Treatment Guidelines for Hyponatremia: Stay the Course

Syndrome of Inappropriate Antidiuresis

Syndrome of inappropriate antidiuresis (SIAD)-the most frequent cause of hypotonic hyponatremia-is mediated by nonosmotic release of arginine vasopressin, which promotes water retention by activating renal vasopressin type 2 (V2) receptors. There are numerous causes of SIAD, including malignancy, pulmonary and central nervous system diseases, and medications. Rare activating mutations of the V2 receptor can also cause SIAD. Determination of the etiology of SIAD is important because removal of the stimulus for inappropriate arginine vasopressin secretion offers the most effective therapy. Treatment of SIAD is guided by symptoms and their severity, as well as the level of plasma sodium. In the absence of severe symptoms, which require urgent intervention, many clinicians focus on fluid restriction as a first-line treatment. Second-line therapeutic options include loop diuretics and salt tablets, urea, and V2 receptor antagonists.

Hyponatremia Correction and Osmotic Demyelination Syndrome Risk: A Systematic Review and Meta-Analysis

Rationale & Objective

Osmotic demyelination syndrome (ODS) is a rare but severe condition often attributed to the rate of sodium collection. We evaluated the association between the overly rapid sodium correction in adult hospitalized patients with ODS.

Study Design

Systematic review and meta-analysis.

Setting & Study Populations

Adults hospitalized hyponatremia patients.

Selection Criteria for Studies

The studies comparing the incidence of ODS with and without rapid sodium correction inception to January 2024.

Data Extraction

Two reviewers independently extracted data and assessed the risk of bias and the certainty of evidence.

Analytic Approach

The incidence of ODS following a rapid and nonrapid sodium correction was pooled using the random effects model. Subgroup and meta-regression analyses were performed for the robustness and the source of heterogeneity.

Results

Eleven cohort studies were included with 26,710 hospitalized hyponatremia patients. The definition of hyponatremia varied from <116 to <130 mmol/L, and overly rapid sodium correction was defined as >8 to 12 mmol/L within 24 hours. The overall incidence of ODS was 0.23%. The incidence of ODS in rapid and nonrapid sodium correction was 0.73% and 0.10%, respectively. Meta-analysis demonstrated that a rapid rate of sodium correction was associated with a higher incidence of ODS (odds ratio 3.16, 95% CI, 1.54-6.49, I2 = 27%), whereas some patients with hyponatremia developed ODS without rapid sodium level correction. The sensitivity analysis based on the quality of the studies was consistent with the main result.

Limitation

Various definition criteria for ODS diagnosis across studies, lack of potential electrolyte and treatment data that may affect the incidence of ODS.

Conclusions

The rapid rate of sodium correction had a statistical correlation with a higher incidence of ODS. Among ODS without rapid correction, further studies are recommended to evaluate and comprehend the relationship for better and proper management of hospitalized patients with hyponatremia.

Treatment of hyponatremia: comprehension and best clinical practice

This review article series on water and electrolyte disorders is based on the 'Electrolyte Winter Seminar' held annually for young nephrologists in Japan. The seminar features dynamic case-based discussions, some of which are included as self-assessment questions in this series. The second article in this series focuses on treatment of hyponatremia, a common water and electrolyte disorder frequently encountered in clinical practice. Hyponatremia presents diagnostic challenges due to its various etiologies and the presence of co-morbidities that affect water and electrolyte homeostasis. Furthermore, limited evidence, including a lack of robust randomized controlled trials, complicates treatment decisions and increases the risk of poor outcomes from inappropriate management of both acute and chronic hyponatremia. This review provides a comprehensive overview of treatment of hyponatremia for better comprehension and improved clinical practice.

Clinical factors associated with hyponatremia correction during treatment with oral urea

BACKGROUND

Oral urea is being used more commonly to treat hyponatremia, but factors contributing to the correction rate are unknown. We hypothesized that clinically relevant factors can be identified to help guide hyponatremia correction with oral urea.

METHODS

This was a retrospective study in two university hospitals including hospitalized patients with hyponatremia (plasma sodium <135 mmol/L) treated with oral urea. Linear mixed-effects models were used to identify factors associated with hyponatremia correction. Rates of overcorrection, osmotic demyelination and treatment discontinuation were also assessed.

RESULTS

We included 161 urea treatment episodes in 140 patients (median age 69 years, 46% females, 93% syndrome of inappropriate antidiuresis). Oral urea succeeded fluid restriction in 117 treatment episodes (73%), was combined with fluid restriction in 104 treatment episodes (65%) and was given as the only treatment in 27 treatment episodes (17%). A median dose of 30 g/day of urea for 4 days (interquartile range 2-7 days) increased plasma sodium from 127 to 134 mmol/L and normalized hyponatremia in 47% of treatment episodes. Older age (β 0.09, 95% CI 0.02-0.16), lower baseline plasma sodium (β -0.65, 95% CI -0.78 to -0.62) and higher cumulative urea dose (β 0.03, 95% CI -0.02 to -0.03) were independently associated with a greater rise in plasma sodium. Concurrent fluid restriction was associated with a greater rise in plasma sodium only during the first 48 h of treatment (β 1.81, 95% CI 0.40-3.08). Overcorrection occurred in 5 cases (3%), no cases of osmotic demyelination were identified and oral urea was discontinued in 11 cases (11%) due to side effects.

CONCLUSION

During treatment with oral urea, older age, higher cumulative dose, lower baseline plasma sodium and initial fluid restriction are associated with a greater correction rate of hyponatremia. These factors may guide clinicians to achieve a gradual correction of hyponatremia with oral urea.

The risk of sodium overcorrections in severe hyponatremia and the utility of desmopressin: a large retrospective study

Background

The suggested narrow rate of serum sodium (sNa) correction in hyponatremia can be difficult to respect, leading to overcorrections. Our ability to anticipate the rapidity of correction according to the mechanism of hyponatremia is uncertain. While desmopressin is often used to pause a rapid rise in sNa, its dose-related effect is also not well described. We studied the rate of hyponatremia overcorrections, its prediction and the utility of desmopressin in its management.

Methods

We retrospectively reviewed all cases of severe hyponatremia (sNa <120 mmol/L) in a large university hospital that occurred over 10 years. We assessed investigations, causes and treatments. We compared all sNa separated by at least 8 h and calculated correction rates. Significant overcorrection rates were defined by any rise of sNa >9 mmol/L per day sustained over at least 24 h.

Results

After exclusions, we found 355 episodes of severe hyponatremia. Low, appropriate and inappropriate antidiuretic hormone (ADH)-defined mechanisms accounted for 17%, 24% and 29% of etiologies, respectively, with the remaining 25% secondary to diuretics and 5% of uncertain causes. First urinary sodium and osmolality were consistent with the final diagnosis in 73%. Significant overcorrections were seen in 45% and were frequent in the setting of low ADH. Desmopressin was given in 82 episodes, more often as a rescue than a preventive measure, with the subsequent sNa dropping by ≥5 mmol/L by 12 h in eight instances. The dose of desmopressin (≥2 µg versus 1 µg) and a higher volume of intravenous free-water coadministration resulted in a clinically meaningful greater reduction in sNa in the following 12 h.

Conclusions

Overcorrections in severe hyponatremia are common, mainly when ADH is low. Initial urinary measurements anticipate this risk. Desmopressin effectively halted the rate of correction in a dose-dependent manner. Caution should be given when coadministrating water, which can significantly lower the sNa.

Correction of profound hyponatraemia following rapid bolus therapy: effectiveness of the Barsoum-Levine formula based on the Edelman equation

Background

The optimal treatment for profound hyponatraemia remains uncertain. Recent clinical studies have demonstrated that a standardized bolus of hypertonic saline is effective, but relying solely on this approach may not fully address the individual variability of hyponatraemia among patients. We evaluated the effectiveness of rapid bolus (RB) administration of hypertonic saline followed by predictive correction (PC) using an infusate and fluid loss formula identical to the Barsoum-Levine formula based on the Edelman equation (RB-PC) for managing profound hyponatraemia.

Methods

In this retrospective observational cohort study, we evaluated 276 patients aged >18 years with s[Na] levels ≤120 mEq/L (January 2014-December 2023). Using propensity score matching (PSM), we assessed s[Na] elevations at 6 h post-treatment initiation and the rate of appropriate hyponatraemia correction between the RB-PC and PC groups. We defined the appropriate correction as a change in s[Na] in the range of 4-10 mEq/L within the first 24 h and ≤18 mEq/L within the first 48 h following corrective treatment initiation.

Results

Among 276 patients with profound hyponatraemia (s[Na] ≤120 mEq/L), 49 and 108 underwent treatment with RB-PC therapy and with PC therapy without RB, respectively. Post-PSM, 84 patients were selected and allocated to the RB-PC (n = 42) or PC group (n = 42). In PSM analysis, patients with RB-PC experienced a higher elevation in s[Na] at 6 h after treatment initiation than PC (4.0 vs 2.4 mEq/L, P < 0.001). The rate of appropriate correction was similar between the RB-PC and PC groups (90.5% vs 90.5%, P = 1).

Conclusions

RB-PC can quickly elevate s[Na] levels and achieve appropriate correction of s[Na] in patients with profound hyponatraemia.

Paraneoplastic endocrine syndromes: a contemporary overview

INTRODUCTION

Endocrine paraneoplastic syndromes (ePNS) are caused by malignant cells that induce hormonal alterations unrelated to the tissue of origin of the neoplasm. The aim of this manuscript is to review the pathophysiology, diagnosis, and treatment of endocrine paraneoplastic syndromes (ePNS).

AREAS COVERED

We searched the PubMed/Medline, Embase, and Scielo databases, including 96 articles. The pathogenesis of ePNS involves mutations that activate hormonal genes. Hypercalcemia, the most common ePNS, is marker of poor prognosis in most cases. The syndrome of inappropriate antidiuresis causes euvolemic hyponatremia. Ectopic Cushing's syndrome is commonly associated with lung cancer. Paraneoplastic acromegaly is very rare and is associated with pancreatic and lung tumors. Paraneoplastic hypoglycemia usually requires surgical treatment. Other endocrine paraneoplastic syndromes include ectopic secretion of hormones such as calcitonin, renin, vasoactive intestinal polypeptide, fibroblast growth factor 23, paraneoplastic autoimmune hypophysitis, and others.

EXPERT OPINION

In addition to the local manifestations and metastasis of neoplasms, some secrete bioactive substances causing PNS. Recognizing and treating PNS early improves clinical outcomes. Larger-scale studies and clinical trials are needed to enhance their management and prognosis.

The Different Paths That Lead to Hypotonic Hyponatremia, and a Safe Approach to Treatment

A knowledge gap may exist when attempting to identify the pathogenetic mechanisms resulting in the syndrome of inappropriate antidiuretic hormone (SIADH) or hypotonic hyponatremia. Ectopic secretion of antidiuretic hormone [ADH] is the classic cause of SIADH. But another form of inappropriate secretion of ADH occurs when interleukin 6 is activated. Hypotonic hyponatremia can also occur in patients with cerebral salt wasting, but the secretion of ADH is appropriate, responding to volume depletion induced by excessive natriuresis. Reset osmostat (RO) is another cause of hypotonic hyponatremia caused by an unknown anomaly in the hypothalamus. This review discusses the pathophysiology of and the identical laboratory findings found in classic ectopic ADH secretion, interleukin 6-mediated ADH secretion, cerebral salt wasting-induced ADH secretion, and RO. This review also discusses potential methods to discern which hypotonic hyponatremic syndrome is present and current recommendations for treatment.

Diagnostic validity and solute-corrected prevalence for hyponatremia and hypernatremia among 1 813 356 admissions

Background and hypothesis

We aimed to evaluate the diagnostic validity of the International Classification of Diseases, 10th Revision (ICD-10) codes for hyponatremia and hypernatremia, using a database containing laboratory data. We also aimed to clarify whether corrections for blood glucose, triglyceride, and total protein may affect the prevalence and the diagnostic validity.

Methods

We retrospectively identified admissions with laboratory values using a Japanese hospital-based database. We calculated the sensitivity, specificity, and positive/negative predictive values of recorded ICD-10-based diagnoses of hyponatremia (E87.1) and hypernatremia (E87.2), using serum sodium measurements during hospitalization (<135 and >145 mmol/l, respectively) as the reference standard. We also performed analyses with corrections of sodium concentrations for blood glucose, triglyceride, and total protein.

Results

We identified 1 813 356 hospitalizations, including 419 470 hyponatremic and 132 563 hypernatremic cases based on laboratory measurements, and 18 378 hyponatremic and 2950 hypernatremic cases based on ICD-10 codes. The sensitivity, specificity, positive predictive value, and negative predictive value of the ICD-10 codes were 4.1%, 99.9%, 92.5%, and 77.6%, respectively, for hyponatremia and 2.2%, >99.9%, 96.5%, and 92.8%, respectively, for hypernatremia. Corrections for blood glucose, triglyceride, and total protein did not largely alter diagnostic values, although prevalence changed especially after corrections for blood glucose and total protein.

Conclusions

The ICD-10 diagnostic codes showed low sensitivity, high specificity, and high positive predictive value for identifying hyponatremia and hypernatremia. Corrections for glucose or total protein did not affect diagnostic values but would be necessary for accurate prevalence calculation.

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.

Transient secondary pseudo-hypoaldosteronism in infants with urinary tract infections: systematic literature review

Infants with a congenital anomaly of the kidney and urinary tract sometimes present with hyponatremia, hyperkalemia, and metabolic acidosis due to under-responsiveness to aldosterone, hereafter referred to as secondary pseudo-hypoaldosteronism. The purpose of this report is to investigate pseudo-hypoaldosteronism in infant urinary tract infection. A systematic review was conducted following PRISMA guidelines after PROSPERO (CRD42022364210) registration. The National Library of Medicine, Excerpta Medica, Web of Science, and Google Scholar without limitations were used. Inclusion criteria involved pediatric cases with documented overt pseudo-hypoaldosteronism linked to urinary tract infection. Data extraction included demographics, clinical features, laboratory parameters, management, and course. Fifty-seven reports were selected, detailing 124 cases: 95 boys and 29 girls, 10 months or less of age (80% of cases were 4 months or less of age). The cases exhibited hyponatremia, hyperkalemia, acidosis, and activated renin-angiotensin II-aldosterone system. An impaired kidney function was found in approximately every third case. Management included antibiotics, fluids, and, occasionally, emergency treatment of hyperkalemia, hyponatremia, or acidosis. The recovery time averaged 1 week for electrolyte, acid-base imbalance, and kidney function. Notably, anomalies of the kidney and urinary tract were identified in 105 (85%) cases.

CONCLUSIONS

This review expands the understanding of overt transient pseudo-hypoaldosteronism complicating urinary tract infection. Management involves antimicrobials, fluid replacement, and consideration of electrolyte imbalances. Raising awareness of this condition within pediatric hospitalists is desirable.

WHAT IS KNOWN

• Infants affected by a congenital anomaly of the kidney and urinary tract may present with clinical and laboratory features resembling primary pseudo-hypoaldosteronism. • Identical features occasionally occur in infant urinary tract infection.

WHAT IS NEW

• Most cases of secondary pseudo-hypoaldosteronism associated with a urinary tract infection are concurrently affected by a congenital anomaly of the kidney and urinary tract. • Treatment with antibiotics and parenteral fluids typically results in the normalization of sodium, potassium, bicarbonate, and creatinine within approximately 1 week.

A Reassessment of Sodium Correction Rates and Hospital Length of Stay Accounting for Admission Diagnosis

Background Slow correction of severe hyponatremia has been historically recommended due to the risk of rare but catastrophic neurologic events with rapid correction. A recent study challenging this paradigm reported that rapid correction is associated with shorter hospital length of stay, but that study did not control for admission diagnosis. The objective of this study was to determine whether rapid correction is associated with shorter length of stay when controlling for admission diagnosis. Methods This retrospective cohort study is based on the fourth edition of the Medical Information Mart for Intensive Care, MIMIC-IV, a deidentified, publicly available clinical research database which includes admissions from 2008-2019. Patients were identified who presented to the hospital with initial sodium <120 mEq/L and were categorized according to total sodium correction achieved in the first day (<6 mEq/L; 6-10 mEq/L; >10 mEq/L). Linear regression was used to assess for an association between correction rate and hospital length of stay, and to determine if this association was significant when controlling for admission diagnosis classifications based on diagnosis related groups (DRGs). Results There were 419 patients with severe hyponatremia (<120 mEq/L) included in this study, of whom 374 survived to discharge. Median [IQR] hospital length of stay was 6 [4, 11] days. In a univariable linear regression, there was a trend towards a significant association between the highest rate of correction (>10 mEq/L) and shorter length of stay, as compared with a moderate rate of correction (coef. -2.764, 95% CI [-5.791, 0.263], p=0.073), but the association was not significant when controlling for admission diagnosis group (coef. -1.561, 95% CI [-4.398, 1.276], p=0.280). There was a significant association in the survivor subset (coef. -3.455, 95% CI [-6.668, -0.242], p=0.035), but it was also not significant when controlling for admission diagnosis group (coef. -2.200, 95% CI [-5.144, 0.743], p=0.142). Conclusions Rapid correction is not associated with shorter length of stay when controlling for admission diagnosis, suggesting that the disease state confounds this association. Findings from prior and future studies reporting this association should not drive clinical decision making if the confounding effect of hospital admission diagnosis and competing risk of death are not fully accounted for.

Case report: Acute severe hyponatremia-induced seizures in a newborn: a community-acquired case and literature review

Severe neonatal hyponatremia represents a critical electrolyte imbalance with potentially severe neurological outcomes, a condition rarely documented in community-acquired, full-term newborns. This report underscores a unique case of a 23-day-old, previously healthy, full-term male neonate experiencing severe hyponatremia that precipitated seizures, underscoring the urgency of prompt recognition and intervention. The neonate presented with symptoms including vomiting, groaning, chills, fixed staring, and limb tremors. Critical findings upon admission encompassed hypothermia, hypotension, tachycardia, and tachypnea accompanied by significant weight loss. The clinical presentation was marked by dehydration, lethargy, weak crying, a fixed gaze, irregular breathing, and coarse lung sounds, yet a distended abdomen, hypertonic limb movements, and recurrent seizures were observed. Immediate interventions included establishing IV access, rewarming, mechanical ventilation, seizure management, volume expansion, dopamine for circulatory support, and initiation of empirical antibiotics. Diagnostic evaluations revealed a sodium ion concentration of 105.9 mmol/L, while amplitude-integrated electroencephalography (aEEG) detected pronounced seizure activity characterized by a lack of sleep-wake rhythmicity, noticeable elevation in both the lower and upper amplitude margins, and a sustained decrease in the lower margin voltage dropping below 5 μV, presenting as sharp or serrated waveforms. The management strategy entailed rapid electrolyte normalization using hypertonic saline and sodium bicarbonate, anticonvulsant therapy, and comprehensive supportive care, with continuous aEEG monitoring until the cessation of seizures. Remarkably, by the third day, the neonate's condition had stabilized, allowing for discharge in good health 10 days post-admission. At a 16-month follow-up, the child exhibited no adverse neurological outcomes and demonstrated favorable growth and development. Our extensive review on the etiology, clinical manifestations, aEEG monitoring, characteristics of seizures induced by severe neonatal hyponatremia, treatment approaches, and the prognosis for seizures triggered by severe hyponatremia aims to deepen the understanding and enhance clinical management of this complex condition. It stresses the importance of early detection, accurate diagnosis, and customized treatment protocols to improve outcomes for affected neonates. Additionally, this review accentuates the indispensable role of aEEG monitoring in managing neonates at elevated risk for seizures. Yet, the safety and efficacy of swiftly administering hypertonic saline for correcting severe hyponatremia-induced seizures necessitate further investigation through medical research.

Long-Term Effects of Tolvaptan in Autosomal Dominant Polycystic Kidney Disease: Predictors of Treatment Response and Safety over 6 Years of Continuous Therapy

Tolvaptan, an oral vasopressin V2 receptor antagonist, reduces renal volume expansion and loss of renal function in patients with autosomal dominant polycystic kidney disease (ADPKD). Data for predictive factors indicating patients more likely to benefit from long-term tolvaptan are lacking. Data were retrospectively collected from 55 patients on tolvaptan for 6 years. Changes in renal function, progression of renal dysfunction (estimated glomerular filtration rate [eGFR], 1-year change in eGFR [ΔeGFR/year]), and renal volume (total kidney volume [TKV], percentage 1-year change in TKV [ΔTKV%/year]) were evaluated at 3-years pre-tolvaptan, at baseline, and at 6 years. In 76.4% of patients, ΔeGFR/year improved at 6 years. The average 6-year ΔeGFR/year (range) minus baseline ΔeGFR/year: 3.024 (-8.77-20.58 mL/min/1.73 m2). The increase in TKV was reduced for the first 3 years. A higher BMI was associated with less of an improvement in ΔeGFR (p = 0.027), and family history was associated with more of an improvement in ΔeGFR (p = 0.044). Hypernatremia was generally mild; 3 patients had moderate-to-severe hyponatremia due to prolonged, excessive water intake in response to water diuresis-a side effect of tolvaptan. Family history of ADPKD and baseline BMI were contributing factors for ΔeGFR/year improvement on tolvaptan. Hyponatremia should be monitored with long-term tolvaptan administration.

[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.

Severe osmotic demyelination syndrome with cortical involvement in the context of severe hyponatremia and central diabetes insipidus: an uncommon presentation of an unusual combination

BACKGROUND

Osmotic demyelination syndrome (ODS) with cerebral cortical involvement is a rare complication of severe hyponatremia correction. Careful management of hyponatremia is crucial, particularly in patients with risk factors, such as alcohol use disorder and diabetes insipidus.

CASE

A patient in his 40s with a history of alcohol use disorder and central diabetes insipidus developed ODS after a 24 mEq/L osmolar increase during the treatment of hyponatremia. The patient's condition progressed into locked-in syndrome and then improved to spastic tetraparesis after cortical basal ganglia ODS improved.

DISCUSSION

The differential diagnosis of cortical demyelination includes laminar cortical necrosis, being the interpretation of Apparent Diffusion Coefficient (ADC) MRI sequence is a useful tool.This case underscores the need to investigate and improve diagnosis and treatment strategies in patients with ODS. It also emphasises the significance of careful hyponatremia correction and frequent monitoring, particularly in patients with known risk factors for ODS.