Patients presenting with severe hypotonic hyponatremia: etiological factors, assessment, and outcomes

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.

Risk Factors for Overly Rapid Correction in Patients with Profound Hyponatremia: A Retrospective Cohort Study

Objective Overly rapid correction of profound hyponatremia can lead to osmotic demyelination syndrome; however, the incidence of and risk factors for overly rapid correction in patients with profound hyponatremia have not been thoroughly examined. Therefore, this study examined the incidence of and risk factors for overly rapid correction in patients with profound hyponatremia. Methods This single-center, retrospective cohort study conducted at an 865-bed teaching hospital analyzed data from 144 new inpatients with profound hyponatremia [initial serum sodium (Na+) level of <125 mEq/L] treated in our department between January 2014 and December 2022. Overly rapid correction was defined as serum Na+ correction of >10 mEq/L at 24 h. We examined the incidence of and risk factors for overly rapid correction. Results Thirty (20.8%) patients met the overly rapid correction criteria; however, none developed osmotic demyelination syndrome. A low initial serum Na+ level, female sex, primary polydipsia, and low frequency of follow-up in 24 h were significant independent risk factors for overly rapid correction in the multivariable analysis (p=0.020, p=0.011, p=0.014, and p=0.025, respectively). Conclusion Our study shows that a low initial serum Na+ level, female sex, primary polydipsia, and low frequency of follow-up within 24 h are associated with an increased risk for overly rapid correction of profound hyponatremia. Therefore, we suggest that physicians perform careful management when managing patients with profound hyponatremia with the risk factors for overly rapid correction identified in this study.

An Instant Relationship Between Hyponatremia, Geriatric Syndromes, and Drugs in Older Adults: A Cross-Sectional Analysis from a Single Geriatric Clinic

Background: Hyponatremia is a common electrolyte disorder in older adults that can lead to poor clinical outcomes and increased mortality. This study aims to evaluate the interrelationship between hyponatremia and geriatric syndromes and drugs in older adults. Methods: This study included 1100 elderly patients admitted to a geriatric clinic. Patient records were used to obtain demographic information, comorbidities, geriatric syndromes, medications, laboratory results, and comprehensive geriatric assessment parameters. Results: The prevalence of hyponatremia was 23.9% in this study (mean age ± SD was 75.59 ± 8.13 years). The frequency of polypharmacy, dementia, falls, malnutrition and risk of malnutrition, frailty, probable sarcopenia, hypertension, cerebrovascular disease, and congestive heart failure was higher, and patients were older in the hyponatremia group (p < 0.05) than in the normonatremia group. After the adjustment of covariates, hyponatremia was shown to be related to drugs including escitalopram (odds ratio [OR]: 1.82, 95% confidence interval [CI]: 1.20-2.76), trazodone (OR: 2.27, 95% CI: 1.26-4.10), renin angiotensin aldosterone system (RAAS) inhibitors (OR: 1.71, 95% CI: 1.18-2.47), hydrochlorothiazide (OR: 1.83, 95% CI: 1.28-2.62), and opioids (OR: 4.46, 95% CI: 1.24-16.02) (p < 0.05). Polypharmacy, falls, and malnutrition with risk of malnutrition were still significantly associated with increased hyponatremia risk even after adjustment for age, sex, and comorbidity burden (p < 0.05). Conclusions: Hyponatremia seems to be associated with certain geriatric syndromes, as well as the use of some antidepressants and cardiovascular drugs in older adults. Malnourished older adults taking RAAS inhibitors, diuretics, opioids, and antidepressants may be at a higher risk of developing hyponatremia. They should be closely monitored, especially if they are taking multiple medications.

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.

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.

Intensive Care Management of Severe Hyponatraemia-An Observational Study

Background and Subject: Hyponatraemia is a common electrolyte disorder. For patients with severe hyponatraemia, intensive care unit (ICU) admission may be required. This will enable close monitoring and allow safe management of sodium levels effectively. While severe hyponatraemia may be associated with significant symptoms, rapid overcorrection of hyponatraemia can lead to complications. We aimed to describe the management and outcomes of severe hyponatraemia in our ICU and identify risk factors for overcorrection. Materials and Methods: This was a retrospective single-centre cohort that included consecutive adults admitted to the ICU with serum sodium < 120 mmol/L between 1 January 2017 and 8 March 2023. Anonymised data were collected from electronic records. We included 181 patients (median age 67 years, 51% male). Results: Median admission serum sodium was 113 mmol/L (IQR: 108-117), with an average rate of improvement over the first 48 h of 10 mmol/L/day (IQR: 5-15 mmol/L). A total of 62 patients (34%) met the criteria for overcorrection at 48 h, and they were younger, presented with severe symptoms (seizures/arrythmias), and had lower admission sodium concentration. They were more likely to be treated with hypertonic saline infusions. Lower admission sodium was an independent risk factor for overcorrection within 48 h, whereas the presence of liver cirrhosis and fluid restriction was associated with normal correction. No difference was identified between the normal and overcorrected cohorts for ICU/hospital length of stay or mortality. Conclusions: In some patients with severe hyponatraemia, overcorrection is inevitable to avoid symptoms such as seizures and arrhythmias, and consequently, we highlight the key factors associated with overcorrection. Overall, we identified that overcorrection was common and concordant with the current literature.

Management of Pediatric Parenteral Fluids

Parenteral fluid therapy in children requires careful consideration of patient-specific factors such as weight, hydration status, and concomitant disease states. Recent literature has changed the standard of care for maintenance fluids for children in the past decade and brought to light more questions. Concentrations of electrolytes in fluids and the use of balanced fluids are still controversial. This article will review the use of parenteral fluids in children, including fluid content, maintenance fluid rate, treatment of dehydration, and the basics of parenteral fluid ingredients. All pediatric patients should have a plan for fluid therapy that includes careful consideration of hydration status and individual response to therapy.

[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.

Effects of correction rate for severe hyponatremia in the intensive care unit on patient outcomes

PURPOSE

Limited evidence exists regarding outcomes associated with different correction rates of severe hyponatremia.

MATERIALS AND METHODS

This retrospective cohort analysis employed a multi-center ICU database to identify patients with sodium ≤120 mEq/L during ICU admission. We determined correction rates over the first 24 h and categorized them as rapid (> 8 mEq/L/day) or slow (≤ 8 mEq/L/day). The primary outcome was in-hospital mortality. Secondary outcomes included hospital-free days, ICU-free days, and neurological complications. We used inverse probability weighting for confounder adjustment.

RESULTS

Our cohort included 1024 patients; 451 rapid and 573 slow correctors. Rapid correction was associated with lower in-hospital mortality (absolute difference: -4.37%; 95% CI, -8.47 to -0.26%), longer hospital-free days (1.80 days; 95% CI, 0.82 to 2.79 days), and longer ICU-free days (1.16 days; 95% CI, 0.15 to 2.17 days). There was no significant difference in neurological complications (2.31%; 95% CI, -0.77 to 5.40%).

CONCLUSION

Rapid correction (>8 mEq/L/day) of severe hyponatremia within the first 24 h was associated with lower in-hospital mortality and longer ICU and hospital-free days without an increase in neurological complication. Despite major limitations, including the inability to identify the chronicity of hyponatremia, the results have important implications and warrant prospective studies.

Tolvaptan versus fluid restriction in acutely hospitalised patients with moderate-profound hyponatraemia (TVFR-HypoNa): design and implementation of an open-label randomised trial

Background

Current hyponatraemia guidelines are divided on the use of tolvaptan in hospitalised patients with moderate to severe hyponatraemia, due to an uncertain risk-benefit ratio. We will conduct a randomised trial to test the hypothesis that early use of tolvaptan improves the rate of serum sodium correction and clinical outcomes compared with current standard first-line therapy, restriction of fluid intake, without increasing the risk of serum sodium overcorrection.

Methods

We will enrol hospitalised patients with euvolaemic or hypervolaemic hyponatraemia and serum sodium of 115–130 mmol/L at Austin Health, a tertiary care centre in Melbourne, Australia. Participants will be randomised 1:1 to receive either tolvaptan (initial dose 7.5 mg) or fluid restriction (initial limit 1000 ml per 24 h), with titration of therapy based on serum sodium response according to a pre-determined protocol over a 72-h intervention period.

The primary endpoint will be the between-group change in serum sodium over time, from study day 1 to day 4. Secondary endpoints include serum sodium increment in the first 24 and 48 h, proportion of participants with normalised serum sodium, length of hospital stay, requirement for serum sodium re-lowering with intravenous dextrose or desmopressin, cognitive and functional measures (Confusion Assessment Method Short form, Timed Up and Go test, hyponatraemia symptom questionnaire), 30-day readmission rate, treatment satisfaction score and serum sodium 30 days after discharge. The trial will be overseen by an independent Data Safety Monitoring Board. Serum sodium will be monitored every 6–12 h throughout the study period, with pre-specified thresholds for commencing intravenous 5% dextrose if serum sodium rise targets are exceeded.

Discussion

We seek to inform future international guidelines with high-quality data regarding the utility and safety of tolvaptan compared to standard therapy fluid restriction in patients with moderate-severe hyponatraemia in hospital. If tolvaptan use in this patient group is endorsed by our findings, we will have established an evidence-based framework for tolvaptan initiation and monitoring to guide its use.

Trial registration

Australia and New Zealand Clinical Trials Registry ACTRN12619001683123. Registered on December 2 2019

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06237-5.

Factors affecting prognosis of the patients with severe hyponatremia

INTRODUCTION

Hyponatremia is one of the most common electrolyte abnormalities in clinical practice. Data regarding factors that have impact on mortality of severe hyponatremia and outcomes of its therapeutic management is insufficient. The present study aimed to examine the factors associated with mortality and the outcomes of treatment in patients with severe hyponatremia.

MATERIALS AND METHODS

Patients with serum Na≤115mequiv./L who were admitted to Ordu State Hospital and Ordu University Training and Research Hospital between 2014 and 2018 were included in the study. Demographic and laboratory features, severity of the symptoms, comorbid diseases, medications, and clinical outcome measures of the patients were obtained retrospectively from their medical records. Factors associated with in-hospital mortality, overcorrection and undercorrection were assessed.

RESULTS

A total of 145 patients (median age 69 years and 58.6% female) met inclusion criteria. Diuretic use was the most common etiologic factor for severe hyponatremia that present in 50 (34.5%) patients. Sixty-seven (46.2%) patients had moderately severe while 8 patients (5.5%) had severe symptoms. The median increase in serum Na 24h after admission in the study population was 8.9mequiv./L (-6 to 19). Nonoptimal correction was seen in 92 (63.4%) patients. Hypertonic saline use was associated with overcorrection (OR, 3.07; 95% CI: 1.47-6.39; p=0.002). Avoidance of hypertonic saline (aOR, 2.52; 95% CI: 1.12-5.66; p=0.029) and having neuropsychiatric disorder (aOR, 2.60; 95% CI: 1.10-6.11; p=0.025) were associated with undercorrection. In-hospital mortality rate was 12.4% and having CKD and cancer, undercorrection of sodium and presence of severe symptoms were significantly associated with in-hospital mortality.

CONCLUSION

Severe hyponatremia in hospitalized patients is associated with substantial mortality. The incidence of non-optimal correction of serum Na is high; under-correction, presence of severe symptoms, chronic kidney disease and cancer were the factors that increase mortality rate.

Extreme hyponatraemia due to primary polydipsia and quetiapine-induced SIAD

SUMMARY

Hyponatraemia is the most common electrolyte disturbance in hospitalised patients and is associated with numerous adverse outcomes. Patients with schizophrenia are particularly susceptible to hyponatraemia, in part due to the close association between this condition and primary polydipsia. We report the case of a 57-year-old woman with schizophrenia and primary polydipsia who was receiving inpatient psychiatric care. She became increasingly confused, had multiple episodes of vomiting, and collapsed 1 week after being commenced on quetiapine 300 mg. On examination, she was hypertensive and her Glasgow coma scale was nine. She had a fixed gaze palsy and a rigid, flexed posture. Investigations revealed extreme hyponatraemia with a serum sodium of 97 mmol/L. A CT brain demonstrated diffused cerebral oedema with sulcal and ventricular effacement. A urine sodium and serum osmolality were consistent with SIAD, which was stimulated by the introduction of quetiapine. The antidiuretic effect of vasopressin limited the kidney's ability to excrete free water in response to the patients' excessive water intake, resulting in extreme, dilutional hyponatraemia. The patient was treated with two 100 mL boluses of hypertonic 3% saline but deteriorated further and required intubation. She had a complicated ICU course but went on to make a full neurological recovery. This is one of the lowest sodium levels attributed to primary polydipsia or second-generation antipsychotics reported in the literature.

LEARNING POINTS

The combination of primary polydipsia and SIAD can lead to a life-threatening, extreme hyponatraemia. SIAD is an uncommon side effect of second-generation anti-psychotics. Serum sodium should be monitored in patients with primary polydipsia when commencing or adjusting psychotropic medications. Symptomatic hyponatraemia is a medical emergency that requires treatment with boluses of hypertonic 3% saline. A serum sodium of less than 105 mmol/L is associated with an increased risk of osmotic demyelination syndrome, therefore the correction should not exceed 8 mmol/L over 24 h.

Factors affecting prognosis of the patients with severe hyponatremia

INTRODUCTION

Hyponatremia is one of the most common electrolyte abnormalities in clinical practice. Data regarding factors that have impact on mortality of severe hyponatremia and outcomes of its therapeutic management is insufficient. The present study aimed to examine the factors associated with mortality and the outcomes of treatment in patients with severe hyponatremia.

MATERIALS AND METHODS

Patients with serum Na≤115mequiv./L who were admitted to Ordu State Hospital and Ordu University Training and Research Hospital between 2014 and 2018 were included in the study. Demographic and laboratory features, severity of the symptoms, comorbid diseases, medications, and clinical outcome measures of the patients were obtained retrospectively from their medical records. Factors associated with in-hospital mortality, overcorrection and undercorrection were assessed.

RESULTS

A total of 145 patients (median age 69 years and 58.6% female) met inclusion criteria. Diuretic use was the most common etiologic factor for severe hyponatremia that present in 50 (34.5%) patients. Sixty-seven (46.2%) patients had moderately severe while 8 patients (5.5%) had severe symptoms. The median increase in serum Na 24h after admission in the study population was 8.9mequiv./L (-6 to 19). Nonoptimal correction was seen in 92 (63.4%) patients. Hypertonic saline use was associated with overcorrection (OR, 3.07; 95% CI: 1.47-6.39; p=0.002). Avoidance of hypertonic saline (aOR, 2.52; 95% CI: 1.12-5.66; p=0.029) and having neuropsychiatric disorder (aOR, 2.60; 95% CI: 1.10-6.11; p=0.025) were associated with undercorrection. In-hospital mortality rate was 12.4% and having CKD and cancer, undercorrection of sodium and presence of severe symptoms were significantly associated with in-hospital mortality.

CONCLUSION

Severe hyponatremia in hospitalized patients is associated with substantial mortality. The incidence of non-optimal correction of serum Na is high; under-correction, presence of severe symptoms, chronic kidney disease and cancer were the factors that increase mortality rate.

The Effect of the Dose of Isotonic Saline on the Correction of Serum Sodium in the Treatment of Hypovolemic Hyponatremia

BACKGROUND

Overcorrection of serum sodium (SNa) during therapy of hyponatremia can result in osmotic demyelination syndrome. Our aim was to determine the relationship between the isotonic saline solution dose (ISSD) administered and the 24-h SNa increase (24SNa) in patients with hypovolemic hyponatremia (HH).

METHODS

Retrospective study of HH patients treated with ISS in a tertiary hospital of Madrid, Spain, between 1 January-30 May 2019. The 24-h ISSD received and corresponding 24SNa were calculated. The latter was classified as 3 groups: ≥8 mmol/L, ≥6 mmol/L, or <4 mmol/L. Multivariate regression analyses were performed and ROC curves calculated to study the relationship between ISSD and 24SNa.

RESULTS

Thirty patients were included, age 72 years (60-80), 50% were women. 24SNa was ≥8 mmol/L/24 h in 33%, ≥6 mmol/L/24 h in 50%, and <4 mmol/L/24 h in 30%. Median ISSD in each group was: 32 mL/kg/24 h (29-37), 31 mL/kg/24 h (25-33), and 20 mL/kg/24 h (14-22), respectively. An ISSD ≥ 30 mL/kg/24 h had an odds ratio (OR) of 16 (95% CI: 2.5-95.1; p = 0.004) for a 24SNa ≥8 mmol/L, with a sensitivity and specificity of 80%.

CONCLUSIONS

The 24SNa depends on ISSD. An ISSD between 23-30 mL/kg/24 h seems to be safe and effective.

Indapamide-induced Severe Hyponatremia in a Middle-aged Male Patient within Two Weeks

Hyponatremia is one of the most common electrolyte abnormalities and is associated with many conditions. It has been reported in patients receiving diuretics as a physiological consequence of the therapy. We report an unusual case of severe hyponatremia of 100 mmol/L (Normal range (NR): 136-145 mmol/L) in a 54-year-old middle-aged gentleman within two weeks of commencement of Indapamide, a thiazide-like diuretic. After immediate treatment with intravenous 3% hypertonic saline infusion, discontinuation of indapamide, and ruling out other possible causes of hyponatremia, his serum sodium level improved. He was discharged without having any complicated hospital course and was also followed up for a further five months. The aim of our case report is to highlight an important and life-threatening complication associated with the most commonly prescribed drug and to manage it through cautious correction and monitoring of sodium levels.

Misconceptions and Barriers to the Use of Hypertonic Saline to Treat Hyponatremic Encephalopathy

Hyponatremic encephalopathy is a potentially life-threatening condition with a high associated morbidity and mortality. It can be difficult to diagnose as the presenting symptoms can be non-specific and do not always correlate with the degree of hyponatremia. It can rapidly progress leading to death from transtentorial herniation. Hypertonic saline is the recommended treatment for hyponatremic encephalopathy, whether acute or chronic, yet it is infrequently used. We believe that the main barriers to its use is the perception that hypertonic saline is associated with a significant risk for cerebral demyelination, that it can't be administered through a peripheral IV and that it requires monitoring in the ICU. Two illustrative cases are presented followed by a discussion of how intermittent bolus's of 100−150 ml of 3% NaCl in rapid succession to acutely increase the plasma sodium by 4−6 mEq/L is a safe and effective way to treat hyponatremic encephalopathy, that can be administered through a peripheral IV in a non-ICU setting.

Investigation and management of moderate to severe inpatient hyponatraemia in an Australian tertiary hospital

BACKGROUND

Hyponatraemia is the most common electrolyte disturbance amongst hospitalised patients. Both American and European guidelines recommend fluid restriction as first line treatment for SIADH, however differ on second line recommendations. The objective of this study was to examine investigation and management of hyponatraemia in hospitalised patients in an Australian tertiary hospital.

METHODS

A retrospective audit was conducted of electronic medical records and laboratory data of inpatients with serum sodium (Na) ≤125 mmol/L, admitted over a 3 month period to the Princess Alexandra Hospital, Brisbane, Australia. The main outcomes measured included: demographic characteristics, investigations, accuracy of diagnosis, management strategy, change in Na and patient outcomes.

RESULTS

The working clinical diagnosis was considered accurate in only 37.5% of cases. Urine Na and osmolality were requested in 72 of 152 patients (47.4%) and in 43 of 70 euvolaemic patients (61.4%). Thyroid function tests (67.1%) and morning cortisol (45.7%) were underutilized in the euvolaemic group. In the SIADH cohort, fluid restriction resulted in a median (IQR) 7.5 mmol/L (4-10.5) increase in Na after 3 days; no treatment resulted in a median 0 mmol/L (- 0.5-1.5) change. Oral urea was utilized in 5 SIADH patients where Na failed to increase with fluid restriction alone. This resulted in a median 10.5 mmol/L (3.5-13) increase in Na from baseline to day 3. There were no cases of osmotic demyelination. The median length of stay was 8 days (4-18.5). Mortality was 11.2% (17 patients). There was a weak but significant correlation between nadir serum Na and mortality (R = 0.18, P = 0.031).

CONCLUSION

Inpatient hyponatraemia is often inadequately investigated, causing errors in diagnosis. Treatment is heterogeneous and often incorrect. In cases with hyponatraemia refractory to fluid restriction, oral urea presents an effective alternative treatment.

Diagnosis and management of hyponatraemia in the older patient

Hyponatraemia (serum sodium concentration below 135 mmol/L) is the most common electrolyte disturbance and occurs commonly in older people. The causes can be complex to diagnose and treat and many published guidelines do not focus on the issues in an older patient group. Here, we are principally concerned with diagnosis and management of euvolaemic and hypervolaemic hyponatraemia in hospitalised patients over 70 years old. We also aim to increase awareness of hyponatraemia in residential aged care facilities and the community. Hyponatraemia can have many causes; in older people, chronic hyponatraemia can often be the result of medications used to treat chronic disease, particularly thiazide or thiazide-like drugs (such as indapamide) or drugs acting on the central nervous system. Where a reversible trigger (such as drug-induced hyponatraemia) can be identified, hyponatraemia may be treated relatively simply. Chronic hyponatraemia due to an irreversible cause will require ongoing treatment. Fluid restriction can be an effective therapy in dilutional hyponatraemia, although poor compliance and the burdensome nature of the restrictions are important considerations. Tolvaptan is an oral vasopressin receptor antagonist that can increase serum sodium concentrations by increasing electrolyte-free water excretion. Tolvaptan use is supported by clinical trial evidence in patients with hypervolaemic or euvolaemic hyponatraemia below 125 mmol/L. Clinical trial evidence also supports its use after a trial of fluid restriction in patients with symptomatic hyponatraemia above 125 mmol/L. The use of tolvaptan is affected by regulatory restriction of chronic therapy due to safety concern and the non-subsidised cost of treatment.

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.

A low initial serum sodium level is associated with an increased risk of overcorrection in patients with chronic profound hyponatremia: a retrospective cohort analysis

Background

Even with abundant evidence for osmotic demyelination in patients with hyponatremia, the risk factors for overcorrection have not been fully investigated. Therefore the purpose of this study is to clarify the risks for overcorrection during the treatment of chronic profound hyponatremia.

Methods

This is a single-center retrospective observational study. We enrolled 56 adult patients with a serum sodium (SNa) concentration of ≤125 mEq/L who were treated in an intensive care unit by nephrologists using a locally developed, fixed treatment algorithm between February 2012 and April 2014. The impact of patient parameters on the incidence of overcorrection was estimated using univariable and multivariable logistic regression models. Overcorrection was defined as an increase of SNa by >10 mEq/L and >18 mEq/L during the first 24 and 48 h, respectively.

Results

The median age was 78 years, 48.2% were male, and 94.6% of the patients presented with symptoms associated with hyponatremia. The initial median SNa was 115 mEq/L (quartile, 111–119 mEq/L). A total of 11 (19.6%) patients met the criteria for overcorrection with 9 (16.0%) occurring at 24 h, 6 (10.7%) at 48 h, and 4 (7.1%) at both 24 and 48 h. However, none of these patients developed osmotic demyelination. Primary polydipsia, initial SNa, and early urine output were the significant risk factors for overcorrection on univariable analysis. Multivariable analysis revealed that the initial SNa had a statistically significant impact on the incidence of overcorrection with an adjusted odds ratio of 0.84 (95% confidence interval, 0.70–0.98; p = 0.037) for every 1 mEq/L increase. Additionaly, the increase in SNa during the first 4 h and early urine output were significantly higher in patients with overcorrection than in those without (p = 0.001 and 0.005, respectively).

Conclusions

An initial low level of SNa was associated with an increased risk of overcorrection in patients with profound hyponatremia. In this regard, the rapid increase in SNa during the first 4 h may play an important role.

Prognosis of patients with severe hyponatraemia is related not only to hyponatraemia but also to comorbidities and to medical management: results of an observational retrospective study

Background

The true cause of death in severe hyponatraemic patients remains controversial. The present study aimed to analyse the relationship between comorbidity, medical management and prognosis in severe hyponatraemic patients.

Methods

Medical records of all patients hospitalised in our institution in 2012 with a plasma sodium ≤120 mmol/l were retrospectively analysed.

Results

One hundred forty-seven of 64 723 adult patients (0.2 %) were identified with severe hyponatraemia. In-hospital mortality rate was 24.5 and 50.3 % after a median follow-up of 431 days. Patients with plasma sodium <110 mmol/l had less comorbidity (Charlson Comorbidity Index 2.2 ± 1.9 vs. 4.0 ± 3.1 (plasma sodium 110–115 mmol/l) and 4.2 ± 3.1 (plasma sodium 116–120 mmol/l); P = .02)) and a small trend for less mortality, respectively 40.0, 51.2 and 52.3 % (P = .64). At discharge, nonsurvivors and survivors had similar plasma sodium with 58.3 % of nonsurvivors being normonatraemic. Urine analysis was performed in 74.2 % of cases and associated with lower in-hospital mortality (20.2 % vs. 36.8 %, P = .05). In multivariate Cox analysis, mortality was significantly associated with plasma sodium normalisation (HR 0.35, P < 0.001), urine analysis (HR 0.48, P = .01), Charlson Comorbidity Index (HR 1.23, P < .001) and serum albumin (HR 0.88, P < .001).

Conclusion

Mortality in severe hyponatraemia appears mainly due to comorbidities although the latter are potentiated by hyponatraemia itself and its management thereby exacerbating the risk of death.

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.

Electrolyte and acid-base abnormalities associated with purging behaviors

OBJECTIVE

Eating disorders that are associated with purging behaviors are complicated by frequent blood electrolyte and acid-base abnormalities. Herein, we review the major electrolyte and acid-base abnormalities and their treatment methods. The body of rigorous, eating disorder-specific literature on this topical area is not robust enough to perform a systematic review as defined by PRISMA guidelines. Therefore, a qualitative review of mostly medical literature was conducted.

RESULTS

Hypokalemia, hyponatremia, and sodium chloride-responsive metabolic alkalosis are the most common serum changes that occur as a result of purging behaviors. They vary depending on the mode and frequency of purging behaviors. They can all potentially cause dangerous medical complications and are in need of definitive medical treatment.

DISCUSSION

Eating disorders that are associated with purging behaviors are associated with a number of electrolyte and acid-base changes which are complex in their origin, documented to be medically dangerous and this definitive treatment is necessary to help achieve a successful treatment outcome, and in need of definitive treatment as described herein.

Hyponatremia in the outpatient setting: clinical characteristics, risk factors, and outcome

PURPOSE

Hyponatremia is a common disorder and hyponatremia in the outpatient setting is not extensively studied. Our aim was to investigate the characteristics of hyponatremia in ambulatory patients.

METHODS

Seventy-six adult outpatients with hyponatremia were enrolled in this prospective study. Demographic features, presenting symptoms and signs, associating morbidities, medications, laboratory findings, mortalities, and length of hospital stay, were recorded.

RESULTS

Mean age was 74.7 ± 12.7 years, and 52 (68.4 %) were female whereas 24 (31.6 %) were male. Mean sodium concentration was 123.6 ± 6.6 mEq/L. Leading cause was thiazide diuretic use (n = 37, 48.7 %) and approximately half of the patients (n = 40, 52.6 %) had a multifactorial etiology. Severe hyponatremia (sodium < 125 mEq/L) was identified in 37 (48.7 %). Thiazide diuretic use, vomiting, and apathy were independent predictors of severe hyponatremia. Eight (10.5 %) patients had a mortal course. A relatively younger age, male gender, presenting sign of lethargy, associating morbidities of malignancy, chronic liver disease, and hypoalbuminemia were risk factors for mortality.

CONCLUSIONS

Hyponatremia is prevalent among elderly, especially in women and with thiazide diuretics. Apart from the trend toward sodium depletion observed in healthy elderly which occurs due to changes in the tubular handling of sodium, a multifactorial etiology including thiazides seems to predict the occurrence and the severity of hyponatremia. Hyponatremia may be a significant cause of mortality in seniors. A relatively younger age, male gender, association of cirrhosis, malignancy, and hypoalbuminemia predict mortality. In elderly outpatients, identification of the risk factors for hyponatremia and close monitoring are imperative to reduce the related mortality and morbidity.

Sodium Correction Practice and Clinical Outcomes in Profound Hyponatremia

OBJECTIVES

To assess the epidemiology of nonoptimal hyponatremia correction and to identify associated morbidity and in-hospital mortality.

PATIENTS AND METHODS

An electronic medical record search identified all patients admitted with profound hyponatremia (sodium <120 mmol/L) from January 1, 2008, through December 31, 2012. Patients were classified as having optimally or nonoptimally corrected hyponatremia at 24 hours after admission. Optimal correction was defined as sodium correction in 24 hours of 6 through 10 mmol/L. We investigated the association between sodium correction and demographic and outcome variables, including occurrence of osmotic demyelination syndrome (ODS). Baseline characteristics by correction outcome categories were compared using the Kruskal-Wallis test for continuous variables and the χ(2) test for categorical variables. Odds ratios for in-hospital mortality between groups were assessed using logistic regression. Adjusted differences in hospital length of stay (LOS) and intensive care unit (ICU) LOS were assessed using the Dunnett 2-tailed t test.

RESULTS

A total of 412 patients satisfied inclusion criteria of whom 174 (42.2%) were admitted to the ICU. A total of 211 (51.2%) had optimal correction of their hyponatremia at 24 hours, 87 (21.1%) had undercorrected hyponatremia, and 114 (27.9%) had overcorrected hyponatremia. Both patient factors and treatment factors were associated with nonoptimal correction. There was a single case of ODS. Overcorrection was not associated with in-hospital mortality or ICU LOS. When adjusted for patient factors, undercorrection of profound hyponatremia was associated with an increase in hospital LOS (9.3 days; 95% CI, 1.9-16.7 days).

CONCLUSION

Nonoptimal correction of profound hyponatremia is common. Fortunately, nonoptimal correction is associated with serious morbidity only infrequently.

Hyponatremia: A Review

Hyponatremia is the most frequently occurring electrolyte abnormality and can lead to life-threatening complications. This disorder may be present on admission to the intensive care setting or develop during hospitalization as a result of treatment or multiple comorbidities. Patients with acute hyponatremia or symptomatic chronic hyponatremia will likely require treatment in the intensive care unit (ICU). Immediate treatment with hypertonic saline is needed to reduce the risk of permanent neurologic injury. Chronic hyponatremia should be corrected at a rate sufficient to reduce symptoms but not at an excessive rate that would create a risk of osmotic injury. Determination of the etiology of chronic hyponatremia requires analysis of serum osmolality, volume status, and urine osmolality and sodium level. Correct diagnosis points to the appropriate treatment and helps identify risk factors for accelerated correction of the serum sodium level. Management in the ICU facilitates frequent laboratory draws and allows close monitoring of the patient's mentation as well as quantification of urine output. Overly aggressive correction of serum sodium levels can result in neurological injury caused by osmotic demyelination. Therapeutic measures to lower the serum sodium level should be undertaken if the rate increases too rapidly.

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.

Clinical review: practical approach to hyponatraemia and hypernatraemia in critically ill patients

Disturbances in sodium concentration are common in the critically ill patient and associated with increased mortality. The key principle in treatment and prevention is that plasma [Na+] (P-[Na+]) is determined by external water and cation balances. P-[Na+] determines plasma tonicity. An important exception is hyperglycaemia, where P-[Na+] may be reduced despite plasma hypertonicity. The patient is first treated to secure airway, breathing and circulation to diminish secondary organ damage. Symptoms are critical when handling a patient with hyponatraemia. Severe symptoms are treated with 2 ml/kg 3% NaCl bolus infusions irrespective of the supposed duration of hyponatraemia. The goal is to reduce cerebral symptoms. The bolus therapy ensures an immediate and controllable rise in P-[Na+]. A maximum of three boluses are given (increases P-[Na+] about 6 mmol/l). In all patients with hyponatraemia, correction above 10 mmol/l/day must be avoided to reduce the risk of osmotic demyelination. Practical measures for handling a rapid rise in P-[Na+] are discussed. The risk of overcorrection is associated with the mechanisms that cause hyponatraemia. Traditional classifications according to volume status are notoriously difficult to handle in clinical practice. Moreover, multiple combined mechanisms are common. More than one mechanism must therefore be considered for safe and lasting correction. Hypernatraemia is less common than hyponatraemia, but implies that the patient is more ill and has a worse prognosis. A practical approach includes treatment of the underlying diseases and restoration of the distorted water and salt balances. Multiple combined mechanisms are common and must be searched for. Importantly, hypernatraemia is not only a matter of water deficit, and treatment of the critically ill patient with an accumulated fluid balance of 20 litres and corresponding weight gain should not comprise more water, but measures to invoke a negative cation balance. Reduction of hypernatraemia/hypertonicity is critical, but should not exceed 12 mmol/l/day in order to reduce the risk of rebounding brain oedema.

Hyponatremia in cirrhosis and end-stage liver disease: treatment with the vasopressin V₂-receptor antagonist tolvaptan

Hyponatremia is common in patients with cirrhosis and portal hypertension, and is characterized by excessive renal retention of water relative to sodium due to reduced solute-free water clearance. The primary cause is increased release of arginine vasopressin. Hyponatremia is associated with increased mortality in cirrhotic patients, those with end-stage liver disease (ESLD) on transplant waiting lists, and, in some studies, posttransplantation patients. Clinical evidence suggests that adding serum sodium to model for ESLD (MELD) scoring identifies patients in greatest need of liver transplantation by improving waiting list mortality prediction. Hyponatremia is also associated with numerous complications in liver disease patients, including severe ascites, hepatic encephalopathy, infectious complications, renal impairment, increased severity of liver disease in cirrhosis, and increased hospital stay and neurologic/infectious complications posttransplant. Vasopressin receptor antagonists, which act to increase free water excretion (aquaresis) and thereby increase serum sodium concentration, have been evaluated in patients with hypervolemic hyponatremia (including cirrhosis and heart failure) and euvolemic hyponatremia (SIADH). Tolvaptan, a selective vasopressin V(2)-receptor antagonist, is the only oral agent in this class approved for raising sodium levels in hypervolemic and euvolemic hyponatremia. The SALT trials showed that tolvaptan treatment rapidly and effectively resolved hyponatremia in these settings, including cirrhosis, and it has been shown that this agent can be safely and effectively used in long-term treatment. Fluid restriction should be avoided during the first 24 h of treatment to prevent overly rapid correction of hyponatremia, and tolvaptan should not be used in patients who cannot sense/respond to thirst, anuric patients, hypovolemic patients, and/or those requiring urgent intervention to raise serum sodium acutely.

Hyponatremia in hospitalized patients: the potential role of tolvaptan

Hyponatremia (typically defined as serum sodium level < 135 mEq/L) is a common electrolyte abnormality among hospitalized patients. Whether present at admission or acquired during hospitalization, hyponatremia is associated with higher mortality and longer hospital stays. Failure to adequately investigate and treat hyponatremia may also be associated with adverse outcomes. The presence and severity of clinical symptoms largely depend on the rate and extent of the decline in serum sodium; rapid or large decreases may cause serious neurologic complications. The approach to treatment depends on the presence and severity of symptoms, the timing of their onset, the underlying etiology, and the patient's volume status. Patients with euvolemic or hypervolemic hyponatremia usually have inappropriately elevated levels of arginine vasopressin, which stimulates water reabsorption even in the presence of low serum osmolality. Tolvaptan is an orally active, selective V2-receptor antagonist that blocks the effects of arginine vasopressin in the renal collecting duct to promote aquaresis without increasing sodium or potassium excretion; as a result, it increases serum sodium in a controlled manner. Tolvaptan offers a mechanism-based treatment option for patients with euvolemic or hypervolemic hyponatremia who have serum sodium levels < 125 mEq/L or persistent symptoms resistant to fluid restriction.

Mortality and serum sodium: do patients die from or with hyponatremia?

BACKGROUND AND OBJECTIVES

Severe hyponatremia (<120 mEq/L) in hospitalized patients has a high mortality rate. We hypothesized that underlying diseases causing hyponatremia attribute to mortality rather than hyponatremia itself.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The relationship between mortality and serum sodium (sNa) was examined in 45,693 patients admitted to a single community teaching hospital between January 1996 and December 2007. We conducted a comprehensive retrospective review of the medical records of 53 patients who died after developing sNa <120 mEq/L before or after admission and of 32 patients who survived after developing sNa <110 mEq/L.

RESULTS

Mortality rates tended to increase as the sNa fell from 134 to 120 mEq/L, rising above 10% for patients with sNa of 120 to 124 mEq/L. However, below sNa of 120 mEq/L, the trend reversed, such that the mortality rate progressively decreased as sNa fell. More than two thirds of patients who died after sNa <120 mEq/L had at least two additional acute severe progressive illnesses, most commonly sepsis and multiorgan failure. Three deaths (5.6%) in 12 years could plausibly be related to adverse consequences of hyponatremia, and one (1.8% of the fatal cases and 0.15% of all patients with sNa <120 mEq/L) was from cerebral edema. Most patients who survived with sNa <110 mEq/L had medication-induced hyponatremia. Severe underlying illnesses were uncommon in this group.

CONCLUSIONS

The nature of underlying illness rather than the severity of hyponatremia best explains mortality associated with hyponatremia. Neurologic complications from hyponatremia are uncommon among patients who die with hyponatremia.