Treatment of symptomatic hyponatremia

Predictive value of hyponatremia for short-term mortality in supratentorial spontaneous intracerebral hemorrhage: a single center study

Background

Hyponatremia is a common electrolyte disturbance in patients with neurological disease; however, its predictive role for outcome in patients with supratentorial spontaneous intracerebral hemorrhage (sICH) is controversial. This study aims to explore the association between hyponatremia within 7 days after bleeding and 90-day mortality in patients with supratentorial sICH.

Methods

A retrospective analysis was conducted at our institution. Patients with sICH meeting the inclusion criteria were enrolled in this study. Multivariate regression analyses were performed to determine the predictive value of hyponatremia (serum sodium <135 mmol/L) for 90-day mortality and functional outcome. Subgroup analysis was performed based on the degree and duration of hyponatremia and therapeutic strategies. The Spearman correlation test was performed to explore the relationship between hyponatremia severity and duration with variables in a multivariate regression model. Kaplan-Meier curve was depicted to reveal the relationship between hyponatremia and mortality. The receiver operating characteristic (ROC) curve was plotted to show the diagnostic effect of the minimum concentration of serum sodium (sodiummin) on 90-day mortality.

Results

A total of 960 patients were enrolled, 19.6% (188) of whom were patients with hyponatremia and 26.0% (250) had 90-day mortality. The incidence of hyponatremia was roughly 2.5 times in non-survivors compared with survivors (34.8% vs. 14.2%). Multivariate regression analysis revealed that hyponatremia was the independent predictor of 90-day mortality (OR 2.763, 95%CI 1.836-4.157) and adverse outcome (OR 3.579, 95%CI 2.332-6.780). Subgroup analysis indicated an increased trend in mortality risk with both duration (more or less than 48 h) and severity of hyponatremia (mild, moderate, and severe) and confirmed the predictive value of hyponatremia for mortality in patients undergoing surgical intervention (external ventricular drainage, craniotomy, and decompressive craniectomy; all p < 0.05). The Spearman correlation test indicated no moderate or strong relationship between hyponatremia severity and duration with other variables in the multivariate model (all |rs| < 0.4). The ROC curve suggested the moderate diagnostic performance of sodiummin for mortality in both general patients and subgroups of therapeutic method patients (AUC from 0.6475 to 0.7384).

Conclusion

Hyponatremia occurring in the first 7 days after bleeding is an independent predictor of 90-day morality and adverse outcome. Rigorous electrolyte scrutiny in patients treated surgically is required.

Review of Hematological and Oncological Emergencies

Patients with hematological malignancies, both treated and untreated, or solid tumors undergoing treatment are at risk of life-threatening complications, which may present in the emergency department (ED). Such emergencies are diverse in etiology and often require prompt treatment. Traditional complications, such as febrile neutropenia, have had recent guideline updates, which incorporate new evidence and a new validated risk stratification tool. In addition, newer approaches to treatment, such as chimeric antigen receptor (CAR) T-cell therapy, are becoming more widely available and have unique associated toxicities. This review discusses the management of the following hematological and oncological emergencies likely to be encountered in the ED: febrile neutropenia, CAR T-cell toxicities, differentiation syndrome, tumor lysis syndrome, hypercalcemia of malignancy, and hyponatremia.

[SYNDROME OF INAPPROPRIATE ANTIDIURETIC HORMONE SECRETION AS A SIDE EFFECT OF CHEMOTHERAPY FOR URACHAL CARCINOMA: A CASE REPORT]

A 54-year-old woman was admitted to our hospital complaining of gross hematuria and difficulty urinating. Cystoscopy revealed a tumor 4 cm in size with calcification on top of the bladder. After diagnosis of urachal carcinoma by transurethral resection of the bladder, partial cystectomy with en bloc resection of the median umbilical ligament and pelvic lymphadenectomy was performed. Pathological diagnosis confirmed urachal carcinoma, pT3b, ly1, v0, pN1, RM0. TS-1 and cisplatin chemotherapy (TS-1 at 100 mg/day on days 1-21, CDDP at 60 mg/m² on day 8) was administered. On day 13, the patient was admitted because of consciousness disorder (Glasgow Coma Scale E2V1M4). Hyponatremia (Na 109 mEq/l) and renal excretion of sodium were present and the patient was diagnosed with the syndrome of inappropriate antidiuretic hormone secretion (SIADH) induced by chemotherapy. Serum sodium level and her consciousness level gradually improved after administration of 3% saline. SIADH caused by chemotherapy containing cisplatin is a relatively rare, but potentially serious adverse effect that requires close attention.

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

INTRODUCTION

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

CASE PRESENTATION

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

CONCLUSION

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

Focus on neonatal and infantile onset of nephrogenic syndrome of inappropriate antidiuresis: 12 years later

Nephrogenic syndrome of inappropriate antidiuresis (NSIAD), first described in 2005, is a rare genetic X-linked disease, presenting with hyponatremia, hyposmolarity, euvolemia, inappropriately concentrated urine, increased natriuresis, and undetectable or very low arginine-vasopressine (AVP) circulating levels. It can occur in neonates, infants, or later in life. NSIAD must be early recognized and treated to prevent severe hyponatremia, which can show a dangerous impact on neonatal outcome. In fact, it potentially leads to death or, in case of survival, neurologic sequelae. This review is an update of NSIAD 12 years after the first description, focusing on reported cases of neonatal and infantile onset. The different molecular patterns affecting the AVP receptor 2 (V2R) and determining its gain of function are reported in detail; moreover, we also provide a comparison between the different triggers involved in the development of hyponatremia, the evolution of the symptoms, and modality and efficacy of the different treatments available.

Impact of long-term potassium supplementation on thiazide diuretic-induced abnormalities of glucose and uric acid metabolisms

Treatment of hypertension with thiazide diuretics may trigger hypokalemia, hyperglycemia, and hyperuricemia. Some studies suggest simultaneous potassium supplementation in hypertensive patients using thiazide diuretics. However, few clinical studies have reported the impact of long-term potassium supplementation on thiazide diuretic-induced abnormalities in blood glucose and uric acid (UA) metabolisms. One hundred hypertensive patients meeting the inclusion criteria were equally randomized to two groups: IND group receiving indapamide (1.25-2.5 mg daily) alone, and IND/KCI group receiving IND (1.25-2.5 mg daily) plus potassium chloride (40 mmol daily), both for 24 weeks. At the end of 24-week follow-up, serum K⁺ level in IND group decreased from 4.27 ± 0.28 to 3.98 ± 0.46 mmol/L (P < 0.001), and fasting plasma glucose (FPG) and UA increased from 5.11 ± 0.52 to 5.31 ± 0.57 mmol/L (P < 0.05), and from 0.404 ± 0.078 to 0.433 ± 0.072 mmol/L (P < 0.05), respectively. Serum K⁺ level in IND/KCl group decreased from 4.27 ± 0.36 to 3.89 ± 0.28 mmol/L (P < 0.001), and FPB and UA increased from 5.10 ± 0.41 to 5.35 ± 0.55 mmol/L (P < 0.01), and from 0.391 ± 0.073 to 0.457 ± 0.128 mmol/L (P < 0.001), respectively. The difference value between the serum K⁺ level and FPG before and after treatment was not statistically significant between the two groups. However, the difference value in UA in IND/KCl group was significantly higher than that in IND group (0.066 (95% confidence interval (CI): 0.041-0.090)  mmol/L vs. 0.029 (95% CI: 0.006-0.058) mmol/L, P < 0.05). The results showed that long-term routine potassium supplementation could not prevent or attenuate thiazide diuretic-induced abnormalities of glucose metabolism in hypertensive patients; rather, it may aggravate the UA metabolic abnormality.

Current management of refractory ascites in patients with cirrhosis

Liver cirrhosis is a health problem worldwide, and ascites is its principal symptom. Refractory ascites is intractable and occurs in 5%-10% of all patients with ascites due to cirrhosis. Refractory ascites leads to a poor quality of life and high mortality rate. Ascites develops as a result of portal hypertension, which leads to water-sodium retention and renal failure. Various therapeutic measures can be used for refractory ascites, including large-volume paracentesis, transjugular intrahepatic portosystemic shunt, vasoconstrictive drugs, and an automated low-flow ascites pump system. However, ascites generally can be resolved only by liver transplantation. Because not all patients can undergo liver transplantation, traditional approaches are still used to treat refractory ascites. The choice of treatment modality for refractory ascites depends, among other factors, on the condition of the patient.

The treatment of vasopressin V2-receptor antagonists in cirrhosis patients with ascites: a meta-analysis of randomized controlled trials

Background

Ascites is the most common complication of cirrhosis. It may lead to the consequence of poor prognosis and the deterioration of quality of life. Asopressin V2 receptor antagonists is a kind of vaptans, and it has been proved to be effective in hyponatremia patients. We conducted a meta-analysis about treatment of vaptans in cirrhosis patients with ascites.

Methods

Following our selection criteria, we collected a total of 14 studies containing 16 randomized controlled trials (2620 patients) from a series of database about the treatment with vaptans for cirrhosis with ascites patients. The included studies compared the treatment effect of lixivaptan (VPA 985), or RMJ-351647, or satavaptan, or tolvaptan with placebo.

Results

The included vaptans (asopressin V2 receptor antagonists) showed significant effect of increasing the serum sodium concentration for cirrhosis patients (WMD = 2.11 mmol/L, p < 0.00001). Patients also could acquire significant improvement of ascites, as this kind of aquaretics can significantly reduce ascites patients’ weight (WMD = −1.53, p < 0.00001), abdominal girth (WMD = −2.04, p < 0.00001), and the ratio of worsening ascites (RR = 0.51, p = 0.001). Though the drug did not produce more total adverse events (RR = 1.04, p = 0.09) and the total serious events (RR = 1.04, p = 0.42), the emergence of excessive correction of serum sodium concentrations (>145 mmol/L) was more frequently noted in patients under the employment of vaptans (RR = 2.14, 95 % CI [1.45, 3.16], p = 0.0001). Whether with the administration of vaptans for short-term or long-term, no survival benefit was detected from the selected studies.

Conclusions

Asopressin V2 receptor antagonists could play an effective and safe role in symptomatic treatment for cirrhosis patients with ascites, especially for refractory ascites patients who presented insufficient response to conventional diuretics.

Severe Hyponatremia due to Phlegmonous Trismus

We describe a patient with dysphagia and trismus associated with lower jaw inflammation due to phlegmon who developed severe hyponatremia from water intoxication due to excessive water intake after diaphoresis caused by abnormally hot weather. A 63-year-old woman presented with severe swelling of the floor of the mouth and trismus. As she had spasms and numbness of the extremities and restlessness and water intoxication caused by excessive water intake was suspected, she was hospitalized for the treatment of inflammation and electrolyte disorder. Although swelling of the floor of the mouth subsided over time after antimicrobial therapy, vomiting, diarrhea, and numbness of the extremities continued. On day 5 of hospitalization, severe vomiting and diarrhea recurred, and serum sodium levels decreased to 108 mEq/L. Decrease in water intake is essential in the treatment of hyponatremia. However, in patients with severe vomiting and diarrhea who can swallow only liquids because of hot weather and eating disorder, the risk of sodium depletion is high. It is important to restore electrolyte balance and fluid volume through supplementation with sodium, chlorine, potassium, and glucose among others, the reduction of intravenous fluid volume, and diuresis in order to correct the sodium level slowly.

Hyponatremia: A Review

Hyponatremia is the most frequently occurring electrolyte abnormality and can lead to life-threatening complications. This disorder may be present on admission to the intensive care setting or develop during hospitalization as a result of treatment or multiple comorbidities. Patients with acute hyponatremia or symptomatic chronic hyponatremia will likely require treatment in the intensive care unit (ICU). Immediate treatment with hypertonic saline is needed to reduce the risk of permanent neurologic injury. Chronic hyponatremia should be corrected at a rate sufficient to reduce symptoms but not at an excessive rate that would create a risk of osmotic injury. Determination of the etiology of chronic hyponatremia requires analysis of serum osmolality, volume status, and urine osmolality and sodium level. Correct diagnosis points to the appropriate treatment and helps identify risk factors for accelerated correction of the serum sodium level. Management in the ICU facilitates frequent laboratory draws and allows close monitoring of the patient's mentation as well as quantification of urine output. Overly aggressive correction of serum sodium levels can result in neurological injury caused by osmotic demyelination. Therapeutic measures to lower the serum sodium level should be undertaken if the rate increases too rapidly.

Impact of perioperative hyponatremia in children: A narrative review

For more than 50 years, hypotonic fluids (crystalloids) have been the standard for maintenance fluid used in children. In the last decade, several studies have evaluated the risk of hyponatremia associated with the use of hypotonic vs isotonic fluids, which has lead to an intense debate. Children undergoing surgery have several stimuli for release of antidiuretic hormone, which controls renal water handling, including pain, nausea, vomiting, narcotic use and blood loss. The body’s primary defense against the development of hyponatremia is the ability of the kidneys to excrete free water and dilute urine. Increased levels of antidiuretic hormone can result in hyponatremia, defined as a plasma sodium level < 136 mmol/L, which causes cells to draw in excess water and swell. This manifests as central nervous system symptoms such as lethargy, irritability and seizures. The risk for symptomatic hyponatremia is higher in children than in adults. It represents an emergency condition, and early diagnosis, prompt treatment and close monitoring are essential to reduce morbidity and mortality. The widespread use of hypotonic fluids in children undergoing surgery is a matter of concern and more focus on this topic is urgently needed. In this paper, we review the literature and describe the impact of perioperative hyponatremia in children.

Effects of Hyponatremia on the Brain

Hyponatremia is a very common electrolyte disorder, especially in the elderly, and is associated with significant morbidity, mortality and disability. In particular, the consequences of acute hyponatremia on the brain may be severe, including permanent disability and death. Also chronic hyponatremia can affect the health status, causing attention deficit, gait instability, increased risk of falls and fractures, and osteoporosis. Furthermore, an overly rapid correction of hyponatremia can be associated with irreversible brain damage, which may be the result of the osmotic demyelination syndrome. This review analyzes the detrimental consequences of acute and chronic hyponatremia and its inappropriate correction on the brain and the underlying physiopathological mechanisms, with a particular attention to the less known in vivo and in vitro effects of chronic hyponatremia.

Hyponatraemic seizures following prostate brachytherapy

Aim

To demonstrate the importance of fluid management in the perioperative period by presenting a case of hyponatraemic seizures following prostate brachytherapy.

Case

A 61-year-old gentleman, who had prostate cancer but was otherwise well, developed confusion and word-finding difficulties the day after prostate brachytherapy. This was followed by tonic–clonic seizures that necessitated treatment, intubation and ventilation, and admission to the intensive care unit. Investigations revealed serum sodium of 116 mmol/L. Fluid balance was inadequately recorded, but the patient had drank more than 3 L of water before he developed hyponatraemia.

Discussion

Postoperative severe hyponatraemia and hyponatraemic encephalopathy develop because of anti-diuretic hormone release and hypotonic fluid administration. These are medical emergencies and should be managed in an intensive care unit. Symptoms range from headache, nausea and confusion to seizures, respiratory arrest and death, and are related to cerebral oedema. Treatment is done using hypertonic sodium chloride to increase the serum sodium to safe levels. Care should be taken to avoid overly rapid correction of serum sodium. Complete documentation of fluid balance is essential to allow proper assessment of fluid status. Patients should be advised on appropriate oral fluids in the postoperative period.

Delayed postoperative hyponatremia after transsphenoidal surgery: prevalence and associated factors

Object

Transient delayed postoperative hyponatremia (DPH) after transsphenoidal surgery (TSS) is common and can have potentially devastating consequences. However, the true prevalence of transient symptomatic and asymptomatic DPH has not been studied in a large patient cohort with close and accurate follow-up.

Methods

A retrospective analysis of a single-institution prospective database was conducted; all patients undergoing TSS for lesions involving the pituitary gland were followed up in a multidisciplinary neuroendocrine clinic, and demographic, imaging, and clinical data were prospectively collected. Patients were examined preoperatively and followed up postoperatively in a standardized fashion, and their postoperative sodium levels were measured at Weeks 1 and 2 postoperatively. Levels of hyponatremia were rated as mild (serum sodium concentration 130–134 mEq/L), moderate (125–129 mEq/L), or severe (< 125 mEq/L). Routine clinical questionnaires were administered at all postoperative office visits. Postoperative hyponatremia was analyzed for correlations with demographic and clinical features and with immediate postoperative physiological characteristics.

Results

Over a 4-year interval, 373 procedures were performed in 339 patients who underwent TSS for sellar and parasellar lesions involving the pituitary gland. The mean (± SD) age of patients was 48 ± 18 years; 61.3% of the patients were female and 46.1% were obese (defined as a body mass index [BMI] ≥ 30). The overall prevalence of DPH within the first 30 days postoperatively was 15.0%; 7.2% of the patients had mild, 3.8% moderate, and 3.8% severe hyponatremia. The incidence of symptomatic hyponatremia requiring hospitalization was 6.4%. The Fisher exact test detected a statistically significant association of DPH with female sex (p = 0.027) and a low BMI (p = 0.001). Spearman rank correlation detected a statistically significant association between BMI and nadir serum sodium concentration (r = 0.158, p = 0.002) and an inverse association for age (r = −0.113, p = 0.031). Multivariate analyses revealed a positive correlation between postoperative hyponatremia and a low BMI and a trend toward association with age; there were no associations between other preoperative demographic or perioperative risk factors, including immediate postoperative alterations in serum sodium concentration. Patients were treated with standardized protocols for hyponatremia, and DPH was not associated with permanent morbidity or mortality.

Conclusions

Delayed postoperative hyponatremia was a common result of TSS; a low BMI was the only clear predictor of which patients will develop DPH. Alterations in immediate postoperative sodium levels did not predict DPH. Therefore, an appropriate index of suspicion and close postoperative monitoring of serum sodium concentration should be maintained for these patients, and an appropriate treatment should be undertaken when hyponatremia is identified.

Syndrome of inappropriate antidiuretic hormone associated with aripiprazole

PURPOSE

A probable case of aripiprazole-induced syndrome of inappropriate antidiuretic hormone (SIADH) is reported.

SUMMARY

A 65-year-old Caucasian man arrived in the emergency department (ED) with dizziness, headache, abdominal pain, nausea, and vomiting. There had been no recent additions or changes to the patient's medication regimen except for an increase in the daily dose of aripiprazole (from 10 to 20 mg) about two months prior. On admission, the patient's serum sodium concentration was 108 meq/L, prompting discontinuation of aripiprazole use and fluid restrictions. Over the next 72 hours, the serum sodium level increased to a near-normal concentration (127 meq/L), and the man was discharged back to a nursing facility. Three days later, the patient was readmitted to the ED with recurrent symptoms and a serum sodium concentration of 118 meq/L, a serum osmolality of 254 mOsm/kg, a urine osmolality of 575 mOsm/kg, and a urine sodium concentration of 101 meq/L. It was learned that aripiprazole use had been inappropriately resumed at the nursing facility. Aripiprazole was again discontinued, and fluid restrictions were imposed, with subsequent abatement of hyponatremia over four days. Application of the adverse drug reaction probability scale of Naranjo et al. in this case yielded a score of 7, indicating probable aripiprazole-associated SIADH.

CONCLUSION

A 65-year-old man developed severe hyponatremia after an aripiprazole dosage increase. Hyponatremia resolved promptly with the discontinuation of aripiprazole. After discharge from the hospital, the patient inadvertently received aripiprazole again and was subsequently readmitted with another episode of severe hyponatremia.

Use of desmopressin acetate in severe hyponatremia in the intensive care unit

BACKGROUND AND OBJECTIVES

Excessive correction of chronic and profound hyponatremia may result in central pontine myelinolysis and cause permanent brain damage. In the case of foreseeable or established hyponatremia overcorrection, slowing down the correction rate of sodium plasma levels (PNa) or reinducing mild hyponatremia may prevent this neurologic complication.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This retrospective and observational study was performed with 20 consecutive patients admitted to two intensive care units for severe hyponatremia, defined by PNa <120 mmol/L and/or neurologic complications ascribable to hyponatremia and subsequently treated by desmopressin acetate (DDAVP) during correction of hyponatremia when the rate of correction was overtly or predictably excessive. The primary endpoint was the effectiveness of DDAVP on PNa control.

RESULTS

DDAVP dramatically decreased the rate of PNa correction (median 0.81 mmol/L per hour [interquartile range, 0.46, 1.48] versus -0.02 mmol/L per hour [-0.16, 0.22] before and after DDAVP, respectively; P<0.001) along with a concurrent decrease in urine output (650 ml/h [214, 1200] versus 93.5 ml/h [43, 143]; P=0.003), and a rise in urine osmolarity (86 mmol/L [66, 180] versus 209 mmol/L [149, 318]; P=0.002). The maximal magnitude of PNa variations was also markedly reduced after DDAVP administration (11.5 mmol/L [8.25, 14.5] versus 5 mmol/L [4, 6.75]; P<0.001). No patient developed seizures after DDAVP or after subsequent relowering of PNa that occurred in 11 patients.

CONCLUSIONS

Desmopressin acetate is effective in curbing the rise of PNa in patients admitted in the intensive care unit for severe hyponatremia, when the initial rate of correction is excessive.

Urine output and resultant osmotic water shift are major determinants of plasma sodium level in syndrome of inappropriate antidiuretic hormone secretion

Although various formulas predicting plasma sodium level ([Na]) are proposed for correction of hyponatremia, it seems that an anticipated [Na] frequently exceeds or falls below the measured [Na], especially in syndrome of inappropriate antidiuretic hormone secretion (SIADH). The causative factors of the fluctuation have never been investigated clearly. The aim of this study was to identify the determining factors for accurate prediction of [Na] by comparing data from previously proposed formulas and a novel osmotic compartment model (O-C model). The O-C model, which simulates the amounts of osmoles in extracellular and intracellular fluids, can estimate resultant osmotic water shift (OWS) and [Na]. The accuracy of representative formulas was verified in a point-to-point study using blood and urine samples obtained every 4 hours from 9 patients. Among 161 measurement points, a large fluctuation of urine volume and urine sodium level was observed. The gap between anticipated and measured [Na] in the widely used Adrogue-Madias formula was -0.5 ± 0.1 mEq/L/4 h (mean ± standard error), showing a marked tendency to underestimate [Na]. The gap in the O-C model including OWS was 0.1 ± 0.1 mEq/L/4 h, and that in the O-C model eliminating OWS was 1.9 ± 0.2 mEq/L/4 h, indicating that measurement of urine output and estimation of resulting OWS are essential for a superior prediction of [Na] in SIADH. A simulation study with the O-C model including OWS unveiled a distinctive correction pattern of [Na] dependent on the urine volume and urine sodium level, providing a useful choice for the proper type and rate of infusion.

Central pontine myelinolysis with meticulous correction of hyponatraemia in chronic alcoholics

Central pontine myelinolysis is a demyelinating disorder that arises due to osmolar disturbances in the cerebral microenvironment characterised by loss of the myelin sheath of neurons. The diffusion-weighting imaging sequence of MRI is the most sensitive diagnostic imaging modality for myelinolysis. The rapid correction of hyponatraemia by >20-25 mmol/L/48 h has been known for a long time as a prime cause of osmotic demyelination. Various other comorbidities in hyponatraemic patients are well known that can lead to osmotic demyelination such as alcoholism, hypoxaemia, severe liver disease, malignancy, burns, liver transplantation and malnutrition. Chronic alcohol abusers with additional liver disease and malnutrition have altered osmotic equilibrium at baseline that predisposes them to osmotic demyelination. We suggest a more cautious and meticulous approach should be followed in these patients to avoid the dreaded complication.

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.

Metabolic encephalopathies

Kinnier Wilson coined the term metabolic encephalopathy to describe a clinical state of global cerebral dysfunction induced by systemic stress that can vary in clinical presentation from mild executive dysfunction to deep coma with decerebrate posturing; the causes are numerous. Some mechanisms by which cerebral dysfunction occurs in metabolic encephalopathies include focal or global cerebral edema, alterations in transmitter function, the accumulation of uncleared toxic metabolites, postcapillary venule vasogenic edema, and energy failure. This article focuses on common causes of metabolic encephalopathy, and reviews common causes, clinical presentations and, where relevant, management.

[Vasopressin receptor antagonists: the vaptans]

The non-peptide vasopressin antagonists (VPA), called vaptans, were developed in the 1990s to antagonize both the pressor and antidiuretic effects of vasopressin. There are three subtypes of VPA receptors: V1a, V1b and V2. V1a receptors are widely distributed in the body, mainly the blood vessels and myocardium. The V1b receptors are located mainly in the anterior pituitary gland and play a role in ACTH release. V2 receptors are located in the collecting tubular renal cells. Both V1a and V1b receptors act through the intracellular phosphoinositol signalling pathway, Ca(++) being the second messenger. V2 receptors work through AMPc generation, which promotes aquaporin 2 (AQP2) trafficking and allows water to enter the cell. The vaptans act competitively at the AVP receptor. The most important are mozavaptan, lixivaptan, satavaptan and tolvaptan, all of which are selective V2 antagonists and are administered through the oral route. In contrast, conivaptan is a dual V1 and V2 antagonist administered through the endovenous route. The main characteristics of vaptans are their effect on free water elimination without affecting electrolyte excretion. There are several studies on the effects of these drugs in hypervolemic hyponatremia (heart failure, hepatic cirrhosis) as well as in normovolemic hyponatremia (inappropriate secretion of ADH [SIADH]). Current studies show that the vaptans are effective and well tolerated, although knowledge of these drugs remains limited. There are no studies of the use of vaptans in severe hyponatremia. Osmotic demyelination syndrome due to excessively rapid correction of hyponatremia has not been described.

Treatment of euvolemic hyponatremia in the intensive care unit by urea

INTRODUCTION

Hyponatremia in the intensive care unit (ICU) is most commonly related to inappropriate secretion of antidiuretic hormone (SIADH). Fluid restriction is difficult to apply in these patients. We wanted to report the treatment of hyponatremia with urea in these patients.

METHODS

Two groups of patients are reported. The first one is represented by a retrospective study of 50 consecutive patients with mild hyponatremia treated with urea. The second group is presented by a series of 35 consecutive patients with severe hyponatremia acquired outside the hospital (≤ 115 mEq/L) who where treated by isotonic saline and urea (0.5 to 1 g/kg/day), administered usually by gastric tube.

RESULTS

In the first group with mild hyponatremia (128 ± 4 mEq/L) the serum sodium (SNa) increased to a mean value of 135 ± 4 mEq/L (P < 0.001) after two days of urea therapy (46 ± 25 g/day), despite a large fluid intake (> 2 L/day). The mean duration of urea therapy was six days (from 2 to 42 days). Six patients developed hyponatremia again once the urea was stopped, which necessitated its reintroduction. Six patients developed hypernatremia (maximum value 155 mEq/L). In the second group, SNa increased from 111 ± 3 mEq/L to 122 ± 4 mEq/L in one day (P < 0.001). All the patients with neurological symptoms made a rapid recovery. No side effects were observed.

CONCLUSIONS

These data show that urea is a simple and inexpensive therapy to treat euvolemic hyponatremia in the ICU.

Diuretics in clinical practice. Part II: electrolyte and acid-base disorders complicating diuretic therapy

IMPORTANCE OF THE FIELD

As with all potent therapeutic agents, the use of diuretic compounds has been linked with several adverse effects that may reduce quality of life and patient compliance and, in some cases, may be associated with considerable morbidity and mortality. Among the various types of adverse effects, disturbances of electrolyte and acid-base balance are perhaps the most common, and some of them are the aetiological factors of other side effects (i.e., hypokalaemia causing ventricular arrhythmias or glucose intolerance). The mechanism and site of action and, therefore, the pharmacological effects of each diuretic class largely determine the specific electrolyte or acid-base abnormalities that will accompany the use of each diuretic agent.

AREAS COVERED IN THE REVIEW

This article reviews the major electrolyte disturbances (hypokalaemia, hyperkalaemia, hyponatraemia, disorders of magnesium and calcium balance), as well as the acid-base abnormalities complicating the use of the various diuretic agents.

WHAT THE READER WILL GAIN

The reader will gain insights into the pathogenesis of the diuretic-induced electrolyte and acid-base disorders together with considerations for their prevention and treatment.

TAKE HOME MESSAGE

Knowledge of the pharmacologic properties of each diuretic class and appropriate monitoring of patients under diuretic treatment represent the most important strategies to prevent the development of diuretic-related adverse events and their consequences.

New aspects in the pathogenesis, prevention, and treatment of hyponatremic encephalopathy in children

Hyponatremia is the most common electrolyte abnormality encountered in children. In the past decade, new advances have been made in understanding the pathogenesis of hyponatremic encephalopathy and in its prevention and treatment. Recent data have determined that hyponatremia is a more serious condition than previously believed. It is a major comorbidity factor for a variety of illnesses, and subtle neurological findings are common. It has now become apparent that the majority of hospital-acquired hyponatremia in children is iatrogenic and due in large part to the administration of hypotonic fluids to patients with elevated arginine vasopressin levels. Recent prospective studies have demonstrated that administration of 0.9% sodium chloride in maintenance fluids can prevent the development of hyponatremia. Risk factors, such as hypoxia and central nervous system (CNS) involvement, have been identified for the development of hyponatremic encephalopathy, which can lead to neurologic injury at mildly hyponatremic values. It has also become apparent that both children and adult patients are dying from symptomatic hyponatremia due to inadequate therapy. We have proposed the use of intermittent intravenous bolus therapy with 3% sodium chloride, 2 cc/kg with a maximum of 100 cc, to rapidly reverse CNS symptoms and at the same time avoid the possibility of overcorrection of hyponatremia. In this review, we discuss how to recognize patients at risk for inadvertent overcorrection of hyponatremia and what measures should taken to prevent this, including the judicious use of 1-desamino-8d-arginine vasopressin (dDAVP).

Osmotic demyelination syndrome

The osmotic demyelination syndrome (ODS) has been a recognized complication of the rapid correction of hyponatremia for decades. However, in recent years, a variety of other medical conditions have been associated with the development of ODS, independent of changes in serum sodium. This finding suggests that the pathogenesis of ODS may be more complex and involve the inability of brain cells to respond to rapid changes in osmolality of the interstitial (extracellular) compartment of the brain, leading to dehydration of energy-depleted cells with subsequent axonal damage that occurs in characteristic areas. Features of the syndrome include quadriparesis and neurocognitive changes in the presence of characteristic lesions found on magnetic resonance imaging of the brain. Although slow correction of hyponatremia seems to be the best way to prevent development of the syndrome, there are new data that suggest reintroduction of hyponatremia in those patients who have undergone inadvertent rapid correction of the serum sodium and corticosteroids may play a role in prevention of ODS.

Hyponatremia in cirrhosis and vaptans

Hyponatremia is a common problem in patients with advanced cirrhosis. Hyponatremia in cirrhosis includes two distinct types: hypovolemic hyponatremia, and hypervolemic or dilutional hyponatremia. The former is characterized by low blood sodium, low blood volume, dehydration and prerenal renal dysfunction, not accompanied by edema and ascites, while the latter is characterized by insufficient circulatory volume and dilutional hyponatremia, accompanied by edema and ascites. Hyponatremia is closely related to various complications of cirrhosis and to early mortality after liver transplantation. Vaptans, a class of selective non-peptide arginine vasopressin (AVP) receptor antagonists, act by antagonizing specifically the effects of AVP V₂ receptor located in the renal collecting tubules to inhibit water reabsorption without affecting electrolytes excretion. Vaptans has been evaluated by several clinical trials for their role in the management of hyponatremia. The short-term treatment with vaptans is associated with a marked increase in renal solute-free water excretion and improvement of hyponatremia with no apparent adverse reactions. The discovery of vaptans is considered a new milestone in the management of hyponatremia in cirrhosis.

Organic osmolytes in hyponatremia and ammonia toxicity

Hyperammonemia (HA) is a major and commonly observed feature of hepatic encephalopathy. Furthermore, hyponatremia is an important pathogenetic factor in patients with hepatic encephalopathy. Both conditions have some features in common, such as the release of organic osmolytes, which might be an adaptive mechanism against cell swelling. However, the consequence of a possible relationship between osmoregulatory response in hyperammonemia and hyponatremia is not completely understood. This review gives a short introduction into the pathogenesis of hepatic encephalopathy and hyponatremia. For a comparison of both pathological events, some basics on cellular osmo- and volume regulation are explained, in particular as the mechanisms involved in the adaption of the cell to volume changes can be different under both pathological conditions. The role of brain glutamine and organic osmolytes in hyponatremia and hyperammonemia and their combination are discussed based on findings in experimental animal models, and finally on data obtained from primary astrocytes in culture. The observations that the decrease of brain organic osmolytes in astrocytes not adequately compensate for an increased intracellular osmolarity caused by glutamine are consistent with results obtained after chronic hyponatremia in rats, in which the release of osmolytes does not protect from ammonia-induced brain edema. Furthermore, a decrease in intracellular osmolarity is attributed both to the release and a reduced de novo synthesis of amino acids.

100 cc 3% sodium chloride bolus: a novel treatment for hyponatremic encephalopathy

Hyponatremic encephalopathy is a potentially lethal condition with numerous reports of death or permanent neurological injury. The optimal treatment for hyponatremic encephalopathy remains controversial. We have introduced a unified approach to the treatment of hyponatremic encephalopathy which uses 3% NaCl (513 mEq/L) bolus therapy. Any patient with suspected hyponatremic encephalopathy should receive a 2 cc/kg bolus of 3% NaCl with a maximum of 100 cc, which could be repeated 1-2 times if symptoms persist. The approach results in a controlled and immediate rise in serum sodium with little risk of inadvertent overcorrection.

Hyponatremia in neurosurgical patients: clinical guidelines development

OBJECTIVE

Neurosurgical patients have a high risk of hyponatremia and associated complications. We critically evaluated the existing literature to identify the determinants for the development of hyponatremia and which management strategies provided the best outcomes.

METHODS

A multidisciplinary panel in the areas of neurosurgery, nephrology, critical care medicine, endocrinology, pharmacy, and nursing summarized and classified hyponatremia literature scientific studies published in English from 1950 through 2008. The panel's recommendations were used to create an evaluation and treatment protocol for hyponatremia in neurosurgical patients at the University of Florida.

RESULTS

Hyponatremia should be further investigated and treated when the serum sodium level is less than 131 mmol/L (class II). Evaluation of hyponatremia should include a combination of physical examination findings, basic laboratory studies, and invasive monitoring when available (class III). Obtaining levels of hormones such as antidiuretic hormone and natriuretic peptides is not supported by the literature (class III). Treatment of hyponatremia should be based on severity of symptoms (class III). The serum sodium level should not be corrected by more than 10 mmol/L/d (class III). Cerebral salt wasting should be treated with replacement of serum sodium and intravenous fluids (class III). Fludrocortisone may be considered in the treatment of hyponatremia in subarachnoid hemorrhage patients at risk of vasospasm (class I). Hydrocortisone may be used to prevent natriuresis in subarachnoid hemorrhage patients (class I). Hyponatremia in subarachnoid hemorrhage patients at risk of vasospasm should not be treated with fluid restriction (class II). Syndrome of inappropriate antidiuretic hormone may be treated with urea, diuretics, lithium, demeclocycline, and/or fluid restriction (class III).

CONCLUSION

The summarized literature on the evaluation and treatment of hyponatremia was used to develop practice management recommendations for hyponatremia in the neurosurgical population. However, the practice management recommendations relied heavily on expert opinion because of a paucity of class I evidence literature on hyponatremia.

Electrolyte complications of malignancy

A thorough working knowledge of the diagnosis and treatment of life-threatening electrolyte abnormalities in cancer patients, especially hyponatremia, hypoglycemia, and hypercalcemia, is essential to the successful practice of emergency medicine. Although most minor abnormalities have no specific treatment, severe clinical manifestations of several notable electrolytes occur with significant frequency in the setting of malignancy. The treatment of life-threatening electrolyte abnormalities is reviewed here. Promising future treatments directed at the underlying physiology are also introduced.

Efficacy and safety of oral conivaptan, a vasopressin-receptor antagonist, evaluated in a randomized, controlled trial in patients with euvolemic or hypervolemic hyponatremia

BACKGROUND

In most cases of hyponatremia, arginine vasopressin secretion is inappropriately high. This placebo-controlled, randomized, double-blind multicenter study evaluated the efficacy and safety of oral conivaptan, a V1A/V2-receptor antagonist, in patients with euvolemic or hypervolemic hyponatremia.

METHODS

Eighty-three patients with serum [Na] less than 130 mEq/L were stratified by volume status and randomly assigned to placebo or conivaptan 40 or 80 mg/d for 5 days.

RESULTS

Conivaptan increased the baseline-adjusted area under the serum [Na]-time curve significantly more than placebo (P = 0.0001). Patients given either dose of conivaptan demonstrated a serum [Na] of 4 mEq/L or greater above baseline significantly faster than those given placebo (P < 0.001) and maintained that increase for a greater total time (P = 0.0001). The least squares mean change in serum [Na] from baseline to end of treatment was also significantly greater with conivaptan 40 and 80 mg/d (6.8 and 8.8 mEq/L, respectively) (P = 0.0001) than that with placebo (1.2 mEq/L). The percentage of patients who obtained an increase from baseline in serum [Na] of 6 mEq/L or greater or normal serum [Na] was significantly higher among patients given conivaptan 40 and 80 mg/d (67% and 88%, respectively) than among those given placebo (20%; P < 0.001). Conivaptan was well tolerated; the most frequent adverse events were urinary tract infection, anemia, pyrexia, cardiac failure, hypotension, and hypokalemia.

CONCLUSION

Oral conivaptan was effective in increasing serum [Na] in patients with euvolemic or hypervolemic hyponatremia and had a favorable safety profile.

Non-peptide arginine-vasopressin antagonists: the vaptans

Arginine-vasopressin is a hormone that plays an important part in circulatory and water homoeostasis. The three arginine-vasopressin-receptor subtypes--V1a, V1b, and V2--all belong to the large rhodopsin-like G-protein-coupled receptor family. The vaptans are orally and intravenously active non-peptide vasopressin receptor antagonists that are in development. Relcovaptan is a selective V1a-receptor antagonist, which has shown initial positive results in the treatment of Raynaud's disease, dysmenorrhoea, and tocolysis. SSR-149415 is a selective V1b-receptor antagonist, which could have beneficial effects in the treatment of psychiatric disorders. V2-receptor antagonists--mozavaptan, lixivaptan, satavaptan, and tolvaptan--induce a highly hypotonic diuresis without substantially affecting the excretion of electrolytes (by contrast with the effects of diuretics). These drugs are all effective in the treatment of euvolaemic and hypervolaemic hyponatraemia. Conivaptan is a V1a/V2 non-selective vasopressin-receptor antagonist that has been approved by the US Food and Drug Administration as an intravenous infusion for the inhospital treatment of euvolaemic or hypervolaemic hyponatraemia.

Review article: hypertonic saline use in the emergency department

Hypertonic saline (HS) is being increasingly used for the management of a variety of conditions, most notably raised intracranial pressure. This article reviews the available evidence on HS solutions as they relate to emergency medicine, and develops a set of recommendations for its use. To conclude, HS is recommended as an alternative to mannitol for treating raised intracranial pressure in traumatic brain injury. HS is also recommended for treating severe and symptomatic hyponatremia, and is worth considering for both recalcitrant tricyclic antidepressant toxicity and for cerebral oedema complicating paediatric diabetic ketoacidosis. HS is not recommended for hypovolaemic resuscitation.

Vasopressin dysregulation and hyponatremia in hospitalized patients

Hyponatremia, which is often due to dysregulation of arginine vasopressin, occurs frequently in hospitalized patients and is associated with increased morbidity and mortality. Nonosmotic secretion of arginine vasopressin is central to the pathophysiology of hyponatremia in patients with euvolemic hyponatremia (due to, for example, the syndrome of inappropriate secretion of antidiuretic hormone) and those with hypervolemic hyponatremia secondary to congestive heart failure or cirrhosis with ascites. Arginine vasopressin-receptor antagonists, a novel class of agents that block the action of arginine vasopressin on V2 receptors in the renal collecting ducts, may provide specific correction of sodium and water imbalance in hyponatremia by promoting free water clearance while sparing electrolytes (aquaresis). Arginine vasopressin antagonism would treat hyponatremia directly, as opposed to other therapies that do not address the effects of arginine vasopressin dysregulation directly.

Diagnosis and management of hyponatremia in cancer patients

BACKGROUND

Hyponatremia is among the metabolic disturbances encountered in oncology. Risk factors for hyponatremia include chemotherapy, treatment-induced nausea and vomiting, hydration, pain, narcotic drugs, and physical and emotional stress. A common cause of hyponatremia in patients with cancer is the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), which may result from ectopic production of arginine vasopressin (AVP) by the tumor tissue.

TREATMENT

The AVP-receptor antagonists, a new class of agents, correct hyponatremia by directly blocking the binding of AVP with its receptors. In clinical trials, conivaptan, lixivaptan, tolvaptan, and satavaptan have increased serum osmolality and normalized the serum [Na(+)] in hyponatremia associated with SIADH, cirrhosis, or congestive heart failure. These drugs may have a potential in cancer-related hyponatremia as well.

Vasopressin-receptor antagonist therapy in patients with hyponatraemia

Hyponatraemia often complicates the treatment of underlying conditions in patients who are seriously ill. Arginine vasopressin receptor antagonists block the action of arginine vasopressin and correct sodium and water imbalance in patients with euvolaemic or hypervolaemic hyponatraemia.

Evaluation and management of hyponatremia: an emerging role for vasopressin receptor antagonists

Vasopressin-2 receptor antagonists, collectively known as the 'vaptans', provide a new approach to the treatment of hyponatremia; therefore, an updated Review of the pathophysiology of hyponatremia is particularly timely. After briefly defining hyponatremia and introducing its clinical aspects and complications, we present an approach to the diagnosis and evaluation of hyponatremia that is based primarily on the often-underused concept of free water clearance and, more specifically, the electrolyte-free water clearance. Then we review the use of vasopressin receptor antagonists in the management of hyponatremia from the standpoint of their pharmacology, their mechanism of action, and available efficacy data from clinical trials.