Treating profound hyponatremia: a strategy for controlled correction

Osmotic demyelination syndrome: revisiting the diagnostic criteria through two fatal cases

BACKGROUND

Osmotic Demyelination Syndrome (ODS) encompasses Central Pontine Myelinolysis and Extrapontine Myelinolysis, both of which are serious neurological conditions linked to the overly rapid correction of hyponatremia. Despite growing evidence, the exact etiology of ODS remains incompletely understood. The present paper describes two case studies, aiming to provide a comprehensive overview of the pathological findings and clinical outcomes associated with ODS.

CASE PRESENTATION

Case #1. A 74-year-old woman was admitted to the emergency department following a head trauma caused by a loss of consciousness. Initial laboratory tests revealed severe hyponatremia (sodium level of 101 mmol/L) and hypokalemia (potassium level of 2.9 mmol/L). The patient underwent corrective therapy with saline and potassium chloride. Despite the correction of electrolyte imbalances, the patient developed a hyperintense lesion in the median portion of the pons on T2-fluid-attenuated inversion recovery (FLAIR) MRI sequence 14 days post-treatment, consistent with ODS. The patient's condition deteriorated, leading to irreversible coma and status epilepticus, culminating in death 32 days after admission. Case #2. An 81-year-old woman with a medical history of hypothyroidism, hypertension, major depression, and stage 3 chronic kidney disease presented with mild gait disturbances. Subsequent testing revealed severe hyponatremia (sodium level of 100 mmol/L). Following an initial clinical improvement due to sodium correction, the patient's condition worsened, with symptoms progressing to confusion, lethargy, and eventually, ODS. Dermatological manifestations, including blistering lesions and facial edema, appeared as the condition advanced. The patient succumbed to irreversible coma 47 days after admission.

CONCLUSION

ODS traditionally carried a poor prognosis, with high mortality rates and diagnoses often made postmortem. However, recent advances in understanding the pathophysiology, along with improvements in diagnostic techniques such as MRI and intensive care treatments, have led to earlier identification, treatment, and recognition of milder forms of the syndrome. Despite these advancements, ODS remains a critical condition with significant risks, particularly following the rapid correction of severe hyponatremia.

Unveiling the Patterns of Water Diuresis in Profound Hyponatremia Management in Intensive Care Unit Settings

Key Points

Water diuresis presents a conundrum during the treatment of profound hyponatremia, but its clinical characteristics remain unclear. This study revealed that water diuresis mostly manifests within 24 hours of treatment, preceded by changes in urinary characteristics. Careful urine monitoring in the early stages of hyponatremia treatment could facilitate the early detection of water diuresis.

Background

Hyponatremia treatment guidelines recommend avoiding excessive increases in serum sodium concentration (s[Na]) to prevent osmotic demyelination syndrome. Although an unexpected rise in s[Na] has been attributed to water diuresis during the treatment of hyponatremia, clinical courses of water diuresis are unclear. We conducted this study to investigate the clinical characteristics of water diuresis during profound hyponatremia management.

Methods

In this retrospective observational study, we examined patients with profound hyponatremia (s[Na] ≤120 mEq/L) admitted to the intensive care unit of a Japanese hospital. The manifestation of water diuresis was defined as a urine volume (UV) ≥2 ml/kg per hour and a urinary sodium plus potassium concentration (u[Na+K]) ≤50 mEq/L. We analyzed changes in UV and u[Na+K] over time for patients experiencing water diuresis. This analysis employed a mixed-effects model with spline terms for time, and the results are graphically presented.

Results

Among 47 eligible patients, 30 (64%) met the criteria for water diuresis. The etiologies of hyponatremia were drug-related hyponatremia (n =10; 33%), primary polydipsia (n =8; 27%), hypovolemic hyponatremia (n =7; 23%), syndrome of inappropriate antidiuresis (n =7; 23%), and acute heart failure (n =1; 3%). Among patients with water diuresis, 27 (90%) experienced the manifestation of water diuresis within 24 hours after the start of correction. The increased UV and decreased u[Na+K] levels began several hours before the peak manifestation of water diuresis. Within 6 hours after the manifestation of water diuresis, 29 patients (97%) received electrolyte-free infusions and 14 (47%) received desmopressin. One patient (3%) with water diuresis experienced overcorrection.

Conclusions

Water diuresis is common during the treatment for profound hyponatremia and typically occurs within the first 24 hours, preceded by changes in urinary characteristics. Early detection and prompt response to water diuresis through urine monitoring during the early periods of hyponatremia treatment may be effective for managing water diuresis.

[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.

Treatment Guidelines for Hyponatremia: Stay the Course

International guidelines designed to minimize the risk of complications that can occur when correcting severe hyponatremia have been widely accepted for a decade. On the basis of the results of a recent large retrospective study of patients hospitalized with hyponatremia, it has been suggested that hyponatremia guidelines have gone too far in limiting the rate of rise of the serum sodium concentration; the need for therapeutic caution and frequent monitoring of the serum sodium concentration has been questioned. These assertions are reminiscent of a controversy that began many years ago. After reviewing the history of that controversy, the evidence supporting the guidelines, and the validity of data challenging them, we conclude that current safeguards should not be abandoned. To do so would be akin to discarding your umbrella because you remained dry in a rainstorm. The authors of this review, who represent 20 medical centers in nine countries, have all contributed significantly to the literature on the subject. We urge clinicians to continue to treat severe hyponatremia cautiously and to wait for better evidence before adopting less stringent therapeutic limits.

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.

Overcorrection and undercorrection with fixed dosing of bolus hypertonic saline for symptomatic hyponatremia

OBJECTIVE

Current guidelines recommend treating symptomatic hyponatremia with rapid bolus-wise infusion of fixed volumes of hypertonic saline regardless of body weight. We hypothesize that this approach is associated with overcorrection and undercorrection in patients with low and high body weight.

DESIGN

Single-center, retrospective cohort study.

METHODS

Data were collected on patients treated with ≥1 bolus 100 or 150 mL 3% NaCl for symptomatic hyponatremia between 2017 and 2021. Outcomes were overcorrection (plasma sodium rise > 10 mmol/L/24 h, > 18 mmol/L/48 h, or relowering therapy) and undercorrection (plasma sodium rise < 5 mmol/L/24 h). Low body weight and high body weight were defined according to the lowest (≤60 kg) and highest (≥80 kg) quartiles.

RESULTS

Hypertonic saline was administered to 180 patients and caused plasma sodium to rise from 120 mmol/L to 126.4 mmol/L (24 h) and 130.4 mmol/L (48 h). Overcorrection occurred in 32 patients (18%) and was independently associated with lower body weight, weight ≤ 60 kg, lower baseline plasma sodium, volume depletion, hypokalemia, and less boluses. In patients without rapidly reversible causes of hyponatremia, overcorrection still occurred more often in patients ≤ 60 kg. Undercorrection occurred in 52 patients (29%) and was not associated with body weight or weight ≥ 80 kg but was associated with weight ≥ 100 kg and lean body weight in patients with obesity.

CONCLUSION

Our real-world data suggest that fixed dosing of bolus hypertonic saline may expose patients with low and high body weight to more overcorrection and undercorrection, respectively. Prospective studies are needed to develop and validate individualized dosing models.

Hypertonic Saline for Hyponatremia: Meeting Goals and Avoiding Harm

Hypertonic saline has been used for the treatment of hyponatremia for nearly a century. There is now general consensus that hypertonic saline should be used in patients with hyponatremia associated with moderate or severe symptoms to prevent neurological complications. However, much less agreement exists among experts regarding other aspects of its use. Should hypertonic saline be administered as a bolus injection or continuous infusion? What is the appropriate dose? Is a central venous line necessary? Should desmopressin be used concomitantly and for how long? This article considers these important questions, briefly explores the historical origins of hypertonic saline use for hyponatremia, and reviews recent evidence behind its indications, dosing, administration modality and route, combined use with desmopressin to prevent rapid correction of serum sodium, and other considerations such as the need and degree for fluid restriction. The authors conclude by offering some practical recommendations for the use of hypertonic saline.

Evaluation of Desmopressin in Critically Ill Patients with Hyponatremia Requiring 3% Hypertonic Saline

BACKGROUND

Desmopressin (DDAVP) is often used for hyponatremia management but has been associated with increases in hospital length of stay and duration of hypertonic saline use. The purpose of this study was to evaluate hyponatremia management strategies and their effect on sodium correction in critically ill patients requiring 3% hypertonic saline (3HS).

METHODS

This retrospective, single-center study included critically ill patients with hyponatremia (serum sodium ≤ 125 mEq/L) receiving 3HS from May 31 2015, to May 31 2019. Patients were divided into those who received 3HS for hyponatremia management (HTS) and those who received proactive or reactive DDAVP in addition to 3HS (D-HTS). Patients in either group could receive rescue DDAVP. The primary outcome was the percentage of patients achieving goal sodium correction of 5-10 mEq/L 24 h after 3HS initiation.

RESULTS

Goal sodium correction was achieved in 52.5% of patients in HTS compared to 65.6% of patients in D-HTS (p = 0.21). Patients in HTS had a shorter duration of 3HS infusion (p = 0.0022) with no difference in ICU length of stay, free water intake, urine output, or serum sodium increases 12 and 24 h after receiving 3HS. Overcorrection during any 24- or 48 h period was not statistically different between groups.

CONCLUSION

Patients in HTS and D-HTS had similar rates of achieving goal sodium correction at 24 h. A proactive or reactive DDAVP strategy led to an increase in 3HS duration and total amount with no significant difference in rates of overcorrection. Prospective, randomized studies assessing standardized strategies for hyponatremia management and DDAVP administration are warranted.

Association of intranasal desmopressin therapy with overcorrection of severe hyponatremia: A retrospective, propensity score-based, single-center cohort study

PURPOSE

Severe hyponatremia, defined as serum sodium concentration ([sNa]) ≤ 120 mEq/L, requires aggressive treatment to prevent potentially fatal cerebral edema, seizures, and other sequelae, but overcorrection can also result in life-threatening cerebral hemorrhage and demyelination. We compared the safety and efficacy of nasal desmopressin to conventional management for the prevention of [sNa] overcorrection.

MATERIAL AND METHODS

This retrospective analysis compared 47 patients treated with desmopressin to 17 patients treated conventionally at a university hospital ICU in Japan between 2013 and 2018 using propensity score-based approaches. The primary outcome was safe [sNa] correction, defined as a ≤ 8 mEq/L difference between baseline and follow-up [sNa] at any time within 24h of diagnosis.

RESULTS

The 24-h safe correction rate was significantly greater in the desmopressin group than the conventional treatment group (68% [32/47] vs. 41% [7/17], P = 0.039), and dose-response analysis indicated a positive association between cumulative 24-h desmopressin dose and safe correction at 24 h (P = 0.003). Few overcorrections precluded reliable assessment at 48 h. Exacerbation of hyponatremia was comparable in the two treatment groups.

CONCLUSIONS

Intranasal desmopressin therapy increased the safe correction of severe hyponatremia. Large prospective trials are warranted to confirm this result.

Treatment of severe symptomatic hyponatremia

Hyponatremia is the most common electrolyte abnormality seen in the hospital. Severe symptomatic hyponatremia is associated with grave consequences including cerebral edema, brain herniation, seizures, obtundation, coma, and respiratory arrest. However, rapid correction of chronic severe hyponatremia may lead to osmotic demyelination syndrome (ODS) and even death. Given the serious consequences of severe hyponatremia or its inadvertent overcorrection, it is of paramount importance for the clinician to be aware of the various scenarios in which hyponatremic patients can present and tailor the management strategies accordingly. We present here a case of severe hyponatremia of unknown duration with the presenting plasma sodium level of 95 mmol/L and use it to illustrate the various treatment strategies - proactive, reactive, or rescue therapy - along with the physiological basis to support these approaches.

Hyponatraemia in heart failure

Hyponatraemia is common in heart failure (HF). It is estimated that over 20% of patients admitted to hospital with HF have hyponatraemia. It has also been repeatedly shown to be a surrogate marker of increased morbidity and mortality in this specific population. This review focuses on the pathophysiology of hyponatraemia through the activation of neurohormonal cascades in HF, the clinical implications of sustained hyponatraemia and treatment options in the management of this challenging phenomenon.

Use of Desmopressin in Hyponatremia: Foe and Friend

Use of desmopressin (1-deamino-8-d-arginine vasopressin; DDAVP), a synthetic vasopressin receptor agonist, has expanded in recent years. Desmopressin leads to renal water retention, and iatrogenic hyponatremia may result if fluid intake is not appropriately restricted. It is common practice to stop a medication that is causing toxicity, and this advice is promulgated in Micromedex, which suggests withholding desmopressin if hyponatremia occurs. If intravenous saline solution is administered and desmopressin is withheld at the same time, rapid changes in serum sodium levels may result, which puts the patient at risk for demyelinating lesions. In the management of desmopressin-associated hyponatremia with neurologic symptoms, the drug should not be withheld despite the presence of hyponatremia. The medication should be continued while administering intravenous hypertonic saline solution. Desmopressin is also used to minimize water excretion during the correction of hyponatremia during water diuresis. When treating hyponatremia, clinicians should monitor closely to avoid free-water diuresis. To prevent ongoing water losses in urine and overly rapid “autocorrection” of serum sodium level, desmopressin can be given to reduce free-water losses. These treatment recommendations are the authors’ perspective from previously published work and personal clinical experience.

Practical document on the management of hyponatremia in critically ill patients

Hyponatremia is the most prevalent electrolyte disorder in Intensive Care Units. It is associated with an increase in morbidity, mortality and hospital stay. The majority of the published studies are observational, retrospective and do not include critical patients; hence it is difficult to draw definitive conclusions. Moreover, the lack of clinical evidence has led to important dissimilarities in the recommendations coming from different scientific societies. Finally, etiopathogenic mechanisms leading to hyponatremia in the critical care patient are complex and often combined, and an intensive analysis is clearly needed. A study was therefore made to review all clinical aspects about hyponatremia management in the critical care setting. The aim was to develop a Spanish nationwide algorithm to standardize hyponatremia diagnosis and treatment in the critical care patient.

Risk Factors and Outcomes of Rapid Correction of Severe Hyponatremia

BACKGROUND AND OBJECTIVES

Rapid correction of severe hyponatremia can result in serious neurologic complications, including osmotic demyelination. Few data exist on incidence and risk factors of rapid correction or osmotic demyelination.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In a retrospective cohort of 1490 patients admitted with serum sodium <120 mEq/L to seven hospitals in the Geisinger Health System from 2001 to 2017, we examined the incidence and risk factors of rapid correction and osmotic demyelination. Rapid correction was defined as serum sodium increase of >8 mEq/L at 24 hours. Osmotic demyelination was determined by manual chart review of all available brain magnetic resonance imaging reports.

RESULTS

Mean age was 66 years old (SD=15), 55% were women, and 67% had prior hyponatremia (last outpatient sodium <135 mEq/L). Median change in serum sodium at 24 hours was 6.8 mEq/L (interquartile range, 3.4-10.2), and 606 patients (41%) had rapid correction at 24 hours. Younger age, being a woman, schizophrenia, lower Charlson comorbidity index, lower presentation serum sodium, and urine sodium <30 mEq/L were associated with greater risk of rapid correction. Prior hyponatremia, outpatient aldosterone antagonist use, and treatment at an academic center were associated with lower risk of rapid correction. A total of 295 (20%) patients underwent brain magnetic resonance imaging on or after admission, with nine (0.6%) patients showing radiologic evidence of osmotic demyelination. Eight (0.5%) patients had incident osmotic demyelination, of whom five (63%) had beer potomania, five (63%) had hypokalemia, and seven (88%) had sodium increase >8 mEq/L over a 24-hour period before magnetic resonance imaging. Five patients with osmotic demyelination had apparent neurologic recovery.

CONCLUSIONS

Among patients presenting with severe hyponatremia, rapid correction occurred in 41%; nearly all patients with incident osmotic demyelination had a documented episode of rapid correction.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2018_06_05_CJASNPodcast_18_7_G.mp3.

Treatment of Severe Hyponatremia

Patients with severe (serum sodium ≤120 mEq/L), symptomatic hyponatremia can develop life-threatening or fatal complications from cerebral edema if treatment is inadequate and permanent neurologic disability from osmotic demyelination if treatment is excessive. Unfortunately, as is true of all electrolyte disturbances, there are no randomized trials to guide the treatment of this challenging disorder. Rather, therapeutic decisions rest on physiologic principles, animal models, observational studies, and single-patient reports. European guidelines and recommendations of an American Expert panel have come to similar conclusions on how much correction of hyponatremia is enough and how much is too much, but there are important differences. We review the evidence supporting these recommendations, identifying areas that rest on relatively solid ground and highlighting areas in greatest need of additional data.

The Role of Desmopressin in the Management of Severe, Hypovolemic Hyponatremia: A Single-Center, Comparative Analysis

Background

The role of desmopressin (DDAVP) to prevent or treat rapid serum sodium concentration ([Na]s) correction during hyponatremia management remains unclear.

Objective

To assess DDAVP use during the first 48 hours of severe, hypovolemic hyponatremia management. The primary study hypothesis was that the use of DDAVP would slow the rate of [Na]s correction compared with those not receiving DDAVP.

Design

A retrospective, observational, comparison study.

Setting

A single, Canadian, tertiary center.

Patients

All admitted patients referred to the nephrology service for severe, hypovolemic hyponatremia ([Na]s < 125 mmol/L) over a 12-month period from November 2015.

Measurements

The primary outcomes measure was the [Na]s after medical management for 48 hours. The length of hospital stay was also measured.

Methods

Patients were grouped based on whether they received DDAVP during the first 48 hours of treatment, and [Na]s correction was compared between groups using linear regression. An exploratory, multivariable, linear regression model was used to adjust for diabetes status, active malignancy, intensive care unit (ICU) admission, and hypertonic saline administration.

Results

Twenty-eight patients were identified, with baseline mean [Na]s of 112.7 ± 6.6 mmol/L versus 117 ± 4.3mmol/L (P = .06) in those receiving (n = 16) and not receiving DDAVP (n = 12), respectively. The DDAVP group had a more rapid [Na]s correction on the first day compared with those not receiving DDAVP, 7.7 ± 3.8 mmol/L/d versus 5.1 ± 2.0 mmol/L/d (P = .04). On the second day, there was a similar rate of [Na]s correction between groups: 1.3 ± 4.3 mmol/L/d versus 2.6 ± 3.2 mmol/L/d (P = .39), respectively. Overall, there was no difference in [Na]s correction after 48 hours between those who received DDAVP and those who did not: 121.7 ± 7.5 mmol/L versus 124.8 ± 5.7 mmol/L (P = .24). Patients who had experienced an overcorrection were successfully treated with DDAVP (n = 5), so that no patient had an ongoing overcorrection by 48 hours.

Limitations

The limited sample size and lack of randomization preclude definitive conclusion on the additional benefit of DDAVP to standard care.

Conclusion

DDAVP appears to be safe and effective in the management of severe, hypovolemic hyponatremia, associated with similar [Na]s correction to those who did not receive DDAVP after 48 hours, despite an initial more rapid correction. A randomized trial should examine what benefit DDAVP confers in addition to standard care in the management of severe, hypovolemic hyponatremia.

Hyponatremia and the Brain

Hyponatremia is defined by low serum sodium concentration and is the most common electrolyte disorder encountered in clinical practice. Serum sodium is the main determinant of plasma osmolality, which, in turn, affects cell volume. In the presence of low extracellular osmolality, cells will swell if the adaptation mechanisms involved in the cell volume maintenance are inadequate. The most dramatic effects of hyponatremia on the brain are seen when serum sodium concentration decreases in a short period, allowing little or no adaptation. The brain is constrained inside a nonextensible envelope; thus, brain swelling carries a significant morbidity because of the compression of brain parenchyma over the rigid skull. Serum sodium concentration is an important determinant of several biological pathways in the nervous system, and recent studies have suggested that hyponatremia carries a significant risk of neurological impairment even in the absence of brain edema. The brain can also be affected by the treatment of hyponatremia, which, if not undertaken cautiously, could lead to osmotic demyelination syndrome, a rare demyelinating brain disorder that occurs after rapid correction of severe hyponatremia. This review summarizes the pathophysiology of brain complications of hyponatremia and its treatment.

Emergency Neurological Life Support: Acute Non-traumatic Weakness

Acute non-traumatic weakness may be life-threatening if it involves the respiratory muscles and/or is associated with autonomic dysfunction. Most patients presenting with acute muscle weakness have a worsening neurological disorder that requires a rapid, systematic evaluation and detailed neurological exam to localize the disorder. Urgent laboratory tests and neuroimaging are needed to confirm the diagnosis. Because acute weakness is a common presenting sign of neurological emergencies, it was chosen as an Emergency Neurological Life Support protocol. Causes of acute non-traumatic weakness are discussed here by both presenting clinical signs and anatomical location. For each diagnosis, key features of the history, examination, investigations, and treatment are outlined in the included tables or in the "Appendix".

Physiopathology, clinical diagnosis, and treatment of hyponatremia

Hyponatremia is the commonest electrolyte disorder encountered in clinical practice. It develops when the mechanisms regulating water and electrolyte handling are impaired, which in many instances occur in the setting of concurrent diseases such as heart failure, liver failure, renal failure etc… Hyponatremia as an electrolyte disorder has several specificities: when profound it can be quickly fatal and when moderate it carries a high risk of mortality and morbidity, but at the same time incorrect treatment of profound hyponatremia can lead to debilitating neurological disease and it remains unclear if treatment of moderate hyponatremia is associated with a decrease in mortality and morbidity. A proper diagnosis is the keystone for an adequate treatment for hyponatremia and in the last few years many diagnosis algorithms have been developed to aid in the evaluation of the hyponatremic patient. Also because of the availability of vasopressin receptor antagonists and the advances made in the research regarding complications associated with hyponatremia treatment, new treatment recommendations have been published recently by several panels. This review will discuss the physiopathology, epidemiology, and clinical manifestations of hyponatremia and also the diagnosis and the treatment of this disorder with special emphasis on the complication from overly rapid correction of hyponatremia.

Challenges in the acute management of profound hyponatremia presenting with severe symptoms

Currently available guidelines in the acute management of severely symptomatic hypotonic hyponatremia vary in their approach to the use of hypertonic saline. In the acute setting, deciding on when to implement available treatment algorithm using hypertonic saline may be difficult, given that the duration of hyponatremia and potential alternative diagnoses presenting with similar symptoms may be hard to establish promptly. We present the case of a young female with symptomatic profound hyponatremia who subsequently developed osmotic demyelination syndrome due to rapid overcorrection of serum sodium concentration. We discuss the interplay between the dynamic pathophysiological processes responsible for hypotonic hyponatremia in adrenal insufficiency and conduct a detailed analysis of currently available guidelines to highlight the challenges in acute and reactive treatment in clinical practice.

Formulas for fixing serum sodium: curb your enthusiasm

A variety of formulas have been proposed to predict changes in serum sodium concentration. All are based on an experiment done over 50 years ago by Edelman, who derived a formula relating the plasma sodium concentration to isotopically measured body sodium, potassium, and water. Some of these formulas fail because they do not include urinary losses of electrolytes and water. Even those that include these essential variables are not accurate enough for clinical use because it is impractical to adjust calculations to rapid changes in urinary composition, and because the formulas do not account for changes in serum sodium caused by internal exchanges between soluble and bound sodium stores or shifts of water into or out of cells resulting from changes in intracellular organic osmolytes. Nephrologists should curb their enthusiasm for predictive formulas and rely instead on frequent measurements of the serum sodium when correcting hyponatremia and hypernatremia.

Desmopressin to Prevent Rapid Sodium Correction in Severe Hyponatremia: A Systematic Review

BACKGROUND

Hyponatremia is common among inpatients and is associated with severe adverse outcomes such as osmotic demyelination syndrome. Current guidelines recommend serum sodium concentration correction targets of no more than 8 mEq/L per day in patients at high risk of osmotic demyelination syndrome. Desmopressin is recommended to control high rates of serum sodium concentration correction in severe hyponatremia. However, recommendations are based on limited data. The objective of this study is to review current strategies for DDAVP use in severe hyponatremia.

METHODS

Systematic literature search of 4 databases of peer-reviewed studies was performed and study quality was appraised.

RESULTS

The literature search identified 17 observational studies with 80 patients. We found 3 strategies for desmopressin administration in hyponatremia: 1) proactive, where desmopressin is administered early based on initial serum sodium concentration; 2) reactive, where desmopressin is administered based on changes in serum sodium concentration or urine output; 3) rescue, where desmopressin is administered after serum sodium correction targets are exceeded or when osmotic demyelination appears imminent. A proactive strategy of desmopressin administration with hypertonic saline was associated with lower incidence of exceeding serum sodium concentration correction targets, although this evidence is derived from a small case series.

CONCLUSIONS

Three distinct strategies for desmopressin administration are described in the literature. Limitations in study design and sample size prevent definitive conclusions about the optimal strategy for desmopressin administration to correct hyponatremia. There is a pressing need for better quality research to guide clinicians in managing severe hyponatremia.

[Hyponatremia and tolvaptan : what is the situation 5 years after approval?]

The diuretic tolvaptan has been approved for more than 5 years for the indications of euvolemic hyponatremia due to syndrome of inappropriate antidiuretic hormone (SIADH) secretion. In recent years many patients have been treated with tolvaptan and many physicians could gather practical experience. Other countries, such as the USA had already gained greater experience, also in the indications for hypervolemic hyponatremia. After approval was granted more than 5000 patients worldwide were included in the so-called hyponatremia register and 22 active centers in Germany with 317 patients participated. Although some details from this now concluded register have been published, the final publication of the multinational post-authorization safety study on tolvaptan in the treatment of SIADH has not yet been published. In the years 2012 and 2013 two warning letters were issued on tolvaptan. The first letter warned of the risk of a faster increase in serum sodium using tolvaptan and provided detailed information on how the risk of osmotic demeyelination can be minimized. So far only one proven case of osmotic demelination syndrome (ODS) is known; however, this occurred following incorrect use of tolvaptan in a monotherapy. The second warning letter provided information on the potential risk (reversible) of liver damage by tolvaptan, which resulted from the TEMPO 3:4 study. In this study tolvaptan was used in a higher dosage for therapy of autosomal dominant polycystic kidney disease. Although the European renal best practice (ERBP) guidelines from 2014 did not recommend tolvaptan for the indications of SIADH, other guidelines came to different conclusions. In summary, 5 years after the approval of tolvaptan there is still no consensus. At the current time many questions still remain unanswered. Initiation of therapy with tolvaptan remains reserved for experienced physicians in hospitals. Treatment must be adapted on the basis of a clinical estimation of the individual situation of each patient.

A systematic review and meta-analysis of thiazide-induced hyponatraemia: time to reconsider electrolyte monitoring regimens after thiazide initiation?

AIMS

Hyponatraemia is one of the major adverse effects of thiazide and thiazide-like diuretics and the leading cause of drug-induced hyponatraemia requiring hospital admission. We sought to review and analyze all published cases of this important condition.

METHODS

Ovid Medline, Embase, Web of Science and PubMed electronic databases were searched to identify all relevant articles published before October 2013. A proportions meta-analysis was undertaken.

RESULTS

One hundred and two articles were identified of which 49 were single patient case reports. Meta-analysis showed that mean age was 75 (95% CI 73, 77) years, 79% were women (95% CI 74, 82) and mean body mass index was 25 (95% CI 20, 30) kg m(-2) . Presentation with thiazide-induced hyponatraemia occurred a mean of 19 (95% CI 8, 30) days after starting treatment, with mean trough serum sodium concentration of 116 (95% CI 113, 120) mm and serum potassium of 3.3 (95% CI 3.0, 3.5) mm. Mean urinary sodium concentration was 64 mm (95% CI 47, 81). The most frequently reported drugs were hydrochlorothiazide, indapamide and bendroflumethiazide.

CONCLUSIONS

Patients with thiazide-induced hyponatraemia were characterized by advanced age, female gender, inappropriate saliuresis and mild hypokalaemia. Low BMI was not found to be a significant risk factor, despite previous suggestions. The time from thiazide initiation to presentation with hyponatraemia suggests that the recommended practice of performing a single investigation of serum biochemistry 7-14 days after thiazide initiation may be insufficient or suboptimal. Further larger and more systematic studies of thiazide-induced hyponatraemia are required.

Hyponatremia in the neurocritical care patient: An approach based on current evidence

In the neurocritical care setting, hyponatremia is the commonest electrolyte disorder, which is associated with significant morbimortality. Cerebral salt wasting and syndrome of inappropriate antidiuretic hormone have been classically described as the 2 most frequent entities responsible of hyponatremia in neurocritical care patients. Nevertheless, to distinguish between both syndromes is usually difficult and useless as volume status is difficult to be determined, underlying pathophysiological mechanisms are still not fully understood, fluid restriction is usually contraindicated in these patients, and the first option in the therapeutic strategy is always the same: 3% hypertonic saline solution. Therefore, we definitively agree with the current concept of "cerebral salt wasting", which means that whatever is the etiology of hyponatremia, initially in neurocritical care patients the treatment will be the same: hypertonic saline solution.

'Dos and don'ts' in the management of hyponatremia

INTRODUCTION AND OBJECTIVE

The management of hyponatremia has evolved in recent years, particularly with the introduction of tolvaptan for hyponatremia secondary to the syndrome of inappropriate antidiuretic hormone secretion (SIADH). This commentary presents a summary of recent international recommendations in the form of a series of didactic 'dos and don'ts', in order to provide concise, practical guidance for practising clinicians focused on the investigation and management of euvolemic hyponatremia (SIADH).

RESEARCH METHODS

A multidisciplinary group of international experts reviewed existing guidelines and the evidence cited within to summarize the recommendations in a practical method for use in clinical practice.

RECOMMENDATIONS

The 'dos and don'ts' are presented under topic headings that include diagnosis and diagnostic tests, specific causes, correction of acute hyponatremia, correction rates for chronic hyponatremia, management of SIADH including fluid restriction, hypertonic saline and pharmacological strategies, and management of overcorrection. Within each topic, the authors summarize the published recommendations on managing hyponatremia and the use of specific agents for the treatment of SIADH.

CONCLUSION

Practising clinicians can use these 'dos and don'ts' to provide clear, up-to-date guidance on how to manage hyponatremia and the use of tolvaptan in SIADH.

Hyponatremia: pathophysiology, classification, manifestations and management

Hyponatremia has complex pathophysiology, is frequent and has potentially severe clinical manifestations, and its treatment is associated with high risks. Hyponatremia can be hypertonic, isotonic or hypotonic. Hypotonic hyponatremia has multiple etiologies, but only two general mechanisms of development, defective water excretion, usually because of elevated serum vasopressin levels, or excessive fluid intake. The acute treatment of symptomatic hypotonic hyponatremia requires understanding of its targets and risks and requires continuous monitoring of the patient's clinical status and relevant serum biochemical values. The principles of fluid restriction, which is the mainstay of management of all types of hypotonic hyponatremia, should be clearly understood and followed. Treatment methods specific to various categories of hyponatremia are available. The indications and risks of these treatments should also be well understood. Rapid correction of chronic hypotonic hyponatremia may lead to osmotic demyelination syndrome, which has severe clinical manifestations, and may lead to permanent neurological disability or death. Prevention of this syndrome should be a prime concern of the treatment of hypotonic hyponatremia.

Management of hyponatremia in the ICU

Hyponatremia is common in critical care units. Avoidance of neurologic injury requires a clear understanding of why the serum sodium (Na) concentration falls and why it rises, how the brain responds to a changing serum Na concentration, and what the goals of therapy should be. A 4 to 6 mEq/L increase in serum Na concentration is sufficient to treat life-threatening cerebral edema caused by acute hyponatremia. In chronic (&gt; 48 h), severe (&lt; 120 mEq/L) hyponatremia, correction by &gt; 8 to 10 mEq/L/d risks iatrogenic osmotic demyelination syndrome (ODS); therefore, a 4 to 6 mEq/L daily increase in serum Na concentration should be the goal in most patients. With the possible exception of hyponatremia caused by heart failure or hepatic cirrhosis, a rapid initial increase in serum Na for severe symptoms and avoidance of overcorrection are best achieved with 3% saline given in either a peripheral or central vein. Inadvertent overcorrection can be avoided in high-risk patients with chronic hyponatremia by administration of desmopressin to prevent excessive urinary water losses. In patients with hyponatremia with oliguric kidney failure, controlled correction can be achieved with modified hemodialysis or continuous renal replacement therapies. ODS is potentially reversible, even in severely affected patients who are quadriplegic, unresponsive, and ventilator dependent. Supportive care should be offered several weeks before concluding that the condition is hopeless.

Diagnosis, evaluation, and treatment of hyponatremia: expert panel recommendations

Hyponatremia is a serious, but often overlooked, electrolyte imbalance that has been independently associated with a wide range of deleterious changes involving many different body systems. Untreated acute hyponatremia can cause substantial morbidity and mortality as a result of osmotically induced cerebral edema, and excessively rapid correction of chronic hyponatremia can cause severe neurologic impairment and death as a result of osmotic demyelination. The diverse etiologies and comorbidities associated with hyponatremia pose substantial challenges in managing this disorder. In 2007, a panel of experts in hyponatremia convened to develop the Hyponatremia Treatment Guidelines 2007: Expert Panel Recommendations that defined strategies for clinicians caring for patients with hyponatremia. In the 6 years since the publication of that document, the field has seen several notable developments, including new evidence on morbidities and complications associated with hyponatremia, the importance of treating mild to moderate hyponatremia, and the efficacy and safety of vasopressin receptor antagonist therapy for hyponatremic patients. Therefore, additional guidance was deemed necessary and a panel of hyponatremia experts (which included all of the original panel members) was convened to update the previous recommendations for optimal current management of this disorder. The updated expert panel recommendations in this document represent recommended approaches for multiple etiologies of hyponatremia that are based on both consensus opinions of experts in hyponatremia and the most recent published data in this field.

Acute kidney injury, sodium disorders, and hypercalcemia in the aging kidney: diagnostic and therapeutic management strategies in emergency medicine

This article summarizes the current literature regarding the structural and functional changes of the aging kidney and describes how these changes make the older patient more susceptible to acute kidney injury and fluid and electrolyte disorders. It discusses the clinical manifestations, evaluation, and management of hyponatremia and shows how the management of hypernatremia in geriatric patients involves addressing the underlying cause and safely correcting the hypernatremia. The current literature regarding evaluation and management of hypercalcemia in older patients is summarized. The management of severe hypercalcemia is discussed in detail. The evaluation and management of acute kidney injury is described.

Hypertonic saline and desmopressin: a simple strategy for safe correction of severe hyponatremia

BACKGROUND

Prompt correction of severe hyponatremia is important, but correction also must be limited to avoid iatrogenic osmotic demyelination. Expert opinion recommends that serum sodium level not be increased by more than 10-12 mEq/L in any 24-hour period and/or 18 mEq/L in any 48-hour period. However, inadvertent overcorrection is common, usually caused by the unexpected emergence of a water diuresis.

STUDY DESIGN

Quality improvement report.

SETTING & PARTICIPANTS

All 25 patients admitted to a community teaching hospital between October 1, 2008, and September 30, 2011, who were treated for serum sodium level <120 mEq/L with concurrently administered desmopressin and hypertonic saline solution.

QUALITY IMPROVEMENT PLAN

Concurrently administered desmopressin (1-2 µg parenterally every 6-8 hours) and hypertonic saline with weight-based doses adjusted to increase the serum sodium concentration by 6 mEq/L, avoiding inadvertent overcorrection of severe hyponatremia.

OUTCOMES

Rate of correction of hyponatremia, predictability of response to the combination, adverse events related to therapy.

MEASUREMENTS

Rate of correction of hyponatremia at 4, 24, and 48 hours; administered dose of 3% saline solution, salt tablets, and potassium; predicted increase in serum sodium level.

RESULTS

Mean changes in serum sodium levels during the first and second 24 hours of therapy were 5.8 ± 2.8 (SD) and 4.5 ± 2.2 mEq/L, respectively, without correction by >12 mEq/L in 24 hours or >18 mEq/L in 48 hours and without a decrease during therapy. There was no significant difference between actual and predicted increases during the first 24 hours. There was no adverse effect associated with therapy.

LIMITATIONS

Without concurrent controls, we cannot be certain that outcomes are improved. Balance studies were not performed.

CONCLUSIONS

Combined 3% saline solution and desmopressin appears to be a valid strategy for correcting severe hyponatremia, but studies comparing the regimen with other therapeutic strategies are needed.

Where vaptans do and do not fit in the treatment of hyponatremia

The treatment of hyponatremia, an exceedingly common electrolyte disorder, has been a subject of controversy for many years. The advent of vasopressin antagonists (vaptans) has added to the treatment arsenal. This review focuses on why hyponatremia should be treated and the role of these antagonists in the treatment. Upon analysis of the available literature, we conclude that there is presently no role for vaptans in acute symptomatic hyponatremia. Although numerous therapeutic approaches are available for chronic symptomatic hyponatremia, vasopressin antagonists provide a simpler treatment option. Vaptans are efficacious in raising serum sodium in long-standing 'asymptomatic' hyponatremia. However, the cost of the only Food and Drug Administration-approved oral agent (tolvaptan) makes its use prohibitive for most patients in this setting.

Pitfalls in the management of severe hyponatraemia

The correction of severe hyponatraemia is complicated by practical and theoretical limitations of formulae used to predict response to treatment, and random errors in the measurement of sodium concentration. We report the case of an elderly woman with a symptomatic serum sodium concentration of 93 mmol/l. Correction of serum sodium unintentionally exceeded conventional targets but, as in the majority of such cases, there were no neurological sequelae.

[Hyponatremia : The water-intolerant patient]

Hyponatremia due to intolerance to water is a frequent clinical condition and associated with increased mortality. Besides the well known neurological symptoms, gait disturbances, falls, fractures and osteoporosis have also been described recently in patients with chronic hyponatremia. Acute hyponatremia is a more dramatic situation and needs rapid action when severe neurological symptoms are present. Hypertonic saline is recommended to treat this condition until relief of severe symptoms. The causes of hyponatremia have to be carefully examined. Especially diuretics, antidepressants and endocrine causes, e.g. hypothyroidism, hypocortisolism and hypoaldosteronism should be excluded by examination of the patient history, clinical examination and by laboratory tests. Patients should be classified as being euvolemic, hypovolemic or hypervolemic. Whereas acute hyponatremia with severe symptom should be treated with hypertonic saline, euvolemic hyponatremia due to the syndrome of inappropriate antidiuretic hormone secretion (SIADH) with mild and moderate symptoms can now be treated with tolvaptan, a selective V(2)-vasopressin antagonist. Oral tolvaptan has been shown to be an effective and potent aquaretic to treat hyponatremia caused by SIADH as evidenced by a simultaneous increase in serum sodium and a decrease in urine osmolality. The condition of patients with mild or moderate hyponatremia is also improved. Side effects associated with tolvaptan include increased thirst, dry mouth, polyuria and hypernatremia. Rapid increases in serum sodium should be avoided by close monitoring in a hospital setting.

The challenge of hyponatremia

Treatment of hypotonic hyponatremia often challenges clinicians on many counts. Despite similar serum sodium concentrations, clinical manifestations can range from mild to life threatening. Some patients require active management, whereas others recover without intervention. Therapeutic measures frequently yield safe correction, yet the same measures can result in osmotic demyelination. To address this challenge, we present a practical approach to managing hyponatremia that centers on two elements: a diagnostic evaluation directed at the pathogenesis and putative causes of hyponatremia, the case-specific clinical and laboratory features, and the associated clinical risk; and a management plan tailored to the diagnostic findings that incorporates quantitative projections of fluid therapy and fluid losses on the patient's serum sodium, balances potential benefits and risks, and emphasizes vigilant monitoring. These principles should enable the clinician to formulate a management plan that addresses expeditiously three critical questions: Which of the determinants of the serum sodium are deranged and what is the underlying culprit? How urgent is the need for intervention? What specific therapy should be instituted and which are the associated pitfalls?