Diagnostic approach to a patient with hyponatraemia: traditional versus physiology-based options

Chloride and Potassium Assessment Is a Helpful Tool for Differential Diagnosis of Thiazide-Associated Hyponatremia

CONTEXT

Differential diagnosis of thiazide-associated hyponatremia (TAH) is challenging. Patients can either have volume depletion or a syndrome of inappropriate antidiuresis (SIAD)-like presentation.

OBJECTIVE

To evaluate the impact of the simplified apparent strong ion difference in serum (aSID; sodium + potassium - chloride) as well as the urine chloride and potassium score (ChU; chloride - potassium in urine) in the differential diagnosis of TAH, in addition to assessment of fractional uric acid excretion (FUA).

METHODS

Post hoc analysis of prospectively collected data from June 2011 to August 2013 from 98 hospitalized patients with TAH < 125 mmol/L enrolled at University Hospital Basel and University Medical Clinic Aarau, Switzerland. Patients were categorized according to treatment response in volume-depleted TAH requiring volume substitution or SIAD-like TAH requiring fluid restriction. We computed sensitivity analyses with ROC curves for positive predictive value (PPV) and negative predictive value (NPV) of aSID, ChU, and FUA in differential diagnosis of TAH.

RESULTS

An aSID > 42 mmol/L had a PPV of 79.1% in identifying patients with volume-depleted TAH, whereas a value < 39 mmol/L excluded it with a NPV of 76.5%. In patients for whom aSID was inconclusive, a ChU < 15 mmol/L had a PPV of 100% and a NPV of 83.3%, whereas FUA < 12% had a PPV of 85.7% and a NPV of 64.3% in identifying patients with volume-depleted TAH.

CONCLUSION

In patients with TAH, assessment of aSID, potassium, and chloride in urine can help identifying patients with volume-depleted TAH requiring fluid substitution vs patients with SIAD-like TAH requiring fluid restriction.

Consensus document on the management of hyponatraemia of the Acqua Group of the Spanish Society of Endocrinology and Nutrition

INTRODUCTION

Hyponatremia is the most prevalent electrolyte disorder in the outpatient and inpatient settings. Despite this frequency, hyponatremia, including severe hyponatremia, is frequently underestimated and inadequately treated, thus highlighting the need to produce consensus documents and clinical practice guidelines geared towards improving the diagnostic and therapeutic approach to it in a structured fashion.

MATERIAL AND METHODS

Members of the Acqua Group of the Spanish Society of Endocrinology and Nutrition (SEEN) met using a networking methodology over a period of 20 months (between October 2019 and August 2021) with the aim of discussing and developing an updated guideline for the management of hyponatraemia. A literature search of the available scientific evidence for each section presented in this document was performed.

RESULTS

A document with 8 sections was produced, which sets out to provide updated guidance on the most clinically relevant questions in the management of hyponatraemia. The management of severe hyponatraemia is based on the i.v. administration of a 3% hypertonic solution. For the management of chronic euvolemic hyponatraemia, algorithms for the initiation of treatment with the two pharmacological therapeutic options currently available in Spain are presented: urea and tolvaptan.

CONCLUSIONS

This document sets out to simplify the approach to and the treatment of hyponatraemia, making it easier to learn and thus improve the clinical approach to hyponatremia.

Differential diagnosis of hyponatremia and hypernatremia

Dysnatremias are among the most common mineral imbalances encountered in clinical practice. Both hyponatremia and hypernatremia are associated with increased morbiditidy and mortality and represent negative prognostic factors regardless of their cause. Serum osmolality, extracellular fluid volume and sodium urine concentration are important parameters for evaluation the cause and differential diagnosis. The rate of onset of ionic disorder and severity of clinical symptoms are essential. While acute disorders with symptoms are treated immediately, in chronic disorders, thorough diagnostic evaluation and a careful approach to their correction are necessary. Especially with rapid substitution of chronic hyponatremia, there is a risk of osmotic demyelination syndrome. Therefore, a slow correction of the serum sodium level with frequent mineralogram checks is required.

Approach to the Patient: Hyponatremia and the Syndrome of Inappropriate Antidiuresis (SIAD)

Hyponatremia is the most common electrolyte disturbance seen in clinical practice, affecting up to 30% of acute hospital admissions, and is associated with significant adverse clinical outcomes. Acute or severe symptomatic hyponatremia carries a high risk of neurological morbidity and mortality. In contrast, chronic hyponatremia is associated with significant morbidity including increased risk of falls, osteoporosis, fractures, gait instability, and cognitive decline; prolonged hospital admissions; and etiology-specific increase in mortality. In this Approach to the Patient, we review and compare the current recommendations, guidelines, and literature for diagnosis and treatment options for both acute and chronic hyponatremia, illustrated by 2 case studies. Particular focus is concentrated on the diagnosis and management of the syndrome of inappropriate antidiuresis. An understanding of the pathophysiology of hyponatremia, along with a synthesis of the duration of hyponatremia, biochemical severity, symptomatology, and blood volume status, forms the structure to guide the appropriate and timely management of hyponatremia. We present 2 illustrative cases that represent common presentations with hyponatremia and discuss the approach to management of these and other causes of hyponatremia.

Changes in Serum Creatinine Levels Can Help Distinguish Hypovolemic from Euvolemic Hyponatremia

Background and Objectives: Differentiating between hypovolemic (HH) and euvolemic hyponatremia (EH) is crucial for correct diagnosis and therapy, but can be a challenge. We aim to ascertain whether changes in serum creatinine (SC) can be helpful in distinguishing HH from EH. Materials and Methods: Retrospective analysis of patients followed in a monographic hyponatremia outpatient clinic of a tertiary hospital during 1 January 2014−30 November 2019. SC changes during HH and EH from eunatremia were studied. The diagnostic accuracy of the SC change from eunatremia to hyponatremia (∆SC) was analyzed. Results: A total of 122 hyponatremic patients, median age 79 years (70−85), 46.7% women. In total, 70/122 patients had EH, 52/122 HH. During hyponatremia, median SC levels increased in the HH group: +0.18 mg/dL [0.09−0.39, p < 0.001], but decreased in the EH group: −0.07 mg/dL (−0.15−0.02, p < 0.001), as compared to SC in eunatremia. HH subjects presented a higher rate of a positive ∆SC than EH (90.4% vs. 25.7%, p < 0.001). EH subjects presented a higher rate of a negative/null ∆SC than HH (74.3% vs. 9.6%, p < 0.001). ROC curve analysis found an AUC of 0.908 (95%CI: 0.853 to 0.962, p < 0.001) for ∆SC%. A ∆SC% ≥ 10% had an OR of 29.0 (95%CI: 10.3 to 81.7, p < 0.001) for HH. A ∆SC% ≤ 3% had an OR of 68.3 (95%CI: 13.0 to 262.2, p < 0.001) for EH. Conclusions: The assessment of SC changes from eunatremia to hyponatremia can be useful in distinguishing between HH and EH.

Drinking to death: Hyponatraemia induced by synthetic phenethylamines

Synthetic phenethylamines are widely abused drugs, comprising new psychoactive substances such as synthetic cathinones, but also well-known amphetamines such as methamphetamine and 3,4-methylenedioxymethamphetamine (MDMA, ecstasy). Cathinones and amphetamines share many toxicodynamic mechanisms. One of their potentially life-threatening consequences, particularly of MDMA, is serotonin-mediated hyponatraemia. Herein, we review the state of the art on phenethylamine-induced hyponatremia; discuss the mechanisms involved; and present the preventive and therapeutic measures. Hyponatraemia mediated by phenethylamines results from increased secretion of antidiuretic hormone (ADH) and consequent kidney water reabsorption, additionally involving diaphoresis and polydipsia. Data for MDMA suggest that acute hyponatraemia elicited by cathinones may also be a consequence of metabolic activation. The literature often reveals hyponatraemia-associated complications such as cerebral oedema, cerebellar tonsillar herniation and coma that may evolve to a fatal outcome, particularly in women. Ready availability of fluids and the recommendation to drink copiously at the rave scene to counteract hyperthermia, often precipitate water intoxication. Users should be advised about the importance of controlling fluid intake while using phenethylamines. At early signs of adverse effects, medical assistance should be promptly sought. Severe hyponatraemia (<130 mmol sodium/L plasma) may be corrected with hypertonic saline or suppression of fluid intake. Also, clinicians should be made aware of the hyponatraemic potential of these drugs and encouraged to report future cases of toxicity to increase knowledge on this potentially lethal outcome.

Practical document on the management of hyponatremia in critically ill patients

Hyponatremia is the most prevalent electrolyte disorder in Intensive Care Units. It is associated with an increase in morbidity, mortality and hospital stay. The majority of the published studies are observational, retrospective and do not include critical patients; hence it is difficult to draw definitive conclusions. Moreover, the lack of clinical evidence has led to important dissimilarities in the recommendations coming from different scientific societies. Finally, etiopathogenic mechanisms leading to hyponatremia in the critical care patient are complex and often combined, and an intensive analysis is clearly needed. A study was therefore made to review all clinical aspects about hyponatremia management in the critical care setting. The aim was to develop a Spanish nationwide algorithm to standardize hyponatremia diagnosis and treatment in the critical care patient.

A low initial serum sodium level is associated with an increased risk of overcorrection in patients with chronic profound hyponatremia: a retrospective cohort analysis

Background

Even with abundant evidence for osmotic demyelination in patients with hyponatremia, the risk factors for overcorrection have not been fully investigated. Therefore the purpose of this study is to clarify the risks for overcorrection during the treatment of chronic profound hyponatremia.

Methods

This is a single-center retrospective observational study. We enrolled 56 adult patients with a serum sodium (SNa) concentration of ≤125 mEq/L who were treated in an intensive care unit by nephrologists using a locally developed, fixed treatment algorithm between February 2012 and April 2014. The impact of patient parameters on the incidence of overcorrection was estimated using univariable and multivariable logistic regression models. Overcorrection was defined as an increase of SNa by >10 mEq/L and >18 mEq/L during the first 24 and 48 h, respectively.

Results

The median age was 78 years, 48.2% were male, and 94.6% of the patients presented with symptoms associated with hyponatremia. The initial median SNa was 115 mEq/L (quartile, 111–119 mEq/L). A total of 11 (19.6%) patients met the criteria for overcorrection with 9 (16.0%) occurring at 24 h, 6 (10.7%) at 48 h, and 4 (7.1%) at both 24 and 48 h. However, none of these patients developed osmotic demyelination. Primary polydipsia, initial SNa, and early urine output were the significant risk factors for overcorrection on univariable analysis. Multivariable analysis revealed that the initial SNa had a statistically significant impact on the incidence of overcorrection with an adjusted odds ratio of 0.84 (95% confidence interval, 0.70–0.98; p = 0.037) for every 1 mEq/L increase. Additionaly, the increase in SNa during the first 4 h and early urine output were significantly higher in patients with overcorrection than in those without (p = 0.001 and 0.005, respectively).

Conclusions

An initial low level of SNa was associated with an increased risk of overcorrection in patients with profound hyponatremia. In this regard, the rapid increase in SNa during the first 4 h may play an important role.

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.

Diagnosis and Treatment of Hyponatremia: Compilation of the Guidelines

Hyponatremia is a common water balance disorder that often poses a diagnostic or therapeutic challenge. Therefore, guidelines were developed by professional organizations, one from within the United States (2013) and one from within Europe (2014). This review discusses the diagnosis and treatment of hyponatremia, comparing the two guidelines and highlighting recent developments. Diagnostically, the initial step is to differentiate hypotonic from nonhypotonic hyponatremia. Hypotonic hyponatremia is further differentiated on the basis of urine osmolality, urine sodium level, and volume status. Recently identified parameters, including fractional uric acid excretion and plasma copeptin concentration, may further improve the diagnostic approach. The treatment for hyponatremia is chosen on the basis of duration and symptoms. For acute or severely symptomatic hyponatremia, both guidelines adopted the approach of giving a bolus of hypertonic saline. Although fluid restriction remains the first-line treatment for most forms of chronic hyponatremia, therapy to increase renal free water excretion is often necessary. Vasopressin receptor antagonists, urea, and loop diuretics serve this purpose, but received different recommendations in the two guidelines. Such discrepancies may relate to different interpretations of the limited evidence or differences in guideline methodology. Nevertheless, the development of guidelines has been important in advancing this evolving field.

Physiopathology, clinical diagnosis, and treatment of hyponatremia

Hyponatremia is the commonest electrolyte disorder encountered in clinical practice. It develops when the mechanisms regulating water and electrolyte handling are impaired, which in many instances occur in the setting of concurrent diseases such as heart failure, liver failure, renal failure etc… Hyponatremia as an electrolyte disorder has several specificities: when profound it can be quickly fatal and when moderate it carries a high risk of mortality and morbidity, but at the same time incorrect treatment of profound hyponatremia can lead to debilitating neurological disease and it remains unclear if treatment of moderate hyponatremia is associated with a decrease in mortality and morbidity. A proper diagnosis is the keystone for an adequate treatment for hyponatremia and in the last few years many diagnosis algorithms have been developed to aid in the evaluation of the hyponatremic patient. Also because of the availability of vasopressin receptor antagonists and the advances made in the research regarding complications associated with hyponatremia treatment, new treatment recommendations have been published recently by several panels. This review will discuss the physiopathology, epidemiology, and clinical manifestations of hyponatremia and also the diagnosis and the treatment of this disorder with special emphasis on the complication from overly rapid correction of hyponatremia.

Prognosis of patients with severe hyponatraemia is related not only to hyponatraemia but also to comorbidities and to medical management: results of an observational retrospective study

Background

The true cause of death in severe hyponatraemic patients remains controversial. The present study aimed to analyse the relationship between comorbidity, medical management and prognosis in severe hyponatraemic patients.

Methods

Medical records of all patients hospitalised in our institution in 2012 with a plasma sodium ≤120 mmol/l were retrospectively analysed.

Results

One hundred forty-seven of 64 723 adult patients (0.2 %) were identified with severe hyponatraemia. In-hospital mortality rate was 24.5 and 50.3 % after a median follow-up of 431 days. Patients with plasma sodium <110 mmol/l had less comorbidity (Charlson Comorbidity Index 2.2 ± 1.9 vs. 4.0 ± 3.1 (plasma sodium 110–115 mmol/l) and 4.2 ± 3.1 (plasma sodium 116–120 mmol/l); P = .02)) and a small trend for less mortality, respectively 40.0, 51.2 and 52.3 % (P = .64). At discharge, nonsurvivors and survivors had similar plasma sodium with 58.3 % of nonsurvivors being normonatraemic. Urine analysis was performed in 74.2 % of cases and associated with lower in-hospital mortality (20.2 % vs. 36.8 %, P = .05). In multivariate Cox analysis, mortality was significantly associated with plasma sodium normalisation (HR 0.35, P < 0.001), urine analysis (HR 0.48, P = .01), Charlson Comorbidity Index (HR 1.23, P < .001) and serum albumin (HR 0.88, P < .001).

Conclusion

Mortality in severe hyponatraemia appears mainly due to comorbidities although the latter are potentiated by hyponatraemia itself and its management thereby exacerbating the risk of death.

[The rate of hyponatremia in neurosurgical patients (comparison between the data from the Burdenko Neurosurgical Instutite and the literature) and recommendations for the diagnosis and treatment]

Hyponatremia is a relatively frequent and serious complication in patients with various neurosurgical pathologies.

OBJECTIVE

This study is aimed at assessing the incidence of hyponatremia in neurosurgical patients depending on the pathology.

MATERIAL AND METHODS

This paper presents a retrospective analysis 39 479 cases of patients operated on at the Burdenko Neurosurgical Institute from 2008 to 2014.

RESULTS

A total of 785 hyponatremic patients with Na level lower than 130 mmol/l (2% of all operated patients) were identified. Mortality in patients with hyponatremia was 14.3%, which is tenfold higher compared to the rest of population of patients without hyponatremia who were operated on during the same period. In adults, hyponatremia most frequently occurred after resection of craniopharyngiomas (11%) and as a result of acute cerebrovascular accident (22%). In children, it occurred after resection of craniopharyngiomas (10%), astrocytomas (7%), ependymomas (24%), and germ cell tumors (10.5%).

CONCLUSION

This study, which was mainly statistical one, was not aimed at detailed investigation of hyponatremia in different groups of neurosurgical patients. We only tried to draw the attention of various experts to those categories of patients, where focused and in-depth developments are more than important. Obviously, already gained international experience should be taken into account for this

PURPOSE

Therefore, this article presents the literature data on the etiology and pathogenesis of hyponatremia. We describe the details of the various classifications of hyponatremia, its clinical symptoms, diagnosis, and treatments, primarily based on the recommendations of the last European consensus of various specialists (2014).

Mid-regional pro-atrial natriuretic peptide and the assessment of volaemic status and differential diagnosis of profound hyponatraemia

BACKGROUND

Hyponatraemia is common and its differential diagnosis and consequent therapy management is challenging. The differential diagnosis is mainly based on the routine clinical assessment of volume status, which is often misleading. Mid-regional pro-atrial natriuretic peptide (MR-proANP) is associated with extracellular and cardiac fluid volume.

METHODS

A total of 227 consecutive patients admitted to the emergency department with profound hypo-osmolar hyponatraemia (Na < 125 mmol L(-1) ) were included in this prospective multicentre observational study conducted in two tertiary centres in Switzerland. A standardized diagnostic evaluation of the underlying cause of hyponatraemia was performed, and an expert panel carefully evaluated volaemic status using clinical criteria. MR-proANP levels were compared between patients with hyponatraemia of different aetiologies and for assessment of volume status.

RESULTS

MR-proANP levels were higher in patients with hypervolaemic hyponatraemia compared to patients with hypovolaemic or euvolaemic hyponatraemia (P = 0.0002). The area under the curve (AUC) to predict an excess of extracellular fluid volume, compared to euvolaemia, was 0.73 [95% confidence interval (CI) 0.62-0.84]. Additionally, in multivariate analysis, MR-proANP remained an independent predictor of excess extracellular fluid volume after adjustment for congestive heart failure (P = 0.012). MR-proANP predicted the syndrome of inappropriate antidiuresis (SIAD) versus hypovolaemic and hypervolaemic hyponatraemia with an AUC of 0.77 (95% CI 0.69-0.84).

CONCLUSION

MR-proANP is associated with extracellular fluid volume in patients with hyponatraemia and remains an independent predictor of hypervolaemia after adjustment for congestive heart failure. MR-proANP may be a marker for discrimination between the SIAD and hypovolaemic or hypervolaemic hyponatraemia.

[Hyponatremia and tolvaptan : what is the situation 5 years after approval?]

The diuretic tolvaptan has been approved for more than 5 years for the indications of euvolemic hyponatremia due to syndrome of inappropriate antidiuretic hormone (SIADH) secretion. In recent years many patients have been treated with tolvaptan and many physicians could gather practical experience. Other countries, such as the USA had already gained greater experience, also in the indications for hypervolemic hyponatremia. After approval was granted more than 5000 patients worldwide were included in the so-called hyponatremia register and 22 active centers in Germany with 317 patients participated. Although some details from this now concluded register have been published, the final publication of the multinational post-authorization safety study on tolvaptan in the treatment of SIADH has not yet been published. In the years 2012 and 2013 two warning letters were issued on tolvaptan. The first letter warned of the risk of a faster increase in serum sodium using tolvaptan and provided detailed information on how the risk of osmotic demeyelination can be minimized. So far only one proven case of osmotic demelination syndrome (ODS) is known; however, this occurred following incorrect use of tolvaptan in a monotherapy. The second warning letter provided information on the potential risk (reversible) of liver damage by tolvaptan, which resulted from the TEMPO 3:4 study. In this study tolvaptan was used in a higher dosage for therapy of autosomal dominant polycystic kidney disease. Although the European renal best practice (ERBP) guidelines from 2014 did not recommend tolvaptan for the indications of SIADH, other guidelines came to different conclusions. In summary, 5 years after the approval of tolvaptan there is still no consensus. At the current time many questions still remain unanswered. Initiation of therapy with tolvaptan remains reserved for experienced physicians in hospitals. Treatment must be adapted on the basis of a clinical estimation of the individual situation of each patient.

Clinical evaluation of hyponatremia and hypovolemia in critically ill adult neurologic patients: contribution of the use of cumulative balance of sodium

PURPOSE

Knowledge of the cumulative balance of sodium (CBS) is important for the diagnosis of salt disorders and water homeostasis and has the potential to predict hypovolemic status in acute neurological patients. However, an extensive application of the use of CBS is still lacking in the intensive care setting, where salt and water homeostasis represents a priority.

METHODS

Records of consecutive series of acute neurological patients admitted to a neurointensive care unit over a 6-month period were retrospectively reviewed. CBS was calculated at the admission to the Emergency Department. Discrimination between cerebral salt-wasting syndrome (CSWS) and the syndrome of inappropriate antidiuretic hormone secretion (SIADH) was performed on the basis of the classical criteria. Additionally, we used the findings of a negative CBS exceeding 2 mEq/kg for the diagnosis of CSWS. Two independent clinicians who were blinded to the CBS results performed diagnosis of the causes of hyponatremia and estimated the daily volemic status of the patients on the basis of clinical parameters. Logistic regression analysis was used to determine the independent prognostic factors of hypovolemia.

RESULTS

Thirty-five patients were studied for a total of 418 days. Four patients (11.4%) fitted the criteria of CSWS and three patients (8.5%) had SIADH. The unavailability of the CBS led to a wrong diagnosis in three of the eight hyponatremic patients (37.5%). The risk of developing hypovolemia in patients with negative CBS was 7.1 times higher (CI 3.86-13.06; p < 0.001). Multivariate analysis revealed that negative cumulative fluid balance, negative CBS >2 mEq/kg, and CVP ≤5 cmH2O were independent prognostic factors for hypovolemia.

CONCLUSIONS

CBS is likely to be a useful parameter in the diagnosis of CSWS and a surrogate parameter for estimating hypovolemia in acute neurological patients.

Clinical practice guideline on diagnosis and treatment of hyponatraemia

Hyponatraemia, defined as a serum sodium concentration <135 mmol/l, is the most common disorder of body fluid and electrolyte balance encountered in clinical practice. It can lead to a wide spectrum of clinical symptoms, from subtle to severe or even life threatening, and is associated with increased mortality, morbidity and length of hospital stay in patients presenting with a range of conditions. Despite this, the management of patients remains problematic. The prevalence of hyponatraemia in widely different conditions and the fact that hyponatraemia is managed by clinicians with a broad variety of backgrounds have fostered diverse institution- and speciality-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 the Clinical Practice Guideline on the diagnostic approach and treatment of hyponatraemia as a joint venture of three societies representing specialists with a natural interest in hyponatraemia. In addition to a rigorous approach to methodology and evaluation, we were keen to ensure that the document focused on patient-important outcomes and included utility for clinicians involved in everyday practice.

Clinical practice guideline on diagnosis and treatment of hyponatraemia

Hyponatraemia, defined as a serum sodium concentration <135 mmol/l, is the most common disorder of body fluid and electrolyte balance encountered in clinical practice. It can lead to a wide spectrum of clinical symptoms, from subtle to severe or even life threatening, and is associated with increased mortality, morbidity and length of hospital stay in patients presenting with a range of conditions. Despite this, the management of patients remains problematic. The prevalence of hyponatraemia in widely different conditions and the fact that hyponatraemia is managed by clinicians with a broad variety of backgrounds have fostered diverse institution- and speciality-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 the Clinical Practice Guideline on the diagnostic approach and treatment of hyponatraemia as a joint venture of three societies representing specialists with a natural interest in hyponatraemia. In addition to a rigorous approach to methodology and evaluation, we were keen to ensure that the document focused on patient-important outcomes and included utility for clinicians involved in everyday practice.

Clinical practice guideline on diagnosis and treatment of hyponatraemia

Hyponatraemia, defined as a serum sodium concentration <135 mmol/L, is the most common disorder of body fluid and electrolyte balance encountered in clinical practice. Hyponatraemia is present in 15-20% of emergency admissions to hospital and occurs in up to 20% of critically ill patients. Symptomatology may vary from subtle to severe or even life threatening. Despite this, the management of patients remains problematic. Against this background, the European Society of Intensive Care Medicine, the European Society of Endocrinology and the European Renal Association-European Dialysis and Transplant Association, represented by European Renal Best Practice have developed a Clinical Practice Guideline on the diagnostic approach and treatment of hyponatraemia as a joint venture of three societies representing specialists with a natural interest in hyponatraemia.

Neurologic complications of electrolyte disturbances and acid-base balance

Electrolyte and acid-base disturbances are common occurrences in daily clinical practice. Although these abnormalities can be readily ascertained from routine laboratory findings, only specific clinical correlates may attest as to their significance. Among a wide phenotypic spectrum, acute electrolyte and acid-base disturbances may affect the peripheral nervous system as arreflexic weakness (hypermagnesemia, hyperkalemia, and hypophosphatemia), the central nervous system as epileptic encephalopathies (hypomagnesemia, dysnatremias, and hypocalcemia), or both as a mixture of encephalopathy and weakness or paresthesias (hypocalcemia, alkalosis). Disabling complications may develop not only when these derangements are overlooked and left untreated (e.g., visual loss from intracranial hypertension in respiratory or metabolic acidosis; quadriplegia with respiratory insufficiency in hypermagnesemia) but also when they are inappropriately managed (e.g., central pontine myelinolisis when rapidly correcting hyponatremia; cardiac arrhythmias when aggressively correcting hypo- or hyperkalemia). Therefore prompt identification of the specific neurometabolic syndromes is critical to correct the causative electrolyte or acid-base disturbances and prevent permanent central or peripheral nervous system injury. This chapter reviews the pathophysiology, clinical investigations, clinical phenotypes, and current management strategies in disorders resulting from alterations in the plasma concentration of sodium, potassium, calcium, magnesium, and phosphorus as well as from acidemia and alkalemia.

Bioelectrical impedance analysis is more accurate than clinical examination in determining the volaemic status of elderly patients with fragility fracture and hyponatraemia

OBJECTIVES

Management of hyponatraemia depends crucially on accurate determination of volaemic (hydration) status but this is notoriously challenging to measure in older people. Bioelectrical impedance analysis (BIA) provides a validated means of determining total body water (TBW), but its clinical utility in determining volaemic status in hyponatraemia has never been tested. This study assessed the utility of BIA in the clinical management of hyponatraemia in elderly patients with fragility fractures (EPFF), a group at high risk of hyponatraemia.

DESIGN

Prospective observational study of consenting patients ≥65 years with fragility fractures (N=127).

SETTING

University teaching hospital in Scotland.

PARTICIPANTS

Patients ≥665 years with fragility fractures with capacity to consent to participation.

MEASUREMENTS

BIA and standard clinical examination procedures (jugular venous distension, skin turgor, mouth and axillary moistness, peripheral oedema, capillary refill time, overall impression) were performed daily throughout each participant's hospital stay. Volaemic status of hyponatraemia was determined by an expert panel using clinical data (history, examination, nursing observations and laboratory tests) blinded to TBW readings. Cohen's kappa was calculated to assess the level of agreement between the expert panel and both BIA and standard clinical examination measures in determining the volaemic state of hyponatraemia.

RESULTS

26/33 (79%) cases of hyponatraemia had sufficient clinical information to allow determination of volaemic status by BIA. There was moderate level of agreement between BIA and the expert panel, kappa 0.52 (p<.001). All kappa values for standard clinical assessments of volaemic status neared zero, indicating nil to slight agreement.

CONCLUSION

BIA outperformed all aspects of the standard clinical examination in determining the volaemic status of hyponatraemic EPFF, suggesting it may be useful in clinical practice.

Tolvaptan for the treatment of hyponatremia and hypervolemia in patients with congestive heart failure

Patients with heart failure often show increased arginine vasopressin secretion and enhanced sympathetic and renin-angiotensin-aldosterone activation, which accelerate renal water reabsorption, causing water retention and volume overload. Tolvaptan is an orally active antagonist of arginine vasopressin type 2 receptors in the collecting duct of the kidney that inhibits water reabsorption without substantially affecting the electrolyte balance. Tolvaptan in combination with conventional diuretics improves fluid retention and congestive symptoms in patients with heart failure and volume overload, with minimal effects on hemodynamics and serum potassium. Tolvaptan slightly increases serum sodium concentrations, generally within the normal range. Although it does not seem to affect long-term mortality, tolvaptan does improve short-term water retention and congestive symptoms in heart failure patients with volume overload despite the use of conventional diuretics, and is approved for this indication in Japan.

Copeptin: a new marker in cardiology

Copeptin, the C-terminal part of the prohormone of vasopressin (AVP), is released together with AVP in stoichiometric concentrations reflecting an individual's stress level. Copeptin has come to be regarded as an important marker for identifying high-risk patients and predicting outcomes in a variety of diseases. It improves the clinical value of commonly used biomarkers and the tools of risk stratification. Elevated AVP activation and higher copeptin concentrations have been previously described in acute systemic disorders. However, the field that could benefit the most from the introduction of copeptin measurements into practice is that of cardiovascular disease. Determination of copeptin level emerges as a fast and reliable method for differential diagnosis, especially in acute coronary syndromes. A particular role in the diagnosis of acute myocardial infarction (AMI) is attributed to the combination of copeptin and troponin. According to available sources, such a combination allows AMI to be ruled out with very high sensitivity and negative predictive value. Moreover, elevated copeptin levels correlate with a worse prognosis and a higher risk of adverse events after AMI, especially in patients who develop heart failure. Some authors suggest that copeptin might be valuable in defining the moment of the introduction of treatment and its monitoring in high-risk patients. The introduction of copeptin into clinical practice might also provide a benefit on a larger scale by suggesting changes in the allocation of financial resources within the health system. Although very promising, further larger trials are required in order to assess the clinical benefits of copeptin in everyday practice and patient care.

[Hyponatremia : The water-intolerant patient]

Hyponatremia due to intolerance to water is a frequent clinical condition and associated with increased mortality. Besides the well known neurological symptoms, gait disturbances, falls, fractures and osteoporosis have also been described recently in patients with chronic hyponatremia. Acute hyponatremia is a more dramatic situation and needs rapid action when severe neurological symptoms are present. Hypertonic saline is recommended to treat this condition until relief of severe symptoms. The causes of hyponatremia have to be carefully examined. Especially diuretics, antidepressants and endocrine causes, e.g. hypothyroidism, hypocortisolism and hypoaldosteronism should be excluded by examination of the patient history, clinical examination and by laboratory tests. Patients should be classified as being euvolemic, hypovolemic or hypervolemic. Whereas acute hyponatremia with severe symptom should be treated with hypertonic saline, euvolemic hyponatremia due to the syndrome of inappropriate antidiuretic hormone secretion (SIADH) with mild and moderate symptoms can now be treated with tolvaptan, a selective V(2)-vasopressin antagonist. Oral tolvaptan has been shown to be an effective and potent aquaretic to treat hyponatremia caused by SIADH as evidenced by a simultaneous increase in serum sodium and a decrease in urine osmolality. The condition of patients with mild or moderate hyponatremia is also improved. Side effects associated with tolvaptan include increased thirst, dry mouth, polyuria and hypernatremia. Rapid increases in serum sodium should be avoided by close monitoring in a hospital setting.

Hyponatraemia: an overview of frequency, clinical presentation and complications

Hyponatraemia (defined as a serum sodium concentration <136 mmol/L) is the most frequently encountered electrolyte disturbance in clinical practice. It is classified according to volume status (hypovolaemia, hypervolaemia or euvolaemia), reflecting the relative proportions of water and sodium within the body. The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is the most common cause of euvolaemic hyponatraemia. Although hyponatraemia is associated with poor prognosis and increased length of hospital stay, it is often poorly managed and sometimes underdiagnosed and undertreated. This article provides an overview of the frequency, pathophysiology and complications associated with this common clinical condition.

Perspectives on the management of hyponatraemia secondary to SIADH across Europe

The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is the most common cause of euvolaemic hyponatraemia. However, although first described over 50 years ago, the management of hyponatraemia secondary to SIADH is not always straightforward. Some of the issues surrounding the management of hyponatraemia secondary to SIADH were explored in the European Hyponatraemia Survey completed by attendees of the European Hyponatraemia Network Academy Meeting 2011. This article describes the findings of this survey and the specific issues raised regarding the management of hyponatraemia secondary to SIADH in Europe. Some of these issues - including awareness, education, diagnosis, management and cost considerations of the condition - were common to countries across Europe.

Evaluation of a protocol for hypertonic saline administration in acute euvolemic symptomatic hyponatremia: A prospective observational trial

Context:

Acute symptomatic hyponatremia is a frequent yet poorly studied clinical problem. Aims: To develop a non-weight based protocol for the treatment of acute symptomatic hyponatremia.

Settings and Design:

Observational study in a Multi-disciplinary Intensive Care Unit of an urban tertiary care hospital.

Materials and Methods:

Patients aged >18 years, admitted with euvolemic acute symptomatic severe hyponatremia (defined as serum sodium <120 meq/l with symptoms <24 hours), formed the study population. On confirmation of euvolemic status clinically and by laboratory investigations, patients were administered 100 ml of 3% NaCl over a period of 4 hours irrespective of the weight of the patient, followed by reassessment of serum Na at the end of 4 hours. The volume of hypertonic saline (in ml) required to increase serum Na by 8 meq/l was calculated using the formula: 100 × 8/increment in serum Na observed with 100 ml hypertonic saline. This volume was infused over the next 20 hours. To monitor renal water diuresis which may contribute to overcorrection, the urine specific gravity was monitored every 4 hours for sudden decrease of ≥ 0.010 from the baseline value. Measurement of serum Na was repeated if a fall in the urine specific gravity was observed and subsequently repeated every 4 hours. If no fall occurs in urine specific gravity, serum Na measurement was repeated at 12, 20 and at 24 hours (0 hour being the initiation of 100 ml hypertonic saline). The volume of infusate was adjusted if an excessive increment of serum Na (greater than 3 meq at 8 hours, 4 meq at 12 hours, 5 meq at 16 hours and 6 meq at 20 hours) was observed. Baseline characteristics were compared using chi-square test and Mann–Whitney U test.

Results:

58 patients formed the study cohort. The mean age was 58 years. The mean serum Na on admission was 114 meq/l. Administration of 100 ml hypertonic saline resulted in a mean increase in serum Na of 2 meq/l. The mean increase in serum Na over 24 hours was 9 meq/l and mean volume of hypertonic saline required for a serum Na increment of 8 meq/l was 600 ml.

Conclusions:

The non-weight based protocol with monitoring for water diuresis is reasonably an effective strategy in the treatment of acute euvolemic symptomatic hyponatremia.

Copeptin: a biomarker of cardiovascular and renal function

Arginine vasopressin (AVP or antidiuretic hormone) is one of the key hormones in the human body responsible for a variety of cardiovascular and renal functions. It has so far escaped introduction into the routine clinical laboratory due to technical difficulties and preanalytical errors. Copeptin, the C-terminal part of the AVP precursor peptide, was found to be a stable and sensitive surrogate marker for AVP release. Copeptin behaves in a similar manner to mature AVP in the circulation, with respect to osmotic stimuli and hypotension. During the past years, copeptin measurement has been shown to be of interest in a variety of clinical indications, including cardiovascular diseases such as heart failure, myocardial infarction, and stroke. This review summarizes the recent progress on the diagnostic use of copeptin in cardiovascular and renal diseases and discusses the potential use of copeptin measurement in the context of therapeutic interventions with vasopressin receptor antagonists.

Endocrine disorders: causes of hyponatremia not to neglect

Hyponatremia is a common electrolyte abnormality with the potential for significant morbidity and mortality. Endocrine disorders, including adrenal deficiency and hypothyroidism, are uncommon causes of hyponatremia. Primary adrenal insufficiency (i.e. Addison's disease) may well be recognized by clear hall-marks of the disease, such as pigmentation, salt craving, hypotension, and concomitant hyperkalemia. Addison's disease is an important diagnosis not to be missed since the consequences can be grave. On the other hand, hypothyroidism and secondary adrenocortical insufficiency originating from diseases of the hypothalamus and/or pituitary (hypopituitarism) require a high index of suspicion, because the clinical signs can be quite subtle. This review focuses on clinical and pathophysiological aspects of hyponatremia due to endocrine disorders.

Creation of a hyponatremia registry supported by an industry-derived quality control methodology

BACKGROUND

A clinical registry encompasses a selective set of rigorously collected and stored clinical data focused on a specific condition. Hyponatremia has multiple, complex underlying causes and is one of the most frequent laboratory abnormalities. No systematic registries of hyponatremic patients have been reported in the medical literature. The purpose of this project was to create a registry for hyponatremia in order to obtain epidemiological data that will help to better understand this condition.

OBJECTIVE

This paper describes the creation of a registry for hyponatremia within a single institution that employs industry-based approaches for quality management to optimize data accuracy and completeness.

METHODS

A prospective registry of incident hyponatremia cases was created for this study. A formalized statistically based quality control methodology was developed and implemented to analyze and monitor all the process indicators that were developed to ensure data quality.

RESULTS

Between December 2006 and April 2009, 2443 episodes of hyponatremia were included. Six process indicators that reflect the integrity of the system were evaluated monthly, looking for variation that would suggest systematic problems. The graphical representation of the process measures through control charts allowed us to identify and subsequently address problems with maintaining the registry.

CONCLUSION

In this project we have created a novel hyponatremia registry. To ensure the quality of the data in this registry we have implemented a quality control methodology based on industrial principles that allows us to monitor the performance of the registry over time through process indicators in order to detect systematic problems. We postulate that this approach could be reproduced for other registries.

[Treatment of hyponatremia: role of vaptans]

Hyponatremia is encountered quite frequently in everyday clinical practice. The symptomatology mainly includes neurological manifestations. In addition, it has been noted in recent years that uncertain gait, falls, fractures, and osteoporosis are also associated with hyponatremia. Based on clinical and laboratory analyses, hyponatremia can be classified into three categories: hypovolemic (decreased volume), hypervolemic (with venous edema), and euvolemic. The severity of the neurological symptoms related to hyponatremia should serve to guide the therapeutic approach. Severe cerebral symptoms due to acute cerebral edema require a prompt and closely monitored course of action with administration of hypertonic saline solution. Milder and moderate symptoms as well as the syndrome of inappropriate ADH secretion (SIADH) can now also be managed with controlled use of the ADH antagonist tolvaptan, one of a new class of vaptans. Tolvaptan is a selective antagonist of the antidiuretic effect of vasopressin without primarily affecting blood pressure and depending on the dose leads to increased excretion of free water (aquaresis). Side effects predominantly concern thirst, polyuria, and hypernatremia. Under these conditions, vaptans represent a valuable asset to the therapeutic spectrum in SIADH. Further studies are needed to determine whether falls and fractures can also be beneficially influenced.

Vasopressin-receptor antagonists

Despite a crucial role in body fluid homeostasis, elevated vasopressin levels can also be pathological in conditions such as congestive heart failure, liver cirrhosis and the syndrome of inappropriate antidiuretic hormone secretion. The result of elevated vasopressin is renal water retention and hyponatremia, a low serum sodium concentration. Hyponatremia is associated with excess morbidity and mortality. Nonpeptide vasopressin-receptor antagonists represent a new drug class of small molecules that competitively inhibit one or more of the vasopressin receptors. There are three vasopressin receptors in humans, including V1a, V1b and V2. Selective V2- and combined V1a/V2-receptor antagonists have been developed for the treatment of hyponatremia resulting from congestive heart failure, liver cirrhosis and the syndrome of inappropriate antidiuretic hormone secretion. Two nonpeptide vasopressin-receptor antagonists, conivaptan and tolvaptan, have recently been approved by American and European drug authorities for clinical use. This article aims to provide a succinct and clinical update on nonpeptide vasopressin-receptor antagonists, including their mechanism of action, performance in randomized clinical trials and current clinical status.

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

BACKGROUND

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

METHOD

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

RESULT

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

CONCLUSION

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

SIADH and hyponatraemia: why does it matter?

The vasopressin-receptor antagonists have received approval for the treatment of hyponatraemia secondary to the syndrome of inappropriate antidiuretic hormone secretion (SIADH). It is therefore necessary that physicians encountering hyponatraemia focus on SIADH. Recent studies show that hyponatraemia is often poorly managed—insufficient diagnostic tests are ordered and patients are undertreated. At the same time, it has become clear that chronic hyponatraemia causes neurological symptoms such as gait disturbances and attention deficits. However, physicians often tolerate chronic hyponatraemia as if it were benign, or as if its treatment would cause significant morbidity. Therefore, physicians must reconsider the diagnostic and therapeutic approaches to hyponatraemia and SIADH.

Current and future treatment options in SIADH

The treatment of hyponatraemia due to SIADH is not always as straightforward as it seems. Although acute treatment with hypertonic saline and chronic treatment with fluid restriction are well established, both approaches have severe limitations. These limitations are not readily overcome by addition of furosemide, demeclocycline, lithium or urea to the therapy. In theory, vasopressin-receptor antagonists would provide a more effective method to treat hyponatraemia, by virtue of their ability to selectively increase solute-free water excretion by the kidneys (aquaresis). In this review we explore the limitations of the current treatment of SIADH and describe emerging therapies for the treatment of SIADH-induced hyponatraemia.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

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

Hyponatremia revisited: translating physiology to practice

The complexity of hyponatremia as a clinical problem is likely caused by the opposite scenarios that accompany this electrolyte disorder regarding pathophysiology (depletional versus dilutional hyponatremia, high versus low vasopressin levels) and therapy (rapid correction to treat cerebral edema versus slow correction to prevent osmotic demyelination, fluid restriction versus fluid resuscitation). For a balanced differentiation between these opposites, an understanding of the pathophysiology of hyponatremia is required. Therefore, in this review an attempt is made to translate the physiology of water balance regulation to strategies that improve the clinical management of hyponatremia. A physiology-based approach to the patient with hyponatremia is presented, first addressing the possibility of acute hyponatremia, and then asking if and if so why vasopressin is secreted non-osmotically. Additional diagnostic recommendations are not to rely too heavily of the assessment of the extracellular fluid volume, to regard the syndrome of inappropriate antidiuresis as a diagnosis of exclusion, and to rationally investigate the pathophysiology of hyponatremia rather than to rely on isolated laboratory values with arbitrary cutoff values. The features of the major hyponatremic disorders are discussed, including diuretic-induced hyponatremia, adrenal and pituitary insufficiency, the syndrome of inappropriate antidiuresis, cerebral salt wasting, and exercise-associated hyponatremia. The treatment of hyponatremia is reviewed from simple saline solutions to the recently introduced vasopressin receptor antagonists, including their promises and limitations. Given the persistently high rates of hospital-acquired hyponatremia, the importance of improving the management of hyponatremia seems both necessary and achievable.

Copeptin: clinical use of a new biomarker

Arginine vasopressin (AVP) is a key hormone in the human body. Despite the clinical relevance of AVP in maintaining fluid balance and vascular tone, measurement of mature AVP is difficult and subject to preanalytical errors. Recently, copeptin, a 39-amino acid glycopeptide that comprises the C-terminal part of the AVP precursor (CT-proAVP), was found to be a stable and sensitive surrogate marker for AVP release, analogous to C-peptide for insulin. Copeptin measurement has been shown to be useful in various clinical indications, including the diagnosis of diabetes insipidus and the monitoring of sepsis and cardiovascular diseases. Here we review recent findings regarding the relationship between AVP and copeptin, and affirm the value of AVP as a surrogate marker for AVP.

[Drug-related disorders of water and electrolyte metabolism]

Pharmacologic treatment may lead to diverse disturbances of water and electrolyte metabolism as adverse drug events. Diuretics are particularly likely to cause these complications typically including volume depletion, metabolic alkalosis, hyponatremia, and hypokalemia. Salt and water retention with edema formation is most frequently elicited by antihypertensives, steroid hormones, and nonsteroidal anti-inflammatory drugs. Drug-induced disorders of Na+ concentration may usually be attributed to altered antidiuretic hormone (ADH) effects, either as diabetes insipidus or as the syndrome of inappropriate ADH secretion. With hyper- and hypokalemia, redistribution between intra- and extracellular fluid as well as renal excretion play a role. Strategies to prevent these adverse drug reactions include careful consideration of risk factors and clinical and laboratory controls in the course of treatment.