A syndrome of renal sodium loss and hyponatremia probably resulting from inappropriate secretion of antidiuretic hormone

Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH): Optimal Management

Hyponatremia, defined as serum sodium concentration <135 mEq/l, is the most common electrolyte balance disorder in clinical practice. Many causes are listed, but syndrome of inappropriate antidiuretic hormone secretion (SIADH) is certainly the most relevant, mainly in oncological and hospitalized patients. In this review, the pathophysiological and clinical aspects are described in detail. Patients’ extensive medical history and structured physical and biochemical tests are considered the milestones marking the way of the SIADH management as to provide early detection and proper correction. We focused our attention on the poor prognostic role and negative effect on patient’s quality of life of SIADH-induced hyponatremia in both malignant and non-malignant settings, stressing how optimal management of this electrolyte imbalance can result in improved outcomes and lower health costs.

Evolution and evolving resolution of controversy over existence and prevalence of cerebral/renal salt wasting

PURPOSE OF REVIEW

The topic of hyponatremia is in a state of flux. We review a new approach to diagnosis that is superior to previous methods. It simplifies identifying the causes of hyponatremia, the most important issue being the differentiation of the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) from cerebral/renal salt wasting (RSW). We also report on the high prevalence of RSW without cerebral disease in the general wards of the hospital.

RECENT FINDINGS

We applied our new approach to hyponatremia by utilizing sound pathophysiologic criteria in 62 hyponatremic patients. Seventeen (27%) had SIADH, 19 (31%) had a reset osmostat, 24 (38%) had RSW with 21 having no evidence of cerebral disease, 1 had Addison's disease, and 1 was because of hydrochlorothiazide. Many had urine sodium concentrations (UNa) less than 30 mmol/l.

SUMMARY

RSW is much more common than perceived in the general wards of the hospital. It is important to change the terminology from cerebral to RSW and to differentiate SIADH from RSW. These changes will improve clinical outcomes because of divergent therapeutic goals of water-restricting in SIADH and administering salt and water to a dehydrated patient with RSW. The present review will hopefully spur others to reflect and act on the new findings and different approaches to hyponatremia.

COVID-19 Pneumonia: An Emerging Cause of Syndrome of Inappropriate Antidiuretic Hormone

Syndrome of inappropriate antidiuretic hormone (SIADH) is the leading cause of hyponatremia. We, herein, report a case of a patient with coronavirus disease-2019 (COVID-19) who developed sudden exertional dyspnea and hypoxia and was found to be hyponatremic. A diagnosis of SIADH was made due to COVID-19 pneumonia. The patient was managed conservatively with a significant improvement during the course of hospitalization and on follow-up.

The Role of Fractional Excretion of Uric Acid in the Differential Diagnosis of Hypotonic Hyponatraemia in Patients with Diuretic Therapy

Hyponatraemia is the most common electrolyte imbalance found in hospital population and worldwide thiazide and loop-diuretics are among the most widely used drugs. Syndrome of inappropriate antidiuresis diagnosis (SIAD) is complicated in the presence of diuretic therapy due to the misleading clinical assessment of the extracellular volume status, and in order to make SIAD diagnosis it is often necessary to withdraw diuretic therapy. Our study aimed to investigate the diagnostic role of these alternative markers of volume status, serum uric acid (sUA) and fractional excretion of uric acid (FEUA), in hyponatraemic patients treated with different diuretic drugs. Eighty-nine patients were enrolled with the diagnosis of SIAD, diuretic-induced hyponatremia (DIH, treated with furosemide and potassium canrenoate) or thiazide-induced hyponatremia (TIH, treated with hydrochlorothiazide, metolazone or indapamide) and investigated with receiver operating characteristic analysis and a sensitivity test. Our results show that FEUA discriminated better than sUA between SIAD and DIH patients (area under curve 0.96, <0.001 vs. 0.88, <0.001) while it was a poor marker to discriminate between SIAD and TIH (0.65, NS vs. 0.67, NS). In conclusions, FEUA is an excellent marker to discriminate SIAD vs. sodium depleted patients treated with furosemide and/or potassium canrenoate while the diuretic withdrawal, beyond obtaining a serum Na normalization, is still mandatory for differential diagnosis of sodium depleted patients affected by thiazide-induced hyponatraemia.

Higher incidence of syndrome of inappropriate antidiuretic hormone secretion during induction chemotherapy of acute lymphoblastic leukemia in indian children

BACKGROUND

Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a well-known adverse effect of vincristine (VCR). Literature suggests that Asians are predisposed to develop SIADH following VCR administration. However, data regarding the occurrence of SIADH in children with malignancy are limited. This study aims to analyze the incidence, clinical picture, risk factors, management, and outcome of SIADH during induction chemotherapy for pediatric acute lymphoblastic leukemia (ALL).

MATERIALS AND METHODS

A prospective study was conducted among the 166 newly diagnosed pediatric ALL patients who were treated at a tertiary cancer center in India between January 2015 and December 2015. Patients who developed hyponatremia during induction chemotherapy were further investigated for SIADH.

RESULTS

The incidence of SIADH was 10.8% (n = 18) with a mean sodium level of 125 mEq/L (114-129 mEq/L). In the preceding 2 weeks, 72% of episodes were associated with the administration of two (n = 6) or three (n = 7) doses of VCR. One child presented with seizures. All the patients were managed with fluid restriction and only two patients required sodium correction with 3% saline. Girls older than 10 years of age showed a marginally significant correlation to develop SIADH (P-value = 0.059).

CONCLUSION

We report a higher incidence of SIADH (10.8%) in Indian children, compared to that described in the literature, during induction chemotherapy for ALL. Regular monitoring of sodium levels during this period of chemotherapy is hence essential for the timely diagnosis and appropriate management of SIADH, which in turn will avert complications, including neurological symptoms secondary to SIADH.

Paraneoplastic Syndromes Associated with Laryngeal Cancer

OBJECTIVES

Paraneoplastic syndromes occur rarely in association with laryngeal cancer. When present, the syndrome may be the first sign of the malignancy. The aim of the present study was to review and report on all published cases in the international literature.

METHODS

A search of PubMed was conducted for "paraneoplastic syndromes in laryngeal cancer" without any restrictions on language or publication year. The full texts of all relevant articles were reviewed and all cases of paraneoplastic syndromes associated with any type of laryngeal cancer were extracted and analyzed.

RESULTS

We identified 59 cases of paraneoplastic syndromes related to laryngeal cancer in the literature published from 1963 until recently. There were 46 squamous cell carcinomas and 10 neuroendocrine carcinomas. Twenty-two of the paraneoplastic syndromes involved the endocrine system, 21 were dermatologic or cutaneous, 8 neurologic, 5 osteoarticular or rheumatologic, 1 ocular, 1 muscular, and 1 hematologic. Treatment strategies included surgery, radiotherapy, chemotherapy, and often multimodal therapy, depending on the histology and stage of the laryngeal cancer.

CONCLUSIONS

Because of their rarity, paraneoplastic syndromes associated with laryngeal cancer are difficult to diagnose. By presenting and systematically reviewing all published cases in the international literature, the present review may help clinicians to recognize them and to suspect the diagnosis of laryngeal cancer at an earlier stage than otherwise might be possible.

Copeptin is not useful as a marker of malignant disease in the syndrome of inappropriate antidiuresis

OBJECTIVE

The syndrome of inappropriate antidiuresis (SIAD) is a common condition in hospitalized patients. It is crucial to establish the cause of SIAD, especially in order to exclude underlying malignancy. As malignant SIAD may be due to a paraneoplastic synthesis of arginine vasopressin, we hypothesized that its stable surrogate marker copeptin can be used as a diagnostic tool to differentiate between malignant and non-malignant SIAD.

METHODS

Prospective observational study. We analyzed data from 146 SIAD patients of two different cohorts from Switzerland and Germany. Patients were included while presenting at the emergency department and underwent a standardized diagnostic assessment including the measurement of copeptin levels.

RESULTS

Thirty-nine patients (median age: 63 years, 51% female) were diagnosed with cancer-related SIAD and 107 (median age: 73 years, 68% female) with non-malignant SIAD. Serum sodium levels were higher in cancer-related versus non-malignant SIAD: median (IQR) 124 mmol/l (120; 127) versus 120 mmol/l (117; 123) (P<0.001). Median (IQR) copeptin levels of patients with cancer-related SIAD were 11.1 pmol/l (5.2; 37.1) and 10.5 pmol/l (5.2; 25.2) with non-malignant SIAD (P = 0.38). Among different cancer entities, patients suffering from small-cell lung cancer showed the highest copeptin values, but overall no significant difference in copeptin levels between cancer types was observed (P = 0.46).

CONCLUSIONS

Copeptin levels are similar in cancer-related and non-malignant SIAD. Therefore, Copeptin does not seem to be suitable as a marker of malignant disease in SIAD.

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

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

Syndrome of inappropriate antidiuretic hormone secretion as a side effect of chemotherapy for testicular cancer: A case report

INTRODUCTION

Inappropriate antidiuretic hormone secretion syndrome can be a serious adverse event of cisplatin-based chemotherapy. Cisplatin had to be changed to other drugs or chemotherapy completely discontinued in earlier reported cases.

CASE PRESENTATION

Three cycles of bleomycin, etoposide, and cisplatin chemotherapy were planned for a 40-year-old man with a diagnosis of lymph node recurrence of testicular cancer. On day 9, he suffered from vomiting and mental disturbance. Severe hyponatremia (110 mEq/L) with low plasma osmolality led to a diagnosis of a syndrome of inappropriate antidiuretic hormone secretion, and infusions of hypertonic saline and salt intake were prescribed. Second and third courses of bleomycin, etoposide, and cisplatin chemotherapy could then be given with careful electrolyte management.

CONCLUSION

Continuation of cisplatin administration with precise electrolyte adjustment can be a treatment option in regimens where cisplatin is essential for achieving optimal antitumor efficacy.

Hyponatraemia and Syndrome of Inappropriate Antidiuretic Hormone Secretion in Non-azotaemic Dogs with Babesiosis Associated with Decreased Arterial Blood Pressure

Introduction

A previous study on canine babesiosis showed low serum tonicity in affected dogs, which may result from syndrome of inappropriate antidiuretic hormone secretion (SIADH). This endocrine disorder was recognised in human malaria which is considered a disease with similar pathogenesis to canine babesiosis. The aim of this study was to investigate the occurrence of SIADH in babesiosis-afflicted dogs.

Material and Methods

Serum and urinary sodium and urine specific gravity (USG) were determined in dogs with babesiosis. Mean arterial pressure (MAP) was measured at the beginning of the clinical examination. Serum tonicity and osmolality were calculated. Correlations were calculated between MAP and serum and urinary sodium concentrations, USG, serum tonicity, and calculated serum osmolality.

Results

Statistically significant correlations were observed between MAP and tonicity, calculated osmolality, USG, and serum and urinary sodium concentrations in non-azotaemic dogs. In three non-azotaemic dogs SIADH was recognised.

Conclusion

SIADH develops in non-azotaemic dogs with babesiosis. It is probably associated with decreased blood pressure in infected dogs. Thus, it seems that in fact it may be appropriate vasopressin secretion in canine babesiosis as a protective mechanism in hypotension which leads to hypoxia and renal failure in affected dogs.

Vasopressin and Copeptin in health and disease

Arginine Vasopressin (AVP) and copeptin derive from the same precursor molecule. Due to the equimolar secretion, copeptin responds as rapidly as AVP to osmotic, hemodynamic and unspecific stress-related stimuli and both peptides show a very strong correlation. The physiological functions of AVP are homeostasis of fluid balance, vascular tonus and regulation of the endocrine stress response. In contrast, the exact function of copeptin remains unknown. Since copeptin, in contrast to AVP, can easily be measured with a sandwich immunoassay, its main function so far that it indirectly indicates the amount of AVP in the circulation. Copeptin has emerged as a useful measure in different diseases. On one hand, through its characteristics as a marker of stress, it provides a unique measure of the individual stress burden. As such, it is a prognostic marker in different acute diseases such as ischemic stroke or myocardial infarction. On the other side, it has emerged as a promising marker in the diagnosis of AVP-dependent fluid disorders. Copeptin reliably differentiates various entities of the polyuria polydipsia syndrome; baseline levels >20 pmol/L without prior fluid deprivation identify patients with nephrogenic diabetes insipidus, whereas levels measured upon osmotic stimulation with hypertonic saline or upon non-osmotic stimulation with arginine differentiate primary polydipsia from central diabetes insipidus. In patients with hyponatremia, low levels of copeptin together with low urine osmolality identify patients with primary polydipsia, but copeptin levels overlap in all other causes of hyponatremia, limiting its diagnostic use in hyponatremia. Copeptin has also been put forward as predictive marker for autosomal dominant polycystic kidney disease and for diabetes mellitus, but more studies are needed to confirm these findings.

Effect of Environmental Temperature on Serum Sodium Level in Hospitalized Non-critically Ill Children

BACKGROUND

Intravenous hypotonic fluid administered in children is associated with an increased risk of developing hyponatremia. This finding has been reported from temperate countries where climate is relatively cold. But whether this risk also occurs in tropical countries has not been elucidated.

OBJECTIVE

The objective of this study was to determine the relationship between environmental temperature and serum sodium in non-critically ill children.

METHODS

A retrospective study.

RESULTS

A total of 1061 hospitalized children were enrolled. Incidences of hyponatremia were not different between patients who received isotonic and hypotonic fluids (29% vs. 31%). Subgroup analysis showed a trend of higher incidence of hyponatremia in patients who received hypotonic fluid than isotonic fluid only in patients admitted to the air-conditioned wards (29% vs. 21%, p = 0.08).

CONCLUSION

Children admitted to the air-conditioned wards who received hypotonic fluid seemed to carry a higher risk of developing hyponatremia than those admitted to the non-air-conditioned ward.

Copeptin and its role in the diagnosis of diabetes insipidus and the syndrome of inappropriate antidiuresis

Copeptin is secreted in an equimolar amount to arginine vasopressin (AVP) but can easily be measured in plasma or serum with a sandwich immunoassay. The main stimuli for copeptin are similar to AVP, that is an increase in osmolality and a decrease in arterial blood volume and pressure. A high correlation between copeptin and AVP has been shown. Accordingly, copeptin mirrors the amount of AVP in the circulation. Copeptin has, therefore, been evaluated as diagnostic biomarker in vasopressin-dependent disorders of body fluid homeostasis. Disorders of body fluid homeostasis are common and can be divided into hyper- and hypoosmolar circumstances: the classical hyperosmolar disorder is diabetes insipidus, while the most common hypoosmolar disorder is the syndrome of inappropriate antidiuresis (SIAD). Copeptin measurement has led to a "revival" of the direct test in the differential diagnosis of diabetes insipidus. Baseline copeptin levels, without prior thirsting, unequivocally identify patients with nephrogenic diabetes insipidus. In contrast, for the difficult differentiation between central diabetes insipidus and primary polydipsia, a stimulated copeptin level of 4.9 pmol/L upon hypertonic saline infusion differentiates these two entities with a high diagnostic accuracy and is clearly superior to the classical water deprivation test. On the contrary, in the SIAD, copeptin measurement is of only little diagnostic value. Copeptin levels widely overlap in patients with hyponatraemia and emphasize the heterogeneity of the disease. Additionally, a variety of factors lead to unspecific copeptin elevations in the acute setting further complicating its interpretation. The broad use of copeptin as diagnostic marker in hyponatraemia and specifically to detect cancer-related disease in SIADH patients can, therefore, not be recommended.

Posterior pituitary dysfunction following traumatic brain injury: review

Neurohypophysial dysfunction is common in the first days following traumatic brain injury (TBI), manifesting as dysnatremia in approximately 1 in 4 patients. Both hyponatremia and hypernatremia can impair recovery from TBI and in the case of hypernatremia, there is a significant association with excess mortality. Hyponatremia secondary to syndrome of inappropriate antidiuretic hormone secretion (SIAD) is the commonest electrolyte disturbance following TBI. Acute adrenocorticotropic hormone (ACTH)/cortisol deficiency occurs in 10-15% of TBI patients and can present with a biochemical picture identical to SIAD. For this reason, exclusion of glucocorticoid deficiency is of particular importance in post-TBI SIAD. Cerebral salt wasting is a rare cause of hyponatremia following TBI. Hyponatremia predisposes to seizures, reduced consciousness, and prolonged hospital stay. Diabetes insipidus (DI) occurs in 20% of cases following TBI; where diminished consciousness is present, appropriate fluid replacement of renal water losses is occasionally inadequate, leading to hypernatremia. Hypernatremia is strongly predictive of mortality following TBI. Most cases of DI are transient, but persistent DI is also predictive of mortality, irrespective of plasma sodium concentration. Persistent DI may herald rising intracranial pressure due to coning. True adipsic DI is rare following TBI, but patients are vulnerable to severe hypernatremic dehydration, exacerbation of neurologic deficits and hypothalamic complications, therefore clinicians should be aware of this possible variant of DI.

Loss of body weight is accompanying cellular brain edema induced by water intoxication in the rat

Induction of cellular cerebral edema (CE) was achieved by a standard method of water intoxication which consisted of fractionated intraperitoneal administration of distilled water (DW) together with the injection of desmopressin (DP). Using metabolic cage, fluid and food balance was studied in two groups of eight animals: group C - control; group CE - cellular edema induced by water intoxication. For each rat the intake (food pellets and water) and excretion (solid excrements and urine) were recorded for 48 h together with the initial and final body weight. CE animals consumed significantly less food, drank less water and eliminated the smallest amount of excrements. The induction of cellular cerebral edema was accompanied with a significant loss of body weight (representing on average 13 % of the initial values) mainly due to a reduction of food intake. This phenomenon has not yet been reported.

Be aware of the effects of glucocorticoids on SIADH: A case report

RATIONALE

Hyponatremia is one of the most common electrolyte disorders in clinic. Due to the complicated etiology and the nonspecific clinical manifestations, the diagnosis of hyponatremia is a complicated process. A variety of clinical disorders can cause inappropriately increased antidiuretic hormone (ADH) secretion, leading to inappropriate water retention and consequent hyponatremia. The most common cause of hyponatremia in hospital inpatients is syndrome of inappropriate antidiuretic (SIADH). The action of glucocorticoid against pituitary posterior lobe can reduce the secretion of ADH. However, the effect of hormone on diuretic hormone during treatment has been less reported.

PATIENT CONCERNS AND DIAGNOSIS

The patient in this case report was misdiagnosed as anterior pituitary hypofunction because of the long-term glucocorticoid therapy was effective in this patient, and the patient was finally diagnosed as SIADH after reassessment. The patient is a 76-year-old male with long-term symptomatic hyponatremia after traumatic brain injury (TBI). The patient has been consistently diagnosed as anterior pituitary hypofunction. Based on the diagnosis, glucocorticoid replacement therapy was administered. The serum sodium of the patient gradually increased to normal level after hydrocortisone intravenous injection but dropped again after switch to hydrocortisone oral administration. Through examination and analysis of the patient status during the five-time hospitalization, syndrome of inappropriate antidiuretic hormone (SIADH) was considered.

INTERVENTIONS

Water intake limitation and oral furosemide and antisterone were administered after glucocorticoid therapy was stopped.

OUTCOME

The serum sodium level of the patient gradually increased and maintained within normal range based on his clinical follow-up.

LESSONS

For hyponatremia with effective glucocorticoid treatment, SIADH should still be excluded.

Syndrome of Inappropriate Antidiuresis

The syndrome of inappropriate antidiuresis (SIAD) is a common cause of hyponatremia in hospitalized children. SIAD refers to euvolemic hyponatremia due to nonphysiologic stimuli for arginine vasopressin production in the absence of renal or endocrine dysfunction. SIAD can be broadly classified as a result of tumors, pulmonary or central nervous system disorders, medications, or other causes such as infection, inflammation, and the postoperative state. The presence of hypouricemia with an elevated fractional excretion of urate can aid in the diagnosis. Treatment options include fluid restriction, intravenous saline solutions, oral sodium supplements, loop diuretics, oral urea, and vasopressin receptor antagonists (vaptans).

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.

Chronic hyponatremia in a patient with renal salt wasting and without cerebral disease: relationship between RSW, risk of fractures and cognitive impairment

Renal salt wasting syndrome (RSW) is defined as a renal loss of sodium leading to hyponatremia and a decrease in extracellular fluid volume (ECV). Differentiation of this disorder from the syndrome of inappropriate antidiuretic hormone secretion (SIADH), a common cause of hyponatremia, can be difficult because both can present with hyponatremia and concentrated urine with natriuresis. Our clinical case about a 78-year-old woman with a recent fracture of the right femur not only confirms that this syndrome can occur in patients without intracranial pathologies (CT documented), but depicts how the hyponatremia caused by RSW can show a chronic, oscillating course. This is an interesting point of view because it suggests to us to consider RSW in the differential diagnosis of patients with chronic hyponatremia.

Determining Fractional Urate Excretion Rates in Hyponatremic Conditions and Improved Methods to Distinguish Cerebral/Renal Salt Wasting From the Syndrome of Inappropriate Secretion of Antidiuretic Hormone

Our evaluation of hyponatremic patients is in a state of confusion because the assessment of the volume status of the patient and determinations of urine sodium concentrations (UNa) >30–40 mEq/L have dominated our approach despite documented evidence of many shortcomings. Central to this confusion is our inability to differentiate cerebral/renal salt wasting (C/RSW) from the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), syndromes with diametrically opposing therapeutic goals. The recent proposal to treat most or all hyponatremic patients makes differentiation even more important and reports of C/RSW occurring without cerebral disease leads to a clinically important proposal to change cerebral to renal salt wasting (RSW). Differentiating SIADH from RSW is difficult because of identical clinical parameters that characterize both syndromes. Determination of fractional urate excretion (FEurate) is central to a new algorithm, which has proven to be superior to current methods. We utilized this algorithm and differences in physiologic response to isotonic saline infusions between SIADH and RSW to evaluate hyponatremic patients from the general medical wards of the hospital. In 62 hyponatremic patients, 17 (27%) had SIADH, 19 (31%) had reset osmostat (RO), 24 (38%) had RSW, 1 due to HCTZ and 1 Addison's disease. Interestingly, 21 of 24 with RSW had no evidence of cerebral disease and 10 of 24 with RSW had UNa < 20 mEqL. We conclude that 1. RSW is much more common than is perceived, 2.the term cerebral salt wasting should be changed to RSW 3. RO should be eliminated as a subclass of SIADH, 4. SIADH should be redefined 5. The volume approach is ineffective and 6. There are limitations to determining UNa, plasma renin, aldosterone or atrial/brain natriuretic peptides. We also present data on a natriuretic peptide found in sera of patients with RSW and Alzheimer's disease.

[Which biological parameters for volemic status estimation?]

INTRODUCTION

Estimation of volemic status can be useful in the diagnosis of some hydro-electrolytic disorders such as hyponatremia and dyskalemia. As a matter of fact, clinical examination and classical biological parameters are not discriminant enough. The aim of this study was to determine the biological parameters that are better correlated to volemic status.

METHOD

Volemic status was established using extracellular fluid volume, measured by apparent distribution of inuline, in non-edematous patients and without cardiac or hepatic insufficiency. Patients were split in three groups according to their extracellular fluid volume: hypovolemic, normovolemic, and hypervolemic. Clinical and biological parameters were compared between the three groups and were correlated to extracellular fluid volume.

RESULTS

Data of 91 explorations were collected. There were no difference between groups regarding clinical parameters, plasma proteins, and urinary sodium excretion. Parameters better correlated to extracellular fluid volume were fasting calcium/creatinine ratio (r=0.51; P<0.0001), fasting urinary pH (r=0.43; P<0.0001), and plasma uric acid (r=-0.39; P=0.002).

CONCLUSION

In addition to uric acid, already proposed as a biological marker to estimate volemic status, fasting calciuria and fasting urinary pH could also be useful.

Endocrine paraneoplastic syndromes in lung cancer

Paraneoplastic syndromes are defined as a combination of clinical disorders associated with malignant diseases that are caused by the secretion of various substances by the tumor without, however, being caused by the direct growth and infiltration of the primary tumor, or due to the development of distant metastases. Despite the fact that lung cancer represents the number one cause of death from cancer worldwide, the new methods of treatment increase patient survival and the incidence of paraneoplastic syndromes. The most important ones of these are humoral hypercalcemia of malignancy, syndrome of inappropriate antidiuretic hormone, hyponatremia of malignancy, ectopic Cushing's syndrome, carcinoid syndrome, and hypoglycemia and are usually a poor prognostic marker. Early diagnosis of those syndromes is achieved using specific criteria and may lead to early diagnosis of the underlying malignancy. It is essential to treat them with the overriding objective of improving the patients' quality of life.

HIV/AIDS-related hyponatremia: an old but still serious problem

Hyponatremia is the most common electrolyte disorder in hospitals. Many medical illnesses, including congestive heart failure, liver failure, renal failure and pneumonia, may be associated with hyponatremia. In addition, hyponatremia in patients with the acquired immunodeficiency syndrome (AIDS) and AIDS-related complex (ARC) was first reported in 1993. The evidence suggests that severe hyponatremia is associated with increased morbidity and mortality in human immunodeficiency virus (HIV)/AIDS patients; however, the incidence of hyponatremic syndrome in HIV/AIDS patients remains very high in clinical practice, as almost 40% of HIV/AIDS inpatients in Xinjiang, a developing region of China, are hyponatremic. A method for identifying the pathogenesis and therapeutic treatments for hyponatremia in HIV/AIDS patients is needed. This review focuses on the clinical and pathophysiological aspects of hyponatremia and highlights the causes, presentation and treatment recommendations for hyponatremic patients with HIV/AIDS.

Endocrinopathy-induced euvolemic hyponatremia

Euvolemic hyponatremia results from either the syndrome of inappropriate antidiuretic hormone secretion (SIADH), hypothyroidism, or adrenal insufficiency. Furthermore, the criteria for diagnosis of SIADH entail the exclusion of hypothyroidism and hypoadrenalism. We aim to assess the yield of euvolemic hyponatremia workup focusing on underlying endocrinopathies in a real-world setting. A single-center retrospective study includes all patients diagnosed with euvolemic hyponatremia in a tertiary hospital between 1.1.2007 and 1.1.2013. Demographic, clinical, and laboratory data were collected from medical charts. Euvolemic hyponatremia was detected in 564 patients. Thyroid function was tested in 69% (391/564) and adrenal function was assessed in 29% (164/564) of cases. Endocrinopathy-induced euvolemic hyponatremia was diagnosed in nine (1.6%) patients: three patients were diagnosed with hypothyroidism-induced hyponatremia, three with adrenal insufficiency as an underlying cause, and three with central hypothyroidism and central hypoadrenalism. All nine had medical history and symptoms suggestive of endocrine deficiencies other than the hyponatremia, which resolved within 1-3 days after administration of hormone replacement therapy. Yield of performed workup for hypothyroidism and hypoadrenalism in euvolemic hyponatremia was low. However, in this real-world study, only a limited number of patients underwent a full ascertainment of hypoadrenalism and hypothyroidism, which was diagnosed only in patients with additional findings supportive of these endocrinopathies; a higher rate of undiagnosed endocrinopathies cannot be ruled out. As both hypoadrenalism and hypothyroidism are easily treatable, potentially life-threatening conditions, there are insufficient data to change current recommendation for their universal evaluation in patients with euvolemic hyponatremia.

Hyponatremia in neuromyelitis optica spectrum disorders: Literature review

Hyponatremia is a potentially serious electrolyte abnormality observed in neuromyelitis optica spectrum disorders (NMOSDs), and its most common cause is syndrome of inappropriate antidiuretic hormone secretion (SIADH). Another potential cause of hyponatremia is cerebral salt-wasting syndrome (CSWS), although CSWS has not previously been reported in NMOSDs. Accurate and early differentiation between SIADH and CSWS is difficult. However, the two conditions have important implications for the selection of therapy. Here, we describe two patients with aquaporin-4 antibody (AQP4-Ab)-positive NMOSDs who developed hyponatremia as a result of CSWS and SIADH, respectively. Additionally, we review all previously reported studies of hyponatremia in patients with NMOSDs and propose several potential pathophysiological mechanisms of hyponatremia. In conclusion, NMOSDs accompanied by hyponatremia are not actually rare, but have previously been given little attention. Furthermore, SIADH should not be the only consideration, before the exclusion of rare but significant CSWS.

Using Electrolyte Free Water Balance to Rationalize and Treat Dysnatremias

Dysnatremias or abnormalities in plasma [Na+] are often termed disorders of water balance, an unclear physiologic concept often confused with changes in total fluid balance. However, most clinicians clearly recognize that hypertonic or hypotonic gains or losses alter plasma [Na+], while isotonic changes do not modify plasma [Na+]. This concept can be conceptualized as the electrolyte free water balance (EFWB), which defines the non-isotonic components of inputs and outputs to determine their effect on plasma [Na+]. EFWB is mathematically proportional to the rate of change in plasma [Na+] (dPNa/dt) and, therefore, is actively regulated to zero so that plasma [Na+] remains stable at its homeostatic set point. Dysnatremias are, therefore, disorders of EFWB and the relationship between EFWB and dPNa/dt provides a rationale for therapeutic strategies incorporating mass and volume balance. Herein, we leverage dPNa/dt as a desired rate of correction of plasma [Na+] to define a stepwise approach for the treatment of dysnatremias.

High Prevalence of Renal Salt Wasting Without Cerebral Disease as Cause of Hyponatremia in General Medical Wards

BACKGROUND

The approach to hyponatremia is in a state of flux, especially in differentiating syndrome of inappropriate antidiuretic hormone secretion (SIADH) from cerebral-renal salt wasting (RSW) because of diametrically opposite therapeutic goals. Considering RSW can occur without cerebral disease, we determined the prevalence of RSW in the general hospital wards.

METHODS

To differentiate SIADH from RSW, we used an algorithm based on fractional excretion (FE) of urate and nonresponse to saline infusions in SIADH as compared to excretion of dilute urines and prompt increase in serum sodium in RSW.

RESULTS

Of 62 hyponatremic patients, (A) 17 patients (27%) had SIADH, 11 were nonresponsive to isotonic saline, and 5 normalized a previously high FEurate after correction of hyponatremia; (B) 19 patients (31%) had a reset osmostat based on normal FEurates and spontaneously excreted dilute urines; (C) 24 patients (38%) had RSW, 21 had no clinical evidence of cerebral disease, 19 had saline-induced dilute urines; 2 had undetectable plasma ADH levels when urine was dilute, 10 required 5% dextrose in water to prevent rapid increase in serum sodium, 11 had persistently increased FEurate after correction of hyponatremia and 10 had baseline urinary sodium < 20 mEq/L; (D) 1 patient had Addison disease with a low FEurate and (E) 1 patient (1.6%) had hyponatremia due to hydrochlorothiazide.

CONCLUSIONS

Of the 24 patients with RSW, 21 had no cerebral disease, supporting our proposal to change cerebral-renal salt wasting to renal salt wasting. Application of established pathophysiological standards and a new algorithm based on determination of FEurate were superior to the volume approach for determination of urinary sodium when identifying the cause of hyponatremia.

A Rare Presentation of the Syndrome of Inappropriate Antidiuretic Hormone in a 12-Year-Old Girl as the Initial Presentation of an Immature Ovarian Teratoma

BACKGROUND

Immature ovarian teratoma is very rare in childhood. We report on a 12-year-old girl with immature ovarian teratoma who presented initially with syndrome of inappropriate antidiuretic hormone.

CASE

A 12-year-old girl presented with acute abdomen and distention. Initial laboratory tests showed hyponatremia (sodium, 123 mmol/L), that did not respond to fluid management. Computed tomography imaging showed a 15 cm × 9 cm × 20 cm mass in the right ovary with multifocal internal fat, and dystrophic calcifications. She underwent exploratory laparotomy with a right salpingo-oophorectomy, omentectomy, and peritoneal stripping. The pathology revealed metastatic immature teratoma. Hyponatremia resolved soon after the surgery.

SUMMARY AND CONCLUSION

Although a rare diagnosis, immature ovarian teratoma must be considered in a girl who presents with abdominal mass and hyponatremia.

Basaloid Squamous Cell Carcinoma of the Lung Associated With Syndrome of Inappropriate Antidiuretic Hormone Secretion

Basaloid squamous cell carcinoma (BSQCC) of the lung is a very rare subtype of squamous cell carcinoma (SCC). There have been no reported cases of syndrome of inappropriate anti-diuretic hormone secretion (SIADH) developing concurrently with this tumor. We herein present a case of a 68-year-old female who was diagnosed with lung mass discovered incidentally on preoperative clearance for surgical fixation of right humeral neck fracture. The patient presented to the hospital with nausea, vomiting, diarrhea and fatigue. Sodium level on admission was 115 mmol/L. Further workup confirmed a diagnosis of BSQCC of the lung and SIADH.

Psychotropics and hyponatraemia

Hyponatraemia is usually defined as a serum sodium concentration below 135 mmol/1. The condition is rarely symptomatic until serum sodium falls below 120 mmol/1 and symptoms are more usually associated with values around 110 mmol/1. These symptoms include confusion and restlessness, progressing to drowsiness, myoclonic jerks, generalised convulsions and eventually coma. In a general hospital population about 1% of patients develop hyponatraemia (Rutsky, 1992), whereas in psychiatric patients the prevalence has been reported to range from 3.3% to 12.2% (Ohsawa et al, 1992).

Syndrome of inappropriate anti-diuresis induces volume-dependent hypercalciuria

Hyponatremia is associated with bone demineralization. We hypothesized that, during hyponatremia, calciuria and calcium balance depend on volemic status. We evaluated calciuria in patients with hyponatremia, secondary to SIAD or hypovolemia. Patients with SIAD exhibited a volemic expansion that was associated with hypercalciuria. Calciuria was proportional to markers of volemia.

INTRODUCTION

Chronic mild hyponatremia has been associated with bone demineralization of unknown mechanisms. During chronic hyponatremia, arginine-vasopressin secretion can result from hypovolemia or from syndrome of inappropriate anti-diuresis (SIAD) that leads to a slightly volemic expansion. Since volemia determines renal calcium excretion and balance, we evaluated calcium homeostasis in patients with chronic hyponatremia, related to SIAD or to hypovolemia.

METHODS

We retrospectively included all patients referred to our Department between May 2006 and May 2014 for hyponatremia, resulting from SIAD or chronic hypovolemia. None had edema, cirrhosis, cardiac, or renal insufficiency. Exploration included estimation of volemia, extracellular fluid volume (ECFV) measurement with inulin, and calcium homeostasis.

RESULTS

In total, the SIAD and hypovolemic groups included 22 and 7 patients, respectively. The SIAD group exhibited signs of increased volemia: higher glomerular filtration rate, higher fractional excretion of uric acid, and lower plasma renin. ECFV exceeded that of the hypovolemic group and was above usual values. There was no difference between the two groups regarding plasma calcium, PTH, and vitamin D. However, in the SIAD group, calciuria was higher than in the hypovolemic group, reaching levels of hypercalciuria. Furthermore, there was a positive correlation between calciuria and markers of volemia.

CONCLUSIONS

Our results show that SIAD results in a volemic expansion tendency that is associated with a decrease in renal calcium reabsorption and thus hypercalciuria, whereas in the hypovolemic group, calciuria was not increased. Therefore, renal loss of calcium and bone demineralization in SIAD patients could be partly induced by volemic expansion.

Managing hyponatremia in lung cancer: latest evidence and clinical implications

Hyponatremia is the most common electrolyte disorder in lung cancer patients. This condition may be related to many causes including incidental medications, concurrent diseases and side effects of antineoplastic treatments or the disease itself. Although not frequently life-threatening, it is usually associated with prolonged hospitalization, delays in scheduled chemotherapy, worsening of patient performance status and quality of life and may also negatively affect treatment response and survival. Most of the available data focus on thoracic tumors, especially small-cell lung cancer (SCLC), where hyponatremia is frequently related to the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Few studies specifically focus on non-small cell lung cancer (NSCLC) patients. Hyponatremia treatment needs to be personalized based on severity and duration of sodium serum reduction, extracellular fluid volume and etiology. However, literature data highlight the importance of early correction of the serum concentration levels. To achieve this the main options are fluid restriction, hypertonic saline, loop diuretics, isotonic saline, tolvaptan and urea. The aim of this review is to analyze the role of hyponatremia in lung cancer patients, evaluating causes, diagnosis, management and clinical implications.

Electrolyte Disorders Associated with Cancer

Cancer patients frequently suffer electrolyte abnormalities that complicate the management of their condition. The most commonly occurring derangement is hyponatremia, while hypercalcemia, hypokalemia, and hypophosphatemia are also encountered. The etiology of these abnormalities is often identifiable, and early diagnosis and management can prevent delays in necessary anti-cancer therapies.

[Hyponatremia in emergency admissions - often dangerous]

Hyponatremia is the most common electrolyte disorder in clinical practice and associated with increased morbidity and mortality, independent of underlying disease. Untreated acute hyponatremia can cause substantial morbidity and mortality as a result of osmotically induced cerebral edema whilst over rapid correction of chronic hyponatremia can cause serious neurologic impairment and death resulting from osmotic demyelination. Still hyponatremia is often neglected and insufficiently addressed, most likely due to limited understanding of its pathophysiological mechanisms. Being familiar with only few basic principles of body fluid regulation may be a worthwhile investment into the clinical career and save patients' lives.

Bortezomib as a probable cause of the syndrome of inappropriate antidiuretic hormone secretion: A case report and review of the literature

Bortezomib is a proteasome inhibitor that has been widely adopted for the treatment of hematological malignancies, including multiple myeloma and lymphoma, and has been considered significantly more tolerable compared with traditional chemotherapeutic drugs. Bortezomib has some potential side effects that involve a number of systems, including the gastrointestinal, hematological, nervous and musculoskeletal systems; however, involvement of the endocrine system is rare. We herein report the case of a patient treated for multiple myeloma who developed the syndrome of inappropriate antidiuretic hormone secretion after bortezomib was added to his chemotherapy regimen. Following treatment with an infusion of hypertonic saline and fluid restriction for >2 months, the serum sodium level gradually recovered.

Medication-induced SIADH: distribution and characterization according to medication class

AIMS

The aims of the current study were to determine the distribution of aetiologies for the drug-induced syndrome of inappropriate antidiuretic hormone secretion (SIADH) in hospitalized patients, and to characterize them according to the different drug groups.

METHODS

A single-centre retrospective study was carried out, including all patients diagnosed with SIADH in a large community hospital and tertiary centre between 1 January 2007 and 1 January 2013 who were treated with drugs known to be associated with SIADH. Two physicians reviewed every patient's medical file for predetermined relevant clinical data.

RESULTS

The study cohort included 198 patients who had SIADH and received drugs associated with SIADH. Most patients [146 (73.7%)] were diagnosed with drug-associated SIADH, while 52 (26.3%) were diagnosed with SIADH due to other aetiologies. The Naranjo algorithm differentiated well between the two groups (P < 0.001). Five drug classes (antidepressants, anticonvulsants, antipsychotic agents, cytotoxic agents and pain medications) were implicated in 82.3% of patients diagnosed with drug-associated SIADH. Specific serotonin reuptake inhibitors and carbamazepine were commonly implicated. There were no clinically significant differences in the characteristics or severity of SIADH according to drug class.

CONCLUSIONS

The clinical characteristics of SIADH caused by different drugs are comparable. Patients with SIADH treated with drugs from five common medication classes will probably be diagnosed with drug-induced SIADH. Physicians should be aware of the significance of these medication classes as SIADH aetiologies.

Hyponatraemia diagnosis and treatment clinical practice guidelines

Hyponatremia, defined as a serum sodium concentration <135mmol/l, is the most common water-electrolyte imbalance encountered in clinical practice. It can lead to a wide spectrum of clinical symptoms, from mild to severe or even life threatening, and is associated with increased mortality, morbidity and length of hospital stay. Despite this, the management of hyponatremia patients remains problematic. The prevalence of hyponatremia in a wide variety of conditions and the fact that hyponatremia is managed by clinicians with a broad variety of backgrounds have fostered diverse institution- and specialty-based approaches to diagnosis and treatment. To obtain a common and holistic view, the European Society of Intensive Care Medicine (ESICM), the European Society of Endocrinology (ESE) and the European Renal Association-European Dialysis and Transplant Association (ERA-EDTA), represented by European Renal Best Practice (ERBP), have developed clinical practice guidelines on the diagnostic approach and treatment of hyponatremia as a joint venture of 3societies representing specialists with a natural interest in hyponatremia. In addition to a rigorous approach to the methodology and evaluation of the evidence, the document focuses on patient-positive outcomes and on providing a useful tool for clinicians involved in everyday practice. In this article, we present an abridged version of the recommendations and suggestions for the diagnosis and treatment of hyponatremia extracted from the full guide.

Thiazide-Associated Hyponatremia, Report of the Hyponatremia Registry: An Observational Multicenter International Study

BACKGROUND

Hyponatremia is a frequent and potentially life-threatening adverse side effect of thiazide diuretics. This sub-analysis of the Hyponatremia Registry database focuses on current management practices of thiazide-associated hyponatremia (TAH) and compares differences between TAH and syndrome of inappropriate antidiuretic hormone secretion (SIADH).

METHODS

We analyzed 477 patients from 225 US and EU sites with euvolemic hyponatremia ([Na+] ≤130 mEq/L) who were receiving a thiazide diuretic. Of these, 118 met criteria for true thiazide-induced hyponatremia (TIH).

RESULTS

Thiazide was withdrawn immediately after hyponatremia was diagnosed only in 57% of TAH; in these patients, the median rate of [Na+] change (Δdaily[Na+]) was significantly higher than those with continued thiazide treatment (3.8 [interquartile range: 4.0] vs. 1.7 [3.8] mEq/L/day). The most frequently employed therapies were isotonic saline (29.6%), fluid restriction (19.9%), the combination of these two (8.2%), and hypertonic saline (5.2%). Hypertonic saline produced the greatest Δdaily[Na+] (8.0[6.4] mEq/L/day) followed by a combination of fluid restriction and normal saline (4.5 [3.8] mEq/L/day) and normal saline alone (3.6 [3.5] mEq/L/day). Fluid restriction was markedly less effective (2.7 [2.7] mEq/L/day). Overly rapid correction of hyponatremia occurred in 3.1% overall, but in up to 21.4% given hypertonic saline. Although there are highly significant differences in the biochemical profiles between TIH and SIADH, no predictive diagnostic test could be derived.

CONCLUSIONS

Despite its high incidence and potential risks, the management of TAH is often poor. Immediate withdrawal of the thiazide is crucial for treatment success. Hypertonic saline is most effective in correcting hyponatremia but associated with a high rate of overly rapid correction. We could not establish a diagnostic laboratory-based test to differentiate TIH from SIADH.

Neurologic Intensive Care Unit Electrolyte Management

Dysnatremia is a common finding in the intensive care unit (ICU) and may be a predictor for mortality and poor clinical outcomes. Depending on the time of onset (ie, on admission vs later in the ICU stay), the incidence of dysnatremias in critically ill patients ranges from 6.9% to 15%, respectively. The symptoms of sodium derangement and their effect on brain physiology make early recognition and correction paramount in the neurologic ICU. Hyponatremia in brain injured patients can lead to life-threatening conditions such as seizures and may worsen cerebral edema and contribute to alterations in intracranial pressure.

Application of established pathophysiologic processes brings greater clarity to diagnosis and treatment of hyponatremia

Hyponatremia, serum sodium < 135 mEq/L, is the most common electrolyte abnormality and is in a state of flux. Hyponatremic patients are symptomatic and should be treated but our inability to consistently determine the causes of hyponatremia has hampered the delivery of appropriate therapy. This is especially applicable to differentiating syndrome of inappropriate antidiuresis (SIAD) from cerebral salt wasting (CSW) or more appropriately, renal salt wasting (RSW), because of divergent therapeutic goals, to water-restrict in SIAD and administer salt and water in RSW. Differentiating SIAD from RSW is extremely difficult because of identical clinical parameters that define both syndromes and the mindset that CSW occurs rarely. It is thus insufficient to make the diagnosis of SIAD simply because it meets the defined characteristics. We review the pathophysiology of SIAD and RSW, the evolution of an algorithm that is based on determinations of fractional excretion of urate and distinctive responses to saline infusions to differentiate SIAD from RSW. This algorithm also simplifies the diagnosis of hyponatremic patients due to Addison’s disease, reset osmostat and prerenal states. It is a common perception that we cannot accurately assess the volume status of a patient by clinical criteria. Our algorithm eliminates the need to determine the volume status with the realization that too many factors affect plasma renin, aldosterone, atrial/brain natriuretic peptide or urine sodium concentration to be useful. Reports and increasing recognition of RSW occurring in patients without evidence of cerebral disease should thus elicit the need to consider RSW in a broader group of patients and to question any diagnosis of SIAD. Based on the accumulation of supporting data, we make the clinically important proposal to change CSW to RSW, to eliminate reset osmostat as type C SIAD and stress the need for a new definition of SIAD.

Euvolemic hyponatremia in cancer patients. Report of the Hyponatremia Registry: an observational multicenter international study

Purpose

Hyponatremia secondary to SIADH is frequent in cancer patients and potentially deleterious. The aim of this sub-analysis of the Hyponatremia Registry database is to analyze current diagnostic and therapeutic management practices in cancer patients with SIADH.

Methods

We analyzed 358 cancer patients who had serum sodium concentration ([Na⁺]) ≤ 130 mEq/L and a clinical diagnosis of SIADH from 225 sites in the USA and EU.

Results

Precise diagnostic testing was performed in only 46%. Almost 12% of all patients did not receive any hyponatremia treatment. The most frequent therapies were fluid restriction (20%), isotonic saline (14%), fluid restriction/isotonic saline (7%), tolvaptan (8%), and salt tablets (7%). Hypertonic saline was used in less than 3%. Tolvaptan produced the greatest median rate of [Na⁺] change (IQR) (3.0 (4.7) mEq/L/day), followed by hypertonic saline (2.0(7.0) mEq/L/day), and fluid restriction/isotonic saline (1.9(3.2) mEq/L/day). Both fluid restriction and isotonic saline monotherapies were significantly less effective (0.8(2.0) mEq/L/day and 1.3(3.0) mEq/L/day, respectively) and were associated with clinically relevant rates of treatment failure. Only 46% of patients were discharged with [Na⁺] ≥ 130 mEq/L. Overly rapid correction of hyponatremia occurred in 11.7%.

Conclusions

Although essential for successful hyponatremia management, appropriate diagnostic testing is not routinely performed in current practice. The most frequently employed monotherapies were often ineffective and sometimes even aggravated hyponatremia. Tolvaptan was used less often but showed significantly greater effectiveness. Despite clear evidence that hyponatremia is associated with poor outcome in oncology patients, most patients were discharged still hyponatremic. Further studies are needed to assess the beneficial impact of hyponatremia correction with effective therapies.

Electronic supplementary material

The online version of this article (doi:10.1007/s00520-017-3638-3) contains supplementary material, which is available to authorized users.

Evaluation of copeptin and commonly used laboratory parameters for the differential diagnosis of profound hyponatraemia in hospitalized patients: 'The Co-MED Study'

OBJECTIVE

Hyponatraemia is common and its differential diagnosis is challenging. Commonly used diagnostic algorithms have limited diagnostic accuracy. Copeptin, the c-terminal portion of the precursor peptide of arginine vasopressin might help in the differential diagnosis of hyponatraemia.

DESIGN

Prospective multicentre observational study.

PATIENTS/METHODS

A total of 298 patients admitted with profound hypoosmolar hyponatraemia (Na < 125 mmol/l) were evaluated. Three experts uninvolved in the patients' care determined the aetiology of hyponatraemia after standardized diagnostic evaluation.

RESULTS

Hyponatraemia differential diagnoses were as follows: syndrome of inappropriate antidiuresis (SIAD), 106 patients (35·6%); 'diuretic-induced', 72 (24·2%); 'hypovolaemic', 59 (19·8%); 'hypervolaemic', 33 (11·1%); primary polydipsia (PP), 24 (8·1%); and cortisol deficiency, 4 (1·3%). Copeptin levels <3·9 pmol/l identified patients with PP with high specificity (91%). Further, copeptin levels >84 pmol/l were highly predictive for hypovolaemic hyponatraemia (specificity: 90%). Urinary sodium levels and copeptin/urinary sodium ratio in patients with SIAD were higher and lower as compared to other hyponatraemia aetiologies (P < 0·0001). However, the specificity to identify SIAD was moderate for both parameters (31% and 61%). Fractional uric acid excretion (FE_UA ) and fractional urea excretion (FE_urea ) were higher in patients with SIAD compared to other hyponatraemia aetiologies (both P < 0·0001). FE_urea values >55% and FE_UA values >12% had a specificity of 96% and 77% to detect patients with SIAD. These results remained similar after excluding patients taking diuretics.

CONCLUSIONS

Overall, there is only limited diagnostic utility of copeptin in the differential diagnosis of profound hyponatraemia. Very low copeptin levels are seen in patients with PP and highest copeptin levels in hypovolaemic hyponatraemia. To discriminate between SIAD and other hyponatraemia aetiologies, FE_urea and FE_UA levels are valuable irrespective of diuretics use.

Clinical aspects of changes in water and sodium homeostasis in the elderly

The population of elderly individuals is increasing worldwide. With aging, various hormonal and kidney changes occur, both affecting water homeostasis. Aging is a risk factor for chronic kidney disease (CKD) and many features of CKD are reproduced in the aging kidney. Dehydration and hyperosmolarity can be triggered by diminished thirst perception in this population. Elderly with dementia are especially susceptible to abnormalities of their electrolyte and body water homeostasis and should be (re-)assessed for polypharmacy. Hypo- and hypernatremia can be life threatening and should be diagnosed and treated promptly, following current practice guidelines. In severe cases of acute symptomatic hyponatremia, a rapid bolus of 100 to 150 ml of intravenous 3% hypertonic saline is appropriate to avert catastrophic outcomes; for asymptomatic hyponatremia, a very gradual correction is preferred. In summary, the body sodium (Na+) balance is regulated by a complex interplay of environmental and individual factors. In this review, we attempt to provide an overview on this topic, including dehydration, hyponatremia, hypernatremia, age-related kidney changes, water and sodium balance, and age-related changes in the vasopressin and renin-angiotensin-aldosterone system.

Syndrome of Inappropriate Antidiuretic Hormone Secretion Associated with Amyotrophic Lateral Sclerosis in a Patient Developing Carbon Dioxide Narcosis

We report a rare case of syndrome of inappropriate antidiuretic hormone secretion (SIADH) associated with amyotrophic lateral sclerosis (ALS). A 69-year-old man was admitted to our hospital with sustained hyponatremia. Hyposmolality with elevated urinary osmolality and sodium excretion was observed, which indicated SIADH. The treatment for SIADH was challenging; the patient developed carbon dioxide narcosis, which led to the diagnosis of ALS. After the initiation of noninvasive positive-pressure ventilation, the patient's serum sodium concentration normalized and became stable. Thus, ALS should be recognized as a possible cause of SIADH in the clinical setting.

Predictors of nonresponse to fluid restriction in hyponatraemia due to the syndrome of inappropriate antidiuresis

BACKGROUND

Fluid restriction (FR), the first-line treatment for hyponatraemia due to the syndrome of inappropriate antidiuresis (SIAD), often does not lead to successful correction of hyponatraemia. Therefore, predictive markers of treatment response are desirable. We evaluated routinely measured serum (s) and urine (u) parameters, s-copeptin and s-mid-regional pro-atrial natriuretic peptide (s-MR-proANP), as possible predictors of FR response.

METHODS

In this prospective observational study, we included patients with profound hyponatraemia (s-sodium <125 mmol L^-1 ) due to SIAD. Patients were classified as FR responders (increase in s-sodium concentration of >3 mmol L^-1 within 24 h) or nonresponders (increase of ≤3 mmol L^-1 within 24 h). Initial laboratory parameters were compared between groups with logistic regression analysis.

RESULTS

Of 106 SIAD patients analysed, 82 underwent treatment with FR; 48 (59%) patients showed a successful response to FR and 34 (41%) were considered nonresponders. High levels of u-sodium and u-osmolality were significantly associated with nonresponse to FR [odds ratio (OR) 15.0, 95% confidence interval (CI) 2.4-95.8, P = 0.004 and OR 34.8, 95% CI 1.2-1038.8, P = 0.041, respectively). The association of u-sodium and nonresponse remained significant also after adjustment for diuretic use. Lower levels of s-MR-proANP were associated with nonresponse (OR 0.03, 95% CI 0.003-0.3, P = 0.004), whereas s-copeptin was not significantly associated with response to FR.

CONCLUSION

Easily measured laboratory parameters, especially u-sodium, correlate with therapeutic response and identify patients most likely to fail to respond to FR. Measurement of these parameters may facilitate early treatment choice in patients with SIAD.

Malignancy associated SIADH: Characterization and clinical implications

PURPOSE

To determine the distribution of etiologies for the syndrome of inappropriate antidiuretic hormone secretion (SIADH) in hospitalized patients with active malignancies and to characterize them according to the different etiologies.

METHODS

A single center retrospective study including all patients with active malignancies diagnosed with SIADH in a large community hospital and tertiary center between 1 January 2007 and 1 January 2013. Two physicians reviewed every patient's medical file for predetermined relevant clinical data.

RESULTS

The study cohort included 204 patients. 74.4% of those with solid tumors had metastatic disease. Most patients (149, 73%) had malignancy associated SIADH, while 55 (27%) had SIADH due to other etiologies. All of the major malignancy types were implicated in SIADH. Patients with breast cancer without lung or brain involvement were significantly less likely to be diagnosed with malignancy associated SIADH compared with other malignancies [Odds ratio (OR) 0.031, 95% CI 0.003-0.25, p < 0.001]. Patients with malignancy associated SIADH had lower serum sodium concentrations on short-term follow-up (p = 0.024) and significantly shorter median survival (58 vs. 910 days, p < 0.001). Short-term hyponatremia correction was associated with better survival.

CONCLUSIONS

SIADH is associated with most malignancy types. Physicians caring for patients with breast cancer without lung or brain involvement diagnosed with SIADH without an obvious etiology should consider obtaining lung and brain imaging to rule out undiagnosed metastatic spread. Patients with malignancy associated SIADH have considerably worse outcomes compared to cancer patient with SIADH due to other etiologies. Short-term sodium concentration can be used as a prognostic marker for these patients.