A 36-year-old unmarried male chef was incidentally diagnosed with hypokalemia during an evaluation for an acute perianal abscess. Despite potassium supplementation, he developed progressive weakness in his lower limbs, culminating in an inability to stand. Investigations confirmed severe hypokalemia, metabolic alkalosis, hypomagnesemia, secondary hyperaldosteronism, and low urinary calcium excretion, with normotension. The patient\'s long-standing stunted growth and lean physique since childhood were noted. Biochemical assays further identified type 2 diabetes mellitus and metabolic syndrome. Genetic analysis revealed three heterozygous SLC12A3 mutations (M1: c.421G>A: p.G141R, M2: c.509T>A:p.L170Q, and M3: c.704C>A: p.T235K), compound heterozygo us and derived from both parents, with M1 and M3 reported here for the first time. Treatment with spironolactone and oral potassium chloride stabilized his potassium levels. Following the administration of SGLT2 inhibitors in patients receiving hypoglycemic therapy, we observed a mild decrease in serum sodium levels. This case highlights the criticality of vigilant metabolic surveillance in Gitelman syndrome and advises prudence with SGLT2 inhibitors in those with concurrent type 2 diabetes, given the risk of potentially aggravate sodium loss.

BACKGROUND: Congenital chloride diarrhoea (CCD) is an autosomal recessive condition that causes secretory diarrhoea and potentially deadly electrolyte imbalances in infants because of solute carrier family 26 member 3 (SLC26A3) gene mutations.
METHODS: A 7-month-old Chinese infant with a history of maternal polyhydramnios presented with frequent watery diarrhoea, severe dehydration, hypokalaemia, hyponatraemia, failure to thrive, metabolic alkalosis, hyperreninaemia, and hyperaldosteronaemia. Genetic testing revealed a compound heterozygous SLC26A3 gene mutation in this patient (c.269_270dup and c.2006 C > A). Therapy was administered in the form of oral sodium and potassium chloride supplements, which decreased stool frequency.
CONCLUSIONS: CCD should be considered when an infant presents with prolonged diarrhoea during infancy, particularly in the context of maternal polyhydramnios and dilated foetal bowel loops.

Hypokalaemia is a side-effect of diuretics. We aimed to use machine learning to identify features predicting hypokalaemia risk in hypertensive patients.
Participants with hypertension in the United States National Health and Nutrition Examination Survey 1999-2018 were included for analysis. To select the most suitable algorithm, we tested and evaluated five machine learning algorithms commonly employed in epidemiological studies: Logistic Regression, k-Nearest Neighbor, Random Forest, Recursive Partitioning and Regression Trees, and eXtreme Gradient Boosting. These algorithms were accessed using a set of 38 screened features. We then selected the key hypokalaemia-associated features in the hypertension group and their cardiovascular diseases (CVD) subgroup using the SHapley Additive exPlanations (SHAP) values. Using SHAP values, the key features and their impact pattern on hypokalaemia risk were determined.
A total of 25,326 hypertensive participants were included for analysis, of whom 4,511 had known CVD. The Random Forest algorithm had the highest AUROC (hypertension dataset: 0.73 [95%CI, 0.71-0.76]; CVD subgroup: 0.72 [95%CI, 0.66-0.78]). Moreover, the nomogram based on the top twelve key features screened by random forest retained good performance: age, sex, race, poverty income ratio, body mass index, systolic and diastolic blood pressure, non-potassium-sparing diuretics use and duration, renin-angiotensin blockers use and duration, and CVD history in hypertension dataset; while in CVD subgroup, the additional key features were comorbid diabetes, education level, smoking status, and use of bronchodilators.
Our predictive model based on the random forest algorithm performed best among the tested and evaluated five algorithms. Hypokalaemia-associated key features have been identified in hypertensive patients and the subgroup with CVD. These findings from machine learning facilitate the development of artificial intelligence to highlight hypokalaemia risk in hypertension patients.
Our predictive model based on the random forest algorithm performed best among the tested and evaluated five algorithms, and hypokalemia-associated key features have been identified in hypertensive patients and the subgroup with cardiovascular disease.The nomogram we developed including twelve key features might be useful and applied in primary clinical consultations to identify the hypertensive patients at risk of hypokalaemia.These findings from machine learning facilitate the development of artificial intelligence to highlight hypokalaemia risk in hypertension patients.

Diuretics are commonly used for the treatment of hypertension. Yet, hypokalaemia is a well-recognised adverse effect. We conducted a retrospective study to evaluate the incidence of severe hypokalaemia, defined as requiring hospitalisation, among patients on indapamide.
We searched a territory-wide database, Clinical Data Analysis and Reporting System of the Hong Kong Hospital Authority. We traced all hypertensive patients who had been prescribed indapamide in 2007-2016 and all admissions due to hypokalaemia in 2007-2018. Factors associated with hospitalisation were studied using multivariable logistic regression.
During the period studied, 62,881 patients were started on indapamide and 509 (0.8%) were hospitalised for hypokalaemia. 53% of these hospitalisations occurred within the first year of treatment, and half of those in the first year occurred during the first 16 weeks. Female sex (adjusted OR, 1.75; 95%CI, 1.45-2.12) and immediate-release formulation (adjusted OR, 1.41; 95%CI, 1.14-1.75) were associated with hospitalisation. In the multivariable model, advanced age was not a significant predictor. There were no deaths during hospitalisation and the median length of hospital stay was one day.
In this large population-based study with 147,319 person-years of follow-up, severe hypokalaemia requiring hospitalisation was uncommon among hypertensive patients on indapamide. The risk is higher in women and in the initial weeks and months after starting therapy. The use of the sustained-release formulation reduces the risk. We conclude that using indapamide to treat hypertension is safe, even in the elderly, especially if the sustained-release formulation is used and electrolytes are monitored periodically.

This study investigated whether enhanced histone acetylation, achieved by inhibiting histone deacetylases (HDACs), could prevent decreased aquaporin-2 (AQP2) expression during hypokalaemia.
Male Wistar rats were fed a potassium-free diet with or without 4-phenylbutyric acid (4-PBA) or the selective HDAC3 inhibitor RGFP966 for 4 days. Primary renal inner medullary collecting duct (IMCD) cells and immortalized mouse cortical collecting duct (mpkCCD) cells were cultured in potassium-deprivation medium with or without HDAC inhibitors.
4-PBA increased the levels of AQP2 mRNA and protein in the kidney inner medullae in hypokalaemic (HK) rats, which was associated with decreased urine output and increased urinary osmolality. The level of acetylated H3K27 (H3K27ac) protein was decreased in the inner medullae of HK rat kidneys; this decrease was mitigated by 4-PBA. The H3K27ac levels were decreased in IMCD and mpkCCD cells cultured in potassium-deprivation medium. Decreased H3K27ac in the Aqp2 promoter region was associated with reduced Aqp2 mRNA levels. HDAC3 protein expression was upregulated in mpkCCD and IMCD cells in response to potassium deprivation, and the binding of HDAC3 to the Aqp2 promoter was also increased. RGFP966 increased the levels of H3K27ac and AQP2 proteins and enhanced binding between H3K27ac and AQP2 in mpkCCD cells. Furthermore, RGFP966 reversed the hypokalaemia-induced downregulation of AQP2 and H3K27ac and alleviated polyuria in rats. RGFP966 increased interstitial osmolality in the kidney inner medullae of HK rats but did not affect urinary cAMP levels.
HDAC inhibitors prevented the downregulation of AQP2 induced by potassium deprivation, probably by enhancing H3K27 acetylation.

Introduction: Hypokalaemia, defined as an extracellular concentration of K+ below 3.5 mM, can cause cardiac arrhythmias by triggered or re-entrant mechanisms. Whilst these effects have been reported in animal and human stem cell-based models, to date there has been no investigation in more complex structures such as the human ventricular cardiac anisotropic sheet (hvCAS). Here, we investigated arrhythmogenicity, electrophysiological, and calcium transient (CaT) changes induced by hypokalaemia using this bioengineered platform. Methods: An optical mapping technique was applied on hvCAS derived from human pluripotent stem cells to visualize electrophysiological and CaT changes under normokalaemic (5 mM KCl) and hypokalaemic (3 mM KCl) conditions. Results: Hypokalaemia significantly increased the proportion of preparations showing spontaneous arrhythmias from 0/14 to 7/14 (Fisher\'s exact test, p = 0.003). Hypokalaemia reduced longitudinal conduction velocity (CV) from 7.81 to 7.18 cm⋅s-1 (n = 9, 7; p = 0.036), transverse CV from 5.72 to 4.69 cm⋅s-1 (n = 12, 11; p = 0.030), prolonged action potential at 90% repolarization (APD90) from 83.46 to 97.45 ms (n = 13, 15; p < 0.001), increased action potential amplitude from 0.888 to 1.195 ΔF (n = 12, 14; p < 0.001) and CaT amplitude from 0.76 to 1.37 ΔF (n = 12, 13; p < 0.001), and shortened effective refractory periods from 242 to 165 ms (n = 12, 13; p < 0.001). Conclusion: Hypokalaemia exerts pro-arrhythmic effects on hvCAS, which are associated with alterations in CV, repolarization, refractoriness, and calcium handling. These preparations provide a useful platform for investigating electrophysiological substrates and for conducting arrhythmia screening.

OBJECTIVE: To compare the effectiveness of dynamic stratified potassium supplementation at high concentrations with enteral potassium supplementation in older patients with chronic heart failure and moderate to severe hypokalaemia.
METHODS: We performed a single-centre, short-term, randomised, controlled, open-labelled, clinical trial, and patients were randomly allocated to the control or intervention group. The intervention group received intermittent infusions of 30 mmol/100 mL potassium chloride. In the control group, 10% potassium chloride was administered orally in a bolus dose. Short-term efficacy and adverse events were compared.
RESULTS: The intervention group received less potassium than that in the control group. T-wave normalisation and U-wave disappearance occurred sooner in the intervention group than in the control group after potassium supplementation. The rate of increase in potassium concentrations gradually became similar in both groups. The initial blood potassium concentration, method of potassium supplementation, potassium supplement dose, and 24-hour urinary potassium excretion significantly affected the rate of increase in blood potassium concentrations after supplementation.
CONCLUSIONS: The efficacy of enteral potassium supplementation is equivalent to that of supplementation with high intravenous potassium concentrations in elderly patients with chronic heart failure and moderate to severe hypokalaemia. High intravenous potassium concentrations may lead to a superior potassium recovery rate.

BACKGROUND: Liddle syndrome is an autosomal dominant hereditary disease caused by a single gene mutation. Typical clinical manifestations are early-onset hypertension and hypokalaemia and can be treated using ENaC blockers (amiloride and aminopterin).
METHODS: This report describes a 17-year-old male with hypertension and hypokalaemia. We performed a Captopril inhibition test and a postural stimulation test for the diagnosis and typing of primary aldosteronism.
RESULTS: The serum renin was low, and aldosterone was high, so the patient was initially misdiagnosed as primary aldosteronism. After a genetic analysis, a diagnosis of Liddle syndrome was made due to the presence of an SCNN1B p.Pro617Ser mutation. After diagnosis, the patient was administered one tablet of amiloride twice a day (each tablet contains 2.5mg of amiloride hydrochloride and 25mg of hydrochlorothiazide 25mg). The patient\'s blood pressure (average of 120-135/70-80mmHg) and serum potassium levels (3.6-4.0mmol/L) returned to normal and were well-controlled after treatment.
CONCLUSIONS: The patient is an atypical case of Liddle syndrome; genetic analysis is helpful and essential for diagnosis.

BACKGROUND: Manifestations of hypokalaemia in ectopic adrenocorticotropic hormonesyndrome(EAS) vary from mild muscle weakness to life-threatening arrhythmia. Herein, we present a rare case of EAS with concomitant rhabdomyolysis(RM) as a result of intractable hypokalaemia.
METHODS: A 64-year-old man was admitted for limb weakness and facial hyperpigmentation for 2 weeks. Lab tests revealed intractable hypokalaemia (lowest at 1.8 mmol/L) and metabolic alkalosis. The diagnosis of RM was based on a creatine kinase(CK)level of 5 times the upper limit. The elevated CK and myohemoglobin (Mb) levels returned to within the normal range after the alleviation of hypokalaemia. The patient was diagnosed with ACTH-dependent Cushing\'s syndrome (CS) based on unsuppressed serum cortisol after a low-dose dexamethasone suppression test(LDDST) and remarkably elevated ACTH levels. The diagnosis of EAS was made based on the results of a high-dose dexamethasone suppression test(HDDST) and bilateral inferior petrosal sinus sampling(BIPSS). Multiple lymph nodes in the left supraclavicular fossa, right root of neck, mediastinum and bilateral hili of the lung were found with abnormal uptake of 68Ga-DOTA-NOC. Mediastinoscopic lymph node biopsy was performed. The pathological diagnosis was small-cell and large-cell neuroendocrine carcinoma with positive ACTH staining. The patient was prescribed mifepristone and received one cycle of chemotherapy. The patient could not tolerate subsequent chemotherapy and died of dyscrasia.
CONCLUSIONS: RM is a rare complication of EAS with insidious onset and atypical clinical manifestations. Serum potassium levels should be vigilantly monitored to avoid RM in EAS.

Potassium is the predominant intracellular cation, with its extracellular concentrations maintained between 3. 5 and 5 mM. Among the different potassium disorders, hypokalaemia is a common clinical condition that increases the risk of life-threatening ventricular arrhythmias. This review aims to consolidate pre-clinical findings on the electrophysiological mechanisms underlying hypokalaemia-induced arrhythmogenicity. Both triggers and substrates are required for the induction and maintenance of ventricular arrhythmias. Triggered activity can arise from either early afterdepolarizations (EADs) or delayed afterdepolarizations (DADs). Action potential duration (APD) prolongation can predispose to EADs, whereas intracellular Ca2+ overload can cause both EADs and DADs. Substrates on the other hand can either be static or dynamic. Static substrates include action potential triangulation, non-uniform APD prolongation, abnormal transmural repolarization gradients, reduced conduction velocity (CV), shortened effective refractory period (ERP), reduced excitation wavelength (CV × ERP) and increased critical intervals for re-excitation (APD-ERP). In contrast, dynamic substrates comprise increased amplitude of APD alternans, steeper APD restitution gradients, transient reversal of transmural repolarization gradients and impaired depolarization-repolarization coupling. The following review article will summarize the molecular mechanisms that generate these electrophysiological abnormalities and subsequent arrhythmogenesis.