 7% of the adequate adult daily intake.