Thiazides and the risk of hypokalemia in the general population

Effects of thiazides and new findings on kidney stones and dysglycemic side effects

Thiazide and thiazide-like diuretics (thiazides) belong to the most frequently prescribed drugs worldwide. By virtue of their natriuretic and vasodilating properties, thiazides effectively lower blood pressure and prevent adverse cardiovascular outcomes. In addition, through their unique characteristic of reducing urine calcium, thiazides are also widely employed for the prevention of kidney stone recurrence and reduction of bone fracture risk. Since their introduction into clinical medicine in the early 1960s, thiazides have been recognized for their association with metabolic side effects, particularly impaired glucose tolerance, and new-onset diabetes mellitus. Numerous hypotheses have been advanced to explain thiazide-induced glucose intolerance, yet underlying mechanisms remain poorly defined. Regrettably, the lack of understanding and unpredictability of these side effects has prompted numerous physicians to refrain from prescribing these effective, inexpensive, and widely accessible drugs. In this review, we outline the pharmacology and mechanism of action of thiazides, highlight recent advances in the understanding of thiazide-induced glucose intolerance, and provide an up-to-date discussion on the role of thiazides in kidney stone prevention.

Renal upregulation of NCC counteracts empagliflozin-mediated NHE3 inhibition in normotensive but not in hypertensive male rat

Sodium-glucose cotransporter-2 inhibitors (SGLT2i) reduce blood pressure (BP) in patients with hypertension, yet the precise molecular mechanisms remain elusive. SGLT2i inhibits proximal tubule (PT) NHE3-mediated sodium reabsorption in normotensive rodents, yet no hypotensive effect is observed under this scenario. This study examined the effect of empagliflozin (EMPA) on renal tubular sodium transport in normotensive and spontaneously hypertensive rats (SHRs). It also tested the hypothesis that EMPA-mediated PT NHE3 inhibition in normotensive rats is associated with upregulation of distal nephron apical sodium transporters. EMPA administration for 14 days reduced BP in 12-wk-old SHRs but not in age-matched Wistar rats. PT NHE3 activity was inhibited by EMPA treatment in both Wistar and SHRs. In Wistar rats, EMPA increased NCC activity, mRNA expression, protein abundance, and phosphorylation levels, but not in SHRs. SHRs showed higher NKCC2 activity and an abundance of cleaved ENaC α and γ subunits compared with Wistar rats, none of which were affected by EMPA. Another set of male Wistar rats was treated with EMPA, the NCC inhibitor hydrochlorothiazide (HCTZ), and EMPA combined with HCTZ or vehicle for 14 days. In these rats, BP reduction was observed only with combined EMPA and HCTZ treatment, not with either drug alone. These findings suggest that NCC upregulation counteracts EMPA-mediated inhibition of PT NHE3 in male normotensive rats, maintaining their baseline BP. Moreover, the reduction of NHE3 activity without further upregulation of major apical sodium transporters beyond the PT may contribute to the BP-lowering effect of SGLT2i in experimental models and patients with hypertension.NEW & NOTEWORTHY This study suggests that reduced NHE3-mediated sodium reabsorption in the renal proximal tubule may account, at least in part, for the BP-lowering effect of SGLT2 inhibitors in the setting of hypertension. It also demonstrates that chronic treatment with SGLT2 inhibitors upregulates NCC activity, phosphorylation, and expression in the distal tubule of normotensive but not hypertensive rats. SGLT2 inhibitor-mediated upregulation of NCC seems crucial to counteract proximal tubule natriuresis in subjects with normal BP.

Strategies for Identifying Patients for Deprescribing of Blood Pressure Medications in Routine Practice: An Evidence Review

PURPOSE OF REVIEW

To summarise the evidence regarding which patients might benefit from deprescribing antihypertensive medications.

RECENT FINDINGS

Older patients with frailty, multi-morbidity and subsequent polypharmacy are at higher risk of adverse events from antihypertensive treatment, and therefore may benefit from antihypertensive deprescribing. It is possible to examine an individual's risk of these adverse events, and use this to identify those people where the benefits of treatment may be outweighed by the harms. While such patients might be considered for deprescribing, the long-term effects of this treatment strategy remain unclear. Evidence now exists to support identification of those who are at risk of adverse events from antihypertensive treatment. These patients could be targeted for deprescribing interventions, although the long-term benefits and harms of this approach are unclear.

PERSPECTIVES

Randomised controlled trials are still needed to examine the long-term effects of deprescribing in high-risk patients with frailty and multi-morbidity.

Risk factors for hypokalemia and its association with postoperative recovery in patients scheduled for radical gastrectomy: a retrospective study

BACKGROUND

Hypokalemia is common in patients of various operations, especially gastrointestinal surgery, which seriously affects the safety and enhanced recovery after surgery. Our study aims to explore the risk factors of preoperative hypokalemia of radical gastrectomy for gastric cancer and analyze its impact on postoperative recovery.

METHODS

A total of 122 patients scheduled for radical gastrectomy from September, 2022 to December, 2022 were retrospectively analyzed. According to the serum potassium level before skin incision, patients were divided into hypokalemia group (n = 64) and normokalemia group (n = 58). Factors including age, gender, BMI, ASA classification, glutamic pyruvic transaminase (ALT), glutamic oxaloacetic transaminase (AST), creatinine, blood urea nitrogen (BUN), albumin, hypertension history, whether taking calcium channel blockers, β-receptor blockers, angiotensin converting enzyme inhibitors (ACEI) or angiotensin receptor antagonist (ARB), thiazide diuretics and other drugs, anemia history, diabetes mellitus history, inability to eat or intestinal obstruction, vomiting, diarrhea, hypokalemia on admission and whether under cooperation with clinical nurse specialist were compared between groups. Univariate logistic regression analysis was used to determine risk factors for hypokalemia with p < 0.2 included as a cutoff. Multivariate logistic regression was used to analyze the influencing factors of preoperative hypokalemia for the indicators with differences. A receiver operating characteristic (ROC) curve was used to evaluate the efficacy of the regression model. Primary exhaust time and defecation time after surgery were compared between the two groups.

RESULTS

The use of ACEI or ARB [OR 0.08, 95% CI (0.01 to 0.58), p = 0.012] and thiazide diuretics [OR 8.31, 95% CI (1.31 to 52.68), p = 0.025], inability to eat for more than 3 days or intestinal obstruction [OR 17.96, 95% CI (2.16 to 149.43), p = 0.008], diarrhea for more than 48 h [OR 6.21, 95% CI (1.18 to 32.61), p = 0.031] and hypokalemia on admission [OR 8.97, 95% CI (1.05 to 77.04), p = 0.046] were independent influencing factors of hypokalemia before skin incision. Primary postoperative exhaust time and defecation time was significantly longer in the hypokalemia group than in the normokalemia group, no matter after laparoscopic radical gastrectomy (p = 0.044, p = 0.045, respectively) or open radical gastrectomy (p = 0.033, p = 0.019, respectively).

CONCLUSION

Early attention and management of serum potassium in patients undergoing radical gastrectomy can better reduce perioperative adverse reactions and promote recovery of gastrointestinal function.

TRPV4 expression in the renal tubule is necessary for maintaining whole body K+ homeostasis

The Ca2+-permeable transient receptor potential vanilloid type 4 (TRPV4) channel serves as the sensor of tubular flow, thus being well suited to govern mechanosensitive K+ transport in the distal renal tubule. Here, we directly tested whether the TRPV4 function is significant in affecting K+ balance. We used balance metabolic cage experiments and systemic measurements with different K+ feeding regimens [high (5% K+), regular (0.9% K+), and low (<0.01% K+)] in newly created transgenic mice with selective TRPV4 deletion in the renal tubule (TRPV4fl/fl-Pax8Cre) and their littermate controls (TRPV4fl/fl). Deletion was verified by the absence of TRPV4 protein expression and lack of TRPV4-dependent Ca2+ influx. There were no differences in plasma electrolytes, urinary volume, and K+ levels at baseline. In contrast, plasma K+ levels were significantly elevated in TRPV4fl/fl-Pax8Cre mice on high K+ intake. K+-loaded knockout mice exhibited lower urinary K+ levels than TRPV4fl/fl mice, which was accompanied by higher aldosterone levels by day 7. Moreover, TRPV4fl/fl-Pax8Cre mice had more efficient renal K+ conservation and higher plasma K+ levels in the state of dietary K+ deficiency. H+-K+-ATPase levels were significantly increased in TRPV4fl/fl-Pax8Cre mice on a regular diet and especially on a low-K+ diet, pointing to augmented K+ reabsorption in the collecting duct. Consistently, we found a significantly faster intracellular pH recovery after intracellular acidification, as an index of H+-K+-ATPase activity, in split-opened collecting ducts from TRPV4fl/fl-Pax8Cre mice. In summary, our results demonstrate an indispensable prokaliuretic role of TRPV4 in the renal tubule in controlling K+ balance and urinary K+ excretion during variations in dietary K+ intake. NEW & NOTEWORTHY The mechanoactivated transient receptor potential vanilloid type 4 (TRPV4) channel is expressed in distal tubule segments, where it controls flow-dependent K+ transport. Global TRPV4 deficiency causes impaired adaptation to variations in dietary K+ intake. Here, we demonstrate that renal tubule-specific TRPV4 deletion is sufficient to recapitulate the phenotype by causing antikaliuresis and higher plasma K+ levels in both states of K+ load and deficiency.

Nalfurafine, a G-Protein-Biased KOR (Kappa Opioid Receptor) Agonist, Enhances the Diuretic Response and Limits Electrolyte Losses to Standard-of-Care Diuretics

Nalfurafine is a G-protein-biased KOR (kappa opioid receptor) agonist that produces analgesia and lacks central nervous system adverse effects. Here, we examined the cardiovascular and renal responses to intravenous and oral nalfurafine alone and in combination with furosemide, hydrochlorothiazide, or amiloride. We hypothesized that nalfurafine, given its distinct mechanism of vasopressin inhibition, would increase urine output to these diuretics and limit electrolyte loss. Following catheterization, conscious Sprague-Dawley rats received an isotonic saline infusion and were then administered an intravenous bolus of nalfurafine, a diuretic, or a combination. Mean arterial pressure, heart rate, and urine output were recorded for 90 minutes. In another study, rats were placed in metabolic cages and administered drug in an oral volume load. Hourly urine samples were then collected for 5 hours. Intravenous and oral nalfurafine produced a marked diuresis, antinatriuresis, antikaliuresis, and a decrease in mean arterial pressure. Compared with diuretic treatment alone, intravenous coadministration with nalfurafine significantly increased urine output to furosemide and hydrochlorothiazide and decreased sodium and potassium excretion. Notably, mean arterial pressure was reduced with nalfurafine/diuretic combination therapy compared to diuretics alone. Similarly, oral coadministration of nalfurafine significantly increased urine output to hydrochlorothiazide and decreased sodium and potassium excretion, whereas combination with furosemide only limited the amount of sodium excreted. Further, both intravenous and oral coadministration of nalfurafine enhanced the diuresis to amiloride and decreased sodium excretion. Together, these findings demonstrate that nalfurafine enhances the diuresis to standard-of-care diuretics without causing an excessive loss of electrolytes, offering a new approach to treat several cardiovascular conditions.

Impact of plasma potassium normalization on short-term mortality in patients with hypertension and hypokalemia or low normal potassium

Background

Hypokalemia is common in patients treated with antihypertensive drugs, but the impact of correcting hypokalemia is insufficiently studied. We examined the consequences of hypokalemia and borderline hypokalemia correction in patients with hypertension.

Methods

We identified 8976 patients with hypertension and plasma potassium concentrations ≤3.7 mmol/L within 100 days from combination antihypertensive therapy initiation. The first measurement between 6 and 100 days after the episode with potassium ≤3.7 mmol/L was retained. We investigated all-cause and cardiovascular mortality within 60-days from the second potassium measurement using Cox regression. Mortality was examined for seven predefined potassium intervals derived from the second measurement: 1.5–2.9 mmol/L (n = 271), 3.0–3.4 mmol/L (n = 1341), 3.5–3.7 (n = 1982) mmol/L, 3.8–4.0 mmol/L (n = 2398, reference), 4.1–4.6 mmol/L (n = 2498), 4.7–5.0 mmol/L (n = 352) and 5.1–7.1 mmol/L (n = 134).

Results

Multivariable analysis showed that potassium concentrations 1.5–2.9 mmol/L, 3.0–3.4 mmol/L, 4.7–5.0 mmol/L and 5.1–7.1 mmol/L were associated with increased all-cause mortality (HR 2.39, 95% CI 1.66–3.43; HR 1.36, 95% CI 1.04–1.78; HR 2.36, 95% CI 1.68–3.30 and HR 2.62, 95% CI 1.73–3.98, respectively). Potassium levels <3.0 and > 4.6 mmol/L were associated with increased cardiovascular mortality. The adjusted standardized 60-day mortality risks in the seven strata were: 11.7% (95% CI 8.3–15.0%), 7.1% (95% CI 5.8–8.5%), 6.4% (95% CI 5.3–7.5%), 5.4% (4.5–6.3%), 6.3% (5.4–7.2%), 11.6% (95% CI 8.7–14.6%) and 12.6% (95% CI 8.2–16.9%), respectively.

Conclusions

Persistent hypokalemia was frequent and associated with increased all-cause and cardiovascular mortality. Increase in potassium to levels > 4.6 mmol/L in patients with initial hypokalemia or low normal potassium was associated with increased all-cause and cardiovascular mortality.

Predictors of Hyperkalemia and Hypokalemia in Individuals with Diabetes: a Classification and Regression Tree Analysis

BACKGROUND

Both hyperkalemia and hypokalemia can lead to cardiac arrhythmias and are associated with increased mortality. Information on the predictors of potassium in individuals with diabetes in routine clinical practice is lacking.

OBJECTIVE

To identify predictors of hyperkalemia and hypokalemia in adults with diabetes.

DESIGN

Retrospective cohort study, with classification and regression tree (CART) analysis.

PARTICIPANTS

321,856 individuals with diabetes enrolled in four large integrated health care systems from 2012 to 2013.

MAIN MEASURES

We used a single serum potassium result collected in 2012 or 2013. Hyperkalemia was defined as a serum potassium ≥ 5.5 mEq/L and hypokalemia as < 3.5 mEq/L. Predictors included demographic factors, laboratory measurements, comorbidities, medication use, and health care utilization.

KEY RESULTS

There were 2556 hypokalemia events (0.8%) and 1517 hyperkalemia events (0.5%). In univariate analyses, we identified concordant predictors (associated with increased probability of both hyperkalemia and hypokalemia), discordant predictors, and predictors of only hyperkalemia or hypokalemia. In CART models, the hyperkalemia "tree" had 5 nodes and a c-statistic of 0.76. The nodes were defined by prior potassium results and eGFRs, and the 5 terminal "leaves" had hyperkalemia probabilities of 0.2 to 7.2%. The hypokalemia tree had 4 nodes and a c-statistic of 0.76. The hypokalemia tree included nodes defined by prior potassium results, and the 4 terminal leaves had hypokalemia probabilities of 0.3 to 17.6%. Individuals with a recent potassium between 4.0 and 5.0 mEq/L, eGFR ≥ 45 mL/min/1.73m², and no hypokalemia in the previous year had a < 1% rate of either hypokalemia or hyperkalemia.

CONCLUSIONS

The yield of routine serum potassium testing may be low in individuals with a recent serum potassium between 4.0 and 5.0 mEq/L, eGFR ≥ 45 mL/min/1.73m², and no recent history of hypokalemia. We did not examine the effect of recent changes in clinical condition or medications on acute potassium changes.

Redefining diuretics use in hypertension: why select a thiazide-like diuretic?

Diuretics are listed in hypertension guidelines as one of three equally weighted first-line treatment options. In order to differentiate between antihypertensives, a lot of discussion has been directed at side effect profiles and as a result, has created a perhaps disproportionate fear of the metabolic effects that can be associated with diuretics. Data, however, show that the risk of a clinically meaningful change in laboratory parameters is very low, whereas the benefits of volume control and natriuresis are high and the reductions in morbidity and mortality are clinically significant. Moreover, as clinically significant differences in safety and efficacy profiles exist among diuretics, several international guidelines have started making a distinction between thiazides (hydrochlorothiazide) and thiazide-like (chlorthalidone, indapamide) diuretics; and some of them now recommend longer acting thiazide-like diuretics. In time, pending more data, chlorthalidone and indapamide may need to be subdivided further into separate classifications.

Risk of Developing Hypokalemia in Patients With Hypertension Treated With Combination Antihypertensive Therapy

Little is known about the occurrence of hypokalemia due to combination therapy for hypertension. Using data from Danish administrative registries, we investigated the association between different combinations of antihypertensive therapy and risk of developing hypokalemia. Using incidence density matching, 2 patients without hypokalemia were matched to a patient with hypokalemia (K, <3.5 mmol/L) on age, sex, renal function, and time between index date and date of potassium measurement. Combination therapies were subdivided into 10 groups including β-blockers (BB)+thiazides (BB+thiazides), calcium channel blockers (CCB)+renin angiotensin system inhibitors (RASi)+thiazides (CCB+RASi+Thiazides), calcium channel blockers+thiazides (CCB+thiazides), and β-blockers+renin angiotensin system inhibitors+thiazides (BB+RASi+thiazides). We used conditional logistic regression to estimate the odds of developing hypokalemia for different combinations of antihypertensive drugs within 90 days of combination therapy initiation. We matched 463 patients with hypokalemia to 926 patients with normal potassium concentrations. The multivariable analysis showed 5.82× increased odds of developing hypokalemia if administered CCB+thiazides (95% CI, 3.06–11.08) compared with CCB+RASi. Other combinations significantly associated with increased hypokalemia odds were BB+thiazides (odds ratio, 3.34 [95% CI, 1.67–6.66]), CCB+RASi+thiazides (odds ratio, 3.07 [95% CI, 1.72–5.46]), and BB+RASi+thiazides (odds ratio, 2.78 [95% CI, 1.41–5.47]). Combinations of thiazides with CCB, RASi, or BB were strongly associated with increased hypokalemia risk within 90 days of treatment initiation.

Prevalence and risk factors for hypokalemia in patients scheduled for laparoscopic colorectal resection and its association with post-operative recovery

Background

Perioperative serum potassium levels are closely associated with postoperative clinical outcomes after gastrointestinal surgery. The aim of our retrospective study was to identify the prevalence and risk factors for preoperative hypokalemia (before pneumoperitoneum) and to evaluate the influence of preoperative hypokalemia on the recovery of postoperative gastrointestinal function.

Methods

In this retrospective study, patients scheduled for laparoscopic colorectal resection from November 11 2014 to October 20 2016, were considered for inclusion. A blood potassium level between 3.5 and 5.5 mmol/L was defined as normal, with levels between 3.0 to 3.5 mmol/L, 2.5 to 3.0 mmol/L and < 2.5 mmol/L considered as slight, moderate, and severe level of hypokalemia. The factors including age, gender, ASA grade, BMI, hypertension, diabetes, anti-hypertension drugs, lactose oral soluble, oral cathartics, oral cathartics, cathartic enemas, and blood potassium level before gastrointestinal preparation which might be associated with blood potassium level before pneumoperitoneum were analysed. The time to postoperative first flatus (FFL) and first feces (FFE) was compared between patients with and without hypokalemia.

Results

The final analysis was based on the data of 108 patients. Hypokalemia was identified in 70.37% patients, with the following distribution of blood potassium levels before pneumoperitoneum: slight, 49 (45.37%) patients; moderate, 23 (21.30%); and severe, 4 (3.70%) patients. Hypokalemia was significantly associated with hypertension and the use of ≥2 types of oral cathartics for preoperative gastrointestinal preparation. With treatment, potassium levels recovered to normal levels in all patients within 48 h postoperatively. Hypokalemia was associated with a longer postoperative time to first feces, compared to patients with a normal potassium level before pneumoperitoneum.

Conclusions

Our findings underlie the importance of early monitoring and management of serum potassium levels in these patients.

Hypokalemia during antibiotic treatment for bone and joint infections

PURPOSE

During treatment of bone and joint infections (BJIs) with multiple antibiotic therapy, hypokalemia has been reported as a rare side effect. The aim of this study was to evaluate incidence and risk factors for hypokalemia in a cohort of patients treated with multidrug therapy for BJIs, in a single center.

METHODS

We retrospectively reviewed 331 clinical files of 150 consecutive patients (65% males; median age 59 years, 95% CI 55-62) admitted repeatedly to our Osteomyelitis Department for treatment of chronic BJIs. Besides surgical debridement, patients received a combination of oral and intravenous antibiotics. Routine laboratory tests were performed at admittance and repeated at least weekly. Possible hypokalemia risk factors were recorded and analyzed.

RESULTS

Progressive kalemia reduction occurred in > 39% of patients during hospitalization; prevalence of marked hypokalemia (K ⁺ < 3.5 mEq/l) increased from 5% at admission to 11% (up to 22%) at day 14. Correlated factors were: age ≥ 68 years (p = 0.033), low serum albumin (p = 0.034), treatment with vancomycin (p < 0.001), rifampicin (p = 0.017) and ciprofloxacin (p < 0.001) and use of thiazide (p = 0.007) or loop diuretics (p = 0.029 for K ⁺ < 3.5 mEq/l). At multivariate regression analysis, the main determinants of hypokalemia were simultaneous use of diuretics (p = 0.007) and older age (p < 0.049).

CONCLUSIONS

Appearance of severe hypokalemia is a frequent event among patients treated for BJIs with multiple antibiotic therapy, when this is prescribed in older age patients and associated with simultaneous use of diuretics. Due to possible increase in mortality risk in the short term, particular caution should be paid during intensive antibiotic treatment in these groups of patients.

Prevalence of hypokalemia before and after bowel preparation for colonoscopy in high-risk patients

BACKGROUND AND AIMS

Bowel preparation for colonoscopy should not cause significant shifts in systemic electrolyte concentrations. We recently encountered 2 cases of severe postcolonoscopy hypokalemia with fatal consequences, prompting us to conduct a study to explore the magnitude of and risk factors for hypokalemia associated with bowel preparation. We paid specific attention to higher-risk subgroups, in particular, diuretic users, hospitalized patients, and patients estimated to be at high risk by the gastroenterologist.

METHODS

From January 1 to December 31, 2014, we included all patients at risk for hypokalemia (diuretic users, hospitalized patients, and patients estimated at high risk by the gastroenterologist) who underwent colonoscopy at our institution. We measured serum potassium levels before low-volume polyethylene glycol bowel preparation for colonoscopy. In a subset of patients who had normal serum potassium levels before bowel cleansing, serum potassium levels after bowel cleansing also were measured.

RESULTS

In total, 5515 colonoscopies were performed, including 1822 procedures in diuretic users or hospitalized patients. Of these, 77 (4.2%) patients had hypokalemia before bowel cleansing. A logistic regression model showed that hospitalized patients were more likely to have hypokalemia than non-hospitalized patients. 301 patients with normal potassium levels had potassium controls after bowel cleansing, of whom 71 (23.6%) developed hypokalemia. A logistic regression model showed that diuretic users were more likely to develop hypokalemia than those who did not use diuretics.

CONCLUSIONS

Hypokalemia is frequently encountered after low-volume polyethylene glycol bowel cleansing in high-risk patients. Additional large-scale studies are needed on the prevalence of hypokalemia in unselected populations undergoing bowel cleansing and on the occurrence of potentially very serious side effects in order to decide on screening of high-risk groups in daily clinical practice. (Clinical trial registration number: NTR5400.).

Role of abnormal repolarization in the mechanism of cardiac arrhythmia

In cardiac patients, life-threatening tachyarrhythmia is often precipitated by abnormal changes in ventricular repolarization and refractoriness. Repolarization abnormalities typically evolve as a consequence of impaired function of outward K⁺ currents in cardiac myocytes, which may be caused by genetic defects or result from various acquired pathophysiological conditions, including electrical remodelling in cardiac disease, ion channel modulation by clinically used pharmacological agents, and systemic electrolyte disorders seen in heart failure, such as hypokalaemia. Cardiac electrical instability attributed to abnormal repolarization relies on the complex interplay between a provocative arrhythmic trigger and vulnerable arrhythmic substrate, with a central role played by the excessive prolongation of ventricular action potential duration, impaired intracellular Ca²⁺ handling, and slowed impulse conduction. This review outlines the electrical activity of ventricular myocytes in normal conditions and cardiac disease, describes classical electrophysiological mechanisms of cardiac arrhythmia, and provides an update on repolarization-related surrogates currently used to assess arrhythmic propensity, including spatial dispersion of repolarization, activation-repolarization coupling, electrical restitution, TRIaD (triangulation, reverse use dependence, instability, and dispersion), and the electromechanical window. This is followed by a discussion of the mechanisms that account for the dependence of arrhythmic vulnerability on the location of the ventricular pacing site. Finally, the review clarifies the electrophysiological basis for cardiac arrhythmia produced by hypokalaemia, and gives insight into the clinical importance and pathophysiology of drug-induced arrhythmia, with particular focus on class Ia (quinidine, procainamide) and Ic (flecainide) Na⁺ channel blockers, and class III antiarrhythmic agents that block the delayed rectifier K⁺ channel (dofetilide).

Community-acquired hypokalemia in elderly patients: related factors and clinical outcomes

PURPOSE

Electrolyte imbalance is a common problem affecting the elderly. Increased number of comorbidities and frequent use of drugs may contribute to increased risk of hypokalemia in the elderly. This study was performed to investigate the prevalence of community-acquired hypokalemia (CAH), risk factors for its development, related factors with hypokalemia, and morbidities and all-cause mortality rates (MR) of CAH in the elderly patients.

METHODS

Total of 36,361 patients aged above 65 years were screened retrospectively. Group 1 consisted of 269 elderly patients with potassium level ≤3.5 mmol/L, and group 2 (control group) consisted of 182 subjects with potassium level between 3.6 and 5.5 mmol/L. Etiologic factors of CAH, presence of comorbidities, duration of hospital stay, hospital cost, and clinical outcomes were recorded.

RESULTS

Prevalence of hypokalemia was found 3.24% in patients aged above 65 years. Duration of hospital stay, presence of ≥2 comorbid diseases, hospital cost, and MR were significantly higher in group 1 compared to group 2 (p < 0.001 for all). Loop diuretics, hydrochlorothiazides, beta agonists, inadequate oral intake, and female gender were all independent risk factors for CAH in elderly patients. Patients with ≥2 comorbid diseases were found to have greater risk of hypokalemia than the patients with <2 comorbidities.

CONCLUSIONS

Length of hospital stay, hospital cost, and MR were higher in elderly with CAH. Female gender, hydrochlorothiazides, loop diuretics, and ≥2 comorbid diseases are the leading risk factors associated with CAH in elderly.

Hydrochlorothiazide Potentiates Contractile Activity of Mouse Cavernosal Smooth Muscle

Introduction

Hydrochlorothiazide has a negative influence on penile erection but little is known about the mechanism(s) involved.

Aims

To characterize the effects of this diuretic on mouse corpus cavernosum (CC) smooth muscle in vitro and ex vivo.

Methods

CC strips of C57BL/6 mice (12–16 weeks old) were mounted in organ baths containing Krebs-Henseleit solution and tissue reactivity was evaluated. Expression of genes encoding diuretic targets and enzymes involved in penile erection were evaluated by polymerase chain reaction.

Main Outcome Measures

Stimulation-response curves to phenylephrine (10 nmol/L–100 μmol/L) or to electrical field stimulation (1–32 Hz) were constructed, with or without hydrochlorothiazide. Strips of CC from mice after long-term hydrochlorothiazide treatment (6 mg/kg/day for 4 weeks) with or without amiloride (0.6 mg/kg/day for 4 weeks) in vivo also were studied. Nitric oxide and Rho-kinase pathways were evaluated.

Results

Hydrochlorothiazide (100 μmol/L) increased the maximum response to phenylephrine by 64% in vitro. This effect was unaffected by the addition of indomethacin (5 μmol/L) but was abolished by N(^ω)-nitro-L-arginine methyl ester (100 μmol/L). Hydrochlorothiazide (100 μmol/L) potentiated electrical field stimulation-induced contraction in vitro, but not ex vivo. Long-term treatment with hydrochlorothiazide increased the maximum response to phenylephrine by 60% and resulted in a plasma concentration of 500 ± 180 nmol/L. Amiloride (100μmol/L) caused rightward shifts in concentration-response curves to phenylephrine in vitro. Long-term treatment with hydrochlorothiazide plus amiloride did not significantly increase the maximum response to phenylephrine (+13%). Reverse transcriptase polymerase chain reaction did not detect the NaCl cotransporter in mouse CC. Hydrochlorothiazide did not change Rho-kinase activity, whereas amiloride decreased it in vitro and ex vivo (approximately 18% and 24% respectively). A 40% decrease in Rock1 expression also was observed after long-term treatment with hydrochlorothiazide plus amiloride.

Conclusion

Hydrochlorothiazide potentiates contraction of smooth muscle from mouse CC. These findings could explain why diuretics such as hydrochlorothiazide are associated with erectile dysfunction.

The Rotterdam Study: 2016 objectives and design update

The Rotterdam Study is a prospective cohort study ongoing since 1990 in the city of Rotterdam in The Netherlands. The study targets cardiovascular, endocrine, hepatic, neurological, ophthalmic, psychiatric, dermatological, otolaryngological, locomotor, and respiratory diseases. As of 2008, 14,926 subjects aged 45 years or over comprise the Rotterdam Study cohort. The findings of the Rotterdam Study have been presented in over 1200 research articles and reports (see www.erasmus-epidemiology.nl/rotterdamstudy ). This article gives the rationale of the study and its design. It also presents a summary of the major findings and an update of the objectives and methods.

Diuretics and bioimpedance-measured fluid spaces in hypertensive patients

The authors examined the relationship between thiazide-type diuretics and fluid spaces in a cohort of hypertensive patients in a retrospective study of 60 stable hypertensive patients without renal abnormalities who underwent whole-body bioimpedance analysis. Overhydration was greater in the diuretic group, but only to a nonsignificant degree (5.9 vs. 2.9%; P=.21). The total body water did not differ in the two groups (41.8 L vs. 40.5 L; P=.64). Extracellular fluid volume (ECV) (19.7 L vs. 18.5 L; P=.35) and intracellular fluid volume (ICV) spaces (20.8 L vs. 21.3 L; P=.75) were also not significantly different in the two groups. The ratio of ICV:ECV, however, appeared different: 1.05 vs 1.15 (P=.017) and the effect was maintained in the linear regression-adjusted model (β coefficient: -0.143; P=.001). The diuretic-related distortion of ICV:ECV ratio indicates potential fluid redistribution in hypertensive patients, with ICV participating in the process.