Assessment of the efficacy and safety of intravenous conivaptan in euvolemic and hypervolemic hyponatremia

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

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

Prevalence and Prognostic Significance of Hyponatremia in Patients With Lung Cancer: Systematic Review and Meta-Analysis

Background: The prevalence of hyponatremia is highly variable among patients with lung cancer. However, its prevalence and prognostic significance in subgroups of patients with lung cancer have not yet been evaluated in a meta-analysis. Methods: We have registered our meta-analysis and review protocol to the PROSPERO International Prospective Register of Systematic Reviews, with the following registration number: CRD42020167013. A systematic search was done in the following sources: MEDLINE, Embase, CENTRAL, Web of Science, ClinicalTrials.gov, a WHO Global Health Library. Results: We identified a total of 8,962 potentially eligible studies, and we included 31 articles in our evaluation. The prevalence of hyponatremia in patients with lung cancer varied between 3 and 94.8% with an average of 25% without any significant differences between the following subgroups: histotype, gender, age, Eastern Cooperative Oncology Group (ECOG) state, and the extent of disease. The overall survival (OS) was significantly lower in hyponatremic compared to normonatremic patients at 10 months [RR.59 (95% CI.47-0.74), p < 0.001] and at 20 months [RR.44 (95% CI.33-0.59), p < 0.001], with worse survival rates in non-small cell lung cancer (NSCLC) [RR.27 (95% CI.12-0.44), p < 0.001] than in small cell lung cancer (SCLC) [RR.42 (95% CI.27-0.57), p < 0.001]. If hyponatremia was corrected, OS at 10 months was significantly higher than in the uncorrected hyponatremia group [RR 1.83 (95% CI 1.37-2.44), p < 0.001], but, at 20 months, no statistically significant difference could be found between these subgroups [RR 2.65 (95% CI.94-7.50), p = 0.067]. Conclusions: Patients with lung cancer diagnosed with hyponatremia, especially patients with NSCLC, seem to have significantly lower survival rates than normonatremic patients. If hyponatremia remains uncorrected, the mortality rates might be even higher.

Management of SIADH-related hyponatremia due to psychotropic medications - An expert consensus from the Association of Medicine and Psychiatry

OBJECTIVE

Hyponatremia is the most common electrolyte imbalance encountered in clinical practice and is associated with negative healthcare outcomes and cost. SIADH is thought to account for one third of all hyponatremia cases and is typically an insidious process. Psychotropic medications are commonly implicated in the etiology of drug induced SIADH. There is limited guidance for clinicians on management of psychotropic-induced SIADH.

METHODS

After an extensive review of the existing literature, clinical-educators from the Association of Medicine and Psychiatry developed expert consensus recommendations for management of psychotropic-induced SIADH. A risk score was proposed based on risk factors for SIADH to guide clinical decision-making.

RESULTS

SSRIs, SNRIs, antipsychotics, carbamazepine, and oxcarbazepine have moderate to high level of evidence demonstrating their association with SIADH. Evaluation for an avoidance of medications that cause hyponatremia is particularly important. Substitution with medication that is less likely to cause SIADH should be considered when appropriate. We propose an algorithmic approach to monitoring hyponatremia with SIADH and corresponding treatment depending on symptom severity.

CONCLUSIONS

The proposed algorithm can help clinicians in determining whether psychotropic medication should be stopped, reduced or substituted where SIADH is suspected with recommendations for sodium (Na+) monitoring. These recommendations preserve a role for clinical judgment in the management of hyponatremia with consideration of the risks and benefits, which may be particularly relevant for complex patients that present with medical and psychiatric comorbidities. Further studies are needed to determine whether baseline and serial Na+ monitoring reduces morbidity and mortality.

Risks of vaptans in hypernatremia and serum sodium overcorrection: A systematic review and meta-analysis of randomised controlled trials

OBJECTIVE

Serum sodium overcorrection and hypernatremia are significant health risks. We conducted a systematic review and meta-analysis to evaluate the risks of vaptans in hypernatremia and serum sodium overcorrection.

METHODS

We searched PubMed, Embase, and CENTRAL for randomised controlled trials. We included studies comparing vaptans and placebo with data on hypernatremia and serum sodium overcorrection. The study quality was assessed using the Cochrane Collaboration's risk-of-bias assessment tool. Fixed-effect model meta-analysis was used to pool the data. Different analyses were performed to ensure the accuracy of the results.

RESULTS

Twenty-eight studies were included in the meta-analysis of hypernatremia incidence. Treatment with vaptans resulted in a higher risk of hypernatremia than placebo (3.8% vs 1.0%, odds ratio [OR] 2.69; 95% confidence interval [CI] 1.97-3.68). The subgroup with baseline hyponatremia had a lower risk of hypernatremia incidence; however, the use of loop diuretics increased the risk. Fourteen studies were included in the analysis of the incidence of serum sodium overcorrection. A higher risk of serum sodium overcorrection was found in using vaptans vs placebo (4.4% vs 1.4%; OR 2.26; 95% CI 1.32-3.86).

CONCLUSION

Vaptans showed higher risks in the incidence of hypernatremia and serum sodium overcorrection than placebo. In addition, combination with loop diuretics increased the risk of hypernatremia. The risk of serum sodium overcorrection should be concerned in patients with hyponatremia and normal serum sodium equally. Using a low dose of vaptans can reduce both risks.

Mechanism, spectrum, consequences and management of hyponatremia in tuberculous meningitis

Hyponatremia is the commonest electrolyte abnormality in hospitalized patients and is associated with poor outcome. Hyponatremia is categorized on the basis of serum sodium into severe (< 120 mEq/L), moderate (120-129 mEq/L) and mild (130-134mEq/L) groups. Serum sodium has an important role in maintaining serum osmolality, which is maintained by the action of antidiuretic hormone (ADH) secreted from the posterior pituitary, and natriuretic peptides such as atrial natriuretic peptide and brain natriuretic peptide. These peptides act on kidney tubules via the renin angiotensin aldosterone system. Hyponatremia <120mEq/L or a rapid decline in serum sodium can result in neurological manifestations, ranging from confusion to coma and seizure. Cerebral salt wasting (CSW) and syndrome of inappropriate secretion of ADH (SIADH) are important causes of hyponatremia in tuberculosis meningitis (TBM). CSW is more common than SIADH. The differentiation between CSW and SIADH is important because treatment of one may be detrimental for the other; evidence of hypovolemia in CSW and euvolemia or hypervolemia in SIADH is used for differentiation. In addition, evidence of dehydration, polyuria, negative fluid balance as assessed by intake output chart, weight loss, laboratory evidence and sometimes central venous pressure are helpful in the diagnosis of these disorders. Volume contraction in CSW may be more protracted than hyponatremia and may contribute to border zone infarctions in TBM. Hyponatremia should be promptly and carefully treated by saline and oral salt, while 3% saline should be used in severe hyponatremia with coma and seizure. In refractory patients with hyponatremia, fludrocortisone helps in early normalization of serum sodium without affecting polyuria or functional outcome. In SIADH, V2 receptor antagonist conivaptan or tolvaptan may be used if the patient is not responding to fluid restriction. Fluid restriction in SIADH has not been found to be beneficial in TBM and should be avoided.

Mechanism, spectrum, consequences and management of hyponatremia in tuberculous meningitis

Hyponatremia is the commonest electrolyte abnormality in hospitalized patients and is associated with poor outcome. Hyponatremia is categorized on the basis of serum sodium into severe (< 120 mEq/L), moderate (120-129 mEq/L) and mild (130-134mEq/L) groups. Serum sodium has an important role in maintaining serum osmolality, which is maintained by the action of antidiuretic hormone (ADH) secreted from the posterior pituitary, and natriuretic peptides such as atrial natriuretic peptide and brain natriuretic peptide. These peptides act on kidney tubules via the renin angiotensin aldosterone system. Hyponatremia <120mEq/L or a rapid decline in serum sodium can result in neurological manifestations, ranging from confusion to coma and seizure. Cerebral salt wasting (CSW) and syndrome of inappropriate secretion of ADH (SIADH) are important causes of hyponatremia in tuberculosis meningitis (TBM). CSW is more common than SIADH. The differentiation between CSW and SIADH is important because treatment of one may be detrimental for the other; evidence of hypovolemia in CSW and euvolemia or hypervolemia in SIADH is used for differentiation. In addition, evidence of dehydration, polyuria, negative fluid balance as assessed by intake output chart, weight loss, laboratory evidence and sometimes central venous pressure are helpful in the diagnosis of these disorders. Volume contraction in CSW may be more protracted than hyponatremia and may contribute to border zone infarctions in TBM. Hyponatremia should be promptly and carefully treated by saline and oral salt, while 3% saline should be used in severe hyponatremia with coma and seizure. In refractory patients with hyponatremia, fludrocortisone helps in early normalization of serum sodium without affecting polyuria or functional outcome. In SIADH, V2 receptor antagonist conivaptan or tolvaptan may be used if the patient is not responding to fluid restriction. Fluid restriction in SIADH has not been found to be beneficial in TBM and should be avoided.

Hyponatremia in Heart Failure: Pathogenesis and Management

Hyponatremia is a very common electrolyte abnormality, associated with poor short- and long-term outcomes in patients with heart failure (HF). Two opposite processes can result in hyponatremia in this setting: Volume overload with dilutional hypervolemic hyponatremia from congestion, and hypovolemic hyponatremia from excessive use of natriuretics. These two conditions require different therapeutic approaches. While sodium in the form of normal saline can be lifesaving in the second case, the same treatment would exacerbate hyponatremia in the first case. Hypervolemic hyponatremia in HF patients is multifactorial and occurs mainly due to the persistent release of arginine vasopressin (AVP) in the setting of ineffective renal perfusion secondary to low cardiac output. Fluid restriction and loop diuretics remain mainstay treatments for hypervolemic/dilutional hyponatremia in patients with HF. In recent years, a few strategies, such as AVP antagonists (Tolvaptan, Conivaptan, and Lixivaptan), and hypertonic saline in addition to loop diuretics, have been proposed as potentially promising treatment options for this condition. This review aimed to summarize the current literature on pathogenesis and management of hyponatremia in patients with HF.

Management of hyponatremia: causes, clinical aspects, differential diagnosis and treatment

INTRODUCTION

Hyponatremia is the most frequent electrolyte disorder in hospitalised patients. Acute and severe hyponatremia may be a life-threatening situation. However, also mild and chronic hyponatremia may negatively affect the health status (i.e. gait disturbances, attention deficits, falls and fractures, and bone loss) and may increase the risk of death. Therefore, it is of paramount importance for clinicians to have an in-depth knowledge on this topic, in order to appropriately manage patients affected by hyponatremia.

AREAS COVERED

This review will cover different areas related to this electrolyte disorder. Because many pathologic conditions may be associated with hyponatremia, thorough investigations have to be performed in order to establish the underlying etiology. To establish the cause of hyponatremia is of great importance, because an appropriate therapeutic strategy is strictly dependent on a correct diagnosis. A description of the different available therapeutic approaches for the correction of hyponatremia, including vaptans, will follow.

EXPERT COMMENTARY

Undoubtedly, the studies that have been published in recent years and the introduction of vaptans in clinical practice have contributed to increase the awareness on hyponatremia among clinicians. Nevertheless, additional studies are needed in order to clarify some partially uncovered areas.

Correction of Hyponatremia May Be a Treatment Stratification Biomarker: A Two-Stage Systematic Review and Meta-Analysis

Changes in serum sodium concentration ([Na⁺]_serum) can permit evaluation of the treatment effect of vasopressin antagonists (vaptans) in patients with worsening heart failure (HF) or cirrhotic ascites; that is, they may act as a treatment stratification biomarker. A two-stage systematic review and meta-analysis were carried out and contextualized by experts in fluid resuscitation and translational pharmacology (registration ID in the International Prospective Register of Systematic Reviews (PROSPERO): CRD42017051440). Meta-analysis of aggregated dichotomous outcomes was performed. Pooled estimates for correction of hyponatremia (normalization or an increase in [Na⁺]_serum of at least 3–5 mEq/L) under treatment with vaptans (Stage 1) and for clinical outcomes in both worsening HF (rehospitalization and/or death) and cirrhotic ascites (ascites worsening) when correction of hyponatremia is achieved (Stage 2) were calculated. The body of evidence was assessed. Correction of hyponatremia was achieved under vaptans (odds ratio (OR)/95% confidence interval (95% CI)/I²/number of studies (n): 7.48/4.95–11.30/58%/15). Clinical outcomes in both worsening HF and cirrhotic ascites improved when correction of hyponatremia was achieved (OR/95% CI/I²/n: 0.51/0.26–0.99/52%/3). Despite the appropriateness of the study design, however, there are too few trials to consider that correction of hyponatremia is a treatment stratification biomarker. Patients with worsening HF or with cirrhotic ascites needing treatment with vaptans, have better clinical outcomes when correction of hyponatremia is achieved. However, the evidence base needs to be enlarged to propose formally correction of hyponatremia as a new treatment stratification biomarker. Markers for use with drugs are needed to improve outcomes related to the use of medicines.

Interventions for chronic non-hypovolaemic hypotonic hyponatraemia

BACKGROUND

Chronic (present > 48 hours) non-hypovolaemic hyponatraemia occurs frequently, can be caused by various conditions, and is associated with shorter survival and longer hospital stays. Many treatments, such as fluid restriction or vasopressin receptor antagonists can be used to improve the hyponatraemia, but whether that translates into improved patient-important outcomes is less certain.

OBJECTIVES

This review aimed to 1) look at the benefits and harms of interventions for chronic non-hypovolaemic hypotonic hyponatraemia when compared with placebo, no treatment or head-to-head; and 2) determine if benefits and harms vary in absolute or relative terms dependent on the specific compound within a drug class, on the dosage used, or the underlying disorder causing the hyponatraemia.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 1 December 2017 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov. We also screened the reference lists of potentially relevant studies, contacted authors, and screened the websites of regulatory agencies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-RCTs that compared the effects of any intervention with placebo, no treatment, standard care, or any other intervention in patients with chronic non-hypovolaemic hypotonic hyponatraemia. We also included subgroups with hyponatraemia from studies with broader inclusion criteria (e.g. people with chronic heart failure or people with cirrhosis with or without hyponatraemia), provided we could obtain outcomes for participants with hyponatraemia from the report or the study authors.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data and assessed risk of bias. We expressed treatment effects as mean difference (MD) for continuous outcomes (health-related quality of life, length of hospital stay, change from baseline in serum sodium concentration, cognitive function), and risk ratio (RR) for dichotomous outcomes (death, response and rapid increase in serum sodium concentration, hypernatraemia, polyuria, hypotension, acute kidney injury, liver function abnormalities) together with 95% confidence intervals (CI).

MAIN RESULTS

We identified 35 studies, enrolling 3429 participants. Twenty-eight studies (3189 participants) compared a vasopressin receptor antagonist versus placebo, usual care, no treatment, or fluid restriction. In adults with chronic, non-hypovolaemic hypotonic hyponatraemia, vasopressin receptor antagonists have uncertain effects on death at six months (15 studies, 2330 participants: RR 1.11, 95% CI 0.92 to 1.33) due to risk of selective reporting and serious imprecision; and on health-related quality of life because results are at serious risk of performance, selective reporting and attrition bias, and suffer from indirectness related to the validity of the Short Form Health Survey (SF-12) in the setting of hyponatraemia. Vasopressin receptor antagonists may reduce hospital stay (low certainty evidence due to risk of performance bias and imprecision) (3 studies, 610 participants: MD -1.63 days, 95% CI -2.96 to -0.30), and may make little or no difference to cognitive function (low certainty evidence due to indirectness and imprecision). Vasopressin receptor antagonists probably increase the intermediate outcome of serum sodium concentration (21 studies, 2641 participants: MD 4.17 mmol/L, 95% CI 3.18 to 5.16), corresponding to two and a half as many people having a 5 to 6 mmol/L increase in sodium concentration compared with placebo at 4 to 180 days (moderate certainty evidence due to risk of attrition bias) (18 studies, 2014 participants: RR 2.49, 95% CI 1.95 to 3.18). But they probably also increase the risk of rapid serum sodium correction - most commonly defined as > 12 mmol/L/d (moderate certainty evidence due to indirectness) (14 studies, 2058 participants: RR 1.67, 95% CI 1.16 to 2.40) and commonly cause side-effects such as thirst (13 studies, 1666 participants: OR 2.77, 95% CI 1.80 to 4.27) and polyuria (6 studies, 1272 participants): RR 4.69, 95% CI 1.59 to 13.85) (high certainty evidence). The potential for liver toxicity remains uncertain due to large imprecision. Effects were generally consistent across the different agents, suggesting class effect.Data for other interventions such as fluid restriction, urea, mannitol, loop diuretics, corticosteroids, demeclocycline, lithium and phenytoin were largely absent.

AUTHORS' CONCLUSIONS

In people with chronic hyponatraemia, vasopressin receptor antagonists modestly raise serum sodium concentration at the cost of a 3% increased risk of it being rapid. To date there is very low certainty evidence for patient-important outcomes; the effects on mortality and health-related quality of life are unclear and do not rule out appreciable benefit or harm; there does not appear to be an important effect on cognitive function, but hospital stay may be slightly shorter, although available data are limited. Treatment decisions must weigh the value of an increase in serum sodium concentration against its short-term risks and unknown effects on patient-important outcomes. Evidence for other treatments is largely absent.Further studies assessing standard treatments such as fluid restriction or urea against placebo and one-another would inform practice and are warranted. Given the limited available evidence for patient-important outcomes, any study should include these outcomes in a standardised manner.

Safety and Efficacy of Tolvaptan in Korean Patients with Hyponatremia Caused by the Syndrome of Inappropriate Antidiuretic Hormone

BACKGROUND

The aim of this multicenter study was to evaluate the safety and efficacy of tolvaptan (TLV) in Korean patients with the syndrome of inappropriate secretion of antidiuretic hormone (SIADH).

METHODS

Of 51 enrolled patients with SIADH, 39 patients (16 female patients, aged 70.8 ± 11.3 years) were included in an intention to treat analysis. All patients received 15 mg/day as the initial dose, and the dose was then increased up to 60 mg/day (as needed) until day 4.

RESULTS

Serum sodium increased significantly from baseline during the first 24 hours (126.8 ± 4.3 vs. 133.7 ± 3.8 mmol/L, P < 0.001), rose gradually between days 1 and 4 (133.7 ± 3.8 vs. 135.6 ± 3.6 mmol/L, P < 0.05), and then plateaued until day 11 (136.7 ± 4.5 mmol/L). The correlation between the change in serum sodium for the first 24 hours and initial serum sodium concentration was significant (r = -0.602, P < 0.001). In severe hyponatremia (< 125 mmol/L), the change was significantly higher (11.1 ± 4.8 mmol/L) than in moderate (6.4 ± 2.5 mmol/L, P < 0.05) or mild hyponatremia (4.3 ± 3.3 mmol/L, P < 0.01). In addition, logistic regression analysis showed that body weight (odds ratio [OR], 0.858; 95% confidence interval [CI], 0.775-0.976; P = 0.020) and body mass index (BMI) (OR, 0.692; 95% CI, 0.500-0.956; P = 0.026) were associated with rapid correction. No serious adverse events were reported, but in 13% of patients hyponatremia was overcorrected.

CONCLUSION

TLV is effective in correcting hyponatremia and well-tolerated in Korean patients with SIADH. However, those with low body weight, low BMI or severe hyponatremia, could be vulnerable to overcorrection with the initial dose of 15 mg TLV.

Rapidity of Correction of Hyponatremia Due to Syndrome of Inappropriate Secretion of Antidiuretic Hormone Following Tolvaptan

BACKGROUND

Tolvaptan effectively corrects hyponatremia due to the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), but undesired overcorrection can occur. We hypothesized that pretherapy parameters can predict the rapidity of response to tolvaptan in SIADH.

STUDY DESIGN

Multicenter historical cohort study.

SETTING & PARTICIPANTS

Adults with SIADH or congestive heart failure (CHF) treated with tolvaptan for a serum sodium concentration ≤ 130 mEq/L at 5 US hospitals.

PREDICTORS

Demographic and laboratory parameters.

OUTCOMES

Rate of change in serum sodium concentration.

MEASUREMENTS

Spearman correlations, analysis of variance, and multivariable linear mixed-effects models.

RESULTS

28 patients with SIADH and 39 patients with CHF treated with tolvaptan (mean baseline serum sodium, 120.6 and 122.4 mEq/L, respectively) were studied. Correction of serum sodium concentration > 12 mEq/L/d occurred in 25% of patients with SIADH compared to 3% of those with CHF (P<0.001). Among patients with SIADH, the increase in serum sodium over 24 hours was correlated with baseline serum sodium concentration (r=-0.78; P<0.001), serum urea nitrogen concentration (SUN; r=-0.76; P<0.001), and estimated glomerular filtration rate (r=0.58; P=0.01). Baseline serum sodium and SUN concentrations were identified as independent predictors of change in serum sodium concentration in multivariable analyses. When patients were grouped into 4 categories according to baseline serum sodium and SUN median values, those with both low baseline serum sodium (≤121 mEq/L) and low baseline SUN concentrations (≤10mg/dL) exhibited a significantly greater rate of increase in serum sodium concentration (mean 24-hour increase of 15.4 mEq/L) than the other 3 categories (P<0.05). Among patients with CHF, only baseline SUN concentration was identified as an independent predictor of change in serum sodium concentration over time.

LIMITATIONS

Lack of uniformity in serial serum sodium concentration determinations and documentation of water intake.

CONCLUSIONS

Baseline serum sodium and SUN values are predictive of the rapidity of hyponatremia correction following tolvaptan use in SIADH. We advise caution when dosing tolvaptan in patients with both low serum sodium and SUN concentrations.

Efficacy and safety of two different tolvaptan doses in the treatment of hyponatremia in the Emergency Department

Hyponatremia (plasma sodium concentration or _P[Na⁺] <136 mEq/L) is the most common electrolyte unbalance in clinical practice. Although it constitutes a negative prognostic factor, it frequently remains underdiagnosed and undertreated. Tolvaptan is an oral V₂-receptor antagonist which produces aquaresis. Given its emerging role in the treatment of dilutional hyponatremia, we aimed to compare the efficacy and safety of two different doses of this drug in an Emergency Department (ED) setting. Consecutive patients with moderate-severe euvolemic or hypervolemic hyponatremia were sequentially assigned to the 15 mg Group and to the 7.5 mg Group, and were revaluated at 6, 12 and 24 h. Further evaluations and administrations were scheduled daily until _P[Na⁺] correction was achieved or the maximum period of 72 h was exceeded. A 1-month follow-up was performed. Twenty-three patients were enrolled: 12 were included in the 15 mg Group, 11 in the 7.5 mg Group. Both doses significantly elevated the _P[Na⁺] over 24 h, although the 15 mg Group showed faster corrections than the 7.5 mg Group (12 vs 6 mEq/L/24 h; P = 0.025). An optimal correction rate (within 4-8 mEq/L/24 h) was observed in 45.4 % of the 7.5 mg Group against 25.0 % (P n.s.). The standard dose led to dangerous overcorrections (>12 mEq/L/24 h) in 41.7 % of the patients, while the low dose did not cause any (P = 0.037). No osmotic demyelination syndrome was observed. A 7.5 mg tolvaptan dose can be considered both effective and safe in treating hyponatremia in the ED, while a 15 mg dose implicates too high risk of overcorrection.

Vasopressin Receptor Antagonists in Hyponatremia: Uses and Misuses

Decreases in the concentration of sodium in plasma constitute hyponatremia, the commonest electrolyte disorder in clinical medicine. It is now well established that its presence conveys an increased mortality risk even when the decrement is mild. In addition, recent evidence suggests that chronic and apparently asymptomatic hyponatremia is associated with increased morbidity including neurocognitive deficits and bone fractures. Furthermore, hyponatremia is associated with higher health care-related expenses. Consequently, exploring new therapeutic strategies that increase plasma sodium in a safe and effective manner is of paramount importance. In this regard, there are scant data to support the use of traditional management strategies for hyponatremia (fluid restriction, salt tablets, loop diuretics, and normal saline). Furthermore, data from a large hyponatremia registry reveal the limited efficacy of these therapies. More recently vasopressin receptor antagonists provide a promising treatment for hyponatremia by targeting its most common mechanism, namely, increased vasopressin activity. However, uncertainty still lingers as to the optimal indications for the use of vasopressin receptor antagonists in hyponatremia and a few reports have described complications resulting from their misuse. This review summarizes the appropriate and inappropriate uses of vasopressin receptor antagonists in the treatment of hyponatremia.

Hyponatraemia - presentations and management

Hyponatraemia is the most common electrolyte disturbance encountered in clinical practice. It is associated with -significant morbidity and mortality, thus appropriate investigation and treatment is essential. Hyponatraemia presents with a spectrum of clinical presentations ranging from no symptoms to life-threatening neurological sequelae. Hyponatraemia has multiple aetiologies and distinguishing the underlying aetiology facilitates appropriate treatment. This review provides an overview of the presentations and approaches to management of this common clinical condition.

Pharmacokinetics of conivaptan use in patients with severe hepatic impairment

Purpose

Conivaptan is an intravenous dual V_1A/V₂ vasopressin antagonist approved for the treatment of euvolemic and hypervolemic hyponatremia. Earlier studies showed that patients with moderate liver disease could be safely treated with conivaptan by reducing the dose by 50%, whereas patients with mild hepatic impairment needed no dose adjustment. The objective of this Phase 1, open-label study was to assess the pharmacokinetics, protein binding, and safety of 48 h of conivaptan infusion in individuals with severe hepatic impairment.

Patients and methods

Eight subjects with severe hepatic impairment (Child–Pugh score 10–15) and nine subjects with normal liver function were enrolled. Intravenous conivaptan (20 mg) was given as a 30 min loading dose on Day 1 followed by two consecutive 20 mg continuous infusions over 24 h each. Subjects were monitored for adverse events and changes in clinical laboratory parameters. Plasma and urine pharmacokinetic samples were collected at defined times. Subjects were followed through Study Day 5.

Results

Hepatically impaired individuals exhibited higher concentrations of plasma conivaptan throughout the treatment period. Overall exposure, as measured by area under the plasma conivaptan concentration-time curve from time zero through infinity (AUC_INF), was ~60% higher in impaired individuals compared to those with normal liver function. Terminal elimination half-life was slightly longer in impaired subjects (12 h) as compared to normal subjects (9 h), and clearance was 65% higher in subjects with normal liver function, while urinary excretion was higher in impaired individuals. Albumin levels directly, and alkaline phosphatase inversely, correlated with conivaptan clearance.

Conclusion

A 20 mg conivaptan loading dose given >30 min followed by two daily infusions of 20 mg each was well tolerated by patients with severe hepatic impairment as monitored by adverse events and clinical laboratory values. Based on pharmacokinetic data, however, a 50% reduction in the conivaptan dose is recommended for patients with severe liver impairment.

Conivaptan, a Selective Arginine Vasopressin V1a and V2 Receptor Antagonist Attenuates Global Cerebral Edema Following Experimental Cardiac Arrest via Perivascular Pool of Aquaporin-4

BACKGROUND

Cerebral edema is a major cause of mortality following cardiac arrest (CA) and cardiopulmonary resuscitation (CPR). Arginine vasopressin (AVP) and water channel aquaporin-4 (AQP4) have been implicated in the pathogenesis of CA-evoked cerebral edema. In this study, we examined if conivaptan, a V1a and V2 antagonist, attenuates cerebral edema following CA/CPR in wild type (WT) mice as well as mice with targeted disruption of the gene encoding α-syntrophin (α-syn(-/-)) that demonstrate diminished perivascular AQP4 pool.

METHODS

Isoflurane-anesthetized adult male WT C57Bl/6 and α-syn(-/-) mice were subjected to 8 min CA/CPR and treated with either bolus IV injection (0.15 or 0.3 mg/kg) followed by continuous infusion of conivaptan (0.15 mg/kg/day or 0.3 mg/kg/day), or vehicle infusion for 48 h. Serum osmolality, regional brain water content, and blood-brain barrier (BBB) disruption were determined at the end of the experiment. Sham-operated mice in both strains served as controls.

RESULTS

Treatment with conivaptan elevated serum osmolality in a dose-dependent manner. In WT mice, conivaptan at 0.3 mg dose significantly attenuated regional water content in the caudoputamen (81.0 ± 0.5 vs. 82.5 ± 0.4% in controls; mean ± SEM) and cortex (78.8 ± 0.2 vs. 79.4 ± 0.2% in controls), while conivaptan at 0.15 mg was not effective. In α-syn(-/-) mice, conivaptan at 0.3 mg dose did not attenuate water content compared with controls. Conivaptan (0.3 mg/kg/day) attenuated post-CA BBB disruption at 48 h in WT mice but not in α-syn(-/-) mice.

CONCLUSIONS

Continuous IV infusion of conivaptan attenuates cerebral edema and BBB disruption following CA. These effects of conivaptan that are dependent on the presence of perivascular pool of AQP4 appear be mediated via its dual effect on V1 and V2 receptors.

Efficacy and Safety of Vasopressin Receptor Antagonists for Euvolemic or Hypervolemic Hyponatremia: A Meta-Analysis

Hyponatremia, defined as a nonartifactual serum sodium level <135 mmol/L, is the most common fluid and electrolyte abnormality in clinical practice. Traditional managements (fluid restriction, hypertonic saline and loop diuretics, etc.) are difficult to maintain or ineffective. Recently, vasopressin receptor antagonists (VRAs) have shown promise for the treatment of hyponatremia. We aimed to conduct a meta-analysis to evaluate the efficacy and safety of VRAs in patients with euvolemic or hypervolemic hyponatremia. We searched Pubmed, Cochrane Library, Web of Science and Springer, etc. (latest search on June 4, 2015) for English publications with randomized controlled trials. Two authors independently screened the citations and extracted data. We calculated pooled relative risk (RR), risk difference (RD), weighted mean difference (WMD) or standard mean difference (SMD), and 95% confidence intervals (CIs) by using random and fixed effect models. We collected data from 18 trials involving 1806 patients. Both random and fixed effect meta-analyses showed that VRAs significantly increased the net change of serum sodium concentration (WMD(random) = 4.89 mEq/L, 95%CIs = 4.35-5.43 and WMD(fixed) = 4.70 mEq/L, 95%CIs = 4.45-4.95), response rate (RR(random )= 2.77, 95%CIs = 2.29-3.36 and RR(fixed) = 2.95, 95%CIs = 2.56-3.41), and 24-hour urine output (SMD(random) = 0.82, 95%CIs = 0.65-1.00 and SMD(fixed) = 0.79, 95%CIs = 0.66-0.93) compared to placebo. Furthermore, VRAs significantly decreased body weight (WMD(random) = -0.87 kg, 95%CIs = -1.24 to -0.49 and WMD(fixed) = -0.91 kg, 95%CIs = -1.22 to -0.59). In terms of safety, rates of drug-related adverse events (AEs), rapid sodium level correction, constipation, dry mouth, thirst, and phlebitis in the VRA-treated group were greater than those in control group. However, there was no difference in the total number of AEs, discontinuations due to AEs, serious AEs, death, headache, hypotension, nausea, anemia, hypernatremia, urinary tract infection, renal failure, pyrexia, upper gastrointestinal bleeding, diarrhea, vomiting, peripheral edema, and dizziness between the 2 groups. Random effect meta-analyses showed that post treatment urine osmolality, supine systolic blood pressure, and diastolic blood pressure were lowered (WMD(random) = -233.07 mOsmol/kg, 95%CIs = -298.20-147.94; WMD(random) = -6.11 mmHg, 95%CIs = -9.810 to -2.41; WMD(random )= -2.59 mmHg, 95%CIs = -4.06 to -1.11, respectively), but serum osmolality was increased (WMD(random) = 9.29 mOsmol/kg, 95%CIs = 5.56-13.03). There was no significant change from baseline in serum potassium concentration between the 2 groups (WMD(fixed) = 0.00 mmHg, 95%CIs = -0.07-0.06). VRAs are relatively effective and safe for the treatment of hypervolemic and euvolemic hyponatremia.

Vasopressin receptor antagonists: Characteristics and clinical role

Hyponatremia, the most common electrolyte disorder in hospitalized patients is associated with increased risk of mortality even when mild and apparently asymptomatic. Likewise morbidity manifested as attention deficits, gait disturbances, falls, fractures, and osteoporosis is more prevalent in hyponatremic subjects. Hyponatremia also generates a significant financial burden. Therefore, it is important to explore approaches that effectively and safely treat hyponatremia. Currently available strategies are physiologically sound and affordable but lack evidence from clinical trials and are limited by variable efficacy, slow response, and/or poor compliance. The recent emergence of vasopressin receptor antagonists provides a class of drugs that target the primary pathophysiological mechanism, namely vasopressin mediated impairment of free water excretion. This review summarizes the historical development, pharmacology, clinical trials supporting efficacy and safety, shortcomings, as well as practical suggestions for the use of vasopressin receptor antagonists.

Tolvaptan for hyponatremia with preserved sodium pool in critically ill patients

BACKGROUND

Hyponatremia is the most common electrolyte disturbance in hospitalized patients, and it represents a well-established risk factor for ICU/hospital mortality. The majority of hyponatremic states are associated with elevated arginine vasopressin levels and a preserved sodium pool. Conventional treatment is either not pathophysiologically oriented or of limited effectiveness. The aim of the present study is to investigate the use of enteral Tolvaptan in critically ill hyponatremic patients.

METHODS

This is a retrospective observational study in a general ICU. Patients with preserved sodium pool hyponatremia refractory to conventional therapy were enrolled. The hemodynamic, renal, and hepatic functions, together with sodium and water balance as close as possible to the drug administration and up to 72 h thereafter, were analyzed. The main outcome was a serum sodium increase of ≥ 4 mmol/L in 24 h; secondary endpoints were the ability to maintain serum sodium at 24 and 72 h, a decrease in urine sodium concentration and an increase in sodium-free diuresis.

RESULTS

38 patients were enrolled. The average dose of enteral Tolvaptan was 7.5 mg. 31 patients (81.6 %) increased their serum sodium >4 mmol/l/24 h; the average increase was 6.7 ± 3.4 mmol/l during the first 24 h (p < 0.001 vs baseline), and this was sustained at 72 h. No adverse effects were reported. Plasma sodium (R = -0.622, p < 0.001), urine sodium (R = -0.345, p < 0.001), central venous oxygen saturation (R = 0.401, p = 0.013), and BUN (R = -0.416, p = 0.031) before Tolvaptan were all significantly correlated with the absolute increase in serum sodium after the administration.

CONCLUSIONS

Enteral administration of Tolvaptan seems effective in the treatment of hyponatremia with preserved sodium pool in critically ill patients. Even if the study was underpowered to detect significant side effects or complications of unwarranted fast corrections of hyponatremia, we report no complications.

Efficacy of conivaptan and hypertonic (3%) saline in treating hyponatremia due to syndrome of inappropriate antidiuretic hormone in a tertiary Intensive Care Unit

Background:

Hyponatremia is one of the most common electrolyte abnormalities encountered in clinical practice and has a significant impact on morbidity and mortality in hospitalized patients. The optimal management of hyponatremia is still evolving. Over the last decade, vaptans have been increasingly used in clinical practice with promising results.

Materials and Methods:

The study included eighty patients with symptomatic hyponatremia due to syndrome of inappropriate antidiuretic hormone (SIADH) admitted and treated in Intensive Care Unit (ICU) with either conivaptan or hypertonic (3%) saline. They were compared for time taken to achieve normal serum sodium, length of ICU and hospital stay, and adverse effects.

Results:

The demographic data and serum sodium levels at admission were comparable between the two groups. After initiating correction, sodium levels at 6, 12, and 24 h were similar between the two groups. However, at 48 h, patients in the conivaptan group (Group C) had higher sodium levels (133.0 ± 3.8 mEq/L) as compared to hypertonic saline group (Group HS) (128.9 ± 2.6 mEq/L), which was statistically significant (P < 0.001). The length of ICU stay was less in the Group C (3.35 ± 0.89 days) when compared with the Group HS (4.61 ± 0.91 days) (P < 0.001). There was no significant difference in mortality between the two groups.

Conclusion:

In patients with symptomatic hyponatremia due to SIADH, conivaptan with its aquaresis property can achieve a significantly better sodium correction, resulting in reduced ICU and hospital stay with no significant adverse effects.

Hyponatremia in the intensive care unit: How to avoid a Zugzwang situation?

Hyponatremia is a common electrolyte derangement in the setting of the intensive care unit. Life-threatening neurological complications may arise not only in case of a severe (<120 mmol/L) and acute fall of plasma sodium levels, but may also stem from overly rapid correction of hyponatremia. Additionally, even mild hyponatremia carries a poor short-term and long-term prognosis across a wide range of conditions. Its multifaceted and intricate physiopathology may seem deterring at first glance, yet a careful multi-step diagnostic approach may easily unravel the underlying mechanisms and enable physicians to adopt the adequate measures at the patient’s bedside. Unless hyponatremia is associated with obvious extracellular fluid volume increase such as in heart failure or cirrhosis, hypertonic saline therapy is the cornerstone of the therapeutic of profound or severely symptomatic hyponatremia. When overcorrection of hyponatremia occurs, recent data indicate that re-lowering of plasma sodium levels through the infusion of hypotonic fluids and the cautious use of desmopressin acetate represent a reasonable strategy. New therapeutic options have recently emerged, foremost among these being vaptans, but their use in the setting of the intensive care unit remains to be clarified.

Employment of vasopressin receptor antagonists in management of hyponatraemia and volume overload in some clinical conditions

WHAT IS KNOWN AND OBJECTIVE

Hyponatraemia, the most common electrolyte imbalance occurring in hospitalized subjects, is usually classified as hypovolaemic, euvolaemic or hypervolaemic. Hyponatraemia is a predictor of death among subjects with chronic heart failure and cirrhosis. The inappropriate secretion of the antidiuretic hormone (AVP) seems to be of pivotal importance in the decline of serum sodium concentration in these clinical conditions. The objective of this review was to summarize recent progress in management of hyponatraemia in SIADH, cirrhosis and heart failure.

METHODS

Literature searches were conducted on the topics of hyponatraemia and vasopressin receptor antagonists, using PubMed, pharmaceutical company websites and news reports. The information was evaluated for relevance and quality, critically assessed and summarized.

RESULTS AND DISCUSSION

The initial treatment of severe hyponatraemia is directed towards the prevention or management of neurological manifestations and consists of an intravenous infusion of hypertonic saline. Fluid restriction is indicated in oedematous states. Diuretics alone or in combination with other specific drugs remain the main strategy in the management of volume overload in heart failure. In resistant cases, ultrafiltration can lead to effective removal of isotonic fluid preventing new episodes of decompensation; however, aquapheresis is associated with increased costs and other limits. In several trials, the efficacy of vasopressin receptor antagonists in euvolaemic patients (inappropriate antidiuretic hormone secretion) or in hypervolaemic hyponatraemia (chronic heart failure, cirrhosis) has been evaluated. It was found that vaptans, which promote aquaresis, were superior to a placebo in raising and maintaining serum sodium concentrations in these subjects.

WHAT IS NEW AND CONCLUSIONS

Combined with conventional therapy, vasopressin receptor antagonists (AVP-R antagonists) are able to increase the excretion of electrolyte-free water and the sodium concentration. Further studies are needed to assess efficacious outcomes of aquaresis compared with aquapheresis and with conventional therapy.

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.

The syndrome of inappropriate antidiuresis is associated with excess long-term mortality: a retrospective cohort analyses

Introduction

The syndrome of inappropriate antidiuresis (SIAD) is the commonest cause of euvolaemic hyponatraemia in patients admitted to hospital. The mortality after discharge from hospital has not been previously studied in patients with SIAD.

Aims

To compare mortality in patients with SIAD and those with kidney injury (KI). To identify underlying diagnoses associated with deaths due to SIAD.

Methods

Single-centre retrospective cohort analyses of 804 patients with severe hyponatraemia over a 3-year period. Five-year survival data in patients with SIAD and those with KI were compared. The underlying diagnoses that contributed to SIAD in this cohort were analysed using ICD-10 codes.

Results

202 patients had SIAD using biochemical cut-off parameters; 248 patients had KI. Patient with KI had a statistically significant (log-rank p<0.0001) shorter median survival time (2.24 months (95% CI 1.3 to 4.3)) compared with those with SIAD (31.0 months (95% CI 21.6 to 54.8)). 53.8% (n=78) of patients with hyponatraemia due to SIAD died within the first year after admission; the corresponding figure for those presenting with KI was 74.1% (n=166). Five years after admission, 80.8% (n=117) of those with SIAD had died; the corresponding figure for those with KI was 88.4% (n=200). In those patients with SIAD that died within the first year, malignancy appeared to be the most common cause (25.4%) followed by infection (23.8%).

Conclusions

Severe hyponatraemia in SIAD carries a high mortality after discharge, and although this seems often to be attributable to the underlying cause, the extent to which treatment with V2-recptor antagonists may help to correct the hyponatraemia associated with SIAD and influence the medium-to-long-term outcome in such patients is worthy of further study.

Management of hepatic encephalopathy

OPINION STATEMENT

Hepatic encephalopathy management varies depending on the acuity of liver failure. However, in patients with either acute or chronic liver failure five basic steps in management are critical: stabilization, addressing modifiable precipitating factors, lowering blood ammonia, managing elevated intracranial pressure (ICP) (if present), and managing complications of liver failure that can contribute to encephalopathy, particularly hyponatremia. Because liver failure patients are prone to a variety of other medical problems that can lead to encephalopathy (such as coagulopathy associated intracranial hemorrhage, electrolyte disarray, renal failure, hypotension, hypoglycemia, and infection), a thorough history, physical and neurologic examination is mandated in all encephalopathic liver failure patients. There should be a low threshold for brain imaging in patients with focal neurological deficits given the propensity for spontaneous intracranial hemorrhage. In patients with acute liver failure and high grade encephalopathy, identification of the etiology of acute liver failure is essential to guide treatment and antidote administration, particularly in the case of acetaminophen poisoning. Equally critical is management of elevated ICP in acute liver failure. Intracranial hypertension can be treated with hypertonic saline and/or adjustment of the dialysis bath. Placement of an intracranial monitor to guide ICP therapy is risky because of concomitant coagulopathy and remains controversial. Continuous renal replacement therapy may help lower serum ammonia, treat coexisting uremia, and improve symptoms. Liver transplantation is the definitive treatment for patients with acute liver failure and hepatic encephalopathy. In patients with chronic hepatic encephalopathy, lactulose and rifaxamin remain a mainstay of therapy. In these patients, it is essential to identify reversible causes of hepatic encephalopathy such as increased ammonia production and/or decreased clearance (eg, infection, GI bleed, constipation, hypokalemia, dehydration). Chronic hyponatremia should be managed by gradual sodium correction of no more than 8‒12 meq/L per day to avoid central myelinolysis syndrome. Free water restriction and increased dietary sodium are reasonable, cost effective treatment options. Many emerging therapies, both pharmacologic and interventional, are currently being studied to improve management of hepatic encephalopathy.

Clinical practice guideline on diagnosis and treatment of hyponatraemia

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

Clinical practice guideline on diagnosis and treatment of hyponatraemia

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

Pharmacokinetics of intravenous conivaptan in subjects with hepatic or renal impairment

BACKGROUND

Conivaptan is a non-peptide dual antagonist of vasopressin V1A and V2 receptors that is approved in the United States as an intravenous formulation for the treatment of euvolemic and hypervolemic hyponatremia in hospitalized patients. The pharmacokinetics of intravenous conivaptan had not been studied in patients with hepatic or renal impairment.

OBJECTIVE

The objective of this study was to assess the pharmacokinetics and tolerability of intravenous conivaptan in subjects with mild or moderate hepatic or renal impairment compared with subjects with normal function.

STUDY DESIGN

These studies were phase I, open-label pharmacokinetic studies conducted at two sites in the US.

PATIENTS

Men and non-pregnant women 30-70 years of age were allocated to the mild (Child-Pugh classification score of 5-6) or moderate (Child-Pugh classification score of 7-9) hepatically impaired groups (n = 8-9 per group) based on their liver function assessed at screening. For the renal study, men and non-pregnant women between 18 and 70 years of age were assigned to renal function groups (n = 8-9 per group) based on estimated glomerular filtration rate (eGFR) assessed at screening. Normal renal function was defined as an eGFR >80 ml/min, mild renal impairment as 50-80 ml/min, and moderate renal impairment as 30-49 ml/min. Subjects with normal hepatic or renal function were selected to match the race, sex, age, and body mass index of subjects enrolled in the impaired groups.

INTERVENTION

Subjects were administered a 20-mg/30-min intravenous loading dose of conivaptan on day 1, followed by a 20-mg/23.5-h continuous conivaptan infusion. On day 2, immediately following the end of the day 1 infusion, a 20-mg/24-h continuous conivaptan infusion was administered.

MAIN OUTCOME MEASURE

Primary pharmacokinetic parameters estimated were the area under the plasma conivaptan concentration-time curve from time 0 to infinity (AUC∞), plasma conivaptan concentrations at the end of the 20-mg loading dose (C LD), and plasma conivaptan concentrations at the end of the second day 20-mg/24-h continuous infusion (C 48).

RESULTS

For each of C LD, C 48, and AUC∞, the mean values were similar for subjects with mild hepatic impairment and subjects with normal hepatic function. Subjects with moderate hepatic impairment had a 73 % higher C 48 and an 80 % higher AUC∞ compared with subjects with normal hepatic function. There were no clinically relevant changes in conivaptan exposure in the mild and moderate renal impairment groups compared with subjects with normal renal function. Intravenous conivaptan was generally well tolerated in subjects with mild or moderate hepatic or renal impairment. Infusion-site reaction was the most commonly reported adverse event.

CONCLUSION

Overall exposure to conivaptan increased in subjects with moderate hepatic impairment compared with subjects with normal hepatic function. Therefore, in patients with moderate hepatic impairment, conivaptan should be initiated with a loading dose of 10 mg over 30 min followed by 10 mg per day as a continuous infusion for 2-4 days, which is half the approved dose. No dose adjustment is necessary in patients with mild or moderate renal impairment and in patients with mild hepatic impairment.

Therapeutic effect of conivaptan bolus dosing in hyponatremic neurosurgical patients

STUDY OBJECTIVE

To determine the natremic response of a single 20-mg bolus dose of conivaptan, an arginine vasopressin antagonist, in hyponatremic neurosurgical patients with the syndrome of inappropriate antidiuretic hormone secretion (SIADH).

DESIGN

Retrospective medical record review.

SETTING

Neurosurgical intensive care unit of a tertiary care referral hospital.

PATIENTS

Thirty-two hyponatremic patients with SIADH who were admitted to the neurosurgical intensive care unit and received a single 20-mg bolus dose of conivaptan between January and December 2011.

MEASUREMENTS AND MAIN RESULTS

Each patient's natremic response over 48 hours was determined. The primary end point was an increase in serum sodium level of 4 mEq/L or greater over the first 24 hours. The mean ± SD baseline serum sodium level was 129.8 ± 3.4 mEq/L, which increased to 133.1 ± 3.2 mEq/L at 6 hours after administration of the bolus dose of conivaptan. The serum sodium level at 24 hours was 134.2 ± 3.2 mEq/L, indicating a 24-hour natremic response of 4.3 ± 2.6 mEq/L (range 1-13 mEq/L) from baseline (p<0.001). Eighteen patients (56%) met the primary end point. The mean ± SD fluid balance over the first 24 hours was -783 ± 440 ml. The mean ± SD change in serum sodium level from 24 to 48 hours was 0.5 ± 1.3 mEq/L. No adverse effects or injection-site reactions were noted. The patients who failed to reach the primary end point were treated with repeated doses of conivaptan plus other agents.

CONCLUSION

We recommend a single 20-mg dose of conivaptan as the preferred initial approach to treating patients with SIADH who are in the neurosurgical intensive care unit. The 24-hour natremic response should then dictate whether additional doses of conivaptan or other therapeutic interventions are required. We believe that such an approach is safe and will result in a controlled and predictable increase in the serum sodium concentration.

Diagnosis, evaluation, and treatment of hyponatremia: expert panel recommendations

Hyponatremia is a serious, but often overlooked, electrolyte imbalance that has been independently associated with a wide range of deleterious changes involving many different body systems. Untreated acute hyponatremia can cause substantial morbidity and mortality as a result of osmotically induced cerebral edema, and excessively rapid correction of chronic hyponatremia can cause severe neurologic impairment and death as a result of osmotic demyelination. The diverse etiologies and comorbidities associated with hyponatremia pose substantial challenges in managing this disorder. In 2007, a panel of experts in hyponatremia convened to develop the Hyponatremia Treatment Guidelines 2007: Expert Panel Recommendations that defined strategies for clinicians caring for patients with hyponatremia. In the 6 years since the publication of that document, the field has seen several notable developments, including new evidence on morbidities and complications associated with hyponatremia, the importance of treating mild to moderate hyponatremia, and the efficacy and safety of vasopressin receptor antagonist therapy for hyponatremic patients. Therefore, additional guidance was deemed necessary and a panel of hyponatremia experts (which included all of the original panel members) was convened to update the previous recommendations for optimal current management of this disorder. The updated expert panel recommendations in this document represent recommended approaches for multiple etiologies of hyponatremia that are based on both consensus opinions of experts in hyponatremia and the most recent published data in this field.

Hyponatremia in patients with heart failure

The present review analyses the mechanisms relating heart failure and hyponatremia, describes the association of hyponatremia with the progress of disease and morbidity/mortality in heart failure patients and presents treatment options focusing on the role of arginine vasopressin (AVP)-receptor antagonists. Hyponatremia is the most common electrolyte disorder in the clinical setting and in hospitalized patients. Patients with hyponatremia may have neurologic symptoms since low sodium concentration produces brain edema, but the rapid correction of hyponatremia is also associated with major neurologic complications. Patients with heart failure often develop hyponatremia owing to the activation of many neurohormonal systems leading to decrease of sodium levels. A large number of clinical studies have associated hyponatremia with increased morbidity and mortality in patients hospitalized for heart failure or outpatients with chronic heart failure. Treatment options for hyponatremia in heart failure, such as water restriction or the use of hypertonic saline with loop diuretics, have limited efficacy. AVP-receptor antagonists increase sodium levels effectively and their use seems promising in patients with hyponatremia. However, the effects of AVP-receptor antagonists on hard outcomes in patients with heart failure and hyponatremia have not been thoroughly examined.

Efficacy of 3% saline vs. conivaptan in achieving hyponatremia treatment goals

Hyponatremia is the most common electrolyte abnormality encountered in clinical practice, but its optimal management is still evolving. While guidelines for infusion rates of hypertonic saline (HS) have been introduced, there is a risk of underestimating the response in serum sodium concentration after therapy. Guidelines also have evaluated the use of vasopressin receptor antagonists as alternatives or supplements to standard therapies. This single-center retrospective study from The Methodist Hospital (TMH) compared the effect of HS and conivaptan intervention in the management of 49 patients with hyponatremia from January 2009 through November 2010. Demographics, volume status, medical history, medication data, and serum sodium concentration correction over 48 hours were analyzed. No significant difference was noted with regard to age, ethnicity, gender, volume status, use of medications known to cause hyponatremia, or comorbidities. Baseline serum sodium concentration was not significantly different between HS (120.5 ± 3.8 mEq/L) and conivaptan (118.3 ± 6.7 mEq/L) groups. Regardless of whether the patient was euvolemic or hypervolemic, no significant difference was noted in serum sodium concentration at 4, 12, 24, or 48 hours after initiation of treatment or in frequency of over-correction between groups. This study compares the effect of HS to conivaptan intervention in the management of hyponatremia. No significant differences were identified in adherence to treatment guidelines. Further, based on this small retrospective study, neither agent poses a significant risk of over-correction at 4, 24, or 48 hours of therapy.

Lixivaptan - an evidence-based review of its clinical potential in the treatment of hyponatremia

Hyponatremia is the most common electrolyte abnormality seen in clinical practice. Most cases of euvolemic or hypervolemic hyponatremia involve arginine vasopressin (AVP). AVP leads to a concentrated urine and negative free water clearance. Given this primary role of AVP, antagonizing its effect through blockade of its receptor in the distal tubule is an attractive therapeutic target. Lixivaptan is a newer, non-peptide, vasopressin type 2 receptor antagonist. Recent studies have demonstrated efficacy. This review summarizes the clinical pharmacology and data for this new agent.

Vaptans: A new option in the management of hyponatremia

Arginine vasopressin (AVP) plays an important role in water and sodium homeostasis. It acts via three receptor subtypes-V1a, V1b, and V2-distributed widely throughout the body. Vaptans are nonpeptide vasopressin receptor antagonists (VRA). By property of aquaresis, VRAs offer a novel therapy of water retention. Conivaptan is a V1a/V2 nonselective VRA approved for euvolemic and hypervolemic hyponatremia. Tolvaptan is the first oral VRA. Other potential uses of this new class of drugs include congestive heart failure (CHF), cirrhosis of liver, syndrome of inappropriate secretion of antidiuretic hormone, polycystic kidney disease, and so on. These novel drugs score over diuretics as they are not associated with electrolyte abnormalities. Though much remains to be elucidated before the VRAs are applied clinically, the future holds much promise.