Hyponatraemia is an independent predictor of in-hospital mortality

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.

Hyponatremia and Outcome: Is Severity More Important Than Etiology?

BACKGROUND AND OBJECTIVE

Hyponatremia is the most common electrolyte abnormality encountered in a hospital setting, and the data regarding the contribution of hyponatremia to overall mortality are conflicting. The study objective was to determine patients' clinical profiles and outcomes with hyponatremia.

METHODS

 This prospective cross-sectional study was conducted at Dayanand Medical College and Hospital, Ludhiana, and included 375 adult patients aged more than 18 years with a confirmed diagnosis of hyponatremia. Patients were subdivided into three groups based on the severity of hyponatremia: mild (130-135 mmol/L), moderate (125-129 mmol/L), and profound (<125 mmol/L).

RESULTS

The most common symptom was confusion (57.3%) followed by deep somnolence (40%) and nausea (36.8%). The most common cause of hyponatremia was diuretics (30.7%), followed by the syndrome of inappropriate antidiuretic hormone secretion (SIADH) (17.8%) and chronic liver disease (CLD) (14.1%). The severity of hyponatremia did not significantly influence the outcome. Patients with CLD and chronic kidney disease (CKD) as the etiology of hyponatremia had significantly worse outcomes compared to other causes of hyponatremia. The most common type was hypovolemic hypotonic followed by euvolemic hypotonic and hypervolemia hypotonic hyponatremia. Nearly half of the total deaths were observed in the hypervolemic hyponatremia group and were significantly higher compared to the other two groups (p=0.001). Correction of hyponatremia (i.e., serum sodium >135 mmol/L) was significantly linked with good outcomes (p=0.003).

CONCLUSION

Our study showed that the etiology of hyponatremia was a more important prognostic indicator rather than the severity of hyponatremia. Normalization of serum sodium was associated with improved survival.

Predictive value of post-procedural hyponatremia on contrast-induced nephropathy in patients who underwent coronary angiography or percutaneous coronary intervention

OBJECTIVE

Hyponatremia is a prognostic marker for specific pathologies. However, the association between contrast-induced nephropathy (CIN) and post-procedural hyponatremia has not been explored. Our study aims to evaluate the association between hyponatremia developing after contrast media administration and CIN.

MATERIAL AND METHODS

A total number of 236 patients who required nephrology consultation before coronary angiography (CAG) or percutaneous coronary intervention (PCI) because of the high risk for contrast nephropathy, were included. Serum sodium levels were measured at admission and within three consecutive days after contrast media administration.

RESULTS

Hyponatremia was observed in 141patients (59.7%) following angiography. CIN was developed in 149 (63.4%) patients. Among the patients who developed hyponatremia, ejection fraction, serum haemoglobin level and serum albumin level were low whereas, contrast media volume and percentage of the diabetes mellitus were higher. Also, length of hospital stay, percentage of CIN, renal replacement requirement and mortality rate were higher in patients with hyponatremia. In univariable analysis to evaluate the risk factors for CIN, being female gender, age, diabetes mellitus, serum albumin concentration, haemoglobin level, contrast media volume and hyponatremia were associated with development of CIN. Multivariable logistic regression analysis revealed that advanced age, serum albumin concentration and hyponatremia were independent predictors of CIN.

CONCLUSION

Post-procedural hyponatremia was an independent risk factor for CIN in CAG or PCI patients.

The effect of active diuretic therapy on the sodium balance in patients with acute decompensation of chronic heart failure

Background. Active dehydration of patients with acute decompensation of chronic heart failure (АDCHF) was often accompanied by the development of hyponatremia. This increased the time of hospitalization and worsened the prognosis. The complication was associated with the side effects of furosemide. Aim. To compare the effect of dehydration and the state of sodium balance after using different methods of parenteral administration of furosemide at an early stage of treatment of АDCHF. Materials and methods. Patients with АDCHF (n=125) were divided into two groups. Group 1 received furosemide as bolus injections, group 2 as an extended intravenous infusion. The process of dehydration was controlled by the amount of urine and body weight loss per day. The effect was considered satisfactory if the body weight decreased by 1.02.0 kg per day. The plasma sodium level was studied on 1, 5, 10 days. Results. In group 2, the satisfactory effect of dehydration was observed 1.7 times more often than in group 1 (p0.05). In group 2 patients on the 5th day of therapy, the number of cases of hyponatremia was 2.3 times less (p0.05). Hyponatremia developed little in patients with a satisfactory effect of dehydration. On the 10th day, the number of cases of hyponatremia in the groups did not significantly differ. Conclusion. Prolonged intravenous infusion of furosemide allowed more control of the dehydration process and the plasma sodium level at an early stage of therapy in patients with АDCHF.

Risk of Adverse Clinical Outcomes in Hyponatremic Adult Patients Hospitalized for Acute Medical Conditions: A Population-Based Cohort Study

CONTEXT

Hyponatremia has been associated with excess long-term morbidity and mortality. However, effects during hospitalization are poorly studied.

OBJECTIVE

The objective of this work is to examine the association of hyponatremia with the risk of in-hospital mortality, 30-day readmission, and other short-term adverse events among medical inpatients.

DESIGN AND SETTING

A population-based cohort study was conducted using a Swiss claims database of medical inpatients from January 2012 to December 2017.

PATIENTS

Hyponatremic patients were 1:1 propensity-score matched with normonatremic medical inpatients.

MAIN OUTCOME MEASURE

The primary outcome was a composite of all-cause in-hospital mortality and 30-day hospital readmission. Secondary outcomes were intensive care unit (ICU) admission, intubation rate, length-of-hospital stay (LOS), and patient disposition after discharge.

RESULTS

After matching, 94 352 patients were included in the cohort. Among 47 176 patients with hyponatremia, 8383 (17.8%) reached the primary outcome compared with 7994 (17.0%) in the matched control group (odds ratio [OR] 1.06 [95% CI, 1.02-1.10], P = .001). Hyponatremic patients were more likely to be admitted to the ICU (OR 1.43 [95% CI, 1.37-1.50], P < .001), faced a 56% increase in prolonged LOS (95% CI, 1.52-1.60, P < .001), and were admitted more often to a postacute care facility (OR 1.38 [95% CI 1.34-1.42, P < .001). Of note, patients with the syndrome of inappropriate antidiuresis (SIAD) had lower in-hospital mortality (OR 0.67 [95% CI, 0.56-0.80], P < .001) as compared with matched normonatremic controls.

CONCLUSION

In this study, hyponatremia was associated with increased risk of short-term adverse events, primarily driven by higher readmission rates, which was consistent among all outcomes except for decreased in-hospital mortality in SIAD patients.

Prognostic Value of Hyponatremia During Acute Painful Episodes in Sickle Cell Disease

BACKGROUND

Low plasma sodium concentration has been recognized as a prognostic factor in several disorders but never evaluated in sickle cell disease. The present study evaluates its value at admission to predict a complication in adult patients with sickle cell disease hospitalized for an initially uncomplicated acute painful episode.

METHODS

The primary outcome of this retrospective study, performed between 2010 and 2015 in a French referral center for sickle cell disease, was a composite criterion including acute chest syndrome, intensive care unit transfer, red blood cell transfusion or inpatient death. Analyses were adjusted for age, sex, hemoglobin genotype and concentration, lactate dehydrogenase (LDH) concentration, and white blood cell count.

RESULTS

We included 1218 stays (406 patients). No inpatient death occurred during the study period. Hyponatremia (plasma sodium ≤135 mmol/L) at admission in the center was associated with the primary outcome (adjusted odds ratio [OR] 1.95, 95% confidence interval [CI] 1.3-2.91, P = 0.001), with acute chest syndrome (OR 1.95 [95% CI 1.2-3.17, P = 0.008]), and red blood cell transfusion (OR 2.71 [95% CI 1.58-4.65, P <0.001]) but not significantly with intensive care unit transfer (OR 1.83 [95% CI 0.94-3.79, P = 0.074]). Adjusted mean length of stay was longer by 1.1 days (95% CI 0.5-1.6, P <0.001) in patients with hyponatremia at admission.

CONCLUSIONS

Hyponatremia at admission in the medical department for an acute painful episode is a strong and independent prognostic factor of unfavorable outcome and, notably, acute chest syndrome. It could help targeting patients who may benefit from closer monitoring.

Inappropriate Antidiuretic Hormone Secretion and Cerebral Salt-Wasting Syndromes in Neurological Patients

The differential diagnosis of syndrome of inappropriate antidiuretic hormone secretion (SIADH) and cerebral salt-wasting syndrome (CSWS) in patients with neurological disorders has been a perplexing clinical controversy. The purpose of this review is to summarize the characteristics and risk factors of patients with different types of neurological disorders complicated by hyponatremia (HN) and review various methods to distinguish SIADH from CSWS. Common neurological disorders with high rates of HN include subarachnoid hemorrhage (SAH), traumatic brain injuries, stroke, cerebral tumors, central nervous system (CNS) infections, and Guillain-Barré syndrome (GBS), which have their own characteristics. Extracellular volume (ECV) status of patients is a key point to differentiate SIADH and CSWS, and a comprehensive assessment of relevant ECV indicators may be useful in differentiating these two syndromes. Besides, instead of monitoring the urinary sodium excretion, more attention should be paid to the total mass balance, including Na⁺, K⁺, Cl^-, and extracellular fluid. Furthermore, the dynamic detection of fractional excretions (FE) of urate before and after correction of HN and a short-term infusion of isotonic saline solution may be useful in identifying the etiology of HN. As for brain natriuretic peptide (BNP) or N-terminal prohormone of BNP (NT-proBNP), more prospective studies and strong evidence are needed to determine whether there is a pertinent and clear difference between SIADH and CSWS.

Risk Factors for Recurrent Hematoma After Surgery for Acute Traumatic Subdural Hematoma

OBJECTIVE

The development of postcraniotomy hematoma (PCH) after surgery for acute traumatic subdural hematoma (aSDH) has been associated with an increased risk of a poor outcome. The risk factors contributing to PCH remain poorly understood. Our aim was to study the potential risk factors for PCH in a consecutive series of surgically evacuated patients with aSDH.

METHODS

A total of 132 patients with aSDH treated at Turku University Hospital (Turku, Finland) from 2008 to 2012 were enrolled in the present retrospective cohort study. The demographic, clinical, laboratory, and imaging data were collected from the medical records. A comprehensive analysis of the data using 6 different univariate methods, including machine learning and multivariate analyses, was conducted to identify the factors related to PCH.

RESULTS

The incidence of PCH after primary surgery for traumatic aSDH was 10.6%. The patients experiencing PCH were younger (P = 0.04). No difference was found in the use of anticoagulant or antiplatelet medication for the patients with and without PCH. Multivariate analyses identified alcohol inebriation at the time of injury (odds ratio [OR], 12.67; P = 0.041) and hypocapnia (OR, 26.09; P = 0.003) as independent risk factors for PCH. The patients with PCH had had hyponatremia (OR, 0.08; P = 0.018) less often, and their maximal systolic blood pressure was lower (OR, 0.94; P = 0.009). The area under the curve for the multivariate model was 0.96 (P = 0.049), with a Youden index of 0.88.

CONCLUSIONS

The results suggest that alcohol inebriation at the time of injury and hypocapnia during hospitalization are risk factors for the development of PCH.

Could sodium imbalances predispose to postoperative venous thromboembolism? An analysis of the NSQIP database

Background

Hyponatremia is common among patients with pulmonary embolism, while hypernatremia increases the risk of venous thromboembolism (VTE). Our objective was to evaluate the association between sodium imbalances and the incidence of VTE and other selected perioperative outcomes.

Methods

We conducted a retrospective cohort study using the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) and identified 1,108,704 patients undergoing major surgery from 2008 to 2012. We evaluated 30-day perioperative outcomes, including mortality and cardiac, respiratory, neurological, urinary, wound, and VTE outcomes. Multivariate logistic regressions were used to estimate the odds of 30-day perioperative outcomes.

Results

Compared with the normal sodium group, in which VTE occurred in 1.0% of patients, 1.8% of patients in the hyponatremia group (unadjusted odds ratio (OR) 1.84) and 2.4% of patients in the hypernatremia group (unadjusted OR 2.49) experienced VTE. Crude mortality was 1.3% in the normal sodium group, 4.9% in the hyponatremia group (unadjusted OR 3.93) and 8.4% in the hypernatremia group (unadjusted OR 7.01). Crude composite morbidity was 7.1% for the normal sodium group, 16.7% for the hyponatremia group (unadjusted OR 2.63) and 20.6% for the hypernatremia group (unadjusted OR 3.43). After adjusting for potential confounders, hyponatremia and hypernatremia remained significantly and independently associated with an increased risk of VTE (adjusted OR 1.43 and 1.56, respectively), mortality (adjusted OR 1.39 and 1.39, respectively) and composite morbidity (adjusted OR 2.15 and 3.34, respectively).

Conclusions

Pre-operative hyponatremia and hypernatremia are potential prognostic markers for perioperative 30-day morbidity, mortality and VTE.

The prevalence and mortality of hyponatremia is seriously underestimated in Chinese general medical patients: an observational retrospective study

Background

Hyponatremia (serum sodium concentration < 135 mmol/L) is the most common electrolyte abnormality and is a predictor of the mortality of hospitalized patients in Western countries. However, hyponatremia data are lacking in Asian countries. Here we evaluate the epidemiology and mortality of hyponatremia in general medical hospitalized patients in China.

Methods

This is a cohort study of 154,378 adults who were hospitalized between 2008 and 2012 at a teaching hospital in Beijing. We identified hospital patients with hyponatremia and calculated the prevalence and in-hospital mortality of hyponatremia. We also conducted a comprehensive retrospective review of the medical records of patients who had severe hyponatremia (serum sodium <120 mmol/L) during hospitalization in 2012.

Results

The overall prevalence of hyponatremia at some point during hospitalization was 17.5% (26,990 patients), but only 0.26% (394 patients) of cases were identified with the diagnostic code of hyponatremia. Hyponatremia was more common in patients with infectious disease, cancer, or cardiovascular disease as the primary reason for hospitalization based on discharge diagnosis, with prevalences of 33.0, 25.9 and 24.9%, respectively. The in-hospital mortality was 0.48% amongst patients without hyponatremia compared to 3.57 and 20.23% in patients with serum sodium levels of 130–134 and <120 mmol/L, resulting in multivariable adjusted odds ratios (ORs) of 4.8 (95% CI 4.3–5.4) and 32.9 (95% CI 25.2–42.3), respectively. The mortality risk increased with increasing severity of hyponatremia in all diagnostic groups. After the multivariate adjustment, only the Charlson Comorbidity Index and age were independently associated with death risk (OR 1.36, 95% CI 1.14–1.64 and OR 1.04, 95% CI 1.00–1.09, respectively) in the patients with severe hyponatremia.

Conclusions

Hyponatremia is highly prevalent among Chinese hospitalized patients and is associated with increased in-hospital mortality risk. Physicians should raise awareness to improve the prognosis of hyponatremia.

Electronic supplementary material

The online version of this article (10.1186/s12882-017-0744-x) contains supplementary material, which is available to authorized users.

Hyponatremia in Guillain-Barré Syndrome

OBJECTIVES

To evaluate incidence, risk factors, and in-hospital outcomes associated with hyponatremia in patients hospitalized for Guillain-Barré Syndrome (GBS).

METHODS

We identified adult patients with GBS in the Nationwide Inpatient Sample (2002-2011). Univariate and multivariable analyses were used.

RESULTS

Among 54,778 patients hospitalized for GBS, the incidence of hyponatremia was 11.8% (compared with 4.0% in non-GBS patients) and increased from 6.9% in 2002 to 13.5% in 2011 (P < 0.0001). Risk factors associated with hyponatremia in multivariable analysis included advanced age, deficiency anemia, alcohol abuse, hypertension, and intravenous immunoglobulin (all P < 0.0001). Hyponatremia was associated with prolonged length of stay (16.07 vs. 10.41, days), increased costs (54,001 vs. 34,125, $USD), and mortality (20.5% vs. 11.6%) (all P < 0.0001). In multivariable analysis, hyponatremia was independently associated with adverse discharge disposition (odds ratio: 2.07, 95% confidence interval, 1.91-2.25, P < 0.0001).

CONCLUSIONS

Hyponatremia is prevalent in GBS and is detrimental to patient-centered outcomes and health care costs. Sodium levels should be carefully monitored in high-risk patients.

Improving care and outcomes of inpatients with syndrome of inappropriate antidiuresis (SIAD): a prospective intervention study of intensive endocrine input vs. routine care

PURPOSE

The syndrome of inappropriate antidiuresis is often undertreated with most patients discharged with persistent hyponatraemia. This study tested the hypothesis that an endocrine input is superior to routine care in correcting hyponatraemia and can improve patient outcomes.

METHODS

This single-centre prospective-controlled intervention study included inpatients admitted at a UK teaching hospital, with serum sodium ≤ 127 mmol/l, due to syndrome of inappropriate antidiuresis over a 6-month period. The prospective intervention group (18 subjects with mean serum sodium 120.7 mmol/l) received prompt endocrine input, while the historical control group (23 patients with mean serum sodium 124.1 mmol/l) received routine care. The time needed for serum sodium increase ≥ 5 mmol/l was the primary endpoint.

RESULTS

The intervention group achieved serum sodium rise by ≥5 mmol/l in 3.5 vs. 7.1 days in the control group (P = 0.005). In the intervention group, the mean total serum sodium increase was 12 mmol/l with only 5.8 % of patients discharged with serum sodium < 130 vs. 6.3 mmol/l increase (P < 0.001) and 42.1 % of the subjects discharged with serum sodium < 130 mmol/l in the control group (P = 0.012). The mean length of hospital stay in the intervention group (10.9 days) was significantly shorter than in the control group (14.5 days; P = 0.004).The inpatient mortality rate was 5.5 % in intervention arm vs. 17.4 % in control arm, but this difference was not statistically significant.

CONCLUSIONS

Since the endocrine input improved time for correction of hyponatraemia and shortened length of hospitalisation, widespread provision of endocrine input should be considered.

Preoperative hyponatremia in women with ovarian cancer: An additional cause for concern?

OBJECTIVE

To determine if preoperative hyponatremia in women with ovarian, fallopian tube (FT), and primary peritoneal cancers (PPC) is associated with postoperative complications.

METHODS

We performed a retrospective population-based cohort study of women with a postoperative diagnosis of ovarian, FT, or PPC who had a cytoreductive procedure in the National Surgical Quality Improvement Program (NSQIP) database from 2005 to 2013. The primary exposure, preoperative sodium, was classified as normal (135mEq/L-142mEq/L) or hyponatremic (≤134mEq/L). Where appropriate, preoperative characteristics were compared with Chi-squared or Fisher's exact tests. Multivariate logistic regression was used to determine adjusted odds ratios (aOR) with 95% confidence intervals (CI).

RESULTS

4009 subjects met inclusion criteria. Thirty day mortality was higher in the hyponatremic group compared to the normal serum sodium group (3.56% vs 1.18%). When patients of any age were noted to have at least two pertinent preoperative lab abnormalities, including hyponatremia, there was an increased risk of postoperative complications for patients over the age of 65 (Table 3). After adjusting for serum albumin and other confounders, preoperative hyponatremia was associated with an increased risk of hospital stay of >14days (aOR 1.69; 95% CI 1.11-2.57) and 30day postoperative mortality (aOR 2.37; 95% CI 1.13-4.98).

CONCLUSIONS

Hyponatremia is associated with postoperative 30day mortality and morbidity in women with ovarian, FT, and PPC. Serum sodium in conjunction with other markers may have the potential to identify candidates for neoadjuvant chemotherapy. Additional work is needed to determine if correction of hyponatremia in the preoperative period alters outcomes.

Mild prolonged chronic hyponatremia and risk of hip fracture in the elderly

BACKGROUND

Hip fractures are among the most serious bone fractures in the elderly, producing significant morbidity and mortality. Several observational studies have found that mild hyponatremia can adversely affect bone, with fractures occurring as a potential complication. We examined if there is an independent association between prolonged chronic hyponatremia (>90 days duration) and risk of hip fracture in the elderly.

METHODS

We performed a retrospective cohort study in adults >60 years of age from a prepaid health maintenance organization who had two or more measurements of plasma sodium between 2005 and 2012. The incidence of hip fractures was assessed in a very restrictive population: subjects with prolonged chronic hyponatremia, defined as plasma sodium values <135 mmol/L, lasting >90 days. Multivariable Cox regression was performed to determine the hazard ratio (HR) for hip fracture risk associated with prolonged chronic hyponatremia after adjustment for the propensity to have hyponatremia, fracture risk factors and relevant baseline characteristics.

RESULTS

Among 31 527 eligible patients, only 228 (0.9%) had prolonged chronic hyponatremia. Mean plasma sodium was 132 ± 5 mmol/L in hyponatremic patients and 139 ± 3 mmol/L in normonatremic patients (P < 0.001). The absolute risk for hip fracture was 7/282 in patients with prolonged chronic hyponatremia and 411/313 299 in normonatremic patients. Hyponatremic patients had a substantially elevated rate of hip fracture [adjusted HR 4.52 (95% CI 2.14-9.6)], which was even higher in those with moderate hyponatremia (<130 mmol/L) [adjusted HR 7.61 (95% CI 2.8-20.5)].

CONCLUSION

Mild prolonged chronic hyponatremia is independently associated with hip fracture risk in the elderly population, although the absolute risk is low. However, proof that correcting hyponatremia will result in a reduction of hip fractures is lacking.

Hyponatremia predicts mortality after stroke

Background

Hyponatremia, the commonest electrolyte imbalance encountered in clinical practice, is associated with adverse outcomes. Despite this, understanding of the association between hyponatremia and stroke mortality outcome is limited.

Aims

To investigate the association between admission serum sodium and mortality at various time-points after stroke.

Methods

Cases of acute stroke admitted to Norfolk and Norwich University Hospital consecutively from January 2003 until June 2013 were included, with mortality outcomes ascertained until the end of December 2013. Odds ratios or hazards ratios for death were constructed for various time-points (within seven-days, 8-30 days, within one-year, and over full follow-up).

Results

There were 8540 participants included (47.4% male, mean age 77.3 (±12.0) years). Point prevalence of hypernatremia and hyponatremia were 3.3% and 13.8%, respectively. In fully adjusted models controlling for age, gender, prestroke modified Rankin score, stroke type, Oxford community stroke project class, and laboratory biochemical and hematological results, the odds ratio (up to one-year)/hazards ratio (for full follow-up) for the above time-points were 1.00, 1.11, 1.03, 1.05 for mild hyponatremia; 1.97, 0.78, 1.11, 1.2 for moderate hyponatremia; 3.31, 1.57, 2.45, 1.67 for severe hyponatremia; and 0.47, 1.23, 1.30, 1.10 for hypernatremia. When stratified by age groups, outcomes were poorer in younger hyponatremic patients (aged <75 years).

Conclusion

Hyponatremia is prevalent in acute stroke admissions and is independently associated with higher mortality in patients <75 years).

Hyponatremia and mortality risk: a Danish cohort study of 279 508 acutely hospitalized patients

OBJECTIVE

We aimed to investigate the impact of hyponatremia severity on mortality risk and assess any evidence of a dose-response relation, utilizing prospectively collected data from population-based registries.

DESIGN

Cohort study of 279 ,508 first-time acute admissions to Departments of Internal Medicine in the North and Central Denmark Regions from 2006 to 2011.

METHODS

We used the Kaplan-Meier method (1 - survival function) to compute 30-day and 1-year mortality in patients with normonatremia and categories of increasing hyponatremia severity. Relative risks (RRs) with 95% CIs, adjusted for age, gender and previous morbidities, and stratified by clinical subgroups were estimated by the pseudo-value approach. The probability of death was estimated treating serum sodium as a continuous variable.

RESULTS

The prevalence of admission hyponatremia was 15% (41,803 patients). Thirty-day mortality was 3.6% in normonatremic patients compared to 7.3, 10.0, 10.4 and 9.6% in patients with serum sodium levels of 130-134.9, 125-129.9, 120-124.9 and <120 mmol/l, resulting in adjusted RRs of 1.4 (95% CI: 1.3-1.4), 1.7 (95% CI: 1.6-1.8), 1.7 (95% CI: 1.4-1.9) and 1.3 (95% CI: 1.1-1.5) respectively. Mortality risk was increased across virtually all clinical subgroups, and remained increased by 30-40% 1 year after admission. The probability of death increased when serum sodium decreased from 139 to 132  mmol/l. No clear increase in mortality was observed for lower concentrations.

CONCLUSIONS

Hyponatremia is highly prevalent among patients admitted to Departments of Internal Medicine and is associated with increased 30-day and 1-year mortality risk, regardless of underlying disease. This risk seems independent of hyponatremia severity.

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

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

Prognosis of hyponatremia in elderly patients with fragility fractures

BACKGROUND

Hyponatremia (serum sodium < 135 mmol/L) is the commonest electrolyte imbalance encountered in clinical practice. It is associated with multiple poor clinical outcomes including increased length of hospital stay, institutionalization and mortality. Prevalence of hyponatremia is higher in frail patient groups, and elderly patients with fragility fractures (EPFF) are particularly susceptible. This study aimed to establish the impact of hyponatremia on total length of inpatient stay (TLOS), need for inpatient rehabilitation and mortality in EPFF.

METHODS

Prospective observational study of consenting adults aged ≥ 65 years admitted with a fragility fracture to a university hospital between January 7, and April 4, 2013. Demographic and clinical data, length of hospital stay, discharge destination and any participant deaths were recorded. Prevalence of hyponatremia on admission and incidence of cases developing in hospital were reported. Basic demographic data and serum sodium results were included in multivariate linear regression models for TLOS. Difference in mortality rate and proportion of individuals discharged to inpatient rehabilitation between the hyponatremic and normonatremic group were tested using Chi-squared and Fisher's exact tests. Unadjusted odds ratios (ORs) and 95% confidence intervals (CIs) were also calculated.

RESULTS

Of 212 cases, 127 (60%) EPFF were recruited (mean age 79 years, 78% female). Of those not recruited, 66 had incapacity to consent and 19 refused participation. Thirty-three cases of hyponatremia were identified; point prevalence on admission was 13.4% and a further 12.6% developed hyponatremia during admission. There were no statistically significant differences in patient characteristics between the hyponatremic and normonatremic group. Hyponatremic participants had a 66.7% increased time from admission to surgery (P = 0.014) and a 51.5% increased length of index hospital stay (P = 0.006). Factors independently associated with increased TLOS were age (P = 0.03) and drop in sodium during admission (P < 0.001). Mortality rate and proportion of participants discharged to inpatient rehabilitation were higher in the hyponatremic group (OR 4.2 (95% CI: 0.9 - 19.8) and 2.2 (95% CI: 0.9 - 5.1), respectively), but figures did not reach statistical significance.

CONCLUSIONS

Hyponatremia is highly prevalent in EPFF, seen in 33/127 cases (26%), and is associated with increased length of index hospital stay. Drop in serum sodium during admission was independently associated with increased TLOS.

Neurosurgical Hyponatremia

Hyponatremia is a frequent electrolyte imbalance in hospital inpatients. Acute onset hyponatremia is particularly common in patients who have undergone any type of brain insult, including traumatic brain injury, subarachnoid hemorrhage and brain tumors, and is a frequent complication of intracranial procedures. Acute hyponatremia is more clinically dangerous than chronic hyponatremia, as it creates an osmotic gradient between the brain and the plasma, which promotes the movement of water from the plasma into brain cells, causing cerebral edema and neurological compromise. Unless acute hyponatremia is corrected promptly and effectively, cerebral edema may manifest through impaired consciousness level, seizures, elevated intracranial pressure, and, potentially, death due to cerebral herniation. The pathophysiology of hyponatremia in neurotrauma is multifactorial, but most cases appear to be due to the syndrome of inappropriate antidiuretic hormone secretion (SIADH). Classical treatment of SIADH with fluid restriction is frequently ineffective, and in some circumstances, such as following subarachnoid hemorrhage, contraindicated. However, the recently developed vasopressin receptor antagonist class of drugs provides a very useful tool in the management of neurosurgical SIADH. In this review, we summarize the existing literature on the clinical features, causes, and management of hyponatremia in the neurosurgical patient.