Prevalence of Dysnatremia in Pulmonary Tuberculosis

Pulmonary tuberculosis is one of the common diseases with high prevalence of mortality and morbidity in developing countries. It is one of the rare pulmonary infections which can induce hyponatremia and it is important to recognise hyponatremia because of its potential hazards.

OBJECTIVES

To assess the serum sodium levels in patients with pulmonary tuberculosis and to establish a relation between the serum sodium levels and its effect on illness in these patients.

MATERIAL

This is a single-center prospective observational Study conducted on patients with Pulmonary Tuberculosis, irrespective of treatment, in the department of General Medicine, B. R. Ambedkar Medical College, Bangalore from August 2019 to June 2021after obtaining ethical clearance. A total of 100 patients were enrolled in the study who met the predefined inclusion criteria of age more than 18 years and having been diagnosed with active tuberculosis. The collected data was analysed using student's T test and Chi-Square Test and the analysis was done using SPSS software version 24.0.

OBSERVATION

The mean age was 46.46+/- 15.69, with majority of participants in the age group 46-60 years. Gender wise there was male preponderance in our study with 60%. The average serum sodium concentration in our study was 134.20 +/- 5.59 mmol/l, with 44% prevalence of hyponatremia and 4% SIADH Conclusion: Although mild hyponatremia was seen in more than 50% of patients, we found out that hyponatremia in pulmonary tuberculosis is detected in 44% of our patients with male preponderance. The predominant mechanism of hyponatremia was syndrome of inappropriate anti- diuretic hormone secretion (SIADH), which was present in 65% of cases with hyponatremia. Early detection and treatment of underlying electrolyte abnormality can potentially reduce mortality and morbidity associated with tuberculosis and reduce duration of hospitalization. Further research into the prevalence of potassium, magnesium and chloride abnormalities can add to the lacunae of knowledge.

Hyponatraemia in patients with community-acquired pneumonia; prevalence and aetiology, and natural history of SIAD

OBJECTIVE

Hyponatraemia is common in community-acquired pneumonia (CAP) and is associated with increased mortality. The mechanism of hyponatraemia in CAP is not completely understood and treatment is therefore ill-defined. We aimed to define the causation of hyponatraemia in CAP.

DESIGN

Prospective, single-centre, observational study of all patients with CAP and hyponatraemia (≤ 130 mmol/L) during a 9-month period.

PATIENTS

The prevalence of each subtype of hyponatraemia, and the associated mortality, was determined in 143 admissions with CAP (Study 1). A sub-cohort of patients with SIAD (n = 10) was prospectively followed, to document the natural history of SIAD associated with CAP (Study 2).

MEASUREMENTS

In Study 2, blood and urine were collected on day 1, 3, 5 and 7 following admission for measurement of plasma vasopressin, sodium, osmolality and urine osmolality.

RESULTS

In study 1, 143/1723(8.3%) of CAP patients had hyponatraemia (≤130 mmol/L). About 66 had SIAD (46%), 60(42%) had hypovolaemic hyponatraemia (HON), 13(9%) had hypervolaemic hyponatraemia (HEN) and 4(3%) patients had hyponatraemia due to glucocorticoid hormone deficiency. Mortality was higher in the HEN than in the HON, SIAD or normonatraemic groups (P < 0.01). In Study 2, plasma sodium concentration normalized in 8/10 (80%) by day 7. Two patients with persistent hyponatraemia were discovered to have underlying bronchiectasis.

CONCLUSIONS

Hyponatraemia in CAP is most commonly secondary to SIAD or hypovolaemia. HEN is less common, but has worse prognosis. Prospective observation demonstrates that in SIAD, plasma AVP and sodium concentrations normalize with antimicrobials; failure of reversal of suggests underlying lung disease, such as bronchiectasis.

Antipsychotics and severe hyponatremia: A Swedish population-based case-control study

BACKGROUND

Antipsychotics have been claimed to cause hyponatremia. The risk associated with individual antipsychotics, or groups (first-generation [FGAs] or second-generation [SGAs] antipsychotics), is not well-documented. The objective of this study was to investigate the association between antipsychotics and hospitalization due to hyponatremia.

METHODS

The general Swedish population was the base of this register-based case-control study. Comparisons were made between patients hospitalized with a principal diagnosis of hyponatremia (n = 14,359) and matched controls (n = 57,383). Multivariable logistic regression adjusting for concomitant drugs, medical conditions, previous hospitalizations and socioeconomic factors was performed to investigate the association between hyponatremia and antipsychotic use. In addition newly initiated (≤90 days) or ongoing use was analysed separately.

RESULTS

Compared to controls, the adjusted OR (95%CI) for hospitalization due to hyponatremia was for any antipsychotic 1.67(1.5-1.86). Individuals on FGA were more likely to experience severe hyponatremia (2.12[1.83-2.46]) than those on any SGA (1.32[1.15-1.51]). No increased risks, neither as newly initiated nor ongoing therapy, were found for risperidone (0.86[0.56-1.31] and 0.83[0.67-1.02]) and aripiprazole (1.16[0.30-4.46] and 0.62[0.27-1.34]), respectively.

CONCLUSIONS

There was an association between antipsychotic therapy and hospitalization due to hyponatremia. The association was stronger for FGAs than SGAs. Risperidone was not associated with an increased risk.

Management of hyponatremia: causes, clinical aspects, differential diagnosis and treatment

INTRODUCTION

Hyponatremia is the most frequent electrolyte disorder in hospitalised patients. Acute and severe hyponatremia may be a life-threatening situation. However, also mild and chronic hyponatremia may negatively affect the health status (i.e. gait disturbances, attention deficits, falls and fractures, and bone loss) and may increase the risk of death. Therefore, it is of paramount importance for clinicians to have an in-depth knowledge on this topic, in order to appropriately manage patients affected by hyponatremia.

AREAS COVERED

This review will cover different areas related to this electrolyte disorder. Because many pathologic conditions may be associated with hyponatremia, thorough investigations have to be performed in order to establish the underlying etiology. To establish the cause of hyponatremia is of great importance, because an appropriate therapeutic strategy is strictly dependent on a correct diagnosis. A description of the different available therapeutic approaches for the correction of hyponatremia, including vaptans, will follow.

EXPERT COMMENTARY

Undoubtedly, the studies that have been published in recent years and the introduction of vaptans in clinical practice have contributed to increase the awareness on hyponatremia among clinicians. Nevertheless, additional studies are needed in order to clarify some partially uncovered areas.

Strategies to reduce readmissions for hyponatremia after transsphenoidal surgery for pituitary adenomas

PURPOSE

Disorders of water balance, particularly hyponatremia from altered antidiuretic hormone (ADH) secretion, are a common post-operative complication of transsphenoidal surgery (TSS). We present our results from implementation of a 2-week 1.5 liter/daily fluid restriction on readmission rates for hyponatremia.

METHODS

A retrospective chart review was performed on 295 patients that underwent TSS for pituitary adenomas at the University of Colorado, between March 2014 and March 2017. Groups were divided into those before and after the implementation of a two-week, 1.5 liter daily fluid restriction and measurement of a serum sodium level 7 days (+/- 2 days) after discharge. A standard-of-care approach for variable degrees of hyponatremia was also utilized to guide hyponatremia management. Patient demographics, hospital course, post-operative complication rates, and rates of hospital admissions for hyponatremia were then evaluated.

RESULTS

Readmissions for symptomatic hyponatremia within 30 days of TSS occurred in 9 of 118 (7.6%) of patients prior to fluid restriction implementation and in four of 169 (2.4%) of patients in the post-implementation, fluid-restricted group (p-value = 0.04): a 70% reduction in hospitalizations. The two groups were similarly matched for pituitary tumor sub-type, age and gender. None of these factors were predictive for hyponatremia. Importantly, the mild fluid restriction did not result in any hospital readmissions for hypernatremia.

CONCLUSIONS

Mild fluid restriction (to 1.5 liters daily), in addition to a single post-operative serum sodium level, is an effective approach to preventing readmission for hyponatremia after TSS for pituitary adenomas.

Hyponatremia, all-cause mortality, and risk of cancer diagnoses in the primary care setting: A large population study

BACKGROUND

Hyponatremia has been associated with increased all-cause mortality in hospitalized individuals. In this study we examine the risk of all-cause mortality in primary care subjects with hyponatremia, while also exploring the association with subsequent diagnosis of cancer.

METHODS

Retrospective cohort study on subjects who underwent blood tests, consulting their general practitioner 2000-2012 in Copenhagen, Denmark. Reference range for sodium was 135-145mmol/L, and mild, moderate, and severe hyponatremia were defined as 130-135, 125-129, and <125mmol/L, respectively. Primary outcome was all-cause mortality, and secondary outcomes overall and specific types of cancer diagnoses.

RESULTS

Among 625,114 included subjects (mean age 49.9 [SD±18.4] years; 43.5% males), 90,926 (14.5%) deaths occurred. All-cause mortality was increased in mild, moderate, and severe hyponatremia (age-adjusted mortality rates [IRs, incidence rates] 26, 30, and 36 per 1000 person-years (py), respectively and incidence rate ratios [IRRs] 1.81 [95% CI: 1.76-1.85], 2.11 [2.00-2.21], and 2.52 [2.26-2.82], respectively) compared with individuals with normonatremia (IR 14 per 1000 py). For the secondary endpoint an increased level-dependent risk was found with lower sodium levels in relation to cancer overall, head and neck cancers, and pulmonary cancer, with severe hyponatremia associated with the highest IRRs (1.77 [1.39-2.24], 5.24 [2.17-12.63]), and 4.99 [3.49-7.15], respectively).

CONCLUSIONS

All levels of hyponatremia are associated with all-cause mortality in primary care patients and hyponatremia is linked to an increased risk of being diagnosed with any cancer, particularly pulmonary and head and neck cancers.

The syndrome of inappropriate antidiuresis (SIAD)

Hyponatraemia is the commonest electrolyte disturbance encountered in clinical practice and the syndrome of inappropriate antidiuresis (SIADH) is the most frequent underlying disorder. There is a well-recognized relationship between hyponatraemia and increased morbidity and mortality, though it is unknown whether SIADH confers the same mortality as other causes of hyponatraemia. SIADH is the biochemical manifestation of a wide variety of diseases, and the pathophysiology of SIADH is sometimes multiple. There have been significant advances in the treatment of SIADH over the last 10 years, in particular since the introduction of the vasopressin-2 receptor antagonists, which provide a potent, disease-specific tool which targets the underlying pathophysiology of SIADH. The mechanisms and the evidence base recommendations of the available therapies for SIADH are discussed in this article. The various guidelines and recommendations for treatment of hyponatraemia all emphasise that fluid restriction is first line therapy for SIADH, but we feel that it is ineffective or unfeasible in many patients. A number of key points relevant to the use of fluid restriction are presented in the manuscript. The clinical efficacy of tolvaptan in SIADH supported by good quality randomized, placebo controlled, clinical trials. However, the cost of the therapy and the need for long term safety data may limit its widespread use. Finally, new recommendations for the management of acute hyponatraemia, with a focus on the use of bolus therapy with 3% hypertonic sodium chloride is described.

Inpatient hyponatraemia: adequacy of investigation and prevalence of endocrine causes

This study assessed the effect of endocrine input on the investigation of hyponatraemia and examined the prevalence of endocrine causes of hyponatraemia. This single-centre, retrospective study included 139 inpatients (median age, 74 years) with serum sodium (Na) levels ≤128 mmol/l during hospitalisation at a UK teaching hospital over a three-month period. In total, 61.9% of patients underwent assessment of volume status and 28.8% had paired serum and urine osmolality, and Na measured. In addition, 14.4% of patients received endocrine input; 80% of these patients underwent full work-up of hyponatraemia compared with 5% of patients not referred to endocrine services (p < 0.001; relative risk, 15.86; 95% confidence interval, 7.17-31.06). The prevalence of adrenal insufficiency was 0.7%, but basal serum cortisol levels were not measured in around two-thirds of patients. Despite 26.7% of patients having abnormal thyroid function tests, no patient was diagnosed with severe hypothyroidism. More widespread provision of expert input should be considered.

Early water intake restriction to prevent inappropriate antidiuretic hormone secretion following transsphenoidal surgery: low BMI predicts postoperative SIADH

OBJECTIVE

The goals of this study were to assess the incidence of and risk factors for the syndrome of inappropriate antidiuretic hormone secretion (SIADH) in patients following transsphenoidal surgery (TSS), and to validate the effectiveness of early prophylactic restriction of water intake.

DESIGN

Retrospective analysis was performed for 207 patients who had undergone TSS, including 156 patients not placed on early prophylactic water restriction. Sixty-four patients received treatment for SIADH.

METHODS

We compared the incidence of SIADH between patients with and without early water intake restriction, and analyzed various risk factors for SIADH using statistical analyses.

RESULTS

BMI was significantly lower for patients with SIADH than for those patients without SIADH. Statistical analysis revealed that the threshold BMI predicting SIADH was 26. Serum sodium levels on postoperative days 5-10 and daily urine volumes on postoperative days 5-10 were significantly lower in patients with SIADH than in those without SIADH. Postoperative body weight loss on days 6, 8, 10, and 11 was significantly higher in patients with SIADH. The incidence of SIADH after starting prophylactic water intake restriction (14%) was significantly lower than the rate before early water restriction (38%; P<0.05).

CONCLUSIONS

SIADH is relatively common after TSS, and serum sodium concentrations and daily urine volumes should be carefully monitored. Patients with low preoperative BMI should be closely observed, as this represented a significant preoperative risk factor for SIADH. Early prophylactic water intake restriction appears effective at preventing postoperative SIADH.

Severe hyponatremia in older patients at admission in an internal medicine department

Hyponatremia is common in older people, most often of multifactorial origin, and can be associated with poor clinical outcomes. The aim was to analyze the frequency of severe hyponatremia (sodium concentration below 125 mmol/L), risk factors and mortality association in hospitalized older patients. A retrospective study was performed in older patients (over 65 years) with hyponatremia, diagnosed at admission in an Internal Medicine Department during one year. A control group of 127 older patients without hyponatremia was considered. Statistical analysis of the data gathered was made with SPSS Statistics 20. The main results were: a group of 1060 patients with age superior to 65 years was identified (representing 72.26% of total admissions); incidence of hyponatremia in those patients was 27.55% and severe hyponatremia was 5.94%; diagnosis of hyponatremia was mentioned in the discharge note in 66.67% of cases; mortality was 27.0%, against 16.0% in the control group (p=0.057, Odds Ratio (OR)=1.940); drugs were a significant risk factor (p<0.001), specially thiazide diuretics (p=0.029, OR=2.774), angiotensin receptor blockers (ARB) (p=0.001, OR=4.097), proton-pump inhibitors (PPI) (p=0.007, OR=2.561) and spironolactone (p=0.011, OR=4.473); other relevant risk factors were: increased water intake (p=0.004), tube feeding (p<0.001), vomiting (p=0.032, OR=2.492), cirrhosis (p=0.008, OR=10.862) and hyperhidrosis (p=0.017, OR=2.542). We conclude that, although this group of patients had a high mortality, hyponatremia is often not investigated and not always mentioned as a diagnosis. Clinicians should have a clear appreciation of the roles that iatrogenic interventions and lapses in nutrition frequently play in upsetting the homeostatic balance in older patients.

Hyponatremia following mild/moderate subarachnoid hemorrhage is due to SIAD and glucocorticoid deficiency and not cerebral salt wasting

CONTEXT

Hyponatremia is common after acute subarachnoid hemorrhage (SAH) but the etiology is unclear and there is a paucity of prospective data in the field. The cause of hyponatremia is variously attributed to the syndrome of inappropriate antidiuresis (SIAD), acute glucocorticoid insufficiency, and the cerebral salt wasting syndrome (CSWS).

OBJECTIVE

The objective was to prospectively determine the etiology of hyponatremia after SAH using sequential clinical examination and biochemical measurement of plasma cortisol, arginine vasopressin (AVP), and brain natriuretic peptide (BNP).

DESIGN

This was a prospective cohort study.

SETTING

The setting was the National Neurosurgery Centre in a tertiary referral centre in Dublin, Ireland.

PATIENTS

One hundred patients with acute nontraumatic aneurysmal SAH were recruited on presentation.

INTERVENTIONS

Clinical examination and basic biochemical evaluation were performed daily. Plasma cortisol at 0900 hours, AVP, and BNP concentrations were measured on days 1, 2, 3, 4, 6, 8, 10, and 12 following SAH. Those with 0900 hours plasma cortisol<300 nmol/L were empirically treated with iv hydrocortisone.

MAIN OUTCOME MEASURES

Plasma sodium concentration was recorded daily along with a variety of clinical and biochemical criteria. The cause of hyponatremia was determined clinically. Later measurement of plasma AVP and BNP concentrations enabled a firm biochemical diagnosis of the cause of hyponatremia to be made.

RESULTS

Forty-nine of 100 developed hyponatremia<135 mmol/L, including 14/100<130 mmol/L. The cause of hyponatremia, and determined by both clinical examination and biochemical hormone measurement, was SIAD in 36/49 (71.4%), acute glucocorticoid insufficiency in 4/49 (8.2%), incorrect iv fluids in 5/49 (10.2%), and hypovolemia in 5/49 (10.2%). There were no cases of CSWS.

CONCLUSIONS

The most common cause of hyponatremia after acute nontraumatic aneurysmal SAH is SIAD. Acute glucocorticoid insufficiency accounts for a small but significant number of cases. We found no cases of CSWS.

Age-associated abnormalities of water homeostasis

Findley first proposed the presence of age-related dysfunction of the hypothalamic-neurohypophyseal-renal axis more than 60 years ago. More sophisticated studies have since corroborated his findings. As a result, it is now clear that multiple abnormalities in water homeostasis occur commonly with aging, and that the elderly are uniquely susceptible to disorders of body volume and osmolality. This article summarizes the distinct points along the hypothalamic-neurohypophyseal-renal axis where these changes have been characterized, as well as the clinical significance of these changes, with special attention to effects on cognition, gait instability, osteoporosis, fractures, and morbidity and mortality.

Hyponatremia and antidiuresis syndrome

Antidiuretic hormone (ADH), or arginine vasopressin (AVP), is primarily regulated through plasma osmolarity, as well as non-osmotic stimuli including blood volume and stress. Links between water-electrolyte and carbohydrate metabolism have also been recently demonstrated. AVP acts via the intermediary of three types of receptors: V1a, or V1, which exerts vasoconstrictive effects; pituitary gland V1b, or V3, which participates in the secretion of ACTH; and renal V2, which reduces the excretion of pure water by combining with water channels (aquaporin 2). Antidiuresis syndrome is a form of euvolaemic, hypoosmolar hyponatraemia, which is characterised by a negative free water clearance with inappropriate urine osmolality and intracellular hyper-hydration in the absence of renal, adrenal and thyroid insufficiency. Ninety percent of cases of antidiuresis syndrome occur in association with hypersecretion of vasopressin, while vasopressin is undetectable in 10% of cases. Thus the term "antidiuresis syndrome" is more appropriate than the classic name "syndrome of inappropriate ADH secretion" (SIADH). The clinical symptoms, morbidity and mortality of hyponatraemia are related to its severity, as well as to the rapidity of its onset and duration. Even in cases of moderate hyponatraemia that are considered asymptomatic, there is a very high risk of falls due to gait and attention disorders, as well as rhabdomyolysis, which increases the fracture risk. The aetiological diagnosis of hyponatraemia is based on the analysis of calculated or measured plasma osmolality (POsm), as well as blood volume (skin tenting of dehydration, oedema). Hyperglycaemia and hypertriglyceridaemia lead to hyper- and normoosmolar hyponatraemia, respectively. Salt loss of gastrointestinal, renal, cutaneous and sometimes cerebral origin is hypovolaemic, hypoosmolar hyponatraemia (skin tenting), whereas oedema is present with hypervolaemic, hypoosmolar hyponatraemia of heart failure, nephrotic syndrome and cirrhosis. Some endocrinopathies (glucocorticoid deficiency and hypothyroidism) are associated with euvolaemic, hypoosmolar hyponatraemia, which must be distinguished from SIADH. Independent of adrenal insufficiency, isolated hypoaldosteronism can also be accompanied by hypersecretion of vasopressin secondary to hypovolaemia, which responds to mineralocorticoid administration. The causes of SIADH are classic: neoplastic (notably small-cell lung cancer), iatrogenic (particularly psychoactive drugs, chemotherapy), lung and cerebral. Some causes have been recently described: familial hyponatraemia via X-linked recessive disease caused by an activating mutation of the vasopressin 2 receptor; and corticotropin insufficiency related to drug interference between some inhaled glucocorticoids and cytochrome p450 inhibitors, such as the antiretroviral drugs and itraconazole, etc. SIADH in marathon runners exposes them to a risk of hypotonic encephalopathy with fatal cerebral oedema. SIADH treatment is based on water restriction and demeclocycline. V2 receptor antagonists are still not marketed in France. These aquaretics seem effective clinically and biologically, without demonstrated improvement to date of mortality in eu- and hypervolaemic hyponatraemia. Obviously treatment of a corticotropic deficit, even subtle, should not be overlooked, as well as the introduction of fludrocortisone in isolated hypoaldosteronism and discontinuation of iatrogenic drugs.

[Current considerations in syndrome of inappropriate secretion of antidiuretic hormone/syndrome of inappropriate antidiuresis]

The syndrome of inappropriate secretion of antidiuretic hormone (SIADH)/syndrome of inappropriate antidiuresis is characterized by a hypotonic hyponatremia, with an insufficiently diluted urine given the plasmatic hypoosmolality, in the absence of hypovolemia (with or without a third space), hypotension, renal or heart failure, cirrhosis of the liver, hypothyroidism, adrenal insufficiency, vomiting, or other non-osmotic stimuli of ADH secretion. The response of ADH to the infusion of hypertonic saline divides SIADH into 4 different types. In type D, there is no alteration in ADH secretion. Rather, the defect is the maintained permeability of kidney aquaporin-2 channels to water. Activating mutations of the V2 receptor have been identified. The most frequent cause of SIADH is the use of drugs that induce secretion of the hormone. Old age is per se a risk factor for its development. SIADH is underdiagnosed, and hospitalization often worsens the clinical situation, due to an iatrogenic excess in the use of oral and i.v. liquids, often hypotonic, together with a reduction in salt intake. Treatment is directed towards normalization of natremia when possible, together with the avoidance of both hyponatremic encephalopathy as well as the osmotic demyelinization syndrome. Cases of "appropriate" secretion of ADH with normovolemic hyponatremia and high mortality rates should be treated with the same urgency as SIADH--such is the case of post-surgical hyponatremia.

Managing hyponatremia in patients with syndrome of inappropriate antidiuretic hormone secretion

This review will address the management of hyponatremia caused by the syndrome of inappropriate antidiuretic hormone secretion (SIADH) in hospitalized patients. To do so requires an understanding of the pathogenesis and diagnosis of SIADH, as well as currently available treatment options. The review will be structured as responses to a series of questions, followed by a presentation of an algorithm for determining the most appropriate treatments for individual patients with SIADH based on their presenting symptoms.

The syndrome of inappropriate antidiuretic hormone: prevalence, causes and consequences

Hyponatraemia is the commonest electrolyte abnormality found in hospital inpatients, and is associated with a greatly increased morbidity and mortality. The syndrome of inappropriate antidiuretic hormone (SIADH) is the most frequent cause of hyponatraemia in hospital inpatients. SIADH is the clinical and biochemical manifestation of a wide range of disease processes, and every case warrants investigation of the underlying cause. In this review, we will examine the prevalence, pathophysiology, clinical characteristics and clinical consequences of hyponatraemia due to SIADH.

Prevalence and clinical demographics of cerebral salt wasting in patients with aneurysmal subarachnoid hemorrhage

Hyponatremia is a frequent complication following subarachnoid hemorrhage (SAH), and is commonly attributed either to the syndrome of inappropriate antidiuretic hormone secretion (SIADH) or cerebral salt wasting syndrome (CSW). The object of this study is to elucidate the clinical demographics and sequelae of hyponatremia due to CSW in subjects with aneurysmal SAH. Retrospective chart review of patients >18 years with aneurysmal SAH admitted between January 2004 and July 2007 was performed. Subjects with moderate to severe hyponatremia (serum sodium <130 mmol l(-1)) were divided into groups consistent with CSW and SIADH based on urine output, fluid balance, natriuresis, and response to saline infusion. Clinical demographics were compared. Of 316 subjects identified, hyponatremia (serum sodium <135 mmol l(-1)) was detected in 187 (59.2%) subjects and moderate to severe hyponatremia in 48 (15.2%). Of the latter group, 35.4% were categorized with SIADH and 22.9% with CSW. Compared to eunatremic subjects, hyponatremia was associated with significantly longer hospital stay (15.7 +/- 1.9 vs. 9.6 +/- 1.1 days, p < 0.001). Subjects with CSW had similar mortality and duration of hospital stay vs. those with SIADH. Though less common than SIADH, CSW was detected in approximately 23% of patients with history of aneurysmal SAH and was not clearly associated with enhanced morbidity and mortality compared to subjects with SIADH. Further studies regarding the pathogenesis and management, along with the medical consequences, of CSW are important.

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.

A rare case of a pancreatic tumor in association with the syndrome of inappropriate antidiuretic hormone secretion

The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is a well-known complication in malignancy, especially small cell carcinoma of the lung. However its association with pancreatic carcinoma is rare. To the best of our knowledge, only 9 cases have been reported in the literature. We present the case of a 90 year-old woman with pancreatic carcinoma who developed SIADH.

Venlafaxine hyponatraemia: incidence, mechanism and management

OBJECTIVE

This prospective study was performed on patients aged >65 years commencing therapy with venlafaxine, in order to determine the incidence of hyponatraemia induced by the drug, to investigate the underlying pathophysiological mechanisms, and to evaluate a simple approach to management of this condition.

METHOD

All patients aged >65 years seen by one author (MR) from all referral sources were entered into the study. Baseline biochemical tests were ordered, and if hyponatraemia developed (plasma Na <130 mmol L(-1)) additional tests were performed to ascertain the mechanism, while the patient continued on venlafaxine and fluid restriction was instituted.

RESULTS

A total of 58 patients were seen, of whom 10 developed hyponatraemia, giving an incidence of 17.2%. Of these 10 patients, five were excluded from prolonged observation because of either severe medical illness, side-effects from the antidepressant or being lost to follow up. When hyponatraemia developed, it invariably did so within a few days of starting venlafaxine, and was associated with non-suppression of antidiuretic hormone in the face of a low serum osmolality. Fluid restriction (800 mL day(-1)) was effective in raising the plasma sodium to the normal range within 2 weeks, after which the fluid restriction could be relaxed without relapse occurring. These patients remained well for the follow-up period of up to 6 months.

CONCLUSIONS

Patients >65 years of age should have their electrolytes measured 3-5 days after starting venlafaxine therapy. If hyponatraemia develops, it can be managed with modest fluid restriction without discontinuing drug treatment, subject to close continued clinical observation and biochemical monitoring.

Hyponatremia, fluid-electrolyte disorders, and the syndrome of inappropriate antidiuretic hormone secretion: diagnosis and treatment options

OBJECTIVE

To review the types and causes of hyponatremia and examine the various strategies for treatment of this disorder.

METHODS

A systematic review of the current literature is provided, targeting endocrinology clinicians who consult with hospital medical and surgical staff when managing patients with hyponatremia. Treatment for euvolemic and hypervolemic hyponatremia with arginine vasopressin receptor antagonists is presented, which provides a new treatment option for patients with disorders of water metabolism.

RESULTS

Hyponatremia is recognized as the most common electrolyte disorder encountered in the clinical setting and is associated with a variety of conditions including dilutional disorders, such as congestive heart failure and the syndrome of inappropriate antidiuretic hormone secretion, and depletional disorders, such as diarrhea and vomiting or blood loss. Most cases of mild hyponatremia can be treated effectively. Acute, severe hyponatremia that is untreated or treated ineffectively, however, can lead to serious neurologic outcomes or death. With the poor prognosis for morbidity and mortality in patients with severe hyponatremia, hospital-based clinicians must identify those at risk for hyponatremia and suggest appropriate treatment intervention. A new class of drugs, the arginine vasopressin receptor antagonists, targets receptors on collecting duct cells of the nephron and causes aquaresis, the excretion of free water. This therapy leads to the restoration of sodium-water homeostasis in patients with euvolemic and hypervolemic hyponatremia.

CONCLUSION

With many hospitalized patients at risk for hyponatremia, especially elderly patients in critical care and postsurgical units, identification of involved patients, recommendation of appropriate treatment, and awareness of new therapeutic options are critical.

Endocrine Failure After Traumatic Brain Injury in Adults

OBJECTIVE

To review histopathological and clinical data linking endocrine failure to traumatic brain injury (TBI) during acute neurosurgical treatment and rehabilitation.

METHODS

A focused search of the Medline (PubMed) medical literature database and the authors' files were used to identify selected publications.

RESULTS

Endocrine failure may produce clinically important consequences during acute and convalescent care after TBI, and may be caused by direct injury to the hypothalamic- pituitary axis (HPA), neuroendocrinological effects from catecholamines and cytokines, or from systemic infection/inflammation that produces primary gland failure. Autopsy evidence of hemorrhage or ischemia in the HPA is common soon after TBI. The estimated incidence of acute hormone reduction is adrenal 15%, thyroid 5 - 15%, growth hormone 18%, vasopressin 3 - 37%, and gonadal (25 - 80%). Hyperprolactinemia occurs in more than 50% of patients. Inappropriate secretion of antidiuretic hormone (SIADH) and the euthyroid sick syndrome are common. Acute adrenal failure, central hypothyroidism, SIADH, and diabetes insipidus (DI) may cause poor neurological outcomes including death, hypo/hypernatremia, hypotension, and increased vasoactive drug requirements. Treatment of those conditions is warranted. Delayed diagnosis of hypopituitarism is often mistaken for symptoms of residual head injury. Some chronic hormone deficiency occurs in 30 - 40% of selected patients after TBI, more than one deficiency in 10 - 15%, growth hormone in 15 - 20%, gonadal hormones in 15%, and hypothyroidism in 10 - 30%. Chronic adrenal failure and DI are reported over a wide incidence. Prolactin is elevated in 30%. All clinical symptoms respond favorably to replacement therapy.

CONCLUSIONS

Severe TBI associated with basilar skull fracture, hypothalamic edema, prolonged unresponsiveness, hyponatremia, and/or hypotension is associated with a higher occurrence of endocrinopathy. Greater awareness of this possible complication of TBI and appropriate testing are encouraged.

Posterior pituitary dysfunction after traumatic brain injury

Disorders of water balance are well recognized after traumatic brain injury (TBI), but there are no reliable data on their true prevalence in post-TBI patients. We aimed to evaluate the prevalence of posterior pituitary dysfunction in a large cohort of survivors of TBI. One hundred two consecutive patients (85 males) who suffered severe or moderate TBI were evaluated for diabetes insipidus (DI) at a median of 17 months (range 6-36 months) after the event, using the 8-h water deprivation test (WDT). Their results were compared against normative data obtained from 27 matched, healthy controls. Patients' medical records were retrospectively reviewed for the presence of abnormalities of salt and water balance in the immediate post-TBI period. Twenty-two patients (21.6%) developed DI in the immediate post-TBI period (acute DI group), of whom five had abnormal WDT on later testing. In total, seven patients (6.9%) had abnormal WDT (permanent DI group), five of whom had partial DI. Patients in the acute and permanent DI groups were more likely to have more severe TBI, compared with the rest of the cohort (P < 0.05). In the immediate post-TBI period, 13 patients (12.9%) had syndrome of inappropriate secretion of antidiuretic hormone, which persisted in one patient, and one other patient developed cerebral salt wasting. Diabetes insipidus and syndrome of inappropriate secretion of antidiuretic hormone were common in the immediate post-TBI period. Permanent DI was present in 6.9% of patients who survived severe or moderate TBI, which is higher than traditionally thought. Identification of patients with partial posttraumatic DI is important because appropriate treatment may reduce morbidity and optimize the potential for recovery.

Hyponatremia and syndrome of inappropriate antidiuretic hormone secretion complicating stem cell transplantation

Hyponatremia is a common electrolyte disorder in hospitalized patients. Although there are a few case reports of hyponatremia following stem cell transplantation (SCT), no reports concerning the incidence are currently available. We describe the occurrence of hyponatremia and the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) following SCT. In a single center analysis of 140 patients, hyponatremia and SIADH were observed in 40 and 11.4% of patients, respectively, following SCT. Risk factors for SIADH included young age, transplantation from an HLA-mismatched or unrelated donor, cord blood transplantation, and graft-versus-host disease prophylaxis with methyl prednisolone. Multivariate analysis revealed that transplantation from an HLA-mismatched donor and performance of SCT in a child below 4 years of age were risk factors for SIADH. For patients who underwent SCT from an HLA-mismatched or unrelated donor, those with SIADH showed a significantly higher overall survival rate (90.9 vs 40.2%) and event-free survival rate (77.8 vs 33.8%) compared to those without SIADH. Overall, our data show that hyponatremia and SIADH are relatively common complications following SCT, especially in children below 4 years of age and after SCT from an HLA-mismatched donor.

[Inappropriate secretion of antidiuretic hormone and diabetes insipidus after surgery for pituitary adenoma]

The purpose of our study was to evaluate the incidence and risk factors of SIADH (syndrome of inappropriate antidiuretic hormone) and diabetes insipidus after pituitary adenoma surgery in patients and report follow-up data collected in our department of endocrinology. This retrospective study included 78 patients seen in the last 5 years. Possible risk factors of SIADH and diabetes insipidus were studies: patient age and gender, type of secretion, tumor volume, surgical approach, presence of postoperative pituitary failure. The incidence of SIADH and diabetes insipidus were similar: 12.8%. We did not find any risk factor for SIADH associated with postoperative anterior pituitary failure. This study illustrates the importance of postoperative follow-up after pituitary adenoma surgery.

Circulating vasopressin levels in septic shock

OBJECTIVE

To assess the frequency of vasopressin deficiency in septic shock.

DESIGN

Prospective cohort study.

SETTING

Intensive care unit at Raymond Poincaré University Hospital.

PATIENTS

A cohort of 44 patients who met the usual criteria for septic shock for < 7 days. A second cohort of 18 septic shock patients were enrolled within the first 8 hrs of disease onset.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

General demographics, severity scores, vital signs, standard biochemical data, and circulating vasopressin levels were systematically obtained at baseline in the two cohorts. Vasopressin deficiency was defined by a normal plasma vasopressin level in the presence of a systolic blood pressure of <100 mm Hg or in the presence of hypernatremia. Baroreflex sensitivity was systematically evaluated in patients of the first cohort when vasopressin deficiency was noted. In the second cohort of patients, plasma levels of vasopressin were obtained at baseline, 6, 24, 48, and 96 hrs after shock onset. In the first population, plasma vasopressin levels were inversely correlated to the delay from shock onset. Fourteen patients had relative vasopressin deficiency: 12 patients had systolic blood pressure <100 mm Hg, with impaired baroreflex sensitivity in four, and three patients had hypernatremia. In the second population, only two patients had relative vasopressin deficiency. The plasma levels of vasopressin significantly decreased over time (p < 10-3).

CONCLUSIONS

Plasma vasopressin levels are almost always increased at the initial phase of septic shock and decrease afterward. Relative vasopressin deficiency is seen in approximately one-third of late septic shock patients.

Syndrome of inappropriate antidiuretic hormone or arginine vasopressin secretion in patients following neck dissection

OBJECTIVES/HYPOTHESIS

The syndrome of inappropriate antidiuretic hormone or arginine vasopressin secretion (SIADH) is a disorder in which release of antidiuretic hormone is independent of plasma osmolarity, resulting in fluid retention and development of dilutional hyponatremia. The incidence of SIADH following neck dissection was found to be 18% to 30% in two separate reports. The incidence of SIADH in a cohort of patients who underwent neck dissection was prospectively studied.

METHODS

Eighty-six patients were included in the study, along with a control group of 19 patients who underwent other neck procedures. Patient gender, age, physical condition (American Society of Anesthesiologists score), type of neck dissection, prior treatment, and smoking history were noted. Blood and urine osmolarity and sodium levels were sampled before surgery and during the first 24 hours after the surgery. These were recorded daily in cases with SIADH until the syndrome resolved.

RESULTS

The incidence of SIADH was only 1.15% in patients before surgery. The syndrome developed in seven patients following neck dissection (8.14%) and in none of the patients in the control group. SIADH resolved within 72 hours at the latest. No association was found with patient gender, age, physical condition, or type or laterality of neck dissection. A statistically significant connection between the syndrome and history of smoking was noted (P <.05), and it was more commonly seen in patients with node-positive necks (P =.1231).

CONCLUSIONS

SIADH following neck dissection may be less common than formerly reported. Previous studies have presented contradicting data concerning the influence of tumor recurrence or prior radiation therapy on its incidence. Our results indicate no such association. A statistically significant connection between smoking and the syndrome was found. No clinical symptoms developed in the patients with SIADH, but it seems prudent to suggest limiting fluid intake in the first postoperative 24 hours for patients following neck dissection.

Hyponatremia and syndrome of inappropriate anti-diuretic hormone reported with the use of Vincristine: an over-representation of Asians?

PURPOSE

This retrospective study used a pharmaceutical company's global safety database to determine the reporting rate of hyponatremia and/or syndrome of inappropriate secretion of anti-diuretic hormone (SIADH) among vincristine-treated patients and to explore the possibility of at-risk population subgroups.

METHOD

We searched the Eli Lilly and Company's computerized adverse event database for all reported cases of hyponatremia and/or SIADH as of 1 November 1999 that had been reported during the use of vincristine.

RESULTS

A total of 76 cases of hyponatremia and/or SIADH associated with vincristine use were identified. The overall reporting rate was estimated to be 1.3/100,000 treated patients. The average age of patients was 35.6 +/- 28.3 years, and 62% were males. Approximately 75% of the patients were receiving treatment for leukemia or lymphoma. Among the 39 reports that included information on race, the racial distribution was: 1 Black, 3 Caucasian, and 35 Asian.

CONCLUSION

Our data suggest that Asian patients may be at increased risk of hyponatremia and/or SIADH associated with vincristine use. Although the overall reported rate of SIADH associated with vincristine is very low, physicians caring for Asian oncology patients should be aware of this potential serious but reversible adverse event.

Chronic idiopathic hyponatremia in older people due to syndrome of inappropriate antidiuretic hormone secretion (SIADH) possibly related to aging

OBJECTIVE

To determine the prevalence of syndrome of inappropriate antidiuretic hormone secretion (SIADH) among older hyponatremic patients in a subacute geriatric facility, to identify patients with no apparent cause for the SIADH (idiopathic SIADH), and to determine their clinical characteristics.

DESIGN

Prospective analysis of a cohort of older patients over a period of 3 months.

SETTING

Two wards in a geriatric rehabilitation hospital.

PARTICIPANTS

Patients aged 65 and older.

MEASUREMENTS

All patients with hyponatremia (serum sodium <135 mmols/l) were clinically examined and relevant investigations were performed to determine the etiology of hyponatremia. Patients were observed for symptoms of hyponatremia. Hyponatremia was classified into possible SIADH and non-SIADH types. Patients with SIADH type hyponatremia were screened for possible causes. Past medical histories were obtained from the general practitioners.

RESULTS

Of the 172 patients studied, 43 (25%) had hyponatremia. It was symptomatic in only four patients. Twenty-two (51%) had SIADH etiology. In nine (mean age 84 +/- 4), no cause for the SIADH was evident (presumed idiopathic SIADH) and in seven, hyponatremia (128-135 mmols/l) was chronic (12 to 72 months). Further reduction in serum sodium, which was symptomatic, was noted in two of these patients with the onset of pneumonia.

CONCLUSION

Most older hyponatremic patients in a rehabilitation setting seem to have SIADH etiology. This study confirms the presence of a group of older individuals with chronic idiopathic hyponatremia in whom the underlying mechanism may be SIADH related to aging. Hyponatremia is modest in these patients and has little clinical significance. However, they may be at increased risk of developing symptomatic hyponatremia with intercurrent illnesses.

Antidepressant drugs: disturbing and potentially dangerous adverse effects

Adverse effects associated with antidepressant drug therapy rarely cause significant morbidity or mortality. Nevertheless, the successful management of patients with depression requires recognition of potential adverse effects that have serious consequences, which include the discontinuation of otherwise effective therapy. The aim of this overview is to highlight the more common and potentially deleterious adverse effects of both older and newer classes of antidepressant drugs. Major adverse effects attributed to the tricyclic antidepressant drugs (TCAs) include conduction defects and lethal overdose. Most worrisome with the selective serotonin reuptake inhibitor drugs (SSRIs) is the serotonin syndrome. Although rare, this syndrome can be insidious and lethal. Recent trends toward the use of medication combinations and augmentation therapies significantly enhance the risk of serotonin syndrome. Cognitive impairment also may occur, especially with the TCAs. Apathy is occasionally a problem with SSRI therapy. The syndrome of inappropriate antidiuretic hormone (SIADH) has been reported with most antidepressant drugs but appears to be more common with serotonergic agents and in elderly patients. Although seizures are uncommon in patients receiving antidepressant therapy, the risk must be understood by both the patient and the clinician. Adverse effects related to sexual function are common, especially with TCAs, SSRIs, and venlafaxine. Sexual dysfunction often leads to noncompliance and self-discontinuation of therapy. Sleep disturbances are common in patients with depression, and recent data illustrate how crucial sleep regulation is to mood. Antidepressant drugs vary in their sleep effects. Although antidepressant drugs can cause a variety of adverse effects, these drugs save lives and their benefits far exceed their risks.

Syndromes of excess antidiuretic hormone release

Hyponatremia, particularly that due to the syndrome of inappropriate antidiuretic hormone secretion (SIADH), is common in patients seen in the critical care setting. Because of aging-associated changes in the hormonal and renal systems involved in regulation of water and sodium balance, older persons are at higher risk than the young. The high prevalence of disease states and drug use in the elderly can affect water and sodium conservation and further contribute to the risk of hyponatremia in this population. The approach to management is dependent both on the severity of hyponatremia-related symptoms and the rapidity with which hyponatremia has developed. Careful monitoring of serum sodium during treatment is essential to produce prompt resolution of symptoms while avoiding the development of central pontine myelinolysis. Several therapeutic modalities are available for the longterm management of chronic hyponatremia.

[Susceptibility of the elderly patient to hyponatremia induced by selective serotonin reuptake inhibitors]

Numerous spontaneous reports of the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) have followed the increased use of selective serotonin reuptake inhibitors (SSRI). It has been estimated that 1 in 200 patients treated per year developed SIADH, age and low body weight being particular risk factors. No clear gender effect has been detected when confounding factors such as body weight or antidepressant consumption are taken into account. Age-related susceptibility to hyponatraemia may be explained by physiological changes in renal and endocrine function. The high prevalence of polymedication and pluripathology in the elderly may be a contributing factor as well. To date, no study has demonstrated how SSRIs affect the regulation of fluid/sodium balance nor whether they have an independent effect on this regulation in depressed subjects.

Apparent idiopathic hyponatremia in an ambulatory geriatric population

OBJECTIVES

The purpose of this descriptive analysis is to demonstrate that among older patients with hyponatremia, there is a subset with apparent hyponatremia of the syndrome of inappropriate antidiuretic hormone secretion (SIADH) type, which appears associated with the aging process. A retrospective chart review was done to identify patients with hyponatremia and to classify them into non-SIADH, SIADH, and idiopathic categories.

DESIGN

The participants were the ambulatory population of The Mount Sinai Hospital's outpatient geriatric clinic. Pertinent data generated during the antecedent 24 months were collected from outpatient charts and included sets of laboratory values (consisting of one sodium, glucose, BUN and creatinine level), age, sex, race, clinical history, present diagnosis, medications, and prescribed diets for each patient in the total population.

RESULTS

Patients demonstrating hyponatremia with serum sodium levels of less than 135 mEq/L were identified from the total population and were further divided into SIADH and non-SIADH etiologies. The SIADH patients were then subdivided into known etiology SIADH and apparent idiopathic SIADH. In an ambulatory geriatric population of 405 subjects, 46 had hyponatremia, with SIADH the apparent cause in 27. Of the SIADH population, seven patients were considered to have idiopathic SIADH. An apparent predilection for development of this syndrome was observed among non-black patients and the old old.

CONCLUSIONS

The results support the hypothesis that aging is a risk factor for the development of SIADH-like hyponatremia in a subset of older patients who do not have an apparent underlying etiology. Thus, aging may be an independent etiology for the development of hyponatremia.

Abnormalities of water metabolism in children and adolescents following craniotomy for a brain tumor

We conducted a retrospective analysis of the cases of 122 children operated on for various brain tumors, to determine the incidence and natural history of postoperative diabetes insipidus (DI), and the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Abnormalities of water homeostasis were observed in 15 patients (12%). DI, with or without SIADH, was observed in 10 patients (8%), while SIADH alone was seen in five (4%). DI was permanent in five subjects (50%), whereas SIADH resolved completely in all affected individuals. Parenteral desmopressin (dDAVP) was an effective mode of therapy in the postoperative period. The effect did not correlate with a dosage strictly based on body weight.

Hyponatremia and syndrome of inappropriate antidiuretic hormone secretion in adult spinal surgery

STUDY DESIGN

Patients undergoing spinal surgery were monitored for sodium balance, fluid type, and volume input and output during surgery and for the first 3 postoperative days.

OBJECTIVE

To prospectively document the true incidence of the syndrome of inappropriate antidiuretic hormone secretion and hyponatremia, and identify risk and protective factors for the development of the syndrome of inappropriate antidiuretic hormone secretion after spinal surgery.

METHODS

Data on medical history, surgical procedure, estimated blood loss, and volumes and types of intraoperative and postoperative fluids were collected on 116 consecutive spinal surgery patients during March to July 1992.

RESULTS

One hundred one spinal operations in 96 patients were evaluated. There were 48 males and 48 females, with a mean age of 52 years (range, 16 to 90 years). Hyponatremia developed in 45 (44.6%) patients. The etiology of hyponatremia was the syndrome of inappropriate antidiuretic hormone secretion in seven patients (6.9%), hypovolemia in 19 patients (18%), and other causes in six patients.

CONCLUSIONS

Spine patients are at risk for hyponatremia and the syndrome of inappropriate antidiuretic hormone secretion. The incidence of the syndrome of inappropriate antidiuretic hormone secretion was 6.9%. Serum sodium should be monitored postoperatively. Patients who undergo a revision operation have an approximately two to four times greater risk of being affected by the syndrome of inappropriate antidiuretic hormone secretion than those who have primary surgery.

Chlorpropamide-induced hyponatremia in the veteran population

OBJECTIVE

To determine the incidence and possible risk factors associated with chlorpropamide (CPA)-induced hyponatremia in the veteran population.

DESIGN

Retrospective cohort study.

SETTING

Federal tertiary care medical center.

PATIENTS

Veterans receiving CPA from our facility with at least one serum sodium concentration below 135 mmol/L within the past year were eligible. A randomly selected control group consisting of patients taking CPA with normal sodium concentrations was also chosen. One hundred forty-five of 799 patients who had received CPA were included in the study.

RESULTS

The average daily dose of CPA was 425 +/- 207 mg (+/- SD). The incidence of hyponatremia associated with CPA was 7.1 percent (57/799 patients). The majority of patients were mildly hyponatremic (48/57 patients, 84 percent) with serum sodium concentrations between 130 and 134 mmol/L. The incidence of CPA-induced syndrome of inappropriate antidiuretic hormone was 2.1 percent. Concurrent angiotensin-converting enzyme (ACE) inhibitor use was identified as a risk factor; thiazide diuretic use was not.

CONCLUSIONS

The incidence of hyponatremia related to CPA use in elderly veterans is consistent with other reports in the literature. ACE inhibitors may be a predisposing factor for CPA-induced hyponatremia.

Hyponatraemia and the inappropriate ADH syndrome in pneumonia

We studied serum sodium, plasma osmolality and urinary sodium and osmolality on days 1, 3 and 5 of hospitalization of 100 children aged from 1 month to 12 years admitted with a diagnosis of pneumonia. Hyponatraemia (serum sodium concentration < or = 130 mmol/l) was found in 31 patients at the time of admission. The probable cause of hyponatraemia in 94% of cases was the syndrome of inappropriate antidiuretic hormone secretion (SIADH). Symptoms and signs indicative of severe pneumonia were two to three times more frequent and the mean duration of tachypnoea, chest-wall retraction and hospital stay about one and a half times longer in children with hyponatraemia. Four children died (two on day 1, one on day 5 and one on day 8); all four had a serum sodium concentration < or = 125 mmol/l which persisted until death. Of the remaining 27 hyponatraemic children, serum sodium concentrations returned to normal on day 3 in 26, while in one hyponatraemia persisted until day 7. The recovery from hyponatraemia showed a good correlation with improvement in clinical signs of respiratory distress. The SIADH occurred in about one-third of the children hospitalized for pneumonia, and was associated with a more severe disease and a poorer outcome. Perhaps fluid restriction in these cases may improve the outcome.

Hyponatremia hypo-osmolarity in neurosurgical patients. "Appropriate secretion of ADH" and "cerebral salt wasting syndrome"

This prospective study is based on 256 patients with severe brain injury. Six patients (2.3%) developed the clinical picture of inappropriate secretion of antidiuretic hormone (SIADH): 3 in the first 3 days following the injury, 3 after more than a week. Their ADH plasmatic level were measured by radio-immunoassay. In the former, many factors, largely iatrogenic, can explain the increased secretion of ADH we found and which is then definitely "appropriate". It should be prevented by fluid restriction. In the latter, we found adequately low ADH levels, when the hypo-osmolarity is taken into account. Here, the aetiology seems to be a renal salt loss, eventually in relation to a natriuric factor (e.g. atrial natriuretic factor), justifying the term: "Cerebral salt wasting syndrome". With the resistance to fluid restriction, the treatment still remains a problem.

Hyponatremia due to psychotropic drugs

The syndrome of hyponatremia in psychiatric patients is described, and cases associated with psychotropic drug treatment are reviewed. The causative role of the drug should be documented by rechallenge or a water loading test. In some instances it is possible to continue psychotropic treatment by restricting fluids or administering demeclocycline.