Glucocorticoids Reverse Diluted Hyponatremia Through Inhibiting Arginine Vasopressin Pathway in Heart Failure Rats.

Background Arginine vasopressin dependent antidiuresis plays a key role in water-sodium retention in heart failure. In recent years, the role of glucocorticoids in the control of body fluid homeostasis has been extensively investigated. Glucocorticoid deficiency can activate V2R (vasopressin receptor 2), increase aquaporins expression, and result in hyponatremia, all of which can be reversed by glucocorticoid supplement. Methods and Results Heart failure was induced by coronary artery ligation for 8 weeks. A total of 32 rats were randomly assigned to 4 groups (n=8/group): sham surgery group, congestive heart failure group, dexamethasone group, and dexamethasone in combination with glucocorticoid receptor antagonist RU486 group. An acute water loading test was administered 6 hours after drug administration. Left ventricular function was measured by a pressure-volume catheter. Protein expressions were determined by immunohistochemistry and immunoblotting. The pressure-volume loop analysis showed that dexamethasone improves cardiac function in rats with heart failure. Western blotting confirmed that dexamethasone remarkably reduces the expressions of V2R, aquaporin 2, and aquaporin 3 in the renal-collecting ducts. As a result of V2R downregulation, the expressions of glucocorticoid regulated kinase 1, apical epithelial sodium channels, and the furosemide-sensitive Na-K-2Cl cotransporter were also downregulated. These favorable effects induced by dexamethasone were mostly abolished by the glucocorticoid receptor inhibitor RU486, indicating that the aforementioned effects are glucocorticoid receptor mediated. Conclusions Glucocorticoids can reverse diluted hyponatremia via inhibiting the vasopressin receptor pathway in rats with heart failure.

Chronic hyponatremia and association with osteoporosis among a large racially/ethnically diverse population.

Chronic hyponatremia may contribute to decreased bone density. We studied 341,003 men and women who underwent DXA testing and observed that individuals with chronic hyponatremia (sodium < 135 mEq/L) had an 11% greater likelihood of having osteoporosis. There was a dose-dependent effect with lower sodium and stronger association with osteoporosis. INTRODUCTION: Chronic hyponatremia has been associated with both neurologic deficits and increased risk of gait abnormalities leading to falls and resultant bone fractures. Whether chronic hyponatremia contributes to decreased bone density is uncertain. We evaluated whether chronic, mild hyponatremia based on serial sodium measurements was associated with increased risk of osteoporosis within a large, ethnically diverse population. METHODS: This is a retrospective cohort study between January 1, 1998 and December 31, 2014 within Kaiser Permanente Southern California, an integrated healthcare delivery system. Men and women were aged ≥ 55 years with ≥ 2 serum sodium measurements prior to dual-energy X-ray absorptiometry (DXA) testing. Time-weighted (TW) mean sodium values were calculated by using the proportion of time (weight) elapsed between sodium measurements and defined as < 135 mEq/L. Osteoporosis defined as any T-score value ≤ - 2.5 of lumbar spine, femoral neck, or hip. RESULTS: Among 341,003 individuals with 3,330,903 sodium measurements, 11,539 (3.4%) had chronic hyponatremia and 151,505 (44.4%) had osteoporosis. Chronic hyponatremic individuals had an osteoporosis RR (95% CI) of 1.11 (1.09, 1.13) compared to those with normonatremia. A TW mean sodium increase of 3 mEq/L was associated with a lower risk of osteoporosis [adjusted RR (95% CI) 0.95 (0.93, 0.96)]. A similar association was observed when the arithmetic mean sodium value was used for comparison. CONCLUSIONS: We observed a modest increase in risk for osteoporosis in people with chronic hyponatremia. There was also a graded association between higher TW mean sodium values and lower risk of osteoporosis. Our findings underscore the premise that chronic hyponatremia may lead to adverse physiological effects and responses which deserves better understanding.

Corticosteroids in the Management of Hyponatremia, Hypovolemia, and Vasospasm in Subarachnoid Hemorrhage: A Meta-Analysis.

BACKGROUND: Cerebral vasospasm and sodium and fluid imbalances are common sequelae of aneurysmal subarachnoid hemorrhage (SAH) and cause of significant morbidity and mortality. Studies have shown the benefit of corticosteroids in the management of these sequelae. We have reviewed the literature and analyzed the available data for corticosteroid use after SAH. METHODS: PubMed, EMBASE, and Cochrane electronic databases were searched without language restrictions, and 7 observational, controlled clinical studies of the effect of corticosteroids in the management of SAH patients were identified. Data on sodium and fluid balances, symptomatic vasospasm (SVS), and outcomes were pooled for meta-analyses using the Mantel-Haenszel random effects model. RESULTS: Corticosteroids, specifically hydrocortisone and fludrocortisone, decreased natriuretic diuresis and incidence of hypovolemia. Corticosteroid administration is associated with lower incidence of SVS in the absence of nimodipine, but does not alter the neurological outcome. CONCLUSIONS: Supplementation of corticosteroids with mineralocorticoid activity, such as hydrocortisone or fludrocortisone, helps in maintaining sodium and volume homeostasis in SAH patients. Larger trials are warranted to confirm the effects of corticosteroids on SVS and patient outcomes.

The effect of chronic mild hyponatremia on bone mineral loss evaluated by retrospective national Danish patient data.

PURPOSE: To evaluate the effect of chronic mild hyponatremia ([Na+]=130-137mmol/L) on bone mineral content (BMC) and bone mineral density (BMD) loss through multiple, serial dual-energy X-ray absorptiometry (DXA) scans. METHODS: Utilizing biochemical and DXA scan data from two Danish regions between 2004 and 2011, supplemented with national Danish patient diagnosis and prescription reimbursement databases, a retrospective cohort study was performed. All subjects with more than one DXA scan were included, then stratified into "normonatremia" ([Na(+)]=[137.00-147.00] mmol/L) and "mild hyponatremia" ([Na(+)]=[130.00-137.00[mmol/L) based on mean and confidence interval (CI) values calculated from all plasma sodium measurements between each subject's first and last DXA scan. Baseline, follow-up and delta values for hip and lumbar spine BMC and BMD were estimated between groups, then adjusted for comorbidity and medication use. RESULTS: Hip and lumbar spine groups had 884 and 1069 patients with "normonatremia" versus 58 and 58 patients with "mild hyponatremia", respectively. Mild hyponatremia was associated with lower BMC and BMD in nearly all regions of the hip, and with worse losses in the trochanteric, femoral neck and total hip regions. Mild hyponatremia had limited effect on the lumbar spine. CONCLUSIONS: Chronic mild hyponatremia seems to greatly affect bone in the hip, while the effect is limited in the lumbar spine. We suggest further retrospective study of patients with moderate (P-Na=120-130mmol/L) to severe hyponatremia (P-Na<120mmol/L) and prospective studies to further examine the association.

Medical Clearance for Desert and Land Sports, Adventure, and Endurance Events.

Endurance events are increasing in popularity in wilderness and remote settings, and participants face a unique set of potential risks for participation. The purpose of this article is to outline these risks and allow the practitioner to better guide the wilderness adventurer who is anticipating traveling to a remote or desert environment.

Fluid volume kinetics of dilutional hyponatremia; a shock syndrome revisited.

OBJECTIVE: To evaluate whether the pathophysiology of shock syndromes can be better understood by comparing central hemodynamics with kinetic data on fluid and electrolyte shifts. METHODS: We studied the dilutional hyponatremic shock that developed in response to overhydration with electrolyte-free irrigating fluid - the so-called 'transurethral resection syndrome' - by comparing cardiac output, arterial pressures, and volume kinetic parameters in 17 pigs that were administered 150 ml/kg of either 1.5% glycine or 5% mannitol by intravenous infusion over 90 minutes. RESULTS: Natriuresis appeared to be the key factor promoting hypovolemic hypotension 15-20 minutes after fluid administration ended. Excessive sodium excretion, due to osmotic diuresis caused by the irrigant solutes, was associated with high estimates of the elimination rate constant (k10) and low or negative estimates of the rate constant describing re-distribution of fluid to the plasma after translocation to the interstitium (k21). These characteristics indicated a high urinary flow rate and the development of peripheral edema at the expense of plasma volume and were correlated with reductions in cardiac output. The same general effects of natriuresis were observed for both irrigating solutions, although the volume of infused 1.5% glycine had a higher tendency to enter the intracellular fluid space. CONCLUSION: Comparisons between hemodynamics and fluid turnover showed a likely sequence of events that led to hypovolemia despite intravenous administration of large amounts of fluid.

Fluid volume kinetics of dilutional hyponatremia; a shock syndrome revisited

OBJECTIVE: To evaluate whether the pathophysiology of shock syndromes can be better understood by comparing central hemodynamics with kinetic data on fluid and electrolyte shifts. METHODS: We studied the dilutional hyponatremic shock that developed in response to overhydration with electrolyte-free irrigating fluid - the so-called ‘transurethral resection syndrome' - by comparing cardiac output, arterial pressures, and volume kinetic parameters in 17 pigs that were administered 150 ml/kg of either 1.5% glycine or 5% mannitol by intravenous infusion over 90 minutes. RESULTS: Natriuresis appeared to be the key factor promoting hypovolemic hypotension 15-20 minutes after fluid administration ended. Excessive sodium excretion, due to osmotic diuresis caused by the irrigant solutes, was associated with high estimates of the elimination rate constant (k10) and low or negative estimates of the rate constant describing re-distribution of fluid to the plasma after translocation to the interstitium (k21). These characteristics indicated a high urinary flow rate and the development of peripheral edema at the expense of plasma volume and were correlated with reductions in cardiac output. The same general effects of natriuresis were observed for both irrigating solutions, although the volume of infused 1.5% glycine had a higher tendency to enter the intracellular fluid space. CONCLUSION: Comparisons between hemodynamics and fluid turnover showed a likely sequence of events that led to hypovolemia despite intravenous administration of large amounts of fluid. .

An elderly patient with chronic hyponatremia.

Hyponatremia is the most common electrolyte disorder. With the aging of the population and the greater propensity of the elderly to develop hyponatremia, this electrolyte disorder is of increasing importance to the practicing nephrologist. In this Attending Rounds, an illustrative patient with hyponatremia is presented. The reasons for the increased incidence and prevalence of hyponatremia in the elderly are discussed, with emphasis on the effects of aging on urinary dilution, the frequently multifactorial nature of hyponatremia in this population, and the absence of a definite cause for inappropriate and persistent vasopressin release in many such patients. The rationale for treating the hyponatremia, even when apparently asymptomatic, is discussed, with attention to cognitive function, gait, and bone structure disturbances that increase the risk for fractures. The various available treatment approaches, including water restriction, demeclocycline, loop diuretics with NaCl supplementation, urea, and vasopressin antagonists are summarized, with emphasis on the efficacy and limitations of each of these therapies.

Exercise associated hyponatraemia leading to tonic-clonic seizure.

A 34-year-old Filipino lady presented to the emergency department with breathlessness and muscle cramping following a Bikram yoga workout. The patient reported sweating excessively while performing 90 min of strenuous exertion in a humidified room heated to an ambient temperature of 40.6°C. After the workout she drank 3.5 litres of water before experiencing breathlessness, severe muscle cramps, nausea and general malaise. Initial investigations revealed severe hyponatraemia (120 mmol/l). Despite early sodium replacement the patient dropped her Glasgow coma scale to 9/15 and developed tonic clonic seizures, requiring intubation and admission to the intensive care unit. The hyponatraemia was slowly corrected on the intensive care unit and the patient made a full recovery over the course of 5 days. This case highlights the dangers of overzealous fluid replacement following severe exertion in a hot environment.

Tolvaptan for the treatment of hyponatremia and congestive heart failure.

Vasopressin plays a central role in regulating body fluid homeostasis, serum osmolality and vascular tone. In response to elevated serum osmolality, vasopressin acts on V2 renal receptors increasing water reabsorption and causing serum sodium to decrease. Pathological conditions characterized by abnormally elevated vasopressin levels such as heart failure (HF) or syndrome of inappropriate antidiuretic hormone (SIADH) can result in hyponatremia. Tolvaptan is a new selective nonpeptide vasopressin V2 receptor antagonist that has shown to rapidly normalize serum sodium concentrations in hyponatremic patients. In patients with congestive heart failure (CHF) and symptoms of volume overload, tolvaptan prompted rapid free water elimination and improved short-term signs and symptoms of HF, although no effect on long-term mortality or HF-related morbidity was observed. Data from phase III studies including over 5,000 patients have demonstrated that tolvaptan is a safe and well tolerated vasopressin receptor antagonist, whose long-term use is not associated with adverse outcomes. Tolvaptan has been recently approved for the treatment of hyponatremia and a marketing authorization application has been filed for the treatment of CHF.

Transient acute liver failure complicating transurethral resection syndrome.

Transurethral resection (TUR) syndrome, resulting from dilutional hyponatraemia for excessive absorption of irrigating fluid, represents the most relevant complication of transurethral resection of prostate (TURP). Ethanol is used as a tracer in the irrigant solution to monitor fluid absorption with a breathalyser. An unusual case of transient acute liver failure complicating TUR syndrome is reported. A 54-year-old male patient, without risk factors for the development of toxic hepatitis, was subjected to TURP for treatment of benign prostatic hyperplasia. Fluid absorption (2275 ml), estimated by breathalyser, exceeded maximum allowed absorption (2000 ml) only at the end of the surgical intervention. No signs of possible toxicity were evident in the few hours following the intervention. About 10 h after the end of TURP, the patient developed sweating, vomiting and diarrhoea. Laboratory analysis revealed severe hyponatraemia (116 meq/l) with signs of severe liver impairment (total bilirubin 5.8 mg/dl, alanine aminotransferase 56,500 U/l, aspartate aminotransferase 32,700 U/l), kidney failure (serum creatinine 1.93 mg/dl) and serum ethanol levels of 219 mg/dl (0.2%). The patient was treated with acetylcysteine 150 mg/kg i.v. and furosemide 50 mg i.v. Liver and renal functions improved in few days and recovered completely within 30 days. The TUR syndrome observed in this case was probably extravascular in nature, and could have been identified and prevented by measuring ethanol levels 10 min after ending the surgical procedure. The performance of such a test should be strongly recommended to all surgeons. The clinicians attributed the development of liver impairment in this case to ethanol toxicity. However, further studies are warranted to confirm whether hepatic injury can represent a possible complication of TUR syndrome when ethanol solution is used as irrigant fluid.

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.

Central pontine and extrapontine myelinolysis in an infant associated with the treatment of craniopharyngioma: case report.

A 3-year-old girl presented with osmotic demyelination syndrome after undergoing uneventful neuroendoscopic cystostomy for a growing cystic suprasellar craniopharyngioma following microscopic subtotal resection 1 year previously. Endocrinopathy had well been controlled by hormone replacement therapy and administration of 1-amino-8-d-arginine-vasopressin with serum sodium concentration within the normal range. She presented generalized seizure and fever on postoperative day 7, with hyponatremia beginning on postoperative day 4 and deteriorating despite frequent correction. The serum sodium concentration began to fluctuate on the same day, in the range 111-164 mEq/l, which lasted for 2 weeks, refractory for intense management. Her body temperature also fluctuated between hypo- and hyperthermia not correlated with serum inflammatory markers. Her conscious disturbance progressively deteriorated with spastic paraparesis. T(2)-weighted magnetic resonance (MR) imaging taken on postoperative day 19 revealed hyperintense areas in the pons, external capsule, bilateral thalami, and basal nuclei, which had not been recognized before, suggesting osmotic demyelination syndrome causing central pontine and extrapontine myelinolysis. MR imaging taken on postoperative days 230 and 360 showed some diminished lesions but others persisted and resulted in a cavity. The patient's depressed conscious level did not improve. Suprasellar craniopharyngioma with long-standing hypothalamic dysfunction may be associated with severe osmotic demyelination syndrome even after less invasive surgery, so serum sodium derangement after surgery should be promptly corrected even if only subtle signs are present.

Severe hyponatremia, hyperglycemia, and hyperlactatemia are associated with intraoperative hyperthermic intraperitoneal chemoperfusion with oxaliplatin.

BACKGROUND: Since the introduction of surgical debulking in combination with intraoperative hyperthermic intraperitoneal chemoperfusion (HIPEC) with oxaliplatin in our institution, severe hyponatremia (sodium: 126.5 +/- 3.8 mmol/L), hyperglycemia (glucose: 22.37 +/- 4.89 mmol/L), and hyperlactatemia (lactate: 3.17 +/- 1.09 mmol/L) have been observed post HIPEC. This metabolic disorder was not observed in patients in whom cisplatin or mitomycin C was used as a chemotherapeutic drug. METHODS: In order to understand the pathophysiology of this finding, an analysis of our data was made. In a first analysis, plasma sodium was corrected for hyperglycemia based on the formula of Hillier. In a second analysis, the influence of total exchangeable sodium, total exchangeable potassium, and total body water on plasma sodium concentration was modeled. RESULTS: Analysis of our data revealed a double mechanism for the observed metabolic disorder: hyperglycemia caused by dextrose 5%, which is used as a carrier for the oxaliplatin, and major loss of sodium into the dialysate (256.7 +/- 68.7 mmol). CONCLUSION: Better control of hyperglycemia and intravenous compensation of sodium loss into the dialysate can attenuate the reported biochemical disturbance.

Reduced anterior hippocampal formation volume in hyponatremic schizophrenic patients.

Diminished hippocampal volume occurs in the anterior segment of some schizophrenic patients, and in the posterior segment in others. The significance of hippocampal pathology in general and these segmental differences in specific is not known. Several lines of evidence suggest anterior hippocampal pathology underlies the life-threatening hyponatremia seen in a subgroup of patients with schizophrenia; therefore our goal was to determine if this region was preferentially diminished in hyponatremic patients. We studied seven polydipsic hyponatremic, ten polydipsic normonatremic, and nine nonpolydipsic normonatremic schizophrenic inpatients, as well as 12 healthy controls. All underwent structural scanning on a high resolution (3.0 T) magnetic resonance imaging (MRI) scanner. Hippocampal formation, amygdala, and third ventricle volumes were manually traced in each subject. The hippocampus was divided at the posterior extent of the uncus, and all structural volumes were corrected for whole brain volume and other significant recognized factors (i.e., age, gender, height, parental education). Despite being overhydrated, anterior hippocampal formation volume was diminished in those with polydipsia and hyponatremia relative to each of the other three groups. Third ventricle volume was larger in this group than in healthy controls but similar to the two patient groups. Posterior hippocampal and amygdala volumes did not differ between groups. Other potential confounds (e.g., water imbalance) either had no effect or accentuated these differences. We conclude the anterior hippocampal formation is smaller in hyponatremic schizophrenic patients, thereby linking an important and objective clinical feature of schizophrenia to a neural pathway that can be investigated in animal models. The findings strengthen the hypothesis that anterior hippocampal formation pathology disrupts functional connectivity with other limbic structures in schizophrenia.

Revisión a partir de un caso clínico: encefalopatía perdedora de sal secundaria a asfixia por ahorcamiento / Review in relation to a clinical case: cerebral salt wasting secondary to asphyxia by hanging

Siendo la hiponatremia un trastorno frecuente en unidades de tratamiento intensivo en especial neuroquirúrgico, se deben tener en consideración las dos etiologías más frecuentes: SIADH y encepalopatía perdedora de sal. La importancia del diagnóstico diferencial radica en que la forma de aproximación diagnóstica y el tratamiento son diferentes, de tal modo que el manejo inadecuado puede intensificar la hiponatremia poniendo en riesgo vital al paciente. Aún así existen otras causas que pueden aumentar la natriuresis: infusiones prolongadas de soluciones salinas pueden provocar un balance negativo de Na y Cl, por internalización de canales Na/K ATP. Además non todos pacientes con EPS presentan niveles elevados de péptido natriurético cerebral. Por lo que aún está en discusión y no se tiene consenso absoluto respecto de su fisiopatología.

Pathogenesis and diagnosis of hyponatremia.

This discussion emphasizes two aspects of hyponatremia: classification according to effective osmolality of the body fluid, and distinction between appropriate and inappropriate ADH secretion. Assessment of the effective osmolality is important because the main deleterious effect of hyponatremia is cell overhydration, which occurs only when the effective osmolality is reduced. Since most cases of hyponatremia are associated with low effective osmolality, cell overhydration is a hallmark of acute hyponatremia. On the other hand, one must be aware of other types of hyponatremia in which effective osmolality is either normal or even increased. Inappropriateness of ADH secretion is defined as ADH secretion that occurs despite low effective osmolality and normal or expanded effective vascular volume. ADH secretion that occurs in hyponatremia is deemed appropriate if the effective vascular volume is low. The use of laboratory parameters is much more reliable in determining effective vascular volume than is careful physical examination.