Sodium

Cost Issues in Hyponatremia

Purpose

To describe the morbidity and mortality associated with hyponatremia and its impact on health care costs and outcomes in the United States, describe the role of pharmacists in the overall management of hyponatremia, and identify and address cost and resource allocation issues.

Summary

Hyponatremia places a significant burden on overall hospital and health care costs. Underrecognition of the disorder and inappropriate hospital management can lead to worse outcomes, impacting length of stay (LOS), need for intensive care unit (ICU) admission, and clinical outcomes. Risk of mortality rises with increasing severity of hyponatremia, but even mild hyponatremia is associated with increased in-hospital mortality. The association with mortality is particularly robust in patients admitted to the hospital with cardiovascular disease and metastatic cancer. For patients admitted to the ICU, severe hyponatremia is a predictor of mortality. Elderly patients with admission hyponatremia face an especially poor prognosis. Resolving hyponatremia during hospitalization decreases the risk of mortality, suggesting that improved identification and aggressive monitoring may lead to more appropriate treatment. Pharmacoeconomic data can be utilized to support clinical decision-making in the management of hyponatremia by evaluating drug therapy and by monitoring hyponatremia development and therapeutic outcomes.

Conclusion:

Prompt recognition and optimal management of hyponatremia in hospitalized patients may reduce mortality and symptom severity, allow for less intensive care, decrease LOS and associated costs, and improve treatment of underlying comorbid conditions and quality of life. Pharmacists have a key role in optimizing the management of hyponatremia.

Plasma sodium and mortality risk in patients with myocardial infarction and a low LVEF

BACKGROUND

Hyponatremia is a known prognostic factor for mortality in patients with heart failure but has not been extensively studied in patients with myocardial infarction (MI). This study was, therefore, designed to evaluate whether plasma sodium and hyponatremia (< 135 mM) are associated with mortality risk in patients with MI.

MATERIALS AND METHODS

In retrospective analyses using data from the Trandolapril Cardiac Evaluation (TRACE) study--a randomized, double-blind, placebo-controlled trial of trandolapril in 1749 patients with MI and left ventricular ejection fraction (LVEF) ≤ 35%--associations between plasma sodium or hyponatremia and more than 15-year mortality risk were evaluated in multivariate Cox proportional hazard models including traditional clinical confounders before and after additional adjustment for renal function, use of diuretics or both.

RESULTS

During the extended follow-up time, 1462 patients died. Both hyponatremia [Hazard ratio: 1·30 (95% CI: 1·13-1·50), P < 0·001] and plasma sodium [Hazard Ratio(pro mM increase in P-Na): 0·98 (95% CI: 0·96-0·99), P = 0·004] were associated with mortality risk, and the adjusted parameter estimates were not affected by additional adjustment for renal function, use of diuretics or both.

CONCLUSIONS

Hyponatremia and plasma concentrations of sodium are associated with long-term mortality risk in patients with MI complicated by left ventricular systolic dysfunction. Importantly, these associations are independent of renal function and use of diuretics. Whether the associations between plasma sodium or hyponatremia and long-term mortality risk reflect a causation or merely the severity of the underlying cardiac disease remains to be clarified.

Thiazide-induced hyponatraemia: epidemiology and clues to pathogenesis

Thiazide diuretics are one of the most widely used and cost-effective classes of antihypertensive agents worldwide. Thiazides however have a significant side effect profile and are frequently insufficient to normalize blood pressure alone. Thiazide-induced hyponatraemia (TIH) is a major adverse effect, affecting up to one in seven patients receiving these drugs. TIH is more common in females, the elderly and those of low body weight and may cause symptoms such as confusion, falls and seizures. It is a common cause of hospital admission in the elderly. Although TIH occurs at least as frequently as hypokalaemia, much less is understood about the mechanism by which this occurs. Thiazides lower blood pressure by reducing the reabsorption of sodium from the distal nephron by inhibition of the NaCl cotransporter. The molecular mechanism by which this occurs together with the little known role of thiazides in regulating water reabsorbtion from the collecting ducts is discussed and the relevance to TIH evaluated. TIH is highly reproducible by thiazide rechallenge suggesting there may be a genetic predisposition. Both targeted resequencing of candidate genes and genome wide association techniques offer promising strategies by which such genetic contributions may be investigated. The rewards for uncovering the molecular mechanisms underlying TIH and the regulation of distal nephron sodium and water absorption are significant; not only could it inform the design of better tolerated, more efficacious thiazide-like antihypertensive agents but it may also facilitate the pharmacogenomic profiling of hypertensive patients to avoid thiazides in those likely to suffer adverse effects.

Early development of hyponatremia implicates short- and long-term outcomes in ST-elevation acute myocardial infarction

BACKGROUND

Clinical importance of hyponatremia in ST-elevation acute myocardial infarction (STEMI) in the era of primary intervention has not been fully understood. The aim of this study was to investigate the impact of hyponatremia on outcomes in patients with STEMI and secondarily to investigate the contribution of arginine vasopressin (AVP) to hyponatremia in STEMI.

METHODS AND RESULTS

Hyponatremia was defined as a sodium concentration <136 mmol/L at 72h after hospitalization. First, the short-term (in-hospital mortality or congestive heart failure (CHF)) and long-term prognosis (cardiac death, re-admission for CHF) in STEMI patients was conducted. Second, the relationship between serum sodium level and plasma AVP was investigated. In hyponatremic patients the incidence of in-hospital heart failure was significantly greater (P=0.0018), long-term cardiac death was a higher trend (17.2% vs. 6.3%, P=0.19) and re-admission due to CHF was significantly more frequent (20.7% vs. 4.5%, P=0.0024). Plasma AVP level was higher in the hyponatremia group (4.5 vs. 2.7 pg/ml, P=0.003), and it had a negative correlation with serum sodium level (r=-0.28, P=0.02).

CONCLUSIONS

Hyponatremia was frequently found in the early phase of STEMI, and associated with heart failure in both short- and long-term outcomes. Non-osmotic secretion of AVP could be involved in hyponatremia in STEMI patients.

Dehydration influences mood and cognition: a plausible hypothesis?

The hypothesis was considered that a low fluid intake disrupts cognition and mood. Most research has been carried out on young fit adults, who typically have exercised, often in heat. The results of these studies are inconsistent, preventing any conclusion. Even if the findings had been consistent, confounding variables such as fatigue and increased temperature make it unwise to extrapolate these findings. Thus in young adults there is little evidence that under normal living conditions dehydration disrupts cognition, although this may simply reflect a lack of relevant evidence. There remains the possibility that particular populations are at high risk of dehydration. It is known that renal function declines in many older individuals and thirst mechanisms become less effective. Although there are a few reports that more dehydrated older adults perform cognitive tasks less well, the body of information is limited and there have been little attempt to improve functioning by increasing hydration status. Although children are another potentially vulnerable group that have also been subject to little study, they are the group that has produced the only consistent findings in this area. Four intervention studies have found improved performance in children aged 7 to 9 years. In these studies children, eating and drinking as normal, have been tested on occasions when they have and not have consumed a drink. After a drink both memory and attention have been found to be improved.

Plasma sodium levels and dietary sodium intake in manual workers in the Middle East

OBJECTIVES

To investigate the hypothesis that workers who consume a predominantly rice-based, low-sodium diet and perform long periods of manual work in the heat are at risk of chronic hyponatraemia due to inadequate replacement of sweat sodium losses.

METHODS

Plasma sodium levels were assessed at the end of both the summer and winter periods in 44 male dockyard workers in the Middle East. The dietary intake of these workers was recorded and analysed by an Accredited Practicing Dietitian to determine average daily sodium intake.

RESULTS

55% of workers were found to be clinically hyponatraemic during the summer period compared with only 8% during the winter period. Assessment of the daily diet of workers in the labour camp revealed it to be predominantly starch based with low total sodium content. The majority of the fluids provided to workers are also low in sodium content.

CONCLUSIONS

Manual labourers working in the heat and eating a low-sodium starch-based diet are at risk of chronic hyponatraemia. Increasing the sodium content of fluid and food provided to workers is warranted and may reduce the incidence of work-related illness and accidents in this population. The results of this study identify a need for sodium replacement guidelines specific for prolonged work in the heat to be developed.

Study of outcomes associated with hyponatremia and hypernatremia in children

Sodium is usually included in hospitals' critical values lists; however, the values at which sodium is considered to be life threatening (critical) vary among hospitals. Studies of outcomes associated with hyponatremia and hypernatremia in pediatric patients have not been published. We performed a retrospective chart review of sodium values of <124 mmol/L and >155 mmol/L that occurred during a 6-month period. Univariate and multivariate analyses for mortality risk were performed with the different variables. A total of 702 (1.32%) sodium tests fell in the study reference range, with 166 being <124 mmol/L and 536 being >155 mmol/L. Although not statistically significant, mortality was higher (38.5%) in patients with sodium values ≤ 120 mmol/L than in those with values ≥ 170 mmol/L (25%) or in patients with other values (<14%). Underlying conditions prevented assessment of morbidity associated with hyponatremia or hypernatremia. Treatment was instituted within 4 hours in 80% of cases (50% within 1 hour). Multivariate analysis showed increased risk of death for hyponatremic patients if they were premature or had heart abnormalities, while for hypernatremic patients the risk increased when other critical values were present. In conclusion, sodium levels of ≤ 120 mmol/L and ≥ 170 mmol/L have increased mortality in children; however, the risk of death is not statistically different when compared to risk in patients with milder hyponatremia and hypernatremia. Risk factors for death in hyponatremic and hypernatremic patients may primarily reflect the severity of the underlying conditions present in these children, such as prematurity and heart abnormalities, rather than the sodium derangement.

Initial approach to the hyponatremic patient

Hyponatremia with cerebral symptoms is a medical emergency in which treatment delay may prove fatal. However, controversy prevails over which treatment is the best. This paper presents a practical and unified approach based on a literature study of the physiology of plasma [Na(+) ], the brain's response and clinical and experimental studies. Experimental and clinical studies were thoroughly reviewed. The literature was identified through MESH and free text search in the databases PubMed, Embase and Cochrane, and references in the literature. Cerebral water homeostasis is pivotal in hyponatremia. Prompt, repeated boluses of 2 ml/kg 3% saline constitute a rational treatment of symptomatic hyponatremia. After the initial correction, concern is mainly with avoiding overcorrection and osmotic demyelination. Plasma [Na(+)] is determined by the external balances of water and cations. The water balance must therefore be carefully monitored to counter the dramatic increase in plasma [Na(+)] that may result from brisk diuresis. Definitive treatment of hyponatremia should be directed toward its etiology. This can be challenging and the clinical application of traditional classifications based on hydration is difficult. Therefore, a practical approach is proposed based on the mechanisms of impaired urine dilution.

CONCLUSIONS

The conflict between previously opposing standpoints is gradually giving way to an emerging consensus: Prompt bolus treatment of symptomatic hyponatremia with hypertonic saline. After the initial treatment, overcorrection must be avoided. Definitive treatment should be directed toward the nature of the underlying disorder. An approach based on the mechanism governing the impaired urine dilution has been proposed.

Hypo- and hypernatraemia in surgical patients: is there room for improvement?

BACKGROUND

Up to 30% of surgical inpatients develop complications related to fluid and electrolyte therapy. We sought to study the occurrence of hypo- and hypernatraemia in these patients to inform current standards of care.

METHODS

This prospective audit took place over 80 days in a university hospital. Patients with a serum sodium concentration less than 130 or greater than 150 mmol/l were included. Daily intakes of Na(+), K(+) and Cl(-), and fluid balance were recorded before and after development of dysnatraemia. Fluid balance charts were assessed, as was the presence of documented patient weights. Patients were followed up until one of these milestones was reached: normonatraemia, death, or hospital discharge.

RESULTS

During the study period 55 (4%) of the 1,383 surgical admissions met the inclusion criteria. Fifteen patients had hypernatraemia, 13 (87%) of whom were identified on ICU/HDU. In the days preceding the hypernatraemia, patients received (in mmol/day) a median (IQR) of 157 (76-344) Na(+), 38 (6-65) K(+), 157 (72-310) Cl(-), and 1.96 (1.13-2.96) L water. In the days preceding the hyponatraemia, patients received 50 (0-189) Na(+), 0 (0-10) K(+), 56 (0-188) Cl(-), and 1.45 (0-2.60) L water. Before the dysnatraemias only 28% of fluid balance charts were completed accurately. During the audit 42% of patients were not weighed. Dysnatraemic patients had a higher hospital mortality rate than those who did not develop dysnatraemia (12.7 vs. 2.3%, P < 0.001).

CONCLUSIONS

Four percent of surgical inpatients developed dysnatraemias, which were associated with increased mortality. Fluid balance documentation was suboptimal and daily weights were not measured routinely, even in patients with severe electrolyte derangements.

Co-peptin: Role as a novel biomarker in clinical practice

BACKGROUND

Arginine vasopressin (AVP) is a key regulator of water balance, but its instability makes reliable measurement difficult and precludes its routine use. Co-peptin is the C-terminal part of the AVP precursor which plays an important role in the correct structural formation of the AVP precursor and its efficient proteolytic maturation. Because of its stoichiometric generation, co-peptin mirrors the release of AVP and measurement of more stable co-peptin may be an indicator of AVP levels.

METHOD

A comprehensive literature search was conducted from the websites of the National Library of Medicine (http://www.ncbl.nlm.nih.gov) and Pubmed Central, the US National Library of Medicine's digital archive of life sciences literature (http://www.pubmedcentral.nih.gov/). The data was assessed from books and journals that published relevant articles in this field.

RESULT

Recent and ongoing research indicates the diagnostic and prognostic roles of co-peptin in various clinical settings especially in critically ill patients.

CONCLUSION

Co-peptin levels are altered in various physiological and pathological conditions indicating its possible role as a biomarker. However, further research using co-peptin in various clinical settings will prove its cost-effectiveness and clinical usefulness.

Volaemic assessment of the elderly hyponatraemic patient: reliability of clinical assessment and validation of bioelectrical impedance analysis

BACKGROUND

Hyponatraemia is the commonest electrolyte disturbance of hospital inpatients. Assessment of volaemic status is an important part of diagnosis and management.

AIM

To determine reliability of clinical assessment of volaemic state by assessing inter-observer variability of clinical measures of volaemic state. To assess validity of bioelectrical impedance analysis as a tool to measure total body water in elderly hyponatraemic patients.

DESIGN

Observational study conducted in a Department of Medicine for the Elderly.

METHODS

Hospital inpatients >65 years old (n=22) with serum sodium concentration <130 mmol/l were included. Two assessors determined volaemic state on two occasions 72 h apart. Level of agreement between observers was determined on each occasion. Total body water estimation was undertaken with bioelectrical impedance analysis and measurement of dilution of deuterium oxide. Correlation between these two measures was then analysed.

RESULTS

Cohen's κ for agreement between two observers for overall assessment of volaemic state was 0.59 (P<0.01). Values for agreement between individual clinical markers of volaemic state ranged between 0.16 and 0.45. Pearson correlation coefficient (r) for correlation between estimation of total body water undertaken by bioelectrical impedance analysis and by measurement of dilution of deuterium oxide was 0.69 (P<0.001).

CONCLUSION

There was moderate inter-observer agreement of overall clinical volaemic assessment of elderly hyponatraemic patients. Total body water estimation by bioelectrical impedance analysis correlates well with estimation by measurement of dilution of deuterium oxide, providing a potentially useful tool to improve the management of the elderly hyponatraemic patient.

Sodium Disturbances Commonly Encountered in the Neurologic Intensive Care Unit

Disorders of sodium and water balance are common in patients with central nervous system (CNS) disease. These disorders frequently complicate the treatment course by precipitating or worsening neurological symptoms. These patients are not only at risk for symptoms secondary to dysnatremia but also at risk from the consequences of treatment. If not treated properly, this electrolyte disturbance can vastly increase morbidity and can even lead to death. Appropriate diagnosis and intervention requires an understanding of the physiologic and pathophysiologic mechanisms involved in sodium and water homeostasis.

Is salt, vitamin, or endocrinopathy causing this encephalopathy? A review of endocrine and metabolic causes of altered level of consciousness

Altered level of consciousness describes the reason for 3% of critical emergency department (ED) visits. Approximately 85% will be found to have a metabolic or systemic cause. Early laboratory studies such as a bedside glucose test, serum electrolytes, or a urine dipstick test often direct the ED provider toward endocrine or metabolic causes. This article examines common endocrine and metabolic causes of altered mentation in the ED via sections dedicated to endocrine-, electrolyte-, metabolic acidosis-, and metabolism-related causes.

[Hypernatremia in neurointensive care]

Hypernatremia invariably denotes hyperosmolarity and, at least transiently, causes cellular dehydration. Because of blood brain barrier properties, cerebral tissue volume is modified by acute changes in osmolarity. An acute hyperosmolarity (by intravenous sodium or mannitol) temporally decreases intracranial pressure. This treatment is thus useful in critical situations, allowing time for diagnosis and, if possible, other treatment. But in cases of sustained hypernatremia, cellular dehydration is rapidly counterbalanced by an increase in cellular osmolarity. For the brain, it has been shown that cerebral volume is restored in a few hours during prolonged hypernatremia. Moreover, the plasmatic osmotic load induces an increase in diuresis and natriuresis. A tight control is then necessary to prevent hypovolemia and electrolytes disorders. Teams using this treatment should undertake controlled randomized studies to ascertain any beneficial effect that cannot be explained by physiology.

Severe hyponatraemia in elderly hospitalized patients: prevalence, aetiology and outcome

BACKGROUND

Hyponatraemia is the commonest electrolyte disorder in the elderly. Data on severe hyponatraemia and the prevalence of cerebral salt wasting syndrome (CSWS) in elderly hospitalized patients are lacking. We studied the incidence, frequency of various aetiologies, outcome and the possible role of CSWS in severe hyponatraemia in elderly medical patients.

METHODS

A prospective, observational, non-interventional study conducted over a 5-month period in medical wards. Eighty-six patients aged over 65 years with serum sodium levels < or =125 mEq/L were included. All patients were examined by one of the authors, who also evaluated potential contributing factors. Demographic, clinical and outcome data were extracted from the medical records.

RESULTS

The mean age of the patients was 82.1 + 8.7 years. The prevalence of hyponatraemia was 6.2% (8.1% women and 4.0% men (P < 0.001)). There was no increase in incidence of hyponatraemia with age. The leading cause of hyponatraemia was the syndrome of inappropriate antidiuretic hormone secretion (SIADH), whose aetiology could be determined in only 46% of cases. Aetiology was multifactorial in 51% of patients (1.7 aetiological factors per patient). All patients with thiazide-induced hyponatraemia had other contributing factors. Hyperglycaemia and hypoalbuminaemia were predictors of neurological manifestations of hyponatraemia. Overall in-hospital mortality was 19%. Only hypoalbuminaemia was found as an independent risk factor for death. In none of the patients was the hyponatraemia due to CSWS.

CONCLUSION

Severe hyponatraemia in elderly hospitalized medical patients is more frequent in women and of multifactorial aetiology in 50% of cases. It is most commonly caused by SIADH; CSWS is an unlikely cause.

Iatrogenic water intoxication after pelvic ultrasonography imaging

Ultrasound (US) is a simple, easily accessible, and noninvasive method. Thus, it is commonly used. The bladder should be sufficiently filled to acquire pelvic images by US. This report describes water poisoning in 3 patients with no hepatic, cardiac, or renal disease. Both patients had a history of excessive fluid intake.

Hyponatremia in neurosurgical patients: clinical guidelines development

OBJECTIVE

Neurosurgical patients have a high risk of hyponatremia and associated complications. We critically evaluated the existing literature to identify the determinants for the development of hyponatremia and which management strategies provided the best outcomes.

METHODS

A multidisciplinary panel in the areas of neurosurgery, nephrology, critical care medicine, endocrinology, pharmacy, and nursing summarized and classified hyponatremia literature scientific studies published in English from 1950 through 2008. The panel's recommendations were used to create an evaluation and treatment protocol for hyponatremia in neurosurgical patients at the University of Florida.

RESULTS

Hyponatremia should be further investigated and treated when the serum sodium level is less than 131 mmol/L (class II). Evaluation of hyponatremia should include a combination of physical examination findings, basic laboratory studies, and invasive monitoring when available (class III). Obtaining levels of hormones such as antidiuretic hormone and natriuretic peptides is not supported by the literature (class III). Treatment of hyponatremia should be based on severity of symptoms (class III). The serum sodium level should not be corrected by more than 10 mmol/L/d (class III). Cerebral salt wasting should be treated with replacement of serum sodium and intravenous fluids (class III). Fludrocortisone may be considered in the treatment of hyponatremia in subarachnoid hemorrhage patients at risk of vasospasm (class I). Hydrocortisone may be used to prevent natriuresis in subarachnoid hemorrhage patients (class I). Hyponatremia in subarachnoid hemorrhage patients at risk of vasospasm should not be treated with fluid restriction (class II). Syndrome of inappropriate antidiuretic hormone may be treated with urea, diuretics, lithium, demeclocycline, and/or fluid restriction (class III).

CONCLUSION

The summarized literature on the evaluation and treatment of hyponatremia was used to develop practice management recommendations for hyponatremia in the neurosurgical population. However, the practice management recommendations relied heavily on expert opinion because of a paucity of class I evidence literature on hyponatremia.

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

BACKGROUND

Although hospital-acquired hyponatremia is well described, severe community-acquired hyponatremia has been studied less extensively.

AIM

To assess characteristics and outcomes of patients admitted with severe hypotonic hyponatremia (SHH) (defined as serum sodium ≤ 120 mmol/L).

METHODS

All patients with serum sodium of ≤ 120 mmol/L who were admitted to 2 large teaching hospitals from January 2000 to August 2007 were identified, and data were obtained from medical records. Main outcome measures were incidence of osmotic demyelination and mortality.

RESULTS

Two hundred fifty-five patients were admitted who had SHH (female to male ratio 2:1), and the mean age was 72 ± 14 years. The most common etiological factors were thiazide/indapamide diuretics (41%), syndrome of inappropriate antidiuretic hormone secretion (38%), and hypovolemia (24%). Inappropriately rapid correction of serum sodium (> 12 mmol/L over the first 24 hours) occurred in 37 patients (15%), with 4 patients (11%) developing osmotic demyelination. Patients who developed osmotic demyelination were more likely to be younger, abuse alcohol (3 of 4 patients), and have lower serum potassium levels. One patient had a hypoxic-anoxic episode at presentation. The patients also had a mean serum sodium increase in the first 24 and 48 hours of 21 ± 5 mmol/L and 28 ± 8 mmol/L, respectively. None of the patients with osmotic demyelination received hypertonic saline. None of the patients in whom the serum sodium increment was limited to ≤ 12 mmol/L developed osmotic demyelination. Overall, mortality was 10% and was not related to sodium level at presentation.

CONCLUSIONS

Patients treated with thiazide or indapamide (particularly elderly women) may benefit from monitoring of serum sodium levels. Inappropriately rapid serum sodium correction is associated with osmotic demyelination, particularly in patients with risk factors for this condition. In contrast to what has been reported for hyponatremia in hospitalized patients, severity of hyponatremia on admission did not predict increased mortality in our patient population.

Lack of laboratory assessment of severe hyponatraemia is associated with detrimental clinical outcomes in hospitalised patients

OBJECTIVE

Increased mortality with severe hyponatraemia is well known. What is less clear is the mortality risk according to the pattern of the developing hyponatraemia and whether this may be affected by the intervention of the clinician.

METHODS

From our laboratory database, we retrospectively collected data of a 12-month period of adult patients with severe hyponatraemia (< or = 120 mmol/l). One hundred and thirteen patients were identified. Normonatraemic controls (n = 113) were identified by plasma sodium of 135 mmol/l over the same period, and whose nadir during hospitalisation was > or = 130 mmol/l. Results are mean +/- SD unless stated otherwise. Duration of hospitalisation and clinical outcomes was confirmed from hospital records.

RESULTS

The mean nadir plasma sodium of the hyponatraemic group was 116.0 +/- 4.4 mmol/l and 134.0 +/- 2.8 mmol/l in controls. Although the hyponatraemic patients were younger than controls (65.8 +/- 18.4 vs. 72.3 +/- 14.9 years; p = 0.004), they had higher mortality (24 vs. 7, p = 0.002) and longer hospitalisation than controls: median (IQR), 12 (7-22) vs. 7 (3-16.5) days (p < 0.001). A total of 55 patients developed severe hyponatraemia following admission. This subgroup comprised a higher proportion of surgical patients (23.6% vs. 1.7%, p < 0.001) than those with severe hyponatraemia on admission. Furthermore, both mortality (n = 17 vs. n = 7; p = 0.02) and duration of hospitalisation, median 19 days (IQR 10-35) vs. 9.5 (5-15) days (p < 0.001), were greater. Failure to measure plasma and urinary osmolalities was associated with increased mortality.

CONCLUSIONS

Severe hyponatraemia is associated with prolonged admission and increased mortality compared with normonatraemic patients. Progressive hyponatraemia following admission incurs a higher risk of death. This may represent illness-severity, inappropriate management or inadequate investigation.

Mild hyponatremia carries a poor prognosis in community subjects

OBJECTIVE

Hyponatremia has been shown to predict adverse outcome in congestive heart failure and pneumonia among other common clinical entities, but its significance in the general population is elusive.

METHODS

The population-based Copenhagen Holter Study included 671 men and women aged 55 to 75 years with no history of cardiovascular disease, stroke, or cancer. Baseline evaluation included 48-hour ambulatory electrocardiogram monitoring, blood tests, and a questionnaire. Hyponatremia was defined as s-Na < or = 134 mEq/L or s-Na < or = 137 mEq/L according to previously accepted definitions. An adverse outcome was defined as deaths or myocardial infarction. Median follow-up was 6.3 years.

RESULTS

Fourteen subjects (2.1%, group A) had s-Na < or = 134 mEq/L, and 62 subjects (9.2%, group B) had s-Na < or = 137 mEq/L. No subject had s-Na < 129 mEq/L. An adverse outcome occurred in 43% of group A, 27% of group B, and 14% of subjects with s-Na >137 mEq/L (controls) (P < .002). Adjusted hazard ratio for adverse outcome was 3.56 (95% confidence interval [CI], 1.53-8.28, P < .005) in group A compared with controls and 2.21 (95% CI, 1.29-3.80, P < .005) in group B after controlling for age, gender, smoking, diabetes, low-density lipoprotein cholesterol, and blood pressure. The hazard ratios were robust for additional adjusting for variables showing univariate association to hyponatremia (ie, beta-blocker and diuretic use, heart rate variability, creatinine, C-reactive protein, and NT-pro brain natriuretic peptide). By excluding diuretic users (18% of subjects), the adjusted hazard ratio for adverse outcome was 8.00 (95% CI, 3.04-21.0, P < .0001) in group A and 3.17 (95% CI, 1.76-5.72, P = .0001) in group B compared with controls.

CONCLUSION

Hyponatremia is an independent predictor of deaths and myocardial infarction in middle-aged and elderly community subjects.

[A 6-day-old girl with weight loss]

Newborn children normally lose up to 10% of their birth weight during the first week of life. With greater weight loss one must consider low intake and pathological losses. We describe a 6-day-old girl with nearly 19% weight loss and hypertonic dehydration caused by hypogalactia. Principles for treatment of hypertonic dehydration and strategies for finding these children are discussed.

Copeptin in the differential diagnosis of hyponatremia

BACKGROUND

Treatment of patients with hyponatremia varies widely; thus, convenient diagnostic parameters are needed to guide the correct treatment strategy. This study was designed to evaluate the diagnostic potential of copeptin, the C-terminal part of provasopressin, as a new marker in the differential diagnosis of hyponatremia.

METHODS

In this prospective observational study, 106 consecutive hyponatremic patients were classified based on their history, clinical evaluation, and laboratory tests. In patients and 32 healthy control subjects, plasma copeptin concentration and standard biochemical parameters were tested for their utility of diagnosing the syndrome of inappropriate antidiuresis (SIAD).

RESULTS

Four patients (4%) were diagnosed as primary polydipsia, nine (8%) as diuretic-induced hyponatremia, 42 (40%) as SIAD, 29 (27%) as hypovolemic hyponatremia, and 22 patients (21%) as hypervolemic hyponatremia. In controls, a close correlation between plasma copeptin and serum sodium (r(2) = 0.62, P < 0.001) or urine osmolality (r(2) = 0.39, P = 0.001) was observed. Plasma copeptin levels were significantly higher in patients with hypo- and hypervolemic hyponatremia compared with SIAD (P < 0.005, respectively) and primary polydipsia (P < 0.001). The copeptin to U-Na ratio differentiated accurately between volume-depleted and normovolemic disorders (area under the receiver-operating characteristic curve 0.88, 95% confidence interval 0.81-0.95; P < 0.001), resulting in a sensitivity and specificity of 85 and 87% if a cutoff value of 30 pmol/mmol was used. The combined information of plasma copeptin less than 3 pmol/liter and urine osmolality less than 200 mOsm/kg ensured primary polydipsia in 100% of suspected patients.

CONCLUSION

Copeptin measurement reliably identifies patients with primary polydipsia but has limited utility in the differential diagnosis of other hyponatremic disorders. In contrast, the copeptin to U-Na ratio is superior to the reference standard in discriminating volume-depleted from normovolemic hyponatremic disorders.

Hyponatremia in pediatric community-acquired pneumonia

Studies focusing on serum sodium disorders in children with community-acquired-pneumonia (CAP) are nearly entirely lacking, though clinical experience suggests that at least hyponatremia (HN) might be rather common. We evaluated the incidence of hypo- and hypernatremia, in relation to other clinical, laboratory and etiological findings, in pediatric CAP. Serum sodium concentration was measured in 108 ambulatory and hospitalized children with radiologically confirmed CAP of variable severity. The etiology of CAP was revealed by serology in 97 patients. HN (serum sodium < 135 mmol/l) was present in 49 (45.4%) children, and it was mild (> 130 mmol/l) in 92% of the cases. On admission, hyponatremic patients had higher body temperature (38.96 degrees C vs 38.45 degrees C, P = 0.008), white blood cell count (21,074/microl vs 16,592/microl, P = 0.008), neutrophil percentage (78.93% vs 69.33%, P = 0.0001), serum C-reactive protein (168.27 mg/l vs 104.75 mg/l, P = 0.014), and serum procalcitonin (22.35 ng/ml vs 6.87 ng/ml, P = 0.0001), and lower calculated osmolality (263.39 mosmol/l vs 272.84 mosmol/l, P = 0.0001) than normonatremic ones. No association was found with plasma glucose, type of radiological consolidation or etiology of CAP. HN is common but usually mild in children with CAP. HN seems to be associated with the severity of CAP, assessed by fever, need of hospitalization and serum non-specific inflammatory markers.

Interindividual variation in serum sodium and longitudinal blood pressure tracking in the Framingham Heart Study

BACKGROUND

Recent cross-sectional studies have suggested that higher serum sodium levels may be a marker of elevated blood pressure. It is unclear whether serum sodium levels are related to the risk of developing hypertension in the community.

METHODS

We investigated the association of serum sodium with longitudinal blood pressure tracking and incidence of hypertension in 2172 nonhypertensive Framingham Offspring Study participants (mean age 42 years, 54% women). We defined an increase in blood pressure as an increment of at least one category (as defined by the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure), and incident hypertension as a systolic blood pressure of at least 140 or a diastolic blood pressure of at least 90 mmHg, or use of antihypertensive medications. Serum sodium was analyzed as a continuous variable, and as categories.

RESULTS

Cross-sectionally, serum sodium was not associated with systolic or diastolic blood pressure (P exceeded 0.10). On follow-up (mean 4.4 years), 805 participants (37%, 418 women) progressed by at least one blood pressure category, and 318 (15%, 155 women) developed new-onset hypertension. In multivariable logistic regression analyses (adjusting for age, sex, baseline blood pressure, diabetes, BMI, weight gain and smoking), serum sodium was not associated with blood pressure progression (odds ratio per SD increment 0.93, 95% confidence interval 0.85-1.03), or with hypertension incidence (odds ratio per SD increment 0.94, 95% confidence interval 0.82-1.08).

CONCLUSION

In our large community-based sample, serum sodium was not associated with blood pressure cross-sectionally, or with blood pressure tracking or hypertension incidence longitudinally.

[Etiology, diagnostics and therapy of hyponatremias]

Etiopathogenesis, diagnostics and therapy of hyponatremias are summarized for clinicians. Hyponatremia is the most common electrolyte abnormality. Mild to moderate hyponatremia and severe hyponatremia are found in 15-30% and 1-4% of hospitalized patients, respectively. Pathophysiologically, hyponatremias are classified into two groups: hyponatremia due to non-osmotic hypersecretion of vasopressin (hypovolemic, hypervolemic, euvolemic) and hyponatremia of non-hypervasopressinemic origin (pseudohyponatremia, water intoxication, cerebral salt wasting syndrome). Patients with mild hyponatremia are almost always asymptomatic. Severe hyponatremia is usually associated with central nervous system symptoms and can be life-threatening. Diagnostic evaluation of patients with hyponatremia is directed toward identifying the extracellular fluid volume status, the neurological symptoms and signs, the severity and duration of hyponatremia, the rate at which hyponatremia developed. The first step to determine the probable cause of hyponatremia is the differentiation of the hypervasopressinemic and non-hypervasopressinemic hyponatremias with measurement of plasma osmolality, glucose, lipids and proteins. For further differential diagnosis of hyponatremia, the determination of urine osmolality, the clinical assessment of extracellular fluid volume status and the measurement of urine sodium concentration provide important information. The most important representative of euvolemic hyponatremias is SIADH. The diagnosis of SIADH is based on the exclusion of other hyponatremic conditions; low plasma osmolality (<275 mosmol/kg) and inappropriate urine concentration (urine osmolality >100 mosmol/kg) are of pathognomic value. Acute (<48 hrs) severe hyponatremia (<120 mmol/l) necessitates emergency care with rapid restoration of normal osmotic milieu (1 mmol/l/hr increase rate of serum sodium). Patients with chronic symptomatic hyponatremia have a high risk of osmotic demyelination syndrome in brain if rapid correction of the plasma sodium occurs (maximal rate of correction of serum sodium should be 0.5 mmol/l/hr or less). The conventional treatments for chronic asymptomatic hyponatremia (except hypovolemic patients) include water restriction and/or the use of demeclocycline or lithium or furosemide and salt supplementation. Vasopressin receptor antagonists have opened a new forthcoming therapeutic era. V2 receptor antagonists, such as lixivaptan, tolvaptan, satavaptan and the V2+V1A receptor antagonist conivaptan promote the electrolyte-sparing excretion of free water and lead to increased serum sodium.

Blood pressure drug therapy and electrolyte disturbances

Antihypertensive pharmacologic treatment may be associated with diverse disturbances of electrolyte homeostasis. These drug-induced disorders are relatively common, typically including hyponatraemia, hypokalaemia, hyperkalaemia, hypomagnesaemia, hypophosphataemia and hypercalcaemia. Diuretics, beta-blockers, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are particularly likely to cause these complications. Recognised risk factors include high-dosage regimens (especially diuretics), old age, diabetes and impairment of renal function. Strategies to prevent these adverse drug reactions involve careful consideration of risk factors and clinical and laboratory evaluation in the course of treatment.

Mild hyponatremia and risk of fracture in the ambulatory elderly

BACKGROUND

Mild hyponatremia is the commonest electrolyte imbalance in the older population and has been shown to be associated with gait and attention deficits resulting in higher frequency of falls. The association of mild hyponatremia and bone fracture is still unknown.

OBJECTIVE

To determine if mild hyponatremia is associated with increased risk of bone fracture in ambulatory elderly.

DESIGN, SETTING AND PARTICIPANTS

Case control study of 513 cases of bone fracture after incidental fall in ambulatory patients aged 65 or more in general university hospital. Controls were age and sex matched randomly selected ambulatory patients without history of bone fracture.

MAIN EXPOSURE MEASURES

Odds ratio (OR) of bone fracture after incidental fall associated with presence of hyponatremia.

RESULTS

Prevalence of hyponatremia (serum sodium <135 mEq/l,) in patients with bone fracture and in controls patient was, respectively, 13.06% and 3.90%. Hyponatremia was mild and asymptomatic in all patients (mean serum sodium 131 mEq/l) and was found to be associated with bone fracture after incidental fall in ambulatory elderly (unadjusted OR: 3.47, 95% CI: 2.09-5.79, and adjusted OR: 4.16 95% CI: 2.24-7.71). Hyponatremia was either drug induced (36% diuretics, 17% selective serotonin reuptake inhibitors) or resulted from idiopathic syndrome of inappropriate antidiuretic hormone secretion (37%). Hyponatremia was associated with 9.20% of all bone fractures.

CONCLUSION

Mild asymptomatic hyponatremia is associated with bone fracture in ambulatory elderly and avoiding iatrogenic hyponatremia or treating hyponatremia may decrease the number of bone fractures in this population.

The silent epidemic of thiazide-induced hyponatremia

Hyponatremia is a recognized complication of treatment with thiazide diuretics, particularly in patients older than 70 years. Severe and symptomatic hyponatremia requires urgent management, usually requiring infusion of normal or hypertonic saline. Milder, asymptomatic, thiazide-induced hyponatremia requires steps to manage the hyponatremia as well as to prevent its future recurrence. This is a particular problem in patients who despite a history of thiazide-induced hyponatremia might require a diuretic in the management of their hypertension. In this review, the acute management of symptomatic and asymptomatic thiazide-induced hyponatremia is reviewed. Emphasis is also placed on the chronic management of patients who have experienced mild hyponatremia, in whom decisions about treatment with diuretic and nondiuretic antihypertensive agents must be made to satisfy the twin goals of controlling hypertension and avoiding recurrent hyponatremia.

[Central diabetes insipidus: diagnostic difficulties]

Central diabetes insipidus is rare in children. Characteristic features include polyuria and polydipsia due to arginine vasopressin deficiency. The differential diagnosis of polyuric states may be difficult. Etiologic diagnosis of central diabetes insipidus may be an equally difficult task.

OBJECTIVE

To specify the difficulties encountered in the diagnosis of central diabetes insipidus and to point out features of the etiologic work-up and of long-term follow-up of children with idiopathic central diabetes insipidus.

METHODS

A retrospective study of 12 children admitted with a polyuria/polydipsia syndrome to the pediatric - consultation and emergency unit of the children's hospital of Tunis between 1988 and 2005. Children with acquired nephrogenic central diabetes insipidus were excluded. Fourteen-hour fluid restriction test and/or desmopressin test were used without plasma vasopressin measurement.

RESULTS

Eight patients were classified as having central diabetes insipidus, which was severe in seven children and partial in one girl. One patient was classified as having primary polydipsia. The diagnosis remains unclear in three patients. The etiological work-up in eight patients with central diabetes insipidus enabled the identification of Langerhan's-cell histiocytosis in two patients and neurosurgical trauma in one. The cause was considered idiopathic in five patients. The median follow-up of the five patients with idiopathic central diabetes insipidus was five years two months plus or minus six years seven months (range five months, 14.5 years). During this follow-up, neither brain magnetic resonance imaging scans findings nor anterior pituitary function have changed.

CONCLUSION

Fluid restriction and desmopressin tests did not enable an accurate distinction between partial diabetes insipidus and primary polydipsia. Regular surveillance is warranted in patients with idiopathic central diabetes insipidus to identify potential etiologies.

Non-peptide arginine-vasopressin antagonists: the vaptans

Arginine-vasopressin is a hormone that plays an important part in circulatory and water homoeostasis. The three arginine-vasopressin-receptor subtypes--V1a, V1b, and V2--all belong to the large rhodopsin-like G-protein-coupled receptor family. The vaptans are orally and intravenously active non-peptide vasopressin receptor antagonists that are in development. Relcovaptan is a selective V1a-receptor antagonist, which has shown initial positive results in the treatment of Raynaud's disease, dysmenorrhoea, and tocolysis. SSR-149415 is a selective V1b-receptor antagonist, which could have beneficial effects in the treatment of psychiatric disorders. V2-receptor antagonists--mozavaptan, lixivaptan, satavaptan, and tolvaptan--induce a highly hypotonic diuresis without substantially affecting the excretion of electrolytes (by contrast with the effects of diuretics). These drugs are all effective in the treatment of euvolaemic and hypervolaemic hyponatraemia. Conivaptan is a V1a/V2 non-selective vasopressin-receptor antagonist that has been approved by the US Food and Drug Administration as an intravenous infusion for the inhospital treatment of euvolaemic or hypervolaemic hyponatraemia.

Electrolyte and salt disturbances in older people: causes, management and implications

Salt and electrolyte disturbances are commonly encountered in older patients. A sound understanding of the underlying physiological and pathological mechanisms underpinning the predisposition of older people to the common electrolyte imbalances can help clinicians minimize their considerable associated morbidity and mortality. This review focuses on the more common and clinically relevant salt and electrolyte disorders of older people. The epidemiology, causes, symptoms, diagnosis and treatment of hyponatraemia, hypernatraemia, hyperkalaemia, hypokalaemia and calcium and phosphate imbalance in old age are covered from a clinician's perspective.

Severe Hyponatraemia Due to Water Intoxication in a Schizophrenic Patient

A 57-year-old patient with schizophrenia and epilepsy presented to the emergency department with clinical signs of severe hyponatraemia. The patient was incontinent of urine and neurological signs were present; she was eventually transferred to the high dependency unit (HDU). Several causes for the low sodium were considered, but the discovery of a large number of empty water bottles in the patient's home confirmed the suspected diagnosis of water intoxication during a psychotic state. The patient's plasma sodium levels were restored over the course of several days and she was eventually transferred home uneventfully.

Severe hyponatremia in a patient with mantle cell lymphoma treated with bortezomib: a case report and review of the literature

BACKGROUND

Hyponatremia is a known complication of cytotoxic treatment. We observed this side effect in a patient treated with bortezomib. This paper gives an overview of the literature on antineoplastic agents that have been associated with hyponatremia.

CASE REPORT

A 77-year-old female patient with mantle cell lymphoma was admitted with rapidly progressive ataxia, slurred speech, and confusion. 43 days earlier, a second-line treatment with the proteasome inhibitor bortezomib had been started. Neurological examination revealed no focal deficits. Laboratory evaluation showed a combined electrolyte disorder with severe hyponatremia (sodium 112 mmol/l).

RESULTS

A syndrome of inappropriate secretion of antidiuretic hormone (SIADH) was diagnosed, and bortezomib was identified as its cause. The drug was consecutively stopped. CT scan showed a complete remission (CR). Since, the patient has remained in a CR without further tumor-specific treatment.

CONCLUSION

Hyponatremia may be a side effect of treatment with bortezomib and a number of other antineoplastic agents. Because of limited data available, accurate incidences of this complication are not known.

Link between Epilepsy and Malnutrition in a Rural Area of Benin

PURPOSE

Epilepsy and malnutrition are both important public health problems in sub-Saharan Africa. A relationship between epilepsy and malnutrition has been suspected for many years. Our objective was to investigate the association between epilepsy and malnutrition in Djidja, Benin.

METHODS

A matched population-based cross-sectional case-control survey was performed: cases (patients with epilepsy) were matched to controls according to sex, age +/- 5 years, and village of residence. The World Health Organization's criteria for malnutrition was used. Anthropometric measurements (weight, height, mid arm upper circumference, triceps skinfold thickness) were taken. Bioelectrical impedance analysis, a standardized food and social questionnaire and a clinical examination were done. Statistical analysis (conditional logistic regression) was performed using SAS 8.0.

RESULTS

A total of 131 cases and 262 controls were included. The prevalence of malnutrition was higher in cases than in controls (22.1% vs. 9.2%, p = 0.0006). Social factors were significantly different between cases and controls. Feeding difficulties were more frequent and health status was worse in cases. Seven variables were associated with epilepsy: (i) nutritional factors: mid arm upper circumference (prevalence odds ratio (pOR) = 0.7, CI: 0.6-0.9), cereal consumption <3 times during the 3 days before the study (pOR = 4.2, CI: 1.8-10.0), <3 meals/day (pOR = 4.2, CI: 1.6-10.9), tooth decay (pOR = 2.9, CI: 1.1-7.4), food taboos (pOR = 25.0, CI: 8.3-100.0), (ii) social factors: surrogate respondent (pOR = 16.8, CI: 3.1-90.3) and no second job (pOR = 7.1, CI: 2.3-22.3).

CONCLUSION

Epilepsy and nutritional status are linked in sub-Saharan Africa. Programs to improve the nutritional status of people with epilepsy are needed.

Hyponatraemia in clinical practice

Hyponatraemia is defined as a serum sodium concentration below 135 mmol/l. It causes major diagnostic and management problems in practice. Hyponatraemic disorders are divided into euvolaemic, hypervolaemic and hypovolaemic. In the evaluation of the hyponatraemic patient, history taking should focus on identifying the potential cause, duration and symptomatology. Clinical examination should include assessment of volume status. Acute hyponatraemia of less than 48 h duration requires prompt correction. Treatment may involve hypertonic saline, isotonic saline and appropriate hormone replacement therapy depending on the aetiology. Chronic hyponatraemia should be treated with caution because of the risk of central pontine myelinolysis.