Hyponatremia and long-term outcomes in chronic heart failure--an observational study from the Duke Databank for Cardiovascular Diseases. J Card Fail. 2012;18:74-81. [PMID: 22196845 DOI: 10.1016/j.cardfail.2011.09.005]

Hyponatremia in the emergency department: an overview of diagnostic and therapeutic approach

INTRODUCTION

Hyponatremia, defined as a serum sodium concentration <135 mmol/l, is a frequent electrolyte disorder in patients presenting to an emergency department (ED). In this context, appropriate diagnostic and therapeutic management is rarely performed and challenging due to complex pathophysiologic mechanisms and a variety of underlying diseases.

OBJECTIVE

To implement a feasible pathway of central diagnostic and therapeutic steps in the setting of an ED.

METHODS

We conducted a narrative review of the literature, considering current practice guidelines on diagnosis and treatment of hyponatremia. Underlying pathophysiologic mechanisms and management of adverse treatment effects are outlined. We also report four cases observed in our ED.

RESULTS

Symptoms associated with hyponatremia may appear unspecific and range from mild cognitive deficits to seizures and coma. The severity of hyponatremia-induced neurological manifestation and the risk of poor outcome is mainly driven by the rapidity of serum sodium decrease. Therefore, emergency treatment of hyponatremia should be guided by symptom severity and the assumed onset of hyponatremia development, distinguishing acute (<48 hours) versus chronic hyponatremia (>48 hours).

CONCLUSIONS

Especially in moderately or severely symptomatic patients presenting to an ED, the application of a standard management approach appears to be critical to improve overall outcome. Furthermore, an adequate work-up in the ED enables further diagnostic and therapeutic evaluation during hospitalization.

Association Between Early Hyponatremia and Clinical Outcomes in Critically Ill Patients: A Retrospective Cohort Study

INTRODUCTION

Hyponatremia, frequently encountered in intensive care (ICU) settings, plays a critical role in shaping patient outcomes. Despite its prevalence, contemporary research into its newly classified severity categories and their implications on mortality, renal function, and length of stay remains limited. This study aims to fill this gap by examining the impact of hyponatremia severity on these critical outcomes.

METHODS

A retrospective analysis of ICU patients aged >18 years who were admitted between March 2019 and December 2022 was conducted at Hamamatsu University Hospital, Shizuoka, Japan. Patients who were readmitted or had incomplete data were excluded. Hyponatremia was categorized as mild (130-135 mmol/L), moderate (125-129 mmol/L), or severe (<125 mmol/L), following the criteria set by the European Society of Intensive Care Medicine. This classification utilized the lowest sodium concentration within 24 hours of ICU admission. The outcomes were in-hospital mortality, ICU mortality, newly implemented renal replacement therapy (RRT), and length of hospital and ICU stay. Outcomes were analyzed using multivariable logistic and linear regression models, adjusting for relevant covariates including age, sex, Acute Physiology and Chronic Health Evaluation (APACHE) III scores, and the use of mechanical ventilation.

RESULTS

Of the 3,538 patients analyzed, 1,072 (30.3%) experienced hyponatremia: 894 (25.3%) mild, 144 (4.1%) moderate, and 34 (1.0%) severe. Multivariable analysis revealed no significant association between hyponatremia severity and in-hospital mortality rates across normonatremia (3.8%), mild (5.2%), moderate (11.8%), and severe (23.5%) groups, nor with ICU mortality. However, compared to normonatremia, moderate and severe hyponatremia were associated with increased RRT initiation (odds ratios = 3.83 and 6.36, respectively) and prolonged hospital stay (mean difference = 7.06 and 9.66 days, respectively), and ICU stays (mean difference, 1.02 and 2.70 days, respectively). Mild hyponatremia was not significantly associated with RRT or length of stay.

CONCLUSION

Moderate-to-severe hyponatremia did not influence mortality but was associated with increased RRT initiation and prolonged hospital and ICU stay. By contrast, mild hyponatremia was not associated with any clinical outcome. Further research is required to determine if correcting hyponatremia directly improves ICU patient outcomes, given the observational nature of the study.

Association between hyponatremia and adverse clinical outcomes of heart failure: current evidence based on a systematic review and meta-analysis

Background

Heart failure (HF) is a global health challenge. The perturbations in fluid and electrolyte equilibrium, particularly the compromised sodium balance associated with HF lead to high mortality rates. Hence, elucidating the correlation between serum sodium levels and the prognosis of HF is of paramount importance. This study aimed to conduct a comprehensive meta-analysis to thoroughly investigate the interplay between hyponatremia and the prognostic outlook of individuals with HF.

Methods

A comprehensive search of bibliographic databases including PubMed, Embase, and the Cochrane Central Register of Controlled Trials was conducted to identify relevant observational studies examining the association between hyponatremia and prognosis of HF. Data extraction, synthesis, and assessment of risk of bias were conducted. Meta-analytic methods, sensitivity analyses, and heterogeneity test were employed as appropriate to synthesize the data.

Results

A total of 43,316 patients with HF were included spanning 25 selected studies. The pooled data revealed a notable association between hyponatremia and elevated risks across short and long-term mortality of HF. Specifically, hyponatremia was found to significantly increase the likelihood of all-cause mortality (Hazard ratio [HR] = 1.94, 95% confidence interval [CI]: 1.78-2.12); 1-year mortality (HR = 1.67, 95%CI: 1.46-1.90); 30-day mortality (HR = 2.03, 95%CI: 1.73-2.25); cardiac mortality (HR = 2.11, 95%CI: 1.81-2.46); and in-hospital mortality (HR = 1.64, 95%CI: 1.15-2.34).

Conclusion

Our meta-analysis emphasizes the significant impact of hyponatremia on mortality in the HF patient population, highlighting the critical importance of maintaining stable serum sodium levels in HF management.

sST2 and Heart Failure-Clinical Utility and Prognosis

New parameters and markers are constantly being sought to help better assess patients with heart failure (HF). ST2 protein has gained interest as a potential biomarker in cardiovascular disease. It is known that the IL-33/ST2L system belongs to the cardioprotective pathway, which prevents the fibrosis, hypertrophy, and apoptosis of cardiomyocytes and also inhibits the inflammatory response. Soluble ST2 (sST2) is involved in the immune response and secreted in response to the mechanical overload of the myocardium, thus providing information on the processes of myocardial remodeling and fibrosis. A total of 110 hospitalized patients diagnosed with heart failure with reduced ejection fraction (HFrEF) were included in the study. Clinical and biochemical parameters were studied. During the follow-up, 30.9% patients died and 57.3% patients reached the composite endpoint. Using ROC curves, the reference cut-off point for sST2 was determined to be 45.818 pg/mL for all-cause deaths. Significantly higher concentrations of inflammatory parameters and natriuretic peptides were found in the group of patients with higher sST2 concentrations. sST2 protein is an independent risk factor for all-cause deaths of patients with HFrEF.

Hyponatremia Is a Powerful Predictor of Poor Prognosis in Left Ventricular Assist Device Patients

Serum sodium is an established prognostic marker in heart failure (HF) patients and is associated with an increased risk of morbidity and mortality. We sought to study the prognostic value of serum sodium in left ventricular assist device (LVAD) patients and whether hyponatremia reflects worsening HF or an alternative mechanism. We identified HF patients that underwent LVAD implantation between 2008 and 2019. Hyponatremia was defined as Na ≤134 mEq/L at 3 months after implantation. We assessed for differences in hyponatremia before and after LVAD implantation. We also evaluated the association of hyponatremia with all-cause mortality and recurrent HF hospitalizations. There were 342 eligible LVAD patients with a sodium value at 3 months. Among them, there was a significant improvement in serum sodium after LVAD implantation compared to preoperatively (137.2 vs. 134.7 mEq/L, P < 0.0001). Patients with and without hyponatremia had no significant differences in echocardiographic and hemodynamic measurements. In a multivariate analysis, hyponatremia was associated with a markedly increased risk of all-cause mortality (HR 3.69, 95% CI, 1.93-7.05, P < 0.001) when accounting for age, gender, co-morbidities, use of loop diuretics, and B-type natriuretic peptide levels. Hyponatremia was also significantly associated with recurrent HF hospitalizations (HR 2.11, 95% CI, 1.02-4.37, P = 0.04). Hyponatremia in LVAD patients is associated with significantly higher risk of all-cause mortality and recurrent HF hospitalizations. Hyponatremia may be a marker of ongoing neurohormonal activation that is more sensitive than other lab values, echocardiography parameters, and hemodynamic measurements.

Dysnatremia and risk of bloodstream infection in dialysis patients

Background

Emerging data suggest that sodium disarrays including hyponatremia are potential risk factors for infection ensuing from impairments in host immunity, which may be exacerbated by coexisting conditions (i.e. mucosal membrane and cellular edema leading to breakdown of microbial barrier function). While dysnatremia and infection-related mortality are common in dialysis patients, little is known about the association between serum sodium levels and the risk of bloodstream infection in this population.

Methods

Among 823 dialysis patients from the national Biospecimen Registry Grant Program who underwent serum sodium testing over the period January 2008–December 2014, we examined the relationship between baseline serum sodium levels and subsequent rate of bloodstream infection. Bloodstream infection events were directly ascertained using laboratory blood culture data. Associations between serum sodium level and the incidence of bloodstream infection were estimated using expanded case mix–adjusted Poisson regression models.

Results

In the overall cohort, ∼10% of all patients experienced one or more bloodstream infection events during the follow-up period. Patients with both lower sodium levels <134 mEq/l and higher sodium levels ≥140 mEq/l had higher incident rate ratios (IRRs) of bloodstream infection in expanded case mix analyses (reference 136–<138 mEq/l), with adjusted IRRs of 2.30 [95% confidence interval (CI) 1.19–4.44], 0.77 (95% CI 0.32–1.84), 1.39 (95% CI 0.78–2.47), 1.88 (95% CI 1.08–3.28) and 1.96 (95% CI 1.08–3.55) for sodium levels <134, 134–<136, 138–<140, 140–<142 and ≥142 Eq/l, respectively.

Conclusions

Both lower and higher baseline serum sodium levels were associated with a higher rate of subsequent bloodstream infections in dialysis patients. Further studies are needed to determine whether correction of dysnatremia ameliorates infection risk in this population.

Relationship of Dapagliflozin With Serum Sodium: Findings From the DAPA-HF Trial

OBJECTIVES

This study aimed to assess the prognostic importance of hyponatremia and the effects of dapagliflozin on serum sodium in the DAPA-HF (Dapagliflozin And Prevention of Adverse outcomes in Heart Failure) trial.

BACKGROUND

Hyponatremia is common and prognostically important in hospitalized patients with heart failure with reduced ejection fraction, but its prevalence and importance in ambulatory patients are uncertain.

METHODS

We calculated the incidence of the primary outcome (cardiovascular death or worsening heart failure) and secondary outcomes according to sodium category (≤135 and >135 mmol/L). Additionally, we assessed: 1) whether baseline serum sodium modified the treatment effect of dapagliflozin; and 2) the effect of dapagliflozin on serum sodium.

RESULTS

Of 4,740 participants with a baseline measurement, 398 (8.4%) had sodium ≤135 mmol/L. Participants with hyponatremia were more likely to have diabetes, be treated with diuretics, and have lower systolic blood pressure, left ventricular ejection fraction, and estimated glomerular filtration rate. Hyponatremia was associated with worse outcomes even after adjustment for predictive variables (adjusted HRs for the primary outcome 1.50 [95% CI: 1.23-1.84] and all-cause death 1.59 [95% CI: 1.26-2.01]). The benefits of dapagliflozin were similar in patients with and without hyponatremia (HR for primary endpoint: 0.83 [95% CI: 0.57-1.19] and 0.73 [95% CI: 0.63-0.84], respectively, P for interaction = 0.54; HR for all-cause death: 0.85 [95% CI: 0.56-1.29] and 0.83 [95% CI: 0.70-0.98], respectively, P for interaction = 0.96). Between baseline and day 14, more patients on dapagliflozin developed hyponatremia (11.3% vs 9.4%; P = 0.04); thereafter, this pattern reversed and at 12 months fewer patients on dapagliflozin had hyponatremia (4.6% vs 6.7%; P = 0.003).

CONCLUSIONS

Baseline serum sodium concentration was prognostically important, but did not modify the benefits of dapagliflozin on morbidity and mortality in heart failure with reduced ejection fraction. (Study to Evaluate the Effect of Dapagliflozin on the Incidence of Worsening Heart Failure or Cardiovascular Death in Patients With Chronic Heart Failure [DAPA-HF]: NCT03036124).

Hyponatremia in tuberculous meningitis: A systematic review and meta-analysis

BACKGROUND

Tuberculous meningitis (TBM), manifests as the most severe involvement of the nervous system by Mycobacterium tuberculosis, it has a high mortality rate and a spectrum of systemic and neurological complications that can lead to debilitating or fatal sequelae, whereas hyponatremia is the commonly encountered life-threatening electrolyte disturbance. Thus, our study aimed to determine the prevalence, risk factors and differences in outcomes of hyponatremia in TBM.

METHODS

This systematic review was registered in PROSPERO (CRD42018088089). A comprehensive electronic search was conducted through ten databases to find relevant articles.

RESULTS

A total of 42 studies were included, 24 case reports and 18 retrospective studies. The prevalence rate of hyponatremia among TBM patients was 52% and the rate of death among those patients was 29%. The meta-regression analysis revealed that there was no significant effect of sodium level on the death rate in TBM patients (P-value = 0.9). Additionally, there was no significant difference in sodium level based on sex, and etiologies of hyponatremia.

CONCLUSIONS

Hyponatremia is commonly present in patient with TBM, but it is not significantly correlated to the rate of death. However, it is necessary to treat this potentially life-threatening condition appropriately according to its etiology, further research is needed on its pathophysiology in TBM, its risk factors, and the most appropriate treatment.

Hyponatremia in heart failure: not just 135 to 145

One of the most frequent in-hospital electrolyte disturbances is hyponatremia. Hyponatremia in heart failure (HF) is mainly associated with hypervolemia resulting from activation of baroreceptor-mediated hormones, such as arginine vasopressin (AVP), renin-angiotensin-aldosterone system, and catecholamines. Various electrolyte imbalance can occur as heart failure progress. The goal of this review was to outline the current literature on hyponatremia in HF patients.

Resting Heart Rate as an Important Predictor of Mortality and Morbidity in Ambulatory Patients With Heart Failure: A Systematic Review and Meta-Analysis

BACKGROUND

Resting heart rate is a risk factor of adverse heart failure outcomes; however, studies have shown controversial results. This meta-analysis evaluates the association of resting heart rate with mortality and hospitalization and identifies factors influencing its effect.

METHODS AND RESULTS

We systematically searched electronic databases in February 2019 for studies published in 2005 or before that evaluated the resting heart rate as a primary predictor or covariate of multivariable models of mortality and/or hospitalization in adult ambulatory patients with heart failure. Random effects inverse variance meta-analyses were performed to calculate pooled hazard ratios. The Grading of Recommendations, Assessment, Development and Evaluation approach was used to assess evidence quality. Sixty-two studies on 163,445 patients proved eligible. Median population heart rate was 74 bpm (interquartile range 72-76 bpm). A 10-bpm increase was significantly associated with increased risk of all-cause mortality (hazard ratio 1.10, 95% confidence interval 1.08-1.13, high quality). Overall, subgroup analyses related to patient characteristics showed no changes to the effect estimate; however, there was a strongly positive interaction with age showing increasing risk of all-cause mortality per 10 bpm increase in heart rate.

CONCLUSIONS

High-quality evidence demonstrates increasing resting heart rate is a significant predictor of all-cause mortality in ambulatory patients with heart failure on optimal medical therapy, with consistent effect across most patient factors and an increased risk trending with older age.

Costs associated with unplanned readmissions among patients with heart failure with and without hyponatremia

PURPOSE

Costs associated with unplanned readmissions among patients with heart failure with and without hyponatremia were studied.

METHODS

This study estimated the costs of patients hospitalized for heart failure (HF) discharged with or without corrected sodium. A model was developed to monetize the 30-day readmission risk based on hyponatremia correction. Costs of discharging patient with corrected versus uncorrected hyponatremia were estimated using readmission rates from a previously published study and hospitalization costs from the Healthcare Costs and Utilization Cost Project and the Premier Healthcare Database.

RESULTS

Discharging patients with HF and hyponatremia increased costs from $488-$569 per discharge compared to patients with corrected hyponatremia. This range reflected differences in readmission rates and sources of hospitalization costs. Sensitivity analyses showed hospitalization costs and readmission rates had the largest impact on model results.

CONCLUSION

A retrospective study supports the value of upfront monitoring and correction of low serum sodium levels before discharge among patients with HF and hyponatremia by presenting an economic argument in addition to the clinical rational for reducing risk of readmission.

Racial differences and mortality risk in patients with heart failure and hyponatremia

BACKGROUND

Hyponatremia is a well-established poor prognostic marker in patients with heart failure. Whether the mortality risk is comparable among different races of patients with heart failure and hyponatremia is unknown.

MATERIALS AND METHODS

Consecutive patients admitted with acute decompensated heart failure and an admission sodium level<135 mEq/L from 1/1/2001 through 12/31/10 were identified. Patients were divided into four groups based on self-reported race: white, African American, Hispanic and other. African Americans were used as the reference group for statistical analysis. The primary outcome was all-cause mortality.

RESULTS

We included 4,343 patients, from which 1,356 (31%) identified as white, 1,248 (29%) as African American, 780 (18%) as Hispanic and 959 (22%) as other. During a median follow-up of 23 months, a total of 2,384 patients died: 678 were African American, 820 were white, 298 were Hispanic and 588 were other. After adjusting for baseline demographics, comorbidities and medication use, Hispanic patients had a 45% less risk of death as compared to African Americans (HR .55, CI .48-.64, p<0.05). There was no difference in mortality between white and African American patients (HR 1.04, CI .92-1.2, p = 0.79).

CONCLUSION

Hispanic patients admitted for heart failure and who were hyponatremic on admission had an independent lower risk of mortality compared to other groups. These findings may be due to the disparate activity of the renin-angiotensin-aldosterone system among various racial groups. This observational study is hypothesis generating and suggests that treatment of patients with heart failure and hyponatremia should perhaps be focused more on renin-angiotensin-aldosterone system reduction in certain racial groups, yet less in others.

The prognosis of heart failure patients: Does sodium level play a significant role?

Introduction

Heart failure (HF), a major cardiovascular disorder, remains a grievous clinical condition regardless of advances in medical care. Hyponatremia is classified as a serum sodium concentration of <135 mEq/L, and the prevalence, clinical impact and prognostic factor of hyponatremia in heart failure patients varies widely. The current study was conducted with the aim of assessing the prevalence of hyponatremia in patients hospitalized with a diagnosis of HF and comparing baseline clinical characteristic of HF patients based on their sodium status. Survival difference between patients with hyponatremia and normonatremia was also assessed and the clinical prognostic indicators of overall mortality in HF patients were evaluated.

Method

A retrospective cohort study was conducted to assess medical records of heart failure patients who were admitted to Gondar University Referral Hospital. Patients were categorized based on their sodium level status at their first admission to the internal medicine department. Each patient was assigned to either of the following groups: hyponatremia if sodium < 135 mmol/L, or normonatremia if sodium ≥ 135 mmol/L.

Result

Among 388 participants, the prevalence of hyponatremia in the study cohorts was 51.03%. Kaplan-Meier survival curves showed that there was a significant difference in survival status of HF patients among the two cohorts (Log—Rank test, P <0.0001). Hence, patients with normal sodium levels had a higher chance of survival over hyponatremic patients. Multivariate Cox regression has revealed a statistically significant association of mortality with the following variables: advanced age (AHR = 1.035 (1.012–1.058), P = 0.003), hyponatremia (AHR = 4.003 (1.778–9.009), P = 0.001), higher creatinine level (AHR = 1.929 (1.523–2.443), P = <0.0001) and, prescription of angiotensin-converting enzyme inhibitors (AHR = 0.410 (0.199–0.842), P = 0.015) and spironolactone (AHR = 0.511 (0.275–0.949), P = 0.033.

Conclusion

In conclusion, hyponatremia is one of the crucial factors in the clinical prognosis of heart failure patients. However, as other prognostic factors (i.e. medication, creatine level, and age) also played vital roles in overall survival, well-controlled clinical trials (complete with medication dosing, laboratory outputs and long-term prospective follow up) are required to further study the impact of hyponatremia in HF patient’s prognosis in low income nations.

Relationship Between Serum Sodium Level Within the Low-Normal Range on Admission and Long-Term Clinical Outcomes in Patients with Acute Decompensated Heart Failure

Although hyponatremia during hospitalization for acute decompensated heart failure (ADHF) is reportedly related with poor prognosis, the available data regarding the impact of serum sodium level within the low-normal range at admission on clinical events in patients with ADHF is limited.We studied eligible patients admitted to our institution in 2007-2011. All the patients were categorized into 3 groups according to the admission serum sodium levels of < 135 mmol/L (hyponatremia), ≥ 135 and < 140 mmol/L (low-normal range), or ≥ 140 mmol/L (normal range). The association between admission serum sodium levels and long-term clinical events, a composite of all-cause deaths and re-hospitalizations for ADHF, was assessed by multivariable Cox proportional analysis.Of the 584 eligible patients, 208 (35.6%) were in the low-normal range and 99 (16.9%) had hyponatremia on admission. On multivariable analysis, compared with those with a sodium level ≥ 140 mmol/L, patients with hyponatremia were at increased risk for clinical events (hazard ratio [HR], 1.53; P = 0.041), whereas the HR of those in the low-normal range was attenuated and insignificant (HR, 1.08; P = 0.625). However, the HR of each category increased significantly as sodium level decreased (P value for HR trend, 0.024). In addition, when serum sodium level was treated as a continuous variable, the lower the serum sodium level, the greater the risk of clinical events (P = 0.012). The cut-off value of serum sodium level to predict mortality was < 138 mmol/L.In conclusion, a low serum sodium level on admission for ADHF, even if low-normal, can increase the risk of long-term mortality and/or re-hospitalization for ADHF.

Utilization and budget impact of tolvaptan in the inpatient setting among patients with heart failure and hyponatremia

OBJECTIVE

Assess characteristics of patients with heart failure (HF) and hyponatremia (HN) using tolvaptan, a selective vasopressin V2-receptor antagonist, for sodium correction, and estimate the budget impact of tolvaptan use in a hospital.

METHODS

The Premier hospital database was analyzed to assess the utilization of tolvaptan, characteristics of users and non-users, and hospitalization costs among patients with HF and HN. Using these findings, a model was developed to estimate tolvaptan costs in proportion to total medical costs of managing patients with HF and HN, and the budget impact of tolvaptan use. Results were regenerated using data from the Healthcare Cost and Utilization Project (HCUP) database, and robustness was assessed in sensitivity analyses.

RESULTS

Tolvaptan was used in 4.96% of inpatient visits among patients with HF and HN, more commonly among sicker patients as reflected in high utilization during intensive care stays (30.46%). Additionally, utilization increased by length of stay, which can serve as a proxy for disease severity. The model estimated that tolvaptan costs accounted for 0.3% of total hospitalization-related costs for patients with HF and HN, and the budget impact was $52.42 per visit.

CONCLUSIONS

Results demonstrate that tolvaptan is used infrequently among patients with HF and HN, and is utilized among sicker patients. Tolvaptan accounted for 0.3% of total spending on management of inpatient visits with HF and HN, and had a marginal impact on hospital budget when compared with fluid restriction for HN correction. Availability of tolvaptan can provide an additional therapeutic option for sodium correction.

Hyponatremia: A clinical approach

Hyponatremia is the most common electrolyte metabolic abnormality in clinical practice. The unfavorable course of many diseases is associated with hyponatremia. Acute severe hyponatremia is life-threatening because cerebral edema may develop. Less obvious chronic hyponatremia increases the risk of balance problems, falls and fractures, especially in elderly patients. In any occasion, hyponatremia should not be now regarded only as a laboratory phenomenon in critically ill patients, but it necessitates a thorough clinical analysis of each individual case and appropriate therapy. The paper presents approaches to diagnosing and treating hyponatremia in various clinical situations.

Current Management of Hyponatremia in Acute Heart Failure: A Report From the Hyponatremia Registry for Patients With Euvolemic and Hypervolemic Hyponatremia (HN Registry)

Background

Hyponatremia (HN) occurs commonly in patients with acute heart failure and confers a worse prognosis. Current HN treatment varies widely, with no consensus. This study recorded treatment practices currently used for patients hospitalized with acute heart failure and HN.

Methods and Results

Data were collected prospectively from 146 US sites on patients hospitalized with acute heart failure and HN (serum sodium concentration [Na⁺] ≤130 mEq/L) present at admission or developing in the hospital. Baseline variables, HN treatment, and laboratory values were recorded. Of 762 patients, median [Na⁺] was 126 mEq/L (interquartile range, 7) at baseline and increased to 130 mEq/L at discharge. Fluid restriction was the most commonly prescribed therapy (44%), followed by no specific HN treatment beyond therapy for congestion (23%), isotonic saline (5%), tolvaptan (4%), and hypertonic saline (2%). Median rate of change in [Na⁺] varied by treatment (0.5 [interquartile range, 1.0] to 2.3 [8.0] mEq/L/d) and median treatment duration ranged from 1 (interquartile range, 1) to 6 (5) days. Fluid restriction and no specific HN treatment resulted in similar changes in [Na⁺], and were least effective in correcting HN. Few patients (19%) had [Na⁺] ≥135 mEq/L at discharge.

Conclusions

The most commonly used treatment approaches for HN (fluid restriction and no specific treatment) in acute heart failure increased [Na⁺] minimally, and most patients remained hyponatremic at discharge.

Prevalence and Prognostic Significance of Hyponatremia in Patients with Acute Exacerbation of Chronic Obstructive Pulmonary Disease: Data from the Akershus Cardiac Examination (ACE) 2 Study

BACKGROUND

Hyponatremia is prevalent and associated with mortality in patients with heart failure (HF). The prevalence and prognostic implications of hyponatremia in acute exacerbation of chronic obstructive pulmonary (AECOPD) have not been established.

METHOD

We included 313 unselected patients with acute dyspnea who were categorized by etiology of dyspnea according to established guidelines (derivation cohort). Serum Na+ was determined on hospital admission and corrected for hyperglycemia, and hyponatremia was defined as [Na+]<137 mmol/L. Survival was ascertained after a median follow-up of 816 days and outcome was analyzed in acute HF (n = 143) and AECOPD (n = 83) separately. Results were confirmed in an independent AECOPD validation cohort (n = 99).

RESULTS

In the derivation cohort, median serum Na+ was lower in AECOPD vs. acute HF (138.5 [135.9-140.5] vs. 139.2 [136.7-141.3] mmol/L, p = 0.02), while prevalence of hyponatremia (27% [22/83] vs. 20% [29/143], p = 0.28) and mortality rate (42% [35/83] vs. 46% [66/143], p = 0.56) were similar. By univariate Cox regression analysis, hyponatremia was associated with increased mortality in acute HF (HR 1.85 [95% CI 1.08, 3.16], p = 0.02), but not in AECOPD (HR 1.00 [0.47, 2.15], p = 1.00). Analogous to the results of the derivation cohort, hyponatremia was prevalent also in the AECOPD validation cohort (25% [25/99]), but not associated with mortality. The diverging effect of hyponatremia on outcome between AECOPD and acute HF was statistically significant (p = 0.04).

CONCLUSION

Hyponatremia is prevalent in patients with acute HF and AECOPD, but is associated with mortality in patients with acute HF only.

The Economic Burden of Hyponatremia: Systematic Review and Meta-Analysis

BACKGROUND

Hyponatremia is the most common electrolyte abnormality observed in clinical practice. Several studies have demonstrated that hyponatremia is associated with an increased length of hospital stay and of hospital resource utilization. To clarify the impact of hyponatremia on the length of hospitalization and costs, we performed a meta-analysis based on published studies that compared hospital length of stay and cost between patients with and without hyponatremia.

METHODS

An extensive Medline, Embase, and Cochrane search was performed to retrieve all studies published up to April 1, 2015 using the following words: "hyponatremia" or "hyponatraemia" AND "hospitalization" or "hospitalisation." A meta-analysis was performed including all studies comparing duration of hospitalization and hospital readmission rate in subjects with and without hyponatremia.

RESULTS

Of 444 retrieved articles, 46 studies satisfied the inclusion criteria, encompassing a total of 3,940,042 patients; among these, 757,763 (19.2%) were hyponatremic. Across all studies, hyponatremia was associated with a significantly longer duration of hospitalization (3.30 [2.90-3.71; 95% CIs] mean days; P < .000). Similar results were obtained when patients with associated morbidities were analyzed separately. Furthermore, hyponatremic patients had a higher risk of readmission after the first hospitalization (odds ratio 1.32 [1.18-1.48; 95% CIs]; P < .000). A meta-regression analysis showed that the hyponatremia-related length of hospital stay was higher in males (Slope = 0.09 [0.05-0.12; 95% CIs]; P = .000 and Intercept = -1.36 [-3.03-0.32; 95% CIs]; P = .11) and in elderly patients (Slope = 0.002 [0.001-0.003; 95% CIs]; P < .000 and Intercept = 0.89 [0.83-0.97; 95% CIs]; P < .001). A negative association between serum [Na(+)] cutoff and duration of hospitalization was detected. No association between duration of hospitalization, serum [Na(+)], and associated morbidities was observed. Finally, when only US studies (n = 8) were considered, hyponatremia was associated with up to around $3000 higher hospital costs/patient when compared with the cost of normonatremic subjects.

CONCLUSIONS

This meta-analysis confirms that hyponatremia is associated with a prolonged hospital length of stay and higher risk of readmission. These observations suggest that hyponatremia may represent one important determinant of the hospitalization costs.

Urine Aquaporin-2: A Promising Marker of Response to the Arginine Vasopressin Type-2 Antagonist, Tolvaptan in Patients with Congestive Heart Failure

Aquaporin-2, a member of the aquaporin family, is an arginine vasopressin-regulated water channel expressed in the renal collecting duct, and a promising marker of the concentrating and diluting ability of the kidney. The arginine vasopressin type-2 antagonist, tolvaptan, is a new-generation diuretic; it is especially indicated in patients with decompensated heart failure refractory to conventional diuretics. However, the ideal responders to tolvaptan have not yet been identified, and non-responders experience worse clinical courses despite treatment with tolvaptan. Urine aquaporin-2 has recently been demonstrated as a promising predictor of response to tolvaptan. We here validated aquaporin-2-guided tolvaptan therapy in patients with decompensated heart failure. Long-term efficacy of tolvaptan treatment in the responders defined by aquaporin-2 needs to be validated in the future prospective study.

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.

Pre-dialysis serum sodium and mortality in a national incident hemodialysis cohort

BACKGROUND

A consistent association between low serum sodium measured at a single-point-in-time (baseline sodium) and higher mortality has been observed in hemodialysis patients. We hypothesized that both low and high time-varying sodium levels (sodium levels updated at quarterly intervals as a proxy of short-term exposure) are independently associated with higher death risk in hemodialysis patients.

METHODS

We examined the association of baseline and time-varying pre-dialysis serum sodium levels with all-cause mortality among adult incident hemodialysis patients receiving care from a large national dialysis organization during January 2007-December 2011. Hazard ratios were estimated using multivariable Cox models accounting for case-mix+laboratory covariates and incrementally adjusted for inter-dialytic weight gain, blood urea nitrogen and glucose.

RESULTS

Among 27 180 patients, a total of 7562 deaths were observed during 46 194 patient-years of follow-up. Median (IQR) at-risk time was 1.4 (0.6, 2.5) years. In baseline analyses adjusted for case-mix+laboratory results, sodium levels <138 mEq/L were associated with incrementally higher mortality risk, while the association of sodium levels ≥140 mEq/L with lower mortality reached statistical significance only for the highest level of pre-dialysis sodium (reference: 138-<140 mEq/L). In time-varying analyses, we observed a U-shaped association between sodium and mortality such that sodium levels <138 and ≥144 mEq/L were associated with higher mortality risk. Similar patterns were observed in models incrementally adjusted for inter-dialytic weight gain, blood urea nitrogen and glucose.

CONCLUSIONS

We observed a U-shaped association of time-varying pre-dialysis serum sodium and all-cause mortality in hemodialysis patients, suggesting that both hypo- and hypernatremia carry short-term risk in this population.

Hyponatremia during hospitalization and in-hospital mortality in patients hospitalized from heart failure

Background

To date, the majority of studies on hyponatremia focussed on hyponatremia at admission, and came from developed countries. This study aimed to identify the prevalence of hyponatremia during hospitalization in patients hospitalized for HF and its association with in-hospital mortality.

Methods

This was an observational study using retrospective data from patients’ records between 2010–2013. It focused on those patients carrying an ICD-10 code of 150.0(Congestive Heart Failure) as their primary diagnosis.

Hyponatremia during hospitalization was defined as serum sodium level lower than 135 mEq/L obtained from a blood chemistry measurement on the next days after admission. Patients’ characteristics were examined and the association between hyponatremia during hospitalization and in-hospital mortality was analyzed.

Results

Among 464 patients hospitalized for HF, hyponatremia during hospitalization was observed in 22 % of patients with 44 % of this group had normal serum sodium level on admission.

Hyponatremia during hospitalization was associated with lower blood pressure on admission, both systolic and diastolic, peripheral oedema, ascites and fatigue. Patients having history of hospitalization for cardiac diseases and renal failure were higher in patients developing hyponatremia during hospitalization. In this group, amiodarone, heparin, insulin and antibiotics were administered more frequently. Factors potentially increase the risk of hyponatremia during hospitalization include history of fatigue (OR = 3.23, 95 % CI 1.79–5.82), presence of ascites (4.14, 1.84–9.31), and administration of heparin (3.85, 1.78–8.31) and antibiotics (3.08, 1.71–5.53). Length of hospital stay was significantly longer in patients with hyponatremia during hospitalization and in-hospital mortality was also higher compared to non-hyponatremic patients, 7.7 % and 29.1 %, respectively.

Conclusion

This study found that the prevalence of hyponatremia during hospitalization in patients hospitalized for HF was almost the same as hyponatremia on admission and administration of heparin and antibiotics can potentially worsen hyponatremia during hospitalization. In this study population, hyponatremia during hospitalization was found to be associated with in-hospital mortality.

Hyponatremia Predicts New-Onset Cardiovascular Events in Peritoneal Dialysis Patients

Background and Aim

Cardiovascular (CV) disease is the leading cause of morbidity and mortality in patients on peritoneal dialysis (PD). Hyponatremia was recently shown to be a modifiable factor that is strongly associated with increased mortality in PD patients. However, the clinical impact of hyponatremia on CV outcomes in these patients is unclear.

Methods

To determine whether a low serum sodium level predicts the development of CV disease, we carried out a prospective observational study of 441 incident patients who started PD between January 2000 and December 2005. Time-averaged serum sodium (TA-Na) levels were determined to investigate the ability of hyponatremia to predict newly developed CV events in these patients.

Results

During a mean follow-up of 43.2 months, 106 (24.0%) patients developed new CV events. The cumulative incidence of new-onset CV events after the initiation of PD was significantly higher in patients with TA-Na levels ≤ 138 mEq/L than in those with a TA-Na > 138 mEq/L. After adjustment for multiple potentially confounding covariates, an increase in TA-Na level was found to be associated with a significantly lower risk of CV events (subdistribution hazard ratio per 1 mEq/L increase, 0.90; 95% confidence interval, 0.83–0.96; p = 0.003). Patients with a TA-Na ≤ 138 mEq/L had a 2.31-fold higher risk of suffering a CV event.

Conclusions

These results provide evidence of a clear association between low serum sodium and new-onset CV events after dialysis initiation in PD patients. Whether the correction of hyponatremia for this indication provides additional protection for the development of CV disease in these patients remains to be addressed in interventional studies.

Hyponatremia as a predictor of mortality in peritoneal dialysis patients

BACKGROUND AND AIM

Hyponatremia is common in patients with chronic kidney disease and is associated with increased mortality in hemodialysis patients. However, few studies have addressed this issue in peritoneal dialysis (PD) patients.

METHODS

This prospective observational study included a total of 441 incident patients who started PD between January 2000 and December 2005. Using time-averaged serum sodium (TA-Na) levels, we aimed to investigate whether hyponatremia can predict mortality in these patients.

RESULTS

Among the baseline parameters, serum sodium level was positively associated with serum albumin (β = 0.145; p = 0.003) and residual renal function (RRF) (β = 0.130; p = 0.018) and inversely associated with PD ultrafiltration (β = -0.114; p = 0.024) in a multivariable linear regression analysis. During a median follow-up of 34.8 months, 149 deaths were recorded. All-cause death occurred in 81 (55.9%) patients in the lowest tertile compared to 37 (25.0%) and 31 (20.9%) patients in the middle and highest tertiles, respectively. After adjusting for multiple potentially confounding covariates, increased TA-Na level was associated with a significantly decreased risk of all-cause (HR per 1 mEq/L increase, 0.79; 95% CI, 0.73-0.86; p<0.001) and infection-related (HR per 1 mEq/L increase, 0.77; 95% CI, 0.70-0.85; p<0.001) deaths.

CONCLUSIONS

This study showed that hyponatremia is an independent predictor of mortality in PD patients. Nevertheless, whether correcting hyponatremia improves patient survival is unknown. Future interventional studies should address this question more appropriately.

Vasopressin receptor antagonists for the treatment of heart failure: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND/OBJECTIVES

Elevated vasopressin may increase systemic vascular resistance and pulmonary capillary wedge pressure, subsequently decrease stroke volume and cardiac output. Vasopressin receptor antagonists may counteract these effects and improve outcomes in heart failure. We aimed to assess benefits and harms of vasopressin receptor antagonists (VRAs) versus placebo in addition to standard care in adults with heart failure (HF).

METHODS

We conducted a systematic review of randomized controlled trials with searches of CENTRAL and MEDLINE to January 2014 and reference lists without language restriction. Meta-analysis using a random-effects model was done for all-cause and cardiovascular mortality, hospitalization for heart failure, changes in clinical assessment of HF, serum sodium concentration (Na), kidney function and treatment-specific side effects.

RESULTS

We identified 13 trials and 5,525 participants. In 10 trials, participants received standard therapy for HF. In low-quality evidence, VRAs in patients with HF had no effect on all-cause mortality risk ratios (RR 0.98; CI 0.88-1.08), cardiovascular mortality (RR 1.03; CI 0.91-1.16) or change in creatinine mean difference (MD -0.01; CI -0.10 to 0.09 mg/dL), but reduced body weight by 0.8 kg from baseline (MD -0.83; CI -1.10 to -0.55 kg) and increased Na (MD 2.61; 95 % CI 1.88-3.35 mmol/L). Compared with placebo, VRAs increased the risk of adverse events by 14 % (RR 1.14; CI 1.04-1.26). Studies were generally limited to short-term follow-up with limited data available on patient important outcomes.

CONCLUSIONS

Vasopressin receptors antagonists may reduce body weight and increase Na but do not improve all-cause mortality, cardiovascular mortality or kidney function. In addition, acceptability of long-term treatment side effects and hospitalization appears problematic.

Prognostic significance of hyponatremia among ambulatory patients with heart failure and preserved and reduced ejection fractions

Hyponatremia in heart failure (HF) is an established predictor of adverse outcomes in hospitalized patients with reduced ejection fraction (EF). However, there is a paucity of data in ambulatory patients with HF with preserved ejection fraction (HFpEF). We examined the prevalence, risk factors, and long-term outcomes of hyponatremia (serum sodium ≤135 mEq/L) in ambulatory HFpEF and HF with reduced EF (HFrEF) in a national cohort of 8,862 veterans treated in Veterans Affairs clinics. Multivariable logistic regression models were used to identify factors associated with hyponatremia, and multivariable Cox proportional hazard models were used for analysis of outcomes. The cohort consisted of 6,185 patients with HFrEF and 2,704 patients with HFpEF with a 2-year follow-up. Hyponatremia was present in 13.8% and 12.9% patients in HFrEF and HFpEF, respectively. Hyponatremia was independently associated with younger age, diabetes, lower systolic blood pressure, anemia, body mass index <30 kg/m(2), and spironolactone use, whereas African-American race and statins were inversely associated. In multivariate analysis, hyponatremia remained a significant predictor of all-cause mortality in both HFrEF (hazards ratio [HR] 1.26, 95% confidence interval [CI] 1.11 to 1.44, p <0.001) and HFpEF (HR 1.40, 95% CI 1.12 to 1.75, p = 0.004) and a significant predictor of all-cause hospitalization in patients with HFrEF (HR 1.18, 95% CI 1.07 to 1.31, p = 0.001) but not in HFpEF (HR 1.08, 95% CI 0.92 to 1.27, p = 0.33). In conclusion, hyponatremia is prevalent at a similar frequency of over 10% in ambulatory patients with HFpEF and HFrEF. Hyponatremia is an independent prognostic marker of mortality across the spectrum of patients with HFpEF and HFrEF. In contrast, it is an independent predictor for hospitalization in patients with HFrEF but not in patients with HFpEF.

Hyponatraemia is an independent predictor of in-hospital mortality

BACKGROUND

Hyponatraemia increases morbidity and mortality, but the extent to which this condition influences mortality independently of other contributing factors is unclear.

MATERIALS AND METHODS

All hyponatremic patients admitted to the internal medicine department during a six month period were included. Medical records were reviewed and patients' demographics, underlying disease, cause of hyponatremia and in-hospital deaths were noted. Control group consisted of patients with normonatremia admitted to the same department during the same period matched 1:1 by sex, age and underlying disease. Difference in in-hospital mortality rate between the study and control groups was tested by chi-square test. Baseline demographics, underlying diseases, cause of hyponatremia and state of hyponatremia correction as possible risk factors for mortality were tested in a multivariate analysis.

RESULTS

The baseline cohort of all admitted patients consisted of 2,171 patients. Hyponatraemia was found in 278 (13%) patients (160 females and 118 males). The three most common causes of hyponatremia included gastrointestinal loss (52 patients), decreased oral intake (47 patients), and dilution hyponatremia (45 patients). The in-hospital mortality rate in the hyponatremic group was significantly higher compared with the control group (22% vs 7%, respectively; OR 3.75, 95% CI 2.17-6.48, p<0.0001). In a multivariate analysis age above 65 years, dilution hyponatremia, decreased oral intake as etiologic factors of hyponatremia, and unsuccessful hyponatremia correction were independent factors associated with increased mortality.

CONCLUSION

Hyponatraemia represents independent factor associated with in-hospital mortality. Age above 65 years, failure to correct hyponatremia and some specific etiologic factors of hyponatremia are related to increased mortality.

Evaluation of patients with heart failure

Heart failure is one of the most prevalent cardiovascular diseases in the United States, and is associated with significant morbidity, mortality, and costs. Prompt diagnosis may help decrease mortality, hospital stay, and costs related to treatment. A complete heart failure evaluation comprises a comprehensive history and physical examination, echocardiogram, and diagnostic tools that provide information regarding the etiology of heart failure, related complications, and prognosis in order to prescribe appropriate therapy, monitor response to therapy, and transition expeditiously to advanced therapies when needed. Emerging technologies and biomarkers may provide better risk stratification and more accurate determination of cause and progression.

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.

Hyponatremia in patients with heart failure

The present review analyses the mechanisms relating heart failure and hyponatremia, describes the association of hyponatremia with the progress of disease and morbidity/mortality in heart failure patients and presents treatment options focusing on the role of arginine vasopressin (AVP)-receptor antagonists. Hyponatremia is the most common electrolyte disorder in the clinical setting and in hospitalized patients. Patients with hyponatremia may have neurologic symptoms since low sodium concentration produces brain edema, but the rapid correction of hyponatremia is also associated with major neurologic complications. Patients with heart failure often develop hyponatremia owing to the activation of many neurohormonal systems leading to decrease of sodium levels. A large number of clinical studies have associated hyponatremia with increased morbidity and mortality in patients hospitalized for heart failure or outpatients with chronic heart failure. Treatment options for hyponatremia in heart failure, such as water restriction or the use of hypertonic saline with loop diuretics, have limited efficacy. AVP-receptor antagonists increase sodium levels effectively and their use seems promising in patients with hyponatremia. However, the effects of AVP-receptor antagonists on hard outcomes in patients with heart failure and hyponatremia have not been thoroughly examined.

Hyponatremia, mineral metabolism, and mortality in incident maintenance hemodialysis patients: a cohort study

BACKGROUND

Hyponatremia is associated with increased mortality in chronic diseases. Recent animal studies also implicate hyponatremia in bone abnormalities. However, associations between hyponatremia, mineral bone abnormalities, and mortality in incident hemodialysis patients are unknown.

STUDY DESIGN

Nonconcurrent prospective cohort study.

SETTING & PARTICIPANTS

Incident hemodialysis patients from the Accelerated Mortality on Renal Replacement (ArMORR) cohort with available serum sodium measurements from the time of dialysis therapy initiation (n = 6,127) were classified as hyponatremic (sodium, <135 mEq/L) or normonatremic (sodium, 135-145 mEq/L) based on glucose-corrected sodium level at the time of dialysis therapy initiation. Patients with sodium levels >145 mEq/L were excluded (n = 74).

PREDICTOR

Hyponatremia (sodium, <135 mEq/L).

OUTCOMES

Mineral bone abnormalities; rates of falls, fractures, and mortality.

MEASUREMENTS

Hyponatremia and mineral bone abnormalities were assessed at the time of hemodialysis therapy initiation. Data for other outcomes were collected during a 1-year follow-up. Univariate and multivariable logistic and Cox proportion hazard analyses were conducted to compute ORs and HRs, respectively, with 95% CIs.

RESULTS

775 patients were hyponatremic and 5,278 were normonatremic at baseline. In univariate analyses, hyponatremia was associated with hypercalcemia (OR, 1.92; 95% CI, 1.11-3.30), elevated alkaline phosphatase level (OR, 1.36; 95% CI, 1.12-1.66), and hypoparathyroidism (OR, 1.40; 95% CI, 1.18-1.65). Similar relationships were observed in multivariable models. No statistically significant relationships were observed with phosphorus abnormalities, hypovitaminosis D, falls, or fractures. 965 (15.8%) patients had died at the 1-year follow up. Compared with normonatremic patients, hyponatremic patients had higher 1-year mortality in univariate (HR, 1.59; 95% CI, 1.34-1.87) and multivariable analyses (HR, 1.42; 95% CI, 1.19-1.69).

LIMITATIONS

Low rate of falls and fractures, lack of data for bone density and fibroblast growth factor 23.

CONCLUSIONS

In incident hemodialysis patients, hyponatremia is associated with hypercalcemia, elevated alkaline phosphatase levels, hypoparathyroidism, and increased 1-year mortality. Future studies are needed to examine whether treatments to alter hyponatremia have effects on mineral bone abnormalities and mortality.

Hyponatremia and mortality: moving beyond associations

Acute hyponatremia can cause death if cerebral edema is not treated promptly. Conversely, if chronic hyponatremia is corrected too rapidly, osmotic demyelination may ensue, which also potentially is lethal. However, these severe complications of hyponatremia are relatively uncommon and often preventable. More commonly, hyponatremia predicts mortality in patients with advanced heart failure or liver cirrhosis. In these conditions, it generally is assumed that hyponatremia reflects the severity of the underlying disease rather than contributing directly to mortality. The same assumption holds for the recently reported associations between hyponatremia and mortality in patients with pulmonary embolism, pulmonary hypertension, pneumonia, and myocardial infarction. However, recent data suggest that chronic and mild hyponatremia in the general population also are associated with mortality. In addition, hyponatremia has been associated with mortality in long-term hemodialysis patients without residual function in whom the underlying disease cannot be responsible for hyponatremia. These new data raise the question of whether hyponatremia by itself can contribute to mortality or it remains a surrogate marker for other unknown risk factors. We review hyponatremia and mortality and explore the possibility that hyponatremia perturbs normal physiology in the absence of cerebral edema or osmotic demyelination.

Hyponatraemia: more than just a marker of disease severity?

Hyponatraemia--the most common serum electrolyte disorder--has also emerged as an important marker of the severity and prognosis of important diseases such as heart failure and cirrhosis. Acute hyponatraemia can cause severe encephalopathy, but the rapid correction of chronic hyponatraemia can also profoundly impair brain function and even cause death. With the expanding elderly population and the increased prevalence of hyponatraemia in this segment of society, prospective studies are needed to examine whether correcting hyponatraemia in the elderly will diminish cognitive impairment, improve balance and reduce the incidence of falls and fractures. Given that polypharmacy is also common in the elderly population, the various medications that may stimulate arginine vasopressin release and/or enhance the hormone's action to increase water absorption must also be taken into consideration. Whether hyponatraemia in a patient with cancer is merely a marker of poor prognosis or whether its presence may alter the patient's quality of life remains to be examined. In any case, hyponatraemia can no longer be considered as just a biochemical bystander in the ill patient. A systematic diagnostic approach is necessary to determine the specific aetiology of a patient's hyponatraemia. Therapy must then be dictated not only by recognized reversible causes such as advanced hypothyroidism, adrenal insufficiency, diuretics or other medicines, but also by whether the hyponatraemia occurred acutely or chronically. Information is emerging that the vast majority of cases of hyponatraemia are caused by the nonosmotic release of arginine vasopressin. Now that vasopressin V2-receptor blockers are available, a new era of clinical investigation is necessary to examine whether hyponatraemia is just a marker of severe disease or whether correction of hyponatraemia could improve a patient's quality of life. Such an approach must involve prospective randomized studies in different groups of patients with hyponatraemia, including those with advanced heart failure, those with cirrhosis, patients with cancer, and the elderly.

Relationship of serum sodium concentration to mortality in a wide spectrum of heart failure patients with preserved and with reduced ejection fraction: an individual patient data meta-analysis(†): Meta-Analysis Global Group in Chronic heart failure (MAGGIC)

AIMS

Hyponatraemia has been associated with reduced survival in patients with heart failure and reduced ejection fraction (HF-REF). The relationship between serum sodium and outcome is unclear in heart failure with preserved (≥ 50%) ejection fraction (HF-PEF). Therefore, we used a large individual patient data meta-analysis to study the risk of death associated with hyponatraemia in HF-REF and in HF-PEF.

METHODS AND RESULTS

This analysis included 14 766 patients from 22 studies that recruited patients without ejection fraction inclusion criterion at baseline and reported death from any cause. Cox proportional analysis was undertaken for hyponatraemia (sodium <135 mmol/L), adjusted for variables of clinical relevance, and stratified by study. The endpoint was death from any cause at 3 years. Patients with hyponatraemia (n = 1618) and patients with normal serum sodium had similar characteristics as regards to age, gender, and ischaemic aetiology. However, patients with hyponatraemia had higher New York Heart Association class and lower blood pressure. At follow-up, there were 335 deaths among 1618 patients with hyponatraemia (21%) and 2128 deaths among 13 148 patients with normal serum sodium (16%). The risk of death appeared to increase linearly with serum sodium levels <140 mmol/L. Hyponatraemia was identified in 1199 HF-REF patients (11%) and 419 HF-PEF patients (11%). Hyponatraemia was independently predictive of death in both HF-REF [adjusted hazard ratio (HR) 1.69, 95% confidence interval (CI) 1.50-1.91] and HF-PEF (adjusted HR 1.40, 95% CI 1.10-1.79, P for interaction 0.20).

CONCLUSION

Hyponatraemia is a powerful determinant of mortality in patients with HF regardless of ejection fraction. Further work is needed to determine if correction of hyponatraemia translates into clinical benefit.