Tolvaptan and Neurocognitive Function in Mild to Moderate Chronic Hyponatremia: A Randomized Trial (INSIGHT)

Mild Hyponatremia Is Not Associated With Degradation of Trabecular Bone Microarchitecture Despite Bone Mass Loss

CONTEXT

Hyponatremia is associated with increased risk of osteoporosis and fractures. The impact of hyponatremia on noninvasive indices of bone quality, however, is unknown.

OBJECTIVE

To evaluate whether trabecular bone microarchitecture, assessed noninvasively by trabecular bone score (TBS), is altered in patients with hyponatremia.

METHODS

We conducted a cross-sectional analysis of the population-based 2005-2008 cycles of the National Health and Nutrition Examination Survey, in which TBS measurement was performed. The main outcome measures were TBS values and bone mineral density (BMD) T-scores at the lumbar spine, total hip and femoral neck.

RESULTS

A total of 4204 subjects aged 50 years or older were included (4041 normonatremic, 163 hyponatremic-90.8% with mild hyponatremia). Univariate analyses did not show any difference in TBS between patients with and without hyponatremia (1.308 ± 0.145 vs 1.311 ± 0.141, P = .806). Hyponatremic subjects had lower BMD T-score at total hip (-0.70 ± 1.46 vs -0.13 ± 1.32, P < .001) and femoral neck (-1.11 ± 1.26 vs -0.72 ± 1.14, P = .004), while no difference was observed at lumbar spine (-0.27 ± 1.63 vs -0.31 ± 1.51, P = .772). After adjustment for relevant confounders, hyponatremia was confirmed as an independent predictor of lower BMD T-score at the total hip (β = -0.20, 95% confidence interval [CI]: [-0.39, -0.02], P = .029), while the significance was lost at the femoral neck (P = .308). Again, no association between hyponatremia and lumbar spine BMD (P = .236) or TBS (P = .346) was observed.

CONCLUSION

Hyponatremia, at least in mild forms, is not associated with a degradation of trabecular microarchitecture, assessed noninvasively by TBS. An independent association between hyponatremia and loss of bone mass is confirmed, particularly at the total hip.

Case report: Persistent syndrome of inappropriate antidiuresis after traumatic brain injury: spontaneous resolution and impact on RAAS and bone metabolism over five years

The syndrome of Inappropriate Antidiuresis (SIAD) is a well-known cause of hyponatremia and can be associated with various etiologies, including traumatic brain injury (TBI). Most cases of SIAD following TBI exhibit a pattern in which hyponatremia develops several days to weeks after the trauma and resolves within a few weeks. Here, we present a rare case of persistent SIAD caused by TBI that resolved spontaneously after five years. The patient experienced prolonged hyponatremia for several years and was ultimately diagnosed with post-traumatic SIAD after excluding other potential causes. Notably, the patient exhibited an unusual sensitivity to tolvaptan, accompanied by decreased renin levels and increased bone turnover markers. The condition resolved spontaneously after five years, with renin, aldosterone, and bone turnover markers returning to normal upon re-evaluation.

Diagnostic and Therapeutic Strategies to Severe Hyponatremia in the Intensive Care Unit

Hyponatremia is the most common electrolyte abnormality encountered in critically ill patients and is linked to heightened morbidity, mortality, and healthcare resource utilization. However, its causal role in these poor outcomes and the impact of treatment remain unclear. Plasma sodium is the main determinant of plasma tonicity; consequently, hyponatremia commonly indicates hypotonicity but can also occur in conjunction with isotonicity and hypertonicity. Plasma sodium is a function of total body exchangeable sodium and potassium and total body water. Hypotonic hyponatremia arises when total body water is proportionally greater than the sum of total body exchangeable cations, that is, electrolyte-free water excess; the latter is the result of increased intake or decreased (kidney) excretion. Hypotonic hyponatremia leads to water movement into brain cells resulting in cerebral edema. Brain cells adapt by eliminating solutes, a process that is largely completed by 48 h. Clinical manifestations of hyponatremia depend on its biochemical severity and duration. Symptoms of hyponatremia are more pronounced with acute hyponatremia where brain adaptation is incomplete while they are less prominent in chronic hyponatremia. The authors recommend a physiological approach to determine if hyponatremia is hypotonic, if it is mediated by arginine vasopressin, and if arginine vasopressin secretion is physiologically appropriate. The treatment of hyponatremia depends on the presence and severity of symptoms. Brain herniation is a concern when severe symptoms are present, and current guidelines recommend immediate treatment with hypertonic saline. In the absence of significant symptoms, the concern is neurologic sequelae resulting from rapid correction of hyponatremia which is usually the result of a large water diuresis. Some studies have found desmopressin useful to effectively curtail the water diuresis responsible for rapid correction.

Hyponatremia, hypernatremia and impairment of functional, psychological and sexual domains

OBJECTIVE

To determine the influence of serum sodium on physical, psychologic and sexual function.

METHODS

This is a cross-sectional survey on 3340 community-dwelling men aged 40-79 years from a prospective cohort study in eight European countries, the European Male Ageing Study (EMAS). Participants filled-out the Short Form-36 (SF-36), the Physical Activity Scale for the Elderly (PASE), and the EMAS sexual function questionnaire. For all the analyses, serum sodium corrected for glycaemia ([Na+]G) was used.

RESULTS

The relationship between [Na+]G and SF-36 physical function score (F = 3.99; p = 0.01), SF-36 mental health score (F = 7.69; p < 0.001), and PASE score (F = 14.95; p < 0.001) were best described by a quadratic equation, with worse scores for [Na+]G in either the lowest or the highest ends of the range. After dividing the sample into [Na+]G < 136 mmol/L (n = 81), 136-147 mmol/L (n = 3223) and > 147 mmol/L (n = 36), linear regression analyses with linear spline functions adjusted for confounders did not confirm these relationships. Similarly, erectile dysfunction and [Na+]G, were in a quadratic relationship (F = 9.00; p < 0.001). After adjusting for confounders, the linear regression with spline functions denoted a significantly worsened erectile function for increases in serum [Na+]G > 147 mmol/L (B = 0.15 [0.04;0.26], p < 0.01) but no relationship with [Na+]G < 136 mmol/L. Likewise, the relationship of [Na+]G with concerns about sexual dysfunction was confirmed only for men with serum [Na+]G > 147 mmol/L.

CONCLUSIONS

This is the first study supporting an association between [Na+]G and sexual function. A worsening of erection and concerns about sexual function were observed for the highest values of [Na+]G, independently of other relevant factors.

[Consensus recommendations on the diagnosis and treatment of hyponatremia from the Austrian Society for Nephrology 2024]

Hyponatremia is a disorder of water homeostasis. Water balance is maintained by the collaboration of renal function and cerebral structures, which regulate thirst mechanisms and secretion of the antidiuretic hormone. Measurement of serum-osmolality, urine osmolality and urine-sodium concentration help to diagnose the different reasons for hyponatremia. Hyponatremia induces cerebral edema and might lead to severe neurological symptoms, which need acute therapy. Also, mild forms of hyponatremia should be treated causally, or at least symptomatically. An inadequate fast increase of the serum sodium level should be avoided, because it raises the risk of cerebral osmotic demyelination. Basic pathophysiological knowledge is necessary to identify the different reasons for hyponatremia which need different therapeutic procedures.

Serum sodium improvement: change in Comprehensive Geriatric Assessment parameters in geriatric patients with hyponatremia

BACKGROUND

Hyponatremia presents with symptoms considered age-associated in the elderly. We assess the change in Comprehensive Geriatric Assessment (CGA) parameters after hyponatremia improvement in hospitalized geriatric patients.

METHODS

We took 100 hyponatremic and same number of eunatremic geriatric patients (> 60 years) who were comorbidity, presenting-complaints, and age-matched. Four CGA parameters were utilized, the new Hindi Mental State Examination (HMSE), Barthel's index of activities of daily living (ADL), Timed up and go Test (TUG), and handgrip strength by hand dynamometer (HG). We analyzed these at admission and discharge, and their relationship with change in sodium levels.

RESULTS

Average age was 68.1 ± 5.8 years, with males constituting 75%. The CGA parameters demonstrated worse values amongst the hyponatremia than the normonatremia group. Severe hyponatremia group showed worse CGA scores in comparison with moderate and mild. With improvement in sodium level, the improvements in ADL, TUG, and HMSE scores were greater in the hyponatremia group (8.8 ± 10.1, 2.2 ± 2.5, and 1.7 ± 2.3 respectively) in comparison to the normonatremia reference group (4.7 ± 9.0, 1 ± 2.0, and 0.7 ± 1.3 respectively, P < 0.05).

CONCLUSION

Our study is the first utilizing HMSE to assess change in cognitive ability with improvement in serum sodium levels in the Indian elderly. Hyponatremic patients show worse baseline CGA parameters, and hyponatremia severity correlates with worse motor and cognitive function. Improvement in the serum sodium level improves the CGA parameters. Correction of hyponatremia in the geriatric age group significantly impacts life quality.

The characteristics and outcomes in patients with acute heart failure who used tolvaptan: from KCHF registry

AIMS

The use of tolvaptan is increasing in clinical practice in Japan. However, the characteristics of patients who used tolvaptan and the timing of its use in patients with acute heart failure (AHF) are not fully elucidated.

METHODS AND RESULTS

Among consecutive 4056 patients in the Kyoto Congestive Heart Failure registry, we analysed 3802 patients after excluding patients on dialysis, prior or unknown tolvaptan use at admission, and unknown timing of tolvaptan use, and we divided them into two groups: tolvaptan use (N = 773) and no tolvaptan use (N = 3029). The prevalence of tolvaptan use varied widely from 48.7% to 0% across the participating centres. Factors independently associated with tolvaptan use were diabetes, poor medical adherence, oedema, pleural effusion, hyponatraemia, estimated glomerular filtration rate < 30 mL/min/1.73 m2 , moderate/severe tricuspid regurgitation, dobutamine infusion within 24 h, and additional inotropes infusion beyond 24 h after admission. The mortality rate at 90 days after admission was significantly higher in the tolvaptan use group than in the no tolvaptan use group (14.3% vs. 8.6%, P = 0.049). However, after adjustment, the excess mortality risk of tolvaptan use relative to no tolvaptan use was no longer significant (hazard ratio = 1.53, 95% confidence interval = 0.77-3.02, P = 0.22). Patients with tolvaptan use had a longer hospital stay [median (interquartile range): 22 (15-34) days vs. 15 (11-21) days, P < 0.0001] and a higher prevalence of worsening renal failure (47.0% vs. 31.8%, P < 0.0001) and worsening heart failure (24.8% vs. 14.4%, P < 0.0001) than those without.

CONCLUSIONS

AHF patients with tolvaptan use had more congestive status with poorer in-hospital outcomes and higher short-term mortality than those without tolvaptan use.

CLINICAL TRIAL REGISTRATION

https://clinicaltrials.gov/ct2/show/NCT02334891 (NCT02334891) and https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000017241 (UMIN000015238).

An Increase in Plasma Sodium Levels Is Associated With an Increase in Osteoblast Function in Chronic SIAD

CONTEXT

Hyponatremia is associated with increased risk for osteoporosis. Preclinical studies in untreated hyponatremia suggest osteoclast upregulation, whereas a clinical study showed improved osteoblast function after hyponatremia normalization in hospitalized patients with syndrome of inappropriate antidiuresis (SIAD).

OBJECTIVE

This work aimed to investigate the effect of an increase in sodium on bone turnover, that is, the ratio of the osteoblast marker procollagen type 1 N-terminal propeptide (P1NP) to the osteoclast marker cross-linked C-terminal telopeptide of type 1 collagen (CTX), in outpatients with chronic SIAD.

METHODS

A predefined secondary analysis was conducted of the 2-month double-blind, crossover, placebo-controlled SANDx Trial (NCT03202667) performed from December 2017 to August 2021. Participants included 11 outpatients with chronic SIAD: 6 women, median age 73 years, who received a 4-week treatment with 25-mg empagliflozin or placebo. Main outcome measures included the relationship between the change in bone formation index (BFI), defined as P1NP/CTX, and the change in plasma sodium levels.

RESULTS

Changes in sodium were positively correlated with changes in BFI and P1NP (BFI: ρ=.55; P < .001; P1NP: ρ=.45; P = .004) but not with CTX (P = .184) and osteocalcin (P = .149). A sodium increase of 1 mmol/l was associated with an increase of 5.21 in BFI (95% CI, 1.41-9.00; P = .013) and with an increase of 1.48 µg/l in P1NP (95% CI, .26-2.62; P = .03). The effect of sodium change on bone markers was independent of the study medication empagliflozin.

CONCLUSION

An increase in plasma sodium levels in outpatients with chronic hyponatremia due to SIAD, even when mild, was associated with an increase in bone formation index (P1NP/CTX) triggered by an increase in P1NP, a surrogate marker of osteoblast function.

Association of hyponatremia with bone mineral density and fractures: a narrative review

Recent studies suggest a possible association of hyponatremia with osteoporosis, falls and bone fractures. The objectives of this narrative review were to further explore this association and the related pathophysiological mechanisms and to suggest a practical approach to patients with osteoporosis or chronic hyponatremia in clinical practice. We conducted an extensive PubMed search until October 2022 with the combination of the following keywords: 'hyponatremia' or 'sodium' or 'SIADH' and 'fractures' or 'bone' or 'osteoporosis', as MeSH Terms. Review of numerous observational studies confirms a significant independent association of, even mild, hyponatremia with two- to three-fold increase in the occurrence of bone fractures. Hyponatremia is a risk factor for osteoporosis with a predilection to affect the hip, while the magnitude of association depends on the severity and chronicity of hyponatremia. Chronic hyponatremia also increases the risk for falls by inducing gait instability and neurocognitive deficits. Besides the detrimental impact of hyponatremia on bone mineral density and risk of falls, it also induces changes in bone quality. Emerging evidence suggests that acute hyponatremia shifts bone turnover dynamics towards less bone formation, while hyponatremia correction increases bone formation. The key unanswered question whether treatment of hyponatremia could improve osteoporosis and lower fracture risk highlights the need for prospective studies, evaluating the impact of sodium normalization on bone metabolism and occurrence of fractures. Recommendations for clinical approach should include measurement of serum sodium in all individuals with fracture or osteoporosis. Also, hyponatremia, as an independent risk factor for fracture, should be taken into consideration when estimating the likelihood for future fragility fracture and in clinical decision-making about pharmacological therapy of osteoporosis. Until it is proven that normalization of sodium can lower fracture occurrence, correcting hyponatremia cannot be universally recommended on this basis, but should be decided on a case-by-case basis.

Syndrome of Inappropriate Antidiuresis: From Pathophysiology to Management

Hyponatremia is the most common electrolyte disorder, affecting more than 15% of patients in the hospital. Syndrome of inappropriate antidiuresis (SIAD) is the most frequent cause of hypotonic hyponatremia, mediated by nonosmotic release of arginine vasopressin (AVP, previously known as antidiuretic hormone), which acts on the renal V2 receptors to promote water retention. There are a variety of underlying causes of SIAD, including malignancy, pulmonary pathology, and central nervous system pathology. In clinical practice, the etiology of hyponatremia is frequently multifactorial and the management approach may need to evolve during treatment of a single episode. It is therefore important to regularly reassess clinical status and biochemistry, while remaining alert to potential underlying etiological factors that may become more apparent during the course of treatment. In the absence of severe symptoms requiring urgent intervention, fluid restriction (FR) is widely endorsed as the first-line treatment for SIAD in current guidelines, but there is considerable controversy regarding second-line therapy in instances where FR is unsuccessful, which occurs in around half of cases. We review the epidemiology, pathophysiology, and differential diagnosis of SIAD, and summarize recent evidence for therapeutic options beyond FR, with a focus on tolvaptan, urea, and sodium-glucose cotransporter 2 inhibitors.

Tolvaptan for the treatment of the syndrome of inappropriate antidiuresis (SIAD)

The syndrome of inappropriate antidiuresis (SIAD), the commonest cause of hyponatraemia, is associated with significant morbidity and mortality. Tolvaptan, an oral vasopressin V2-receptor antagonist, leads through aquaresis to an increase in serum sodium concentration and is the only medication licenced in Europe for the treatment of euvolaemic hyponatraemia. Randomised controlled trials have shown that tolvaptan is highly efficacious in correcting SIAD-related hyponatraemia. Real-world data have confirmed the marked efficacy of tolvaptan, but they have also reported a high risk of overly rapid sodium increase in patients with a very low baseline serum sodium. The lower the baseline serum sodium, the higher the tolvaptan-induced correction rate occurs. Therefore, a lower starting tolvaptan dose of 7.5 mg has been evaluated in small cohort studies, demonstrating its efficacy, but it still remains unclear as to whether it can reduce the risk of overcorrection. Most international guidelines, except for the European ones, recommend tolvaptan as second-line treatment for SIAD after fluid restriction. However, the risk of unduly rapid sodium correction in combination with its high cost have limited its routine use. Prospective controlled studies are warranted to evaluate whether tolvaptan-related sodium increase can improve patient-related clinical outcomes, such as mortality and length of hospital stay in the acute setting or neurocognitive symptoms and quality of life in the chronic setting. In addition, the potential role of a low tolvaptan starting dose needs to be further explored. Until then, tolvaptan should mainly be used as second-line treatment for SIAD, especially when there is a clinical need for prompt restoration of normonatraemia. Tolvaptan should be used with specialist input according to a structured clinical pathway, including rigorous monitoring of electrolyte and fluid balance and, if needed, implementation of appropriate measures to prevent, or when necessary reverse, overly rapid hyponatraemia correction.

Hyponatremia Demystified: Integrating Physiology to Shape Clinical Practice

Hyponatremia is one of the most common problems encountered in clinical practice and one of the least-understood because accurate diagnosis and management require some familiarity with water homeostasis physiology, making the topic seemingly complex. The prevalence of hyponatremia depends on the nature of the population studied and the criteria used to define it. Hyponatremia is associated with poor outcomes including increased mortality and morbidity. The pathogenesis of hypotonic hyponatremia involves the accumulation of electrolyte-free water caused by either increased intake and/or decrease in kidney excretion. Plasma osmolality, urine osmolality, and urine sodium can help to differentiate among the different etiologies. Brain adaptation to plasma hypotonicity consisting of solute extrusion to mitigate further water influx into brain cells best explains the clinical manifestations of hyponatremia. Acute hyponatremia has an onset within 48 hours, commonly resulting in severe symptoms, while chronic hyponatremia develops over 48 hours and usually is pauci-symptomatic. However, the latter increases the risk of osmotic demyelination syndrome if hyponatremia is corrected rapidly; therefore, extreme caution must be exercised when correcting plasma sodium. Management strategies depend on the presence of symptoms and the cause of hyponatremia and are discussed in this review.

Hyponatremia and Cancer: From Bedside to Benchside

Hyponatremia is the most common electrolyte disorder encountered in hospitalized patients. This applies also to cancer patients. Multiple causes can lead to hyponatremia, but most frequently this electrolyte disorder is due to the syndrome of inappropriate antidiuresis. In cancer patients, this syndrome is mostly secondary to ectopic secretion of arginine vasopressin by tumoral cells. In addition, several chemotherapeutic drugs induce the release of arginine vasopressin by the hypothalamus. There is evidence that hyponatremia is associated to a more negative outcome in several pathologies, including cancer. Many studies have demonstrated that in different cancer types, both progression-free survival and overall survival are negatively affected by hyponatremia, whereas the correction of serum [Na⁺] has a positive effect on patient outcome. In vitro studies have shown that cells grown in low [Na⁺] have a greater proliferation rate and motility, due to a dysregulation in intracellular signalling pathways. Noteworthy, vasopressin receptors antagonists, which were approved more than a decade ago for the treatment of euvolemic and hypervolemic hyponatremia, have shown unexpected antiproliferative effects. Because of this property, vaptans were also approved for the treatment of polycystic kidney disease. In vitro evidence indicated that this family of drugs effectively counteracts proliferation and invasivity of cancer cells, thus possibly opening a new scenario among the pharmacological strategies to treat cancer.

Serum sodium, cognition and incident dementia in the general population

BACKGROUND

Low serum sodium may be associated with cognitive impairment and dementia in the general population, but the data remain inconclusive. Therefore, we aimed to determine the association of low serum sodium with cognitive function and incident dementia in the general population.

METHODS

Participants from a prospective population-based cohort were eligible if data on serum sodium (collected between 1997 and 2008), dementia prevalence and dementia incidence were available (follow-up until 2018). Global cognitive function was assessed with the Mini-Mental State Examination (MMSE) and the general cognitive factor (G-factor, derived from principal component analysis of individual tests). Linear regression and Cox proportional-hazards models were used to assess associations of standardised continuous and categorised low serum sodium (mean - 1.96*SD: cut-off of 137 mmol/L) with overall cognitive function and incident dementia, respectively.

RESULTS

In all, 8,028 participants free of dementia at baseline (mean age 63.6 years, 57% female, serum sodium 142 ± 2 mmol/L), including 217 participants with low serum sodium, were included. Cross-sectionally, continuous serum sodium and/or low serum sodium were not associated with the MMSE or G-factor. However, participants with low serum sodium performed worse on the Stroop and Purdue Pegboard tests. During a median follow-up of 10.7 years, 758 subjects developed dementia. Continuous serum sodium (hazard ratio (HR) 0.98, 95% confidence interval (CI) 0.92;1.05) and low serum sodium (HR 1.27, 95% CI 0.90;1.79) were not associated with a higher risk of incident dementia.

CONCLUSION

We identified no significant associations of low serum sodium with overall cognitive functioning and risk of dementia. However, low serum sodium-including levels above the clinical cut-off for hyponatremia-was associated with impairments in selected cognitive domains including attention and psychomotor function.

Treatment Effect of the SGLT2 Inhibitor Empagliflozin on Chronic Syndrome of Inappropriate Antidiuresis: Results of a Randomized, Double-Blind, Placebo-Controlled, Crossover Trial

BACKGROUND

The syndrome of inappropriate antidiuresis (SIAD) is characterized by a reduction of free water excretion with consecutive hypotonic hyponatremia and is therefore challenging to treat. The sodium-glucose cotransporter 2 (SGLT2) inhibitor empagliflozin promotes osmotic diuresis via urinary glucose excretion, likely leading to increased electrolyte free water clearance.

METHODS

In this randomized, double-blind, placebo-controlled, crossover trial, we compared 4-week treatment with empagliflozin 25 mg/d to placebo in outpatients with chronic SIAD-induced hyponatremia. At baseline and after both treatment cycles, patients underwent different assessments including neurocognitive testing (Montreal Cognitive Assessment [MoCA]). The primary end point was the difference in serum sodium levels between treatments.

RESULTS

Fourteen patients, 50% female, with a median age of 72 years (interquartile range [IQR], 65-77), completed the trial. Median serum sodium level at baseline was 131 mmol/L (IQR, 130-132). After treatment with empagliflozin, median serum sodium level rose to 134 mmol/L (IQR, 132-136), whereas no increase was seen with placebo (130 mmol/L; IQR, 128-132), corresponding to a serum sodium increase of 4.1 mmol/L (95% confidence interval [CI], 1.7 to 6.5; P =0.004). Exploratory analyses showed that treatment with empagliflozin led to improved neurocognitive function with an increase of 1.16 (95% CI, 0.05 to 2.26) in the MoCA score. Treatment was well tolerated; no serious adverse events were reported.

CONCLUSION

The SGLT2 inhibitor empagliflozin is a promising new treatment option for chronic SIAD-induced hyponatremia, possibly improving neurocognitive function. Larger studies are needed to confirm the observed treatment effects.

CLINICAL TRIAL REGISTRATION NUMBER

ClinicalTrials.gov NCT03202667.

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Hyponatremia in the emergency department

Hyponatremia, defined as a serum sodium <135 mmol/L, is frequently encountered in patients presenting to the emergency department. Symptoms are often unspecific and include a recent history of falls, weakness and vertigo. Common causes of hyponatremia include diuretics, heart failure as well as Syndrome of Inappropriate Antidiuresis (SIAD) and correct diagnosis can be challenging. Emergency treatment of hyponatremia should be guided by presence of symptoms and focus on distinguishing between acute and chronic hyponatremia.

Hyponatremia and Oxidative Stress

Hyponatremia, i.e., the presence of a serum sodium concentration ([Na+]) < 136 mEq/L, is the most frequent electrolyte imbalance in the elderly and in hospitalized patients. Symptoms of acute hyponatremia, whose main target is the central nervous system, are explained by the "osmotic theory" and the neuronal swelling secondary to decreased extracellular osmolality, which determines cerebral oedema. Following the description of neurological and systemic manifestations even in mild and chronic hyponatremia, in the last decade reduced extracellular [Na+] was associated with detrimental effects on cellular homeostasis independently of hypoosmolality. Most of these alterations appeared to be elicited by oxidative stress. In this review, we focus on the role of oxidative stress on both osmolality-dependent and -independent impairment of cell and tissue functions observed in hyponatremic conditions. Furthermore, basic and clinical research suggested that oxidative stress appears to be a common denominator of the degenerative processes related to aging, cancer progression, and hyponatremia. Of note, low [Na+] is able to exacerbate multiple manifestations of senescence and to decrease progression-free and overall survival in oncologic patients.

Risks of vaptans in hypernatremia and serum sodium overcorrection: A systematic review and meta-analysis of randomised controlled trials

OBJECTIVE

Serum sodium overcorrection and hypernatremia are significant health risks. We conducted a systematic review and meta-analysis to evaluate the risks of vaptans in hypernatremia and serum sodium overcorrection.

METHODS

We searched PubMed, Embase, and CENTRAL for randomised controlled trials. We included studies comparing vaptans and placebo with data on hypernatremia and serum sodium overcorrection. The study quality was assessed using the Cochrane Collaboration's risk-of-bias assessment tool. Fixed-effect model meta-analysis was used to pool the data. Different analyses were performed to ensure the accuracy of the results.

RESULTS

Twenty-eight studies were included in the meta-analysis of hypernatremia incidence. Treatment with vaptans resulted in a higher risk of hypernatremia than placebo (3.8% vs 1.0%, odds ratio [OR] 2.69; 95% confidence interval [CI] 1.97-3.68). The subgroup with baseline hyponatremia had a lower risk of hypernatremia incidence; however, the use of loop diuretics increased the risk. Fourteen studies were included in the analysis of the incidence of serum sodium overcorrection. A higher risk of serum sodium overcorrection was found in using vaptans vs placebo (4.4% vs 1.4%; OR 2.26; 95% CI 1.32-3.86).

CONCLUSION

Vaptans showed higher risks in the incidence of hypernatremia and serum sodium overcorrection than placebo. In addition, combination with loop diuretics increased the risk of hypernatremia. The risk of serum sodium overcorrection should be concerned in patients with hyponatremia and normal serum sodium equally. Using a low dose of vaptans can reduce both risks.

Association of hyponatraemia and renal function in type 1 cardiorenal syndrome

BACKGROUND

Hyponatraemia predicts type 1 cardiorenal syndrome in acute decompensated heart failure patients, which associates with poor outcome. Recovery from hyponatraemia has been found to associate with better outcome in acute decompensated heart failure patients, but its prognostic value regarding renal function remains unknown.

METHODS

We performed a secondary analysis of CARRESS-HF trial, and all patients included had worsening renal function (≥0.3 mg/dL increase in serum creatinine than the nadir). The serum sodium levels of patients were evaluated at baseline and day 4 and day 7 after randomization. Patients were grouped according to the status of hyponatraemia: recovery from hyponatraemia; no hyponatraemia; persistent hyponatraemia; and new-onset hyponatraemia. Their associations with persistent worsening renal function (serum creatinine ≥ 0.3 mg/dL higher than the nadir at discharge) were explored.

RESULTS

A total of 118 patients suffered from persistent worsening renal function. Baseline hyponatraemia was not associated with persistent worsening renal function (odds ratio = 0.495, P = .086). Patients in the recovery from hyponatraemia group had a lowest risk of persistent worsening renal function among the study population. Further, baseline serum sodium level was not associated with the risk of persistent worsening renal function (odds ratio = 1.055, P = .233), while the increases in serum sodium level at day 4 (odds ratio = 0.858, P = .003) and at day 7 (odds ratio = 0.821, P < .001) significantly predicted a lower risk of persistent worsening renal function.

CONCLUSIONS

Recovery from hyponatraemia associates with a lower risk of persistent worsening renal function, suggesting that hyponatraemia correction may improve renal outcomes in acute decompensated heart failure patients with type 1 cardiorenal syndrome.

Impairment of Neurocognitive Functioning, Motor Performance, and Mood Stability in Hospitalized Patients With Euvolemic Moderate and Profound Hyponatremia

BACKGROUND

The impact of chronic moderate and profound hyponatremia on neurocognitive performance, motor skills, and mood stability has not been investigated systematically so far, and results regarding mild to moderate hyponatremia are inconsistent. Furthermore, it is not known whether treatment has an effect on outcome in these patients.

METHODS

A total of 130 hospitalized patients with confirmed euvolemic hyponatremia (<130 mEq/L) were subjected to a test battery (Mini-Mental State Examination, DemTect, Trail-Making Tests A and B, Beck Depression Inventory, Timed-up-and-go Test) before and after treatment; additionally, 50 normonatremic group-matched patients served as reference group.

RESULTS

The scores of all tested domains were significantly worse in the hyponatremia group (median serum sodium [Na⁺] 122 (119-126) mEq/L) as compared to the reference group (P <0.001), and the odds of obtaining a pathological test result increased markedly with more profound hyponatremic states (odds ratios between 5.0 and 21.8 in the group with Na⁺ <120 mEq/L compared to reference group). Inversely, treatment led to a significant amelioration of all test results with medium to large effect sizes. Linear regression models revealed the increment of Na⁺ as an important predictor of test outcome.

CONCLUSION

We demonstrate a clear association between lower levels of Na⁺ beyond mild hyponatremia and impairment of neurocognitive and motor performance as well as mood disorders. Our analysis further suggests a causal role of hyponatremia in this context. However, there are apparent differences between the distinct tested domains warranting further investigations.

[Hyponatremia in older persons (II)-A clear treatment : How to detect tricks and avoid pitfalls]

The aim of this continuing medical education (CME) article (part II) is to describe the particular challenge of the treatment of hyponatremia, which occurs in older patients. This part II follows on from part I concerning the diagnosis in the previous volume. A staged approach is necessary. The best treatment is always when the underlying cause can be eliminated. Hyponatremia in older patients is mainly induced by the syndrome of inappropriate antidiuretic hormone (SIADH) secretion. The authors use a concept for the first, second and third line strategy: (1) changing or discontinuation of drugs, (2) fluid restriction and (3) tolvaptan medication. The algorithm for treatment should be simple. It also contains recommendations for the correction rate. Caution is also needed in order to avoid the occurrence of an osmotic demyelination syndrome (ODS).

Impact of Resolution of Hyponatremia on Neurocognitive and Motor Performance in Geriatric Patients

This observational study investigated the impact of hyponatremia resolution on the results of a comprehensive geriatric assessment (CGA) in 150 patients with age ≥70 years and serum sodium <130 mEq/L. The test battery including Barthel index of Activities of Daily Living (ADL) and various tests of neurocognitive function, motor performance and mood stability was applied on admission and at discharge. Changes of individual test results (Δ) were analyzed and normonatremic patients matched for age, gender, and ADL served as reference group. Most CGA test results improved. The improvement was more pronounced in the hyponatremia group with respect to ADL (ΔADL: 14.3 ± 17.1 vs. 9.8 ± 14.7; p = 0.002) and MMSE (ΔMMSE: 1.8 ± 3.0 vs. 0.7 ± 1.9; p = 0.002). Effect sizes were small (i.e., >0.2) in the overall analysis for ΔADL and ΔMMSE and moderate (i.e., >0.5) for ΔMMSE in the euvolemic subgroup. Beneficial effects on ΔADL and ΔMMSE were only observed in the subgroup of patients in which [Na⁺] was raised by >5 mEq/L and multivariable linear regression analysis confirmed [Na⁺] increase to be an independent predictor of MMSE improvement. Resolution of hyponatremia has a beneficial impact on the geriatric patients' overall functional status, in particular in euvolemic cases.

Evidence for Effective Multiple K+-Current Inhibitions by Tolvaptan, a Non-peptide Antagonist of Vasopressin V2 Receptor

Tolvaptan (TLV), an oral non-peptide antagonist of vasopressin V2 receptor, has been increasingly used for managements in patients with hyponatremia and/or syndrome of inappropriate antidiuretic hormone secretion. However, none of the studies have thus far been investigated with regard to its possible perturbations on membrane ion currents in endocrine or neuroendocrine cells. In our electrophysiological study, the whole-cell current recordings showed that the presence of TLV effectively and differentially suppressed the amplitude of delayed rectifier K+ (I K(DR)) and M-type K+ current (I K(M)) in pituitary GH3 cells with an IC50 value of 6.42 and 1.91 μM, respectively. This compound was also capable of shifting the steady-state activation curve of I K(M) to less depolarized potential without any appreciable change in the gating charge of this current. TLV at a concentration greater than 10 μM also suppressed the amplitude of erg-mediated K+ current or the activity of large-conductance Ca2+-activated K+ channels; however, this compound failed to alter the amplitude of hyperpolarization-activated cation current in GH3 cells. In vasopressin-preincubated GH3 cells, TLV-mediated suppression of I K(M) remained little altered. Under current-clamp condition, we also observed that addition of TLV increased the firing of spontaneous action potentials in GH3 cells and further addition of flupirtine could reverse TLV-mediated elevation of the firing. In Madin-Darby canine kidney (MDCK) cells, the K+ current elicited by long ramp pulse was also effectively subject to inhibition by this compound. Findings from the present study were thus stated as saying that the suppression by TLV of multiple type K+ currents could be direct and independent of its antagonism of vasopressin V2 receptors. Our study also reveals an important aspect that should be considered when assessing aquaretic effect of TLV or its structurally similar compounds.

Hyponatremia Is Associated With Increased Osteoporosis and Bone Fractures in Patients With Diabetes With Matched Glycemic Control

Context

Patients with diabetes mellitus are at increased risk for bone fragility fracture secondary to multiple mechanisms. Hyperglycemia can induce true dilutional hyponatremia. Hyponatremia is associated with gait instability, osteoporosis, and increased falls and bone fractures, and studies suggest that compromised bone quality with hyponatremia may be independent of plasma osmolality. We performed a case-control study of patients with diabetes mellitus matched by median glycated hemoglobin (HbA1c) to assess whether hyponatremia was associated with increased risk of osteoporosis and/or fragility fracture.

Design

Osteoporosis (n = 823) and fragility fracture (n = 840) cases from the MedStar Health database were matched on age of first HbA1c ≥6.5%, sex, race, median HbA1c over an interval from first HbA1c ≥6.5% to the end of the encounter window, diabetic encounter window length, and type 1 vs type 2 diabetes mellitus with controls without osteoporosis (n = 823) and without fragility fractures (n = 840), respectively. Clinical variables, including coefficient of glucose variation and hyponatremia (defined as serum [Na⁺] <135 mmol/dL within 30 days of the end of the diabetic window), were included in a multivariate analysis.

Results

Multivariate conditional logistic regression models demonstrated that hyponatremia within 30 days of the outcome measure was independently associated with osteoporosis and fragility fractures (osteoporosis OR 3.09; 95% CI, 1.37 to 6.98; fracture OR, 6.41; 95% CI, 2.44 to 16.82).

Conclusions

Our analyses support the hypothesis that hyponatremia is an additional risk factor for osteoporosis and fragility fracture among patients with diabetes mellitus.

Management of hyponatremia: causes, clinical aspects, differential diagnosis and treatment

INTRODUCTION

Hyponatremia is the most frequent electrolyte disorder in hospitalised patients. Acute and severe hyponatremia may be a life-threatening situation. However, also mild and chronic hyponatremia may negatively affect the health status (i.e. gait disturbances, attention deficits, falls and fractures, and bone loss) and may increase the risk of death. Therefore, it is of paramount importance for clinicians to have an in-depth knowledge on this topic, in order to appropriately manage patients affected by hyponatremia.

AREAS COVERED

This review will cover different areas related to this electrolyte disorder. Because many pathologic conditions may be associated with hyponatremia, thorough investigations have to be performed in order to establish the underlying etiology. To establish the cause of hyponatremia is of great importance, because an appropriate therapeutic strategy is strictly dependent on a correct diagnosis. A description of the different available therapeutic approaches for the correction of hyponatremia, including vaptans, will follow.

EXPERT COMMENTARY

Undoubtedly, the studies that have been published in recent years and the introduction of vaptans in clinical practice have contributed to increase the awareness on hyponatremia among clinicians. Nevertheless, additional studies are needed in order to clarify some partially uncovered areas.

Allostasis and the Clinical Manifestations of Mild to Moderate Chronic Hyponatremia: No Good Adaptation Goes Unpunished

When homeostatic regulatory systems are unable to maintain a normal serum sodium concentration, the organism must adapt to demands of a disordered internal environment, a process known as "allostasis." Human cells respond to osmotic stress created by an abnormal serum sodium level with the same adaptations used by invertebrate organisms that do not regulate body fluid osmolality. To avoid intolerable changes in their volume, cells export organic osmolytes when exposed to a low serum sodium concentration and accumulate these intracellular solutes when serum sodium concentration increases. The brain's adaptation to severe hyponatremia (serum sodium < 120 mEq/L) has been studied extensively. However, adaptive responses occur with less severe hyponatremia and other tissues are affected; the consequences of these adaptations are incompletely understood. Recent epidemiologic studies have shown that mild (sodium, 130-135 mEq/L) and moderate (sodium, 121-129 mEq/L) chronic hyponatremia, long thought to be inconsequential, is associated with adverse outcomes. Adaptations of the heart, bone, brain, and (possibly) immune system to sustained mild to moderate hyponatremia may adversely affect their function and potentially the organism's survival. This review explores what is known about the consequences of mild to moderate chronic hyponatremia and the potential benefits of treating this condition.

Impact of chronic hyponatremia on neurocognitive and neuromuscular function

BACKGROUND

Chronic hyponatremia is common and associated with increased morbidity and mortality. However, whether treatment improves outcome in patients without significant symptoms is unclear. We here assessed the therapeutic outcome on clinical symptoms, neurocognitive and neuromuscular function in patients with chronic non profound hyponatremia.

MATERIAL AND METHODS

Prospective case-control study in 19 patients from the University Hospital Würzburg with chronic non profound hyponatremia without clinically apparent symptoms. At baseline and after a 14-day treatment period of hyponatremia, patients were assessed by specific clinical symptoms questionnaire, neurocognitive and neuromuscular function was analysed by five attention tests and a gait test consisting of 3 steps "in tandem." The results were compared to a control group of healthy volunteers.

RESULTS

Compared to healthy volunteers, patients with mild (n = 10, mean serum sodium 132 ± 1.2 mmol/L) and moderate hyponatremia (n = 9, mean 126 ± 3.3 mmol/L) performed significantly worse in the neurocognitive subtests alertness (P = 0.018), divided attention (P = 0.017) and go/no-go (P = 0.026). Performance in the neuromuscular subtests was also lower in the patient group without reaching significance. The extent of hyponatremia had no impact on the specific test and questionnaire results. Fourteen-day treatment of hyponatremia improved clinical symptoms in all patients (P = 0.003) and neurocognitive function in sodium-normalised patients (go/no-go test, P = 0.029).

CONCLUSION

Chronic hyponatremia is symptomatic and impairs neurocognitive and neuromuscular function. Short-time therapeutic intervention led to improved clinical symptoms and neurocognitive function, but had no effect on neuromuscular function. Larger trials with long-term treatment are needed to specify the therapeutic need in chronic hyponatremia.

Pharmacological management of hyponatremia

INTRODUCTION

Hyponatremia is the most common electrolyte disorder with a prevalence of up to 30% in hospitalized patients. Furthermore, it is associated with increased morbidity and mortality.

AREAS COVERED

This review discusses the efficacy and side effects of the currently available treatment options for hyponatremia and the differences in the pharmacological approach between the European and USA guidelines. Additionally, the authors provide their expert perspectives on current treatment strategies and what they expect from this field in the future.

EXPERT OPINION

Several pharmacological options are available for the treatment of hyponatremia, but data from trials examining and comparing these treatments are missing. Regarding chronic hyponatremia, the role of vaptans should be further analyzed, focusing on comparisons with other active treatments on patient-relevant outcomes and not only on serum sodium concentration. Clinicians should be cautious to an overly rapid increase in serum sodium levels with all available treatment strategies. Finally, it is important to ascertain whether correction of serum sodium levels improves mortality in hyponatremic patients.

Interventions for chronic non-hypovolaemic hypotonic hyponatraemia

BACKGROUND

Chronic (present > 48 hours) non-hypovolaemic hyponatraemia occurs frequently, can be caused by various conditions, and is associated with shorter survival and longer hospital stays. Many treatments, such as fluid restriction or vasopressin receptor antagonists can be used to improve the hyponatraemia, but whether that translates into improved patient-important outcomes is less certain.

OBJECTIVES

This review aimed to 1) look at the benefits and harms of interventions for chronic non-hypovolaemic hypotonic hyponatraemia when compared with placebo, no treatment or head-to-head; and 2) determine if benefits and harms vary in absolute or relative terms dependent on the specific compound within a drug class, on the dosage used, or the underlying disorder causing the hyponatraemia.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 1 December 2017 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov. We also screened the reference lists of potentially relevant studies, contacted authors, and screened the websites of regulatory agencies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-RCTs that compared the effects of any intervention with placebo, no treatment, standard care, or any other intervention in patients with chronic non-hypovolaemic hypotonic hyponatraemia. We also included subgroups with hyponatraemia from studies with broader inclusion criteria (e.g. people with chronic heart failure or people with cirrhosis with or without hyponatraemia), provided we could obtain outcomes for participants with hyponatraemia from the report or the study authors.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data and assessed risk of bias. We expressed treatment effects as mean difference (MD) for continuous outcomes (health-related quality of life, length of hospital stay, change from baseline in serum sodium concentration, cognitive function), and risk ratio (RR) for dichotomous outcomes (death, response and rapid increase in serum sodium concentration, hypernatraemia, polyuria, hypotension, acute kidney injury, liver function abnormalities) together with 95% confidence intervals (CI).

MAIN RESULTS

We identified 35 studies, enrolling 3429 participants. Twenty-eight studies (3189 participants) compared a vasopressin receptor antagonist versus placebo, usual care, no treatment, or fluid restriction. In adults with chronic, non-hypovolaemic hypotonic hyponatraemia, vasopressin receptor antagonists have uncertain effects on death at six months (15 studies, 2330 participants: RR 1.11, 95% CI 0.92 to 1.33) due to risk of selective reporting and serious imprecision; and on health-related quality of life because results are at serious risk of performance, selective reporting and attrition bias, and suffer from indirectness related to the validity of the Short Form Health Survey (SF-12) in the setting of hyponatraemia. Vasopressin receptor antagonists may reduce hospital stay (low certainty evidence due to risk of performance bias and imprecision) (3 studies, 610 participants: MD -1.63 days, 95% CI -2.96 to -0.30), and may make little or no difference to cognitive function (low certainty evidence due to indirectness and imprecision). Vasopressin receptor antagonists probably increase the intermediate outcome of serum sodium concentration (21 studies, 2641 participants: MD 4.17 mmol/L, 95% CI 3.18 to 5.16), corresponding to two and a half as many people having a 5 to 6 mmol/L increase in sodium concentration compared with placebo at 4 to 180 days (moderate certainty evidence due to risk of attrition bias) (18 studies, 2014 participants: RR 2.49, 95% CI 1.95 to 3.18). But they probably also increase the risk of rapid serum sodium correction - most commonly defined as > 12 mmol/L/d (moderate certainty evidence due to indirectness) (14 studies, 2058 participants: RR 1.67, 95% CI 1.16 to 2.40) and commonly cause side-effects such as thirst (13 studies, 1666 participants: OR 2.77, 95% CI 1.80 to 4.27) and polyuria (6 studies, 1272 participants): RR 4.69, 95% CI 1.59 to 13.85) (high certainty evidence). The potential for liver toxicity remains uncertain due to large imprecision. Effects were generally consistent across the different agents, suggesting class effect.Data for other interventions such as fluid restriction, urea, mannitol, loop diuretics, corticosteroids, demeclocycline, lithium and phenytoin were largely absent.

AUTHORS' CONCLUSIONS

In people with chronic hyponatraemia, vasopressin receptor antagonists modestly raise serum sodium concentration at the cost of a 3% increased risk of it being rapid. To date there is very low certainty evidence for patient-important outcomes; the effects on mortality and health-related quality of life are unclear and do not rule out appreciable benefit or harm; there does not appear to be an important effect on cognitive function, but hospital stay may be slightly shorter, although available data are limited. Treatment decisions must weigh the value of an increase in serum sodium concentration against its short-term risks and unknown effects on patient-important outcomes. Evidence for other treatments is largely absent.Further studies assessing standard treatments such as fluid restriction or urea against placebo and one-another would inform practice and are warranted. Given the limited available evidence for patient-important outcomes, any study should include these outcomes in a standardised manner.

Safety and Efficacy of Tolvaptan in Korean Patients with Hyponatremia Caused by the Syndrome of Inappropriate Antidiuretic Hormone

BACKGROUND

The aim of this multicenter study was to evaluate the safety and efficacy of tolvaptan (TLV) in Korean patients with the syndrome of inappropriate secretion of antidiuretic hormone (SIADH).

METHODS

Of 51 enrolled patients with SIADH, 39 patients (16 female patients, aged 70.8 ± 11.3 years) were included in an intention to treat analysis. All patients received 15 mg/day as the initial dose, and the dose was then increased up to 60 mg/day (as needed) until day 4.

RESULTS

Serum sodium increased significantly from baseline during the first 24 hours (126.8 ± 4.3 vs. 133.7 ± 3.8 mmol/L, P < 0.001), rose gradually between days 1 and 4 (133.7 ± 3.8 vs. 135.6 ± 3.6 mmol/L, P < 0.05), and then plateaued until day 11 (136.7 ± 4.5 mmol/L). The correlation between the change in serum sodium for the first 24 hours and initial serum sodium concentration was significant (r = -0.602, P < 0.001). In severe hyponatremia (< 125 mmol/L), the change was significantly higher (11.1 ± 4.8 mmol/L) than in moderate (6.4 ± 2.5 mmol/L, P < 0.05) or mild hyponatremia (4.3 ± 3.3 mmol/L, P < 0.01). In addition, logistic regression analysis showed that body weight (odds ratio [OR], 0.858; 95% confidence interval [CI], 0.775-0.976; P = 0.020) and body mass index (BMI) (OR, 0.692; 95% CI, 0.500-0.956; P = 0.026) were associated with rapid correction. No serious adverse events were reported, but in 13% of patients hyponatremia was overcorrected.

CONCLUSION

TLV is effective in correcting hyponatremia and well-tolerated in Korean patients with SIADH. However, those with low body weight, low BMI or severe hyponatremia, could be vulnerable to overcorrection with the initial dose of 15 mg TLV.

Serum Sodium and Cognition in Older Community-Dwelling Men

BACKGROUND AND OBJECTIVES

Mild hyponatremia is a common finding in older adults; however, the association of lower serum sodium with cognition in older adults is currently unknown. We determined whether lower normal serum sodium is associated with cognitive impairment and risk of cognitive decline in community-dwelling older men.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Five thousand four hundred thirty-five community-dwelling men aged ≥65 years who participated in Osteoporotic Fractures in Men, a cohort study with a median follow-up for cognitive function of 4.6 years, were included in this analysis. Multivariable logistic regression was used to examine the association between baseline fasting serum sodium levels and the odds of prevalent cognitive impairment (cross-sectional analysis; modified Mini-Mental Status [3MS] score <1.5 SD [<84] below or Trail Making Test Part B time >1.5 SD above the mean [>223 seconds]) and cognitive decline (prospective analysis [n=3611]; decrease in follow-up 3MS score or increase in Trails B time >1.5 SD of the mean score/time change [>9 or >67 seconds]).

RESULTS

Participants were aged 74±6 years with a fasting mean serum sodium level of 141±3 mmol/L. Fifteen percent (n=274), 12% (n=225), and 13% (n=242) had prevalent cognitive impairment in tertiles 1, 2, and 3, respectively. After adjustment, lower serum sodium was associated with prevalent cognitive impairment (tertile 1 [126-140 mmol/L] versus tertile 2 [141-142 mmol/L], odds ratio [OR], 1.30; 95% confidence interval [95% CI], 1.06 to 1.61). Fourteen percent (n=159), 10% (n=125), and 13% (n=159) had cognitive decline in tertiles 1, 2, and 3, respectively. Lower serum sodium was also associated with cognitive decline (tertile 1 versus tertile 2, OR, 1.37; 95% CI, 1.06 to 1.77). Tertile 3 (143-153 mmol/L) was additionally associated with cognitive decline. Results were similar in sensitivity analyses according to clinical cut-offs and by quartiles.

CONCLUSIONS

In community-dwelling older men, serum sodium between 126-140, and 126-140 or 143-153 mmol/L, are independently associated with prevalent cognitive impairment and cognitive decline, respectively.

Vasopressin Receptor Antagonists in Hyponatremia: Uses and Misuses

Decreases in the concentration of sodium in plasma constitute hyponatremia, the commonest electrolyte disorder in clinical medicine. It is now well established that its presence conveys an increased mortality risk even when the decrement is mild. In addition, recent evidence suggests that chronic and apparently asymptomatic hyponatremia is associated with increased morbidity including neurocognitive deficits and bone fractures. Furthermore, hyponatremia is associated with higher health care-related expenses. Consequently, exploring new therapeutic strategies that increase plasma sodium in a safe and effective manner is of paramount importance. In this regard, there are scant data to support the use of traditional management strategies for hyponatremia (fluid restriction, salt tablets, loop diuretics, and normal saline). Furthermore, data from a large hyponatremia registry reveal the limited efficacy of these therapies. More recently vasopressin receptor antagonists provide a promising treatment for hyponatremia by targeting its most common mechanism, namely, increased vasopressin activity. However, uncertainty still lingers as to the optimal indications for the use of vasopressin receptor antagonists in hyponatremia and a few reports have described complications resulting from their misuse. This review summarizes the appropriate and inappropriate uses of vasopressin receptor antagonists in the treatment of hyponatremia.

The Efficacy and Safety of Tolvaptan in Patients with Hyponatremia: A Meta-Analysis of Randomized Controlled Trials

BACKGROUND AND OBJECTIVES

Comprehensive evaluations regarding the benefits of tolvaptan in the treatment of hyponatremia are lacking. The objective of this meta-analysis was to assess the efficacy and safety of tolvaptan in patients with hyponatremia.

METHODS

Pertinent studies were identified by searching PubMed, EMBASE, Web of Science, and the Cochrane Library for articles published between their respective inception dates and 31 April 2016. Summary relative risks (RRs) or weighted mean differences (WMDs) with their 95 % confidence intervals (CIs) were calculated using fixed-effects or randomized-effects models, depending on the degree of heterogeneity noted among the studies included in the analysis.

RESULTS

Eleven articles comprising 5209 patients were ultimately included in the analysis. Our pooled results showed that tolvaptan was more effective than control with respect to increasing serum sodium concentrations (WMD = 3.99 mEq/L), 95 % CI 2.80-5.19, Z = 6.56, P < 0.001), improving serum sodium correction rates (RR = 3.35, 95 % CI 1.93-5.82, Z = 4.31, P < 0.001), improving 24-h urine output (WMD = 987.64 mL, 95 % CI 850.71-1124.57, Z = 14.14, P < 0.001), and improving net fluid balance (WMD = 795.97 mL, 95 % CI 418.56-1173.38, Z = 4.13, P < 0.001). Tolvaptan treatment also resulted in increased incidences of adverse events compared with control treatment (RR = 1.05, 95 % CI 1.02-1.07, Z = 3.83, P < 0.001). These events included dry mouth (RR = 2.38, 95 % CI 1.41-4.04, Z = 3.23, P = 0.001), thirst (RR = 3.85, 95 % CI 1.96-7.57, Z = 3.92, P < 0.001), pollakiuria (RR = 2.47, 95 % CI 1.41-4.33, Z = 3.16, P = 0.002), and overly rapid hyponatremia correction (RR = 8.43, 95 % CI 1.06-66.96, Z = 2.02, P = 0.04). No significant differences in all-cause mortality (RR = 0.99, 95 % CI 0.90-1.10, Z = 0.17, P = 0.86), serious adverse event rate (RR = 1.01, 95 % CI 0.80-1.29, Z = 0.11, P = 0.92), systolic blood pressure (WMD = 0.1 mmHg, 95 % CI -1.04 to 1.23, Z = 0.17, P = 0.87), or heart rate (WMD = -0.16 bpm, 95 % CI -1.14 to 0.82, Z = 0.31, P = 0.76) were noted between the two groups, based on the results of our meta-analysis.

CONCLUSION

The results of this meta-analysis suggest that tolvaptan can increase serum sodium concentrations, serum sodium correction rates, 24-h urine output, net fluid balance, and total adverse event rates without significantly decreasing all-cause mortality rates or increasing serious adverse event rates in patients with hyponatremia.

Hyponatremia and bone disease

Hip fractures represent a serious health risk in the elderly, causing substantial morbidity and mortality. There is now a considerable volume of literature suggesting that chronic hyponatremia increases the adjusted odds ratio (OR) for both falls and fractures in the elderly. Hyponatremia appears to contribute to falls and fractures by two mechanisms. First, it produces mild cognitive impairment, resulting in unsteady gait and falls; this is probably due to the loss of glutamate (a neurotransmitter involved in gait function) as an osmolyte during brain adaptation to chronic hyponatremia. Second, hyponatremia directly contributes to osteoporosis and increased bone fragility by inducing increased bone resorption to mobilize sodium stores in bone. Low extracellular sodium directly stimulates osteoclastogenesis and bone resorptive activity through decreased cellular uptake of ascorbic acid and the induction of oxidative stress; these effects occur in a sodium level-dependent manner. Hyponatremic patients have elevated circulating arginine-vasopressin (AVP) levels, and AVP acting on two receptors expressed in osteoblasts and osteoclasts, Avpr1α and Avpr2, can increase bone resorption and decrease osteoblastogenesis. Should we be screening for low serum sodium in patients with osteoporosis or assessing bone mineral density (BMD) in patients with hyponatremia? The answers to these questions have not been established. Definitive answers will require randomized controlled studies that allocate elderly individuals with mild hyponatremia to receive either active treatment or no treatment for hyponatremia, to determine whether correction of hyponatremia prevents gait disturbances and changes in BMD, thereby reducing the risk of fractures. Until such studies are conducted, physicians caring for elderly patients must be aware of the association between hyponatremia and bone disorders. As serum sodium is a readily available, simple, and affordable biochemical measurement, clinicians should look for hyponatremia in elderly patients, especially in those receiving medications that can cause hyponatremia. Furthermore, elderly patients with an unsteady gait and/or confusion should be evaluated for the presence of mild hyponatremia, and if present, treatment should be initiated. Finally, elderly patients presenting with an orthopedic injury should have serum sodium checked and hyponatremia corrected, if present.

Diagnosis and Treatment of Hyponatremia: Compilation of the Guidelines

Hyponatremia is a common water balance disorder that often poses a diagnostic or therapeutic challenge. Therefore, guidelines were developed by professional organizations, one from within the United States (2013) and one from within Europe (2014). This review discusses the diagnosis and treatment of hyponatremia, comparing the two guidelines and highlighting recent developments. Diagnostically, the initial step is to differentiate hypotonic from nonhypotonic hyponatremia. Hypotonic hyponatremia is further differentiated on the basis of urine osmolality, urine sodium level, and volume status. Recently identified parameters, including fractional uric acid excretion and plasma copeptin concentration, may further improve the diagnostic approach. The treatment for hyponatremia is chosen on the basis of duration and symptoms. For acute or severely symptomatic hyponatremia, both guidelines adopted the approach of giving a bolus of hypertonic saline. Although fluid restriction remains the first-line treatment for most forms of chronic hyponatremia, therapy to increase renal free water excretion is often necessary. Vasopressin receptor antagonists, urea, and loop diuretics serve this purpose, but received different recommendations in the two guidelines. Such discrepancies may relate to different interpretations of the limited evidence or differences in guideline methodology. Nevertheless, the development of guidelines has been important in advancing this evolving field.

Role of tolvaptan in the management of hyponatremia in patients with lung and other cancers: current data and future perspectives

Hyponatremia is the most frequently observed electrolyte abnormality in clinical practice, and its frequency is almost double in hospitalized cancer patients. As a subset of cancer, hyponatremia is quite common in lung cancer patients, and it is often coupled with the diagnosis of syndrome of inappropriate antidiuretic hormone secretion. The presence of hyponatremia is consequential in that its presence adversely affects cancer patients’ prognosis and outcomes. Limited data suggest that correcting hyponatremia in lung cancer patients can increase response to anticancer treatment, may help reduce length of hospital stay and cost, and reduce morbidity and mortality. The type of treatment for hyponatremia depends on several factors; the key factors are the duration and severity of neurological symptoms of hyponatremia and the status of extracellular volume. When hyponatremia is caused by syndrome of inappropriate antidiuretic hormone, hypertonic saline is indicated for acute symptomatic cases, whereas fluid restriction is recommended in chronic asymptomatic hyponatremia. The latter allows a slower rate of correction, thus avoiding the dreaded complication of osmotic demyelination syndrome. Fluid restriction is, however, insufficient or impractical, and often the use of pharmacological therapy such as antidiuretic hormone receptor antagonists becomes necessary. Availability of these antagonists as an effective treatment in the management of hyponatremia has been a major breakthrough, and furthermore, its clinical or investigational use in cancer-related hyponatremia may offer a potential opportunity to gain further insights into the prognostic impact of hyponatremia correction on cancer patients’ outcomes. Tolvaptan is a prototype of ADH receptor antagonists that acts at renal tubular levels to increase free water excretion without inducing major systemic electrolyte abnormalities such as hypokalemia or alkalosis. The aim of this paper is to provide a brief review while focusing on cancer hyponatremia; (1) of the epidemiology of hyponatremia and its pathophysiology and diagnostic approaches and (2) of the pharmacokinetics of tolvaptan and its clinical efficacy, safety, and compliance.