Chronic Hyponatremia: The Role of Reset Osmostat in Patients with Suspected SIAD.

Background: Hyponatremia is common, particularly among the elderly. Reset osmostat (RO) serves as an alternative diagnosis to the syndrome of inappropriate antidiuresis (SIAD). There is limited information available regarding the prevalence of RO in outpatient clinics and hospital wards. The water-diluting test is considered the gold standard for the diagnosis of RO. The recent identification of copeptin provides an additional diagnostic marker alongside the utilization of fractional uric acid excretion. Methods: This single-center, prospective, observational study involved eight patients undergoing a water-diluting test over a study period of 2 years. Results: Reset osmostat was diagnosed in 50% of cases, while SIAD was confirmed in one patient. The tests were inconclusive for the remaining three patients. Conclusions: Our findings suggest that reset osmostat, despite its rarity, is a plausible diagnosis in chronic hyponatremia. The relevance of copeptin could not be confirmed in this study. Moreover, fractional uric acid excretion might be as effective as the water-diluting test in diagnosing reset osmostat.

Apelin and Copeptin Levels in Patients With Chronic SIAD Treated With Empagliflozin.

Background: Empagliflozin increases sodium levels in patients with a chronic syndrome of inappropriate antidiuresis (SIAD), and dapagliflozin increases apelin levels in patients with diabetes mellitus. Exogenous apelin increases sodium levels in rats with SIAD. We aimed to investigate whether an increase in plasma apelin concentration may contribute to the efficacy of empagliflozin in SIAD. Methods: Post hoc secondary analysis of a double-blind, crossover, placebo-controlled trial performed from December 2017 to August 2021 at the University Hospital Basel, Switzerland, investigating the effect of 4-week treatment with empagliflozin 25 mg/day as compared to placebo in 14 outpatients with chronic SIAD (NCT03202667). The objective was to investigate the effect of empagliflozin on plasma apelin and copeptin concentrations and their ratio. Results: Fourteen patients, 50% female, with a median [interquartile range] age of 72 years [65-77] were analyzed. Median apelin concentration was 956 pmol/L [853, 1038] at baseline. Median [interquartile range] apelin relative changes were +11% [0.7, 21] and +8% [-5, 25] (P = .672) at the end of the placebo and empagliflozin phases, respectively. Median copeptin concentration was 2.6 [2.2, 4.5] pmol/L at baseline and had a relative change of +5 [-2. 11]% and +25% [10, 28] (P = .047) over the placebo and empagliflozin phases, respectively. Conclusion: Empagliflozin did not lead to significant changes in apelin or the apelin/copeptin ratio in patients with chronic SIAD but led to an increase in copeptin. This suggests that the efficacy of empagliflozin in SIAD is independent of apelin and is not blunted by the adaptative increase in copeptin.

Simultaneous Occurrence of Hyponatremia and Hypokalemia in a Patient with Herpes Zoster: A Case Report with a Review of the Literature.

We herein report a patient with herpes zoster (HZ), severe hyponatremia, and hypokalemia. Syndrome of inappropriate antidiuresis (SIAD) leads to euvolemic hyponatremia and hypoosmotic plasma due to inadequate diuresis. Hyponatremia in the current patient was caused by SIAD and associated with HZ of the trigeminal facial nerve (V1). The patient also had hypokalemia, with excessive urinary potassium excretion and elevated cortisol levels. Hypokalemia is caused by hypercortisolemia, which is stimulated by HZ pain. Adequate treatment for HZ and comprehensive pain control play pivotal roles in improving SIAD, cortisol hypersecretion, and the subsequent electrolyte abnormalities.

Worldwide productivity and research trend of publications concerning SIAD: a bibliometric study.

Background: Syndrome of inappropriate antidiuretic(SIAD) occurs secondary to various diseases, which is characterised by hypotonic hyponatremia and impaired urinary diluting capacity. Research on SIAD in both domestic and international contexts has a long history. This study objectively and comprehensively analyses the research trends, hotspots and development of SIAD research of the past 20 years using the method of bibliometric analysis. Methods: The 2003-2022 data in the Web of Science Core Collection database were searched. The Bibliometrix software package, VOSviewer and CiteSpace were used to mine, extract and visualise the retrieved literature, and the generated maps were used in analysing the main topics and trends in the field of SIAD research. Results: A total of 1215 articles published in 623 journals were included in the analysis, with a total of 18,886 citations. Results showed that the research output on SIAD has continuously increased in the past 20 years, and the United States had the highest number of publications and citations. Keywords with the highest burst strength in recent years were the most mentioned keywords, in addition to the search terms 'hyponatremia', 'covid-19', and 'mortality'. Thus, the relationship among SIAD, covid-19 and mortality may become research frontiers and trends. Fifteen milestone articles were identified through co-citation analysis, which mainly focused on the pathophysiology and treatment of SIAD. Conclusion: Based on bibliometric analysis and knowledge mapping, this study summarises development trends in the field of SIAD research, providing references for current and future research into SIAD.

Safety and Efficacy of Vaptans in the Treatment of Hyponatremia from Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH): A Systematic Review and Meta-Analysis.

The utilization of vasopressin receptor antagonists, known as vaptans, in the management of hyponatremia among patients afflicted with the syndrome of inappropriate antidiuretic hormone (SIADH) remains a contentious subject. This meta-analysis aimed to evaluate the safety and efficacy of vaptans for treating chronic hyponatremia in adult SIADH patients. Clinical trials and observational studies were identified by a systematic search using MEDLINE, EMBASE, and Cochrane Database from inception through September 2022. The inclusion criteria were the studies that reported vaptans' safety or efficacy outcomes compared to placebo or standard therapies. The study protocol was registered with the International Prospective Register of Systematic Reviews (PROSPERO; CRD 42022357307). Five studies were identified, comprising three RCTs and two cohort studies, enrolling a total of 1840 participants. Regarding short-term efficacy on days 4-5, vaptans exhibited a significant increase in serum sodium concentration from the baseline in comparison to the control group, with a weighted mean difference of 4.77 mmol/L (95% CI, 3.57, 5.96; I2 = 34%). In terms of safety outcomes, the pooled incidence rates of overcorrection were 13.1% (95% CI 4.3, 33.6; I2 = 92%) in the vaptans group and 3.3% (95% CI 1.6, 6.6; I2 = 27%) in the control group. Despite the higher correction rate linked to vaptans, with an OR of 5.72 (95% CI 3.38, 9.70; I2 = 0%), no cases of osmotic demyelination syndrome were observed. Our meta-analysis comprehensively summarizes the efficacy and effect size of vaptans in managing SIADH. While vaptans effectively raise the serum sodium concentration compared to placebo/fluid restriction, clinicians should exercise caution regarding the potential for overcorrection.

Effect of protein supplementation on plasma sodium levels in the syndrome of inappropriate antidiuresis: a monocentric, open-label, proof-of-concept study-the TREASURE study.

IMPORTANCE: The syndrome of inappropriate antidiuresis (SIAD) can be treated with oral urea; however, compliance is impaired by its poor palatability. OBJECTIVE: To investigate whether dietary proteins could increase plasma sodium levels through urea-induced osmotic diuresis. DESIGN: An open-label, proof-of-concept trial. SETTING: University Hospital of Basel, Switzerland, between October 2021 and February 2023. PARTICIPANTS: Outpatients with chronic SIAD. INTERVENTIONS OR EXPOSURES: Ninety grams of protein daily for 7 days in the form of protein powder, followed by 30 g of oral urea daily for 7 days after a wash-out period of ≥1 week. MAIN OUTCOMES AND MEASURES: The increase in sodium levels from baseline to the end of the 7-day protein supplementation. RESULTS: Seventeen patients were included. After 7 days of 90 g daily protein supplementation (n = 17), plasma sodium levels increased from 131 (129-133) to 133 (132-137), that is, by a median of 3 mmol L-1 (0-5) (P = .01). Plasma urea levels increased by 3 mmol L-1 (1.7-4.9) (P < .01), and urine urea to creatinine ratio increased by 21.2 mmol mmol-1 (6.2-29.1) (P < .01). After 7 days of 30 g oral urea (n = 10), plasma sodium levels increased from 132 (130-133) to 134 (131-136), that is, by a median of 2 mmol L-1 (1-3) (P = .06). Plasma urea levels increased by 5.8 mmol L-1 (2.7-9.2) (P < .01), and urine urea to creatinine ratio increased by 31.0 mmol mmol-1 (18.7-45.1) (P < .01). CONCLUSIONS AND RELEVANCE: Our findings suggest that protein powder increases plasma sodium levels in patients with chronic SIAD through protein-induced ureagenesis and osmotic diuresis. The effects are comparable with oral urea.

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.

Copeptin levels in hospitalized infants and children with suspected vasopressin-dependent disorders: a case series.

OBJECTIVES: There have been recent advances assessing copeptin levels in adults with suspected disorders of vasopressin release. Very limited data exits on copeptin levels in children and infants, especially in a critically-ill hospitalized population where hyper- and hypo-natremia are very common. Our objective is to describe the institutional experience assessing copeptin levels in hospitalized infants and children with hyper- or hypo-natremia. METHODS: We performed a single-center retrospective case series of all infants, children, and adolescents who had an ultrasensitive plasma copeptin level obtained between 2019-2021. RESULTS: A total of 29 critically ill patients (6 infants) were identified with 38 % of patients having copeptin levels after neurosurgical procedures for tumors or trauma. Approximately 13/17 children with hypernatremia had central diabetes insipidus (central diabetes insipidus) to diagnose CDI, A copeptin level ≤ 4.9 pmol/L resulted in an 88 % sensitivity (95 % CI 47-99 %), and 66 % specificity (95 % CI 30-93 %). Amongst those with hyponatremia levels were more variable, 8/12 children had syndrome of inappropriate antidiuresis (SIAD) with copeptin levels ranging 4.7-72.6 pmol/L. CONCLUSIONS: While difficult to conclude due to multiple limitations, this case series highlights that typical copeptin cutoffs used to diagnose DI in adults in an ambulatory setting may also translate to a critically-ill pediatric population. Large prospective studies are needed to confirm this observation. In addition, postoperative copeptin levels could potentially be utilized as an additional marker to predict permanent from transient DI, but much larger studies are needed. Further work is needed to establish normative copeptin levels in infants and patients with SIAD.

Age-Associated Abnormalities of Water Homeostasis.

Deficits in renal function, thirst, and responses to osmotic and volume stimulation have been repeatedly demonstrated in older populations. The lessons learned over the past six decades serve to emphasize the fragile nature of water balance characteristic of aging. Older individuals are at increased risk for disturbances of water homeostasis due to both intrinsic disease and iatrogenic causes. These disturbances have real-life clinical implications in terms of neurocognitive effects, falls, hospital readmission and need for long-term care, incidence of bone fracture, osteoporosis, and mortality.

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.

Hyponatraemia caused by transient syndrome of inappropriate antidiuresis to urinary retention.

Hyponatraemia is frequently seen in the emergency department, possibly caused by the syndrome of inappropriate antidiuresis (SIAD). We report three cases in which we believe urinary retention with bladder distention caused hyponatraemia. Laboratory findings fulfilled the criteria for SIAD, for which no cause was found. Possibly pain or sympathetic nerve system activation leads to SIAD. Brisk diuresis occurred after placement of an indwelling urinary catheter with overly correction of sodium for which treatment was necessary. Clinicians should be aware that placement of an indwelling urinary catheter may prompt brisk water diuresis and a tendency to overcorrection.

Hyponatremia-related liver steatofibrosis and impaired spermatogenesis: evidence from a mouse model of the syndrome of inappropriate antidiuresis.

PURPOSE: Hyponatremia is the most frequent electrolytic disorder in clinical practice. In addition to neurological symptoms, hyponatremia, even when mild/moderate and chronic, has been related to other manifestations, such as bone demineralization and increased risk of fractures. To better elucidate tissue alterations associated with reduced serum sodium concentration [Na+], we developed an in vivo model of hyponatremia secondary to the Syndrome of Inappropriate Antidiuresis. METHODS AND RESULTS: Hyponatremia was induced in Foxn1nu/nu mice by subcutaneous infusion of the vasopressin analog 1-deamino [8-D-arginine] vasopressin (dDAVP) for 14 days via osmotic mini-pumps. Mice in the control group were infused with isotonic saline solution. Serum [Na+] progressively decreased, with a nadir of 123.4 ± 2.3 mEq/L (mean ± SD, dDAVP 0.3 ng/h) and 111.6 ± 4.7 mEq/L (mean ± SD, dDAVP 0.5 ng/h). Evident signs of liver steatofibrosis were observed at histology in hyponatremic mice. Accordingly, the expression of proteins involved in lipid metabolism (SREBP-1, PPARα and PPARγ) and in myofibroblast formation (αSMA and CTGF) significantly increased. Furthermore, heme oxygenase 1 expression was up-regulated in Kupffer and hepatic stellate cells in the liver of hyponatremic mice. Testis alterations were also observed. In particular, the thickness of the seminiferous epithelium appeared reduced. The expression levels of PCNA and PTMA, which are involved in DNA replication and germ cells maturation, were markedly reduced in the testis of hyponatremic mice. CONCLUSION: Overall, these findings shed new light on the possible consequences of chronic hyponatremia and prompt a more thorough evaluation of hyponatremic patients.

Relationship between hyponatremia at hospital admission and cardiopulmonary profile at follow-up in patients with SARS-CoV-2 (COVID-19) infection.

PURPOSE: Hyponatremia occurs in about 30% of patients with pneumonia, including those with SARS-CoV-2 (COVID-19) infection. Hyponatremia predicts a worse outcome in several pathologic conditions and in COVID-19 has been associated with a higher risk of non-invasive ventilation, ICU transfer and death. The main objective of this study was to determine whether early hyponatremia is also a predictor of long-term sequelae at follow-up. METHODS: In this observational study, we collected 6-month follow-up data from 189 laboratory-confirmed COVID-19 patients previously admitted to a University Hospital. About 25% of the patients (n = 47) had hyponatremia at the time of hospital admission. RESULTS: Serum [Na+] was significantly increased in the whole group of 189 patients at 6 months, compared to the value at hospital admission (141.4 ± 2.2 vs 137 ± 3.5 mEq/L, p < 0.001). In addition, IL-6 levels decreased and the PaO2/FiO2 increased. Accordingly, pulmonary involvement, evaluated at the chest X-ray by the RALE score, decreased. However, in patients with hyponatremia at hospital admission, higher levels of LDH, fibrinogen, troponin T and NT-ProBNP were detected at follow-up, compared to patients with normonatremia at admission. In addition, hyponatremia at admission was associated with worse echocardiography parameters related to right ventricular function, together with a higher RALE score. CONCLUSION: These results suggest that early hyponatremia in COVID-19 patients is associated with the presence of laboratory and imaging parameters indicating a greater pulmonary and right-sided heart involvement at follow-up.

Changes in Serum Creatinine Levels Can Help Distinguish Hypovolemic from Euvolemic Hyponatremia.

Background and Objectives: Differentiating between hypovolemic (HH) and euvolemic hyponatremia (EH) is crucial for correct diagnosis and therapy, but can be a challenge. We aim to ascertain whether changes in serum creatinine (SC) can be helpful in distinguishing HH from EH. Materials and Methods: Retrospective analysis of patients followed in a monographic hyponatremia outpatient clinic of a tertiary hospital during 1 January 2014−30 November 2019. SC changes during HH and EH from eunatremia were studied. The diagnostic accuracy of the SC change from eunatremia to hyponatremia (∆SC) was analyzed. Results: A total of 122 hyponatremic patients, median age 79 years (70−85), 46.7% women. In total, 70/122 patients had EH, 52/122 HH. During hyponatremia, median SC levels increased in the HH group: +0.18 mg/dL [0.09−0.39, p < 0.001], but decreased in the EH group: −0.07 mg/dL (−0.15−0.02, p < 0.001), as compared to SC in eunatremia. HH subjects presented a higher rate of a positive ∆SC than EH (90.4% vs. 25.7%, p < 0.001). EH subjects presented a higher rate of a negative/null ∆SC than HH (74.3% vs. 9.6%, p < 0.001). ROC curve analysis found an AUC of 0.908 (95%CI: 0.853 to 0.962, p < 0.001) for ∆SC%. A ∆SC% ≥ 10% had an OR of 29.0 (95%CI: 10.3 to 81.7, p < 0.001) for HH. A ∆SC% ≤ 3% had an OR of 68.3 (95%CI: 13.0 to 262.2, p < 0.001) for EH. Conclusions: The assessment of SC changes from eunatremia to hyponatremia can be useful in distinguishing between HH and EH.

Macroprolactinoma-Induced Syndrome of Inappropriate Antidiuresis and Its Reversal with Dopamine Agonist Therapy.

Hyponatremia is an uncommon manifestation of pituitary adenomas. Herein, I report a case of syndrome of inappropriate antidiuresis (SIAD) caused by a macroprolactinoma that rapidly resolved with dopamine agonist therapy. A 29-year-old White woman presented with euvolemic, hypotonic hyponatremia, normal thyroid and glucocorticoid axes, and inappropriately concentrated urine. She was found to have a 1.2-cm sellar mass. Investigation of additional pituitary axes revealed an elevated prolactin level of 193.7 ng/mL. The SIAD experienced by the patient corrected rapidly with initiation of cabergoline. The patient could not tolerate dopamine agonist therapy, and after 1 year, she underwent transsphenoidal resection of the mass after the prolactin began to increase. Pathological examination confirmed the diagnosis of macroprolactinoma. There was no recurrence of the tumor, and the patient continued to have normonatremia and normoprolactinemia 7 years after her operation. To my knowledge, this is the first report in the literature of pathology-confirmed macroprolactinoma marked by SIAD that showed rapid normalization of water metabolism with dopamine agonist therapy.