Vasopressin excess and hyponatremia

Mortality predictors of patients diagnosed with severe hyponatremia in the emergency department

PURPOSE

To determine the factors affecting mortality as a result of the analysis of the demographic and clinical characteristics and laboratory parameters of patients whose serum Na value was determined to be 125 mEq/L or below at the time of admission to the emergency department (ED).

METHOD

Patients over 18 years of age who admitted to the ED of a tertiary hospital between September 2021 and September 2022 and whose serum sodium level was determined to be 125 mEq/L and below were included in the study. Demographic and clinical characteristics, admission complaints, medications used, Charles comorbidity index (CCI), laboratory parameters, and outcomes of the patients included in the study were recorded in the data form.

RESULTS

Three hundred ninety-nine patients were included in the study. When the 30-day mortality of the patients is examined, the mortality rate was found to be 21.6%. In the analyses performed for the predictive power of laboratory parameters for mortality, it was determined that the highest predictive power among the predictive values determined by the area under the curve (AUC) was the albumin level (AUC 0.801, 95% CI 0.753-0.849, p < 0.001). In the binary logistic regression analysis, urea and albumin were independent predictors of 30-day mortality.

CONCLUSION

According to study data, albumin and urea levels are independent predictors of 30-day mortality in patients diagnosed with severe hyponatremia in the emergency department.

Clinical Profile of Patients Admitted with Hyponatremia in the Medical Intensive Care Unit

Background and Aims

Hyponatremia is the predominant electrolyte abnormality with an incidence rate of approximately 22%. It is the leading cause of morbidity and mortality with scarce data in Indian intensive care settings. The aim of this study is to evaluate the clinical features and etiology of hyponatremia in patients admitted to an Intensive Care Unit (ICU) of a tertiary care hospital.

Materials and Methods

A 1-year prospective cross-sectional observational study was conducted, including 100 adult patients with moderate-to-severe hyponatremia admitted to the Medical ICU. Patients underwent investigations such as serum creatinine, blood urea nitrogen, serum osmolality, serum sodium, urine sodium, and urine osmolality, sputum culture, cerebrospinal fluid analysis, and neuroimaging. Data were analyzed using independent sample t-test, Chi-square test, and Fisher's exact test.

Results

Vomiting (28) followed by confusion (26) was the most common complaint. Syndrome of inappropriate antidiuretic hormone secretion (SIADH) (46) was the most common etiology for hyponatremia, and euvolemic hypoosmolar hyponatremia (50) was the most common type of hyponatremia. Confusion was significantly high in patients with severe hyponatremia as compared to patients with moderate hyponatremia (22 vs. 4, P < 0.001). In majority of the patients (46), SIADH was the main cause of euvolemic type of hyponatremia (P < 0.001). Increased urine sodium levels were observed in patients with SIADH (46), renal dysfunction (12), and drug-induced etiology (8, P < 0.001).

Conclusion

Patients with hyponatremia secondary to an infectious cause should be meticulously screened for tuberculosis. The timely and effective treatment of hyponatremia is determined by the effective understanding of pathophysiology and associated risk factors of hyponatremia.

Scientific Basis of Hyponatremia and Its Clinical Presentations

Purpose

To describe causes, pathophysiologic mechanisms, and classifications of hyponatremia, and to describe clinical symptoms and underlying disease states associated with different levels of hyponatremia.

Summary

The key to comprehending hyponatremia is to understand body water content and plasma osmolality and accurately assess arterial volume. Hyponatremia results from sodium dilution because of retained water or sodium depletion because of electrolyte loss in excess of water loss. Body sodium, water, and extracellular fluid (ECF) volume are tightly regulated by mechanisms that act to maintain a closely controlled concentration of solutes in the ECF. These forces act to regulate water content and sodium excretion to maintain normal intravascular volume. The body closely defends normal plasma osmolality within a narrow range primarily by controlling the release of arginine vasopressin (AVP) and via the thirst mechanism. A number of factors can stimulate inappropriate AVP release and cause or worsen hyponatremia. Dysregulation of AVP plays an important role in heart failure and cirrhosis, common causes of hypervolemic hyponatremia.

Conclusion

Body water content and plasma osmolality are tightly regulated by the action of AVP. A variety of disease states are associated with hyponatremia related to inappropriate AVP release. The cause of the electrolyte disturbance must be determined, because it can have profound implications for treatment. Differential diagnosis can be guided by observation of the rapidity of onset as well as volume status changes. If untreated or treated inappropriately, hyponatremia can impact morbidity and mortality.

Hyponatremia in a Teenager: A Rare Diagnosis

INTRODUCTION

Hyponatremia is a common electrolyte alteration which has the potential for significant morbidity and mortality. Endocrine disorders, such as primary hypothyroidism and adrenal insufficiency are uncommon causes of hyponatremia. We present the case of a teenager with symptomatic hyponatremia caused by a rare disorder.

CASE

A 17-year-old boy was admitted to the emergency department with abdominal pain, nausea and vomiting, asthenia, and weight loss. He was in poor general condition, hypotensive, and he had dry mucous membranes and skin as well as mucosa hyperpigmentation. The laboratory findings showed severe hyponatremia, hyperkalemia, and renal dysfunction. The patient started inotropic support and antibiotics. Plasma cortisol and corticotropin levels allowed the diagnosis of primary adrenal insufficiency. He began replacement therapy with hydrocortisone and fludrocortisone, with gradual symptom resolution. An abdominal computed tomography scan showed adrenal hypoplasia. Findings for antiadrenal and antithyroid antibodies were positive, allowing the diagnosis of autoimmune polyglandular syndrome type II.

DISCUSSION

Adrenal insufficiency is a rare disease, especially in children, and its clinical manifestations are due to glucocorticoid and mineralocorticoid deficiency. In most of the cases, symptoms are nonspecific, requiring a high index of clinical suspicion. If the diagnosis and treatment are delayed, acute adrenal insufficiency carries a high morbidity and mortality.

Hyponatremia: pathophysiology, classification, manifestations and management

Hyponatremia has complex pathophysiology, is frequent and has potentially severe clinical manifestations, and its treatment is associated with high risks. Hyponatremia can be hypertonic, isotonic or hypotonic. Hypotonic hyponatremia has multiple etiologies, but only two general mechanisms of development, defective water excretion, usually because of elevated serum vasopressin levels, or excessive fluid intake. The acute treatment of symptomatic hypotonic hyponatremia requires understanding of its targets and risks and requires continuous monitoring of the patient's clinical status and relevant serum biochemical values. The principles of fluid restriction, which is the mainstay of management of all types of hypotonic hyponatremia, should be clearly understood and followed. Treatment methods specific to various categories of hyponatremia are available. The indications and risks of these treatments should also be well understood. Rapid correction of chronic hypotonic hyponatremia may lead to osmotic demyelination syndrome, which has severe clinical manifestations, and may lead to permanent neurological disability or death. Prevention of this syndrome should be a prime concern of the treatment of hypotonic hyponatremia.

Relative bioavailability of tolvaptan administered via nasogastric tube and tolvaptan tablets swallowed intact

PURPOSE

The bioavailability of a crushed tolvaptan tablet suspended in water and administered by nasogastric (NG) tube was compared to the bioavailability from the tablet administered whole.

METHODS

In a randomized crossover study, 28 healthy adults received a single 15-mg dose of tolvaptan on two occasions (one dose given as an intact tablet swallowed whole and the other as a crushed tablet in suspension given by NG tube), with a washout interval of ≥7 days. During each administration period, blood samples were collected at 15 time points over 36 hours. A validated liquid chromatography-tandem mass spectrometry assay was used to obtain plasma tolvaptan concentrations. Plasma tolvaptan time-concentration data were analyzed using noncompartmental methods, and pharmacokinetic data including maximum concentration (Cmax), time to Cmax (tmax), area under the concentration-time curve (AUC) from time zero to the time of the last measurable concentration (AUCt), and AUC extrapolated to infinity (AUC∞) resulting from oral and NG tube tolvaptan delivery were compared via repeated-measures, mixed-effects analysis of variance. Due to differences in total drug exposure seen, an in vitro experiment was conducted on three dose levels to quantify drug sequestration.

RESULTS

The ratios of geometric mean Cmax, AUCt, and AUC∞ values (expressed as a percentage) with NG tube versus oral tolvaptan administration were 88.9%, 74.3%, and 74.2%, respectively; the latter two values were not within the specified bioequivalence tolerance limits (80-125%). In vitro analysis showed that approximately 11% of all tolvaptan doses evaluated was sequestered by the NG tube.

CONCLUSION

In healthy adults, a single 15-mg dose of tolvaptan administered as a crushed tablet suspended in water by NG tube resulted in AUCt and AUC∞ values that were approximately 25% lower than those observed after oral administration of a 15-mg tolvaptan tablet swallowed intact.

Hyponatremia due to pulmonary tuberculosis: review of 200 cases

Background

Pulmonary Tuberculosis (PTB) is one of the common diseases with high prevalence of mortality and morbidity in developing countries. Various complications have been reported along with PTB. The subclinical electrolyte imbalances are customary in cases with PTB.

Objectives

The aim of this study was the evaluation of patients with PTB and hyponatremia.

Patients and Methods

We evaluated patients with diagnosis of secondary PTB who have been admitted to Baqiyatallah hospital, Tehran, Iran from 2005 till 2010. The diagnosis of PTB was based on the appearance of acid fast bacilli in sputum smears or sputum cultures, without any evidence of miliary TB. Demographic and laboratory characteristics relative to electrolytes were recorded according inclusion and exclusion criteria.

Results

The mean age was 59.22 ± 20.57 years and 91 (45.5%) patients were male. The mean serum sodium concentration was 134.54 ± 4.95 mmol/L and more than half of subjects (51%) have shown hyponatremia. The mean age difference between hyponatremic and eunatremic groups was statistically significant (61.95 versus 56.02 years) (P = 0.047). No significant relationship was found between hyponatremia and gender, anti-TB medications and co-morbidity conditions.

Conclusions

In this study, an older age was suggested as an important predisposing factor for hyponatremia in patients with PTB which had been observed as less of a determinant. We recommend further evaluations for hyponatremia in patients presenting with PTB, particularly for those who are older.

Hyponatremia caused by polydipsia

Hyponatremia (serum sodium <135 mEq/L) is the most common electrolyte disorder. The severity of symptoms is related to how rapidly the condition develops and the degree of cerebral edema that results from the low serum level of sodium. Hypertonic saline and the new vasopressin receptor antagonists are highly effective treatments for severe symptomatic hyponatremia, yet they can result in severe neurological complications if sodium levels are restored too quickly. Hyponatremia is classified as hypovolemic, euvolemic, and hypervolemic. Treatments include administration of high-risk medications and fluid restriction to restore fluid and electrolyte balance and relieve cerebral effects. Nursing care to ensure safe outcomes involves multidisciplinary collaboration, close monitoring of serum sodium levels and intake and output, and assessment for neurological changes.

Hyponatremia in patients with infectious diseases

Hyponatremia is a common electrolyte disturbance associated with considerable morbidity and mortality. Hyponatremia may not infrequently be present during the course of an infection, does not cause specific symptoms and may be overlooked by clinicians. Nonetheless, it may reflect the severity of the underlying process. This review focuses on the clinical and pathophysiological aspects of hyponatremia associated with infectious diseases. In the majority of cases, the fall in serum sodium concentration is of multifactorial origin owing to increased secretion of the anti-diuretic hormone either appropriately or inappropriately. Inadvertent administration of fluids may worsen hyponatremia and prolong morbidity.

Conivaptan: a step forward in the treatment of hyponatremia?

Hyponatremia is one of the most common electrolyte abnormalities linked to adverse outcomes and increased mortality in hospitalized patients. While the differential diagnosis for hyponatremia is diverse, most cases stem from arginine vasopressin (AVP) dysregulation, where hypoosmolality fails to suppress AVP synthesis and release. The physiological effects of AVP are currently known to depend on its interaction with any of 3 receptor subtypes V1A, V2, and V1B. Activation of V2 by AVP is the key in renal water regulation and maintenance of total body volume and plasma tonicity. Despite the long-recognized problem with excess AVP in euvolemic and hypervolemic hyponatremia, traditional therapeutic options have relied on nonspecific and potentially problematic strategies. More recently, a new class of drugs, introduced as “aquaretics,” has gained great attention among clinicians because of its ability to correct hyponatremia via direct competitive inhibition of AVP at V2 receptors to induce renal electrolyte-free water excretion. In this paper, we aim to review available clinical data on the only FDA-approved aquaretic, dual V1A/V2 receptor antagonist conivaptan, discuss its clinical indications, efficacy, safety profile, and comment on its clinical limitations.

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.

Leucyl/cystinyl aminopeptidase gene variants in septic shock

BACKGROUND

Vasopressin is an essential peptide hormone regulating cardiovascular homeostasis and an adjunctive vasopressor therapy for septic shock.

METHODS

We tested for association between single nucleotide polymorphisms (SNPs) in vasopressin pathway genes and altered outcome in derivation (n = 589) and replication (n = 616) cohorts of patients with septic shock. The primary outcome was 28-day mortality and the secondary outcome was vasopressin clearance. In a third cardiac surgical cohort (n = 977), we tested for locus-specific heritability of serum sodium concentrations.

RESULTS

Of 17 tested tag SNPs in five vasopressin pathway genes (arginine vasopressin [AVP], arginine vasopressin receptor 1A and 1B [AVPR1A, AVPR1B], leucyl/cystinyl aminopeptidase [LNPEP], and oxytocin receptor [OXTR]), rs18059 in LNPEP (also known as vasopressinase) was associated with 28-day mortality in the derivation cohort (P = .037). Therefore, we resequenced the 160-kb haplotype block encompassing the LNPEP gene, including rs18059, and genotyped the 230 identified SNPs in the derivation cohort. The strongest signal was found for LNPEP rs4869317 (adjusted P = .044). The rs4869317 TT genotype was associated with increased 28-day mortality in the derivation cohort (51.0% [TT] vs 34.5% [AA/AT]; adjusted hazard ratio [HR], 1.58; 95% CI, 1.21-2.06; P = .00073) and the replication cohort (38.6% vs 29.6%; HR, 1.36; 95% CI, 1.03-1.80; P = .030). We found that the TT genotype was associated with increased plasma vasopressin clearance (P = .028), and the rs4869317 genotype accounted for 80% of the variance of serum sodium concentrations (locus-specific heritability) in cardiac surgical patients.

CONCLUSIONS

The genetic variation in LNPEP (vasopressinase) is associated with 28-day mortality in septic shock and is associated with biologic effects on vasopressin clearance and serum sodium regulation. Further confirmation in additional cohorts is required.

Hyponatremia: evaluation and management

BACKGROUND

Hyponatremia is one of the most common electrolyte disorders encountered in clinical practice. The pathophysiology is complex, but its understanding is vital to the disorder's evaluation and treatment. The clinical manifestations of hyponatremia include headache, dizziness, nausea/vomiting, seizures, obtundation, and death. Undercorrection must be avoided, but overly aggressive treatment can also be detrimental.

OBJECTIVES

We review normal water physiology, including central osmosensory mechanisms, that are now becoming better understood. We will then review the classification and causes of hyponatremia and the clinical evaluation and workup of the disorder. Treatment options will be briefly reviewed.

DISCUSSION

Evaluation of hyponatremia begins with a detailed history and physical examination. Appropriate urine and serum studies can contribute to the evaluation and classification of the disorder. Treatment decisions are based on the underlying cause and severity of symptoms.

CONCLUSION

We present an extensive review of the physiology, pathophysiology, clinical evaluation, and management ofhyponatremia.

An unusual case of hyponatraemia

The differential diagnosis of hyponatraemia is manifold and includes hormonal disorders such as primary adrenal insufficiency or hypothyroidism. The diagnosis of adrenal insufficiency is always suggestive in cases of hypotension associated with hyponatraemia, hyperkalaemia and metabolic acidosis. We herein report a case of severe hyponatraemia in a patient with Addison's disease. The underlying cause was disseminated adrenal tuberculosis without any evidence of other organ involvement. To date, tuberculosis remains a frequent cause of adrenal insufficiency although the pathophysiology of adrenal tropism is poorly understood.

New topics in vasopressin receptors and approach to novel drugs: research and development of conivaptan hydrochloride (YM087), a drug for the treatment of hyponatremia

Hyponatremia is the most common electrolyte disorder in hospitalized patients and is associated with the risk of intractable seizures and death. The effectiveness of conventional therapies for hyponatremia is inconsistent, and the rapid correction of plasma sodium levels is thought to result in the occurrence of neurological complications. Arginine vasopressin (AVP) is the primary regulator of renal electrolyte-free water reabsorption via AVP-receptor type 2 (V2-R), and inappropriate or excessive AVP secretion independent of serum osmolality frequently causes excessive water retention, which is the etiological basis of hyponatremia. Therefore, the use of V2-R antagonists as anti-hyponatremic drugs in the clinical setting is anticipated to be reliable and safe. Conivaptan hydrochloride (YM087) is a novel dual AVP-R antagonist for AVP-R types 1a (V1a) and V2-R. In vitro studies have shown that it possesses high affinity for V1a-R and V2-R without any species differences. It also potently inhibited AVP-induced intracellular signaling through human V2 and V1a receptors with no agonistic activity. Conivaptan hydrochloride improved the plasma sodium concentration and plasma osmolality in hyponatremic rats, and its effectiveness was demonstrated in hyponatremic patients. This drug has been approved for use in the United States, which will bring relief to patients with hyponatremia.

Evaluation and management of patients with refractory ascites

Some patients with ascites due to liver cirrhosis become no longer responsive to diuretics. Once other causes of ascites such as portal vein thrombosis, malignancy or infection and non-compliance with medications and low sodium diet have been excluded, the diagnosis of refractory ascites can be made based on strict criteria. Patients with refractory ascites have very poor prognosis and therefore referral for consideration for liver transplantation should be initiated. Search for reversible components of the underlying liver pathology should be undertaken and targeted therapy, when available, should be considered. Currently, serial large volume paracentesis (LVP) and transjugular intrahepatic portasystemic stent-shunt (TIPS) are the two mainstay treatment options for refractory ascites. Other treatment options are available but not widely used either because they carry high morbidity and mortality (most surgical options) rates, or are new interventions that have shown promise but still need further evaluation. In this comprehensive review, we describe the evaluation and management of patients with refractory ascites from the prospective of the practicing physician.