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      Mechanisms, Risks, and New Treatment Options for Hyponatremia

      Cardiology

      S. Karger AG

      Sodium-water imbalance, Heart failure, Aquaresis, Arginine vasopressin, Arginine vasopressin receptor antagonists

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          Abstract

          Hyponatremia is the most common electrolyte abnormality in hospitalized patients and is associated with increased mortality, morbidity, and longer hospital stays. Because patients with this disorder are often asymptomatic, hyponatremia is frequently undiagnosed and untreated. Serious neurologic complications may ensue when hyponatremia develops too rapidly or the serum sodium concentration ([Na<sup>+</sup>]) falls below 120 mEq/l. Hypotonic dilutional hyponatremia is the most common form of this disorder, which may present as euvolemic [e.g., due to failure to suppress secretion of arginine vasopressin (AVP)] or hypervolemic (due to edema-forming conditions such as heart failure). Hypovolemic hyponatremia is due to conditions promoting renal or extrarenal sodium loss. Because AVP, which is intimately involved in regulating osmolar homeostasis, is often elevated in patients with hypervolemic and euvolemic hyponatremia, treatments that directly target the effects of this hormone may provide a more predictable correction of serum [Na<sup>+</sup>] than those traditionally used. The AVP receptor antagonists (conivaptan, tolvaptan, lixivaptan, and satavaptan) are a new class of agents that have been shown to normalize serum [Na<sup>+</sup>] by promoting aquaresis – the electrolyte-sparing excretion of free water.

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          Most cited references 37

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          Effects of oral tolvaptan in patients hospitalized for worsening heart failure: the EVEREST Outcome Trial.

          Vasopressin mediates fluid retention in heart failure. Tolvaptan, a vasopressin V2 receptor blocker, shows promise for management of heart failure. To investigate the effects of tolvaptan initiated in patients hospitalized with heart failure. The Efficacy of Vasopressin Antagonism in Heart Failure Outcome Study With Tolvaptan (EVEREST), an event-driven, randomized, double-blind, placebo-controlled study. The outcome trial comprised 4133 patients within 2 short-term clinical status studies, who were hospitalized with heart failure, randomized at 359 North American, South American, and European sites between October 7, 2003, and February 3, 2006, and followed up during long-term treatment. Within 48 hours of admission, patients were randomly assigned to receive oral tolvaptan, 30 mg once per day (n = 2072), or placebo (n = 2061) for a minimum of 60 days, in addition to standard therapy. Dual primary end points were all-cause mortality (superiority and noninferiority) and cardiovascular death or hospitalization for heart failure (superiority only). Secondary end points included changes in dyspnea, body weight, and edema. During a median follow-up of 9.9 months, 537 patients (25.9%) in the tolvaptan group and 543 (26.3%) in the placebo group died (hazard ratio, 0.98; 95% confidence interval [CI], 0.87-1.11; P = .68). The upper confidence limit for the mortality difference was within the prespecified noninferiority margin of 1.25 (P<.001). The composite of cardiovascular death or hospitalization for heart failure occurred in 871 tolvaptan group patients (42.0%) and 829 placebo group patients (40.2%; hazard ratio, 1.04; 95% CI, 0.95-1.14; P = .55). Secondary end points of cardiovascular mortality, cardiovascular death or hospitalization, and worsening heart failure were also not different. Tolvaptan significantly improved secondary end points of day 1 patient-assessed dyspnea, day 1 body weight, and day 7 edema. In patients with hyponatremia, serum sodium levels significantly increased. The Kansas City Cardiomyopathy Questionnaire overall summary score was not improved at outpatient week 1, but body weight and serum sodium effects persisted long after discharge. Tolvaptan caused increased thirst and dry mouth, but frequencies of major adverse events were similar in the 2 groups. Tolvaptan initiated for acute treatment of patients hospitalized with heart failure had no effect on long-term mortality or heart failure-related morbidity. clinicaltrials.gov Identifier: NCT00071331
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            Short-term clinical effects of tolvaptan, an oral vasopressin antagonist, in patients hospitalized for heart failure: the EVEREST Clinical Status Trials.

            Heart failure causes more than 1 million US hospitalizations yearly, mostly related to congestion. Tolvaptan, an oral, nonpeptide, selective vasopressin V2-receptor antagonist, shows promise in this condition. To evaluate short-term effects of tolvaptan when added to standard therapy in patients hospitalized with heart failure. Two identical prospective, randomized, double-blind, placebo-controlled trials at 359 sites in North America, South America, and Europe were conducted during the inpatient period of the Efficacy of Vasopressin Antagonism in Heart Failure Outcome Study With Tolvaptan (EVEREST) between October 7, 2003, and February 3, 2006. A total of 2048 (trial A) and 2085 (trial B) patients hospitalized with heart failure and congestion were studied. Patients were randomized to receive either tolvaptan (30 mg/d) or matching placebo, within 48 hours of admission. Primary end point was a composite of changes in global clinical status based on a visual analog scale and body weight at day 7 or discharge if earlier. Secondary end points included dyspnea (day 1), global clinical status (day 7 or discharge), body weight (days 1 and 7 or discharge), and peripheral edema (day 7 or discharge). Rank sum analysis of the composite primary end point showed greater improvement with tolvaptan vs placebo (trial A, mean [SD], 1.06 [0.43] vs 0.99 [0.44]; and trial B, 1.07 [0.42] vs 0.97 [0.43]; both trials P<.001). Mean (SD) body weight reduction was greater with tolvaptan on day 1 (trial A, 1.71 [1.80] vs 0.99 [1.83] kg; P<.001; and trial B, 1.82 [2.01] vs 0.95 [1.85] kg; P<.001) and day 7 or discharge (trial A, 3.35 [3.27] vs 2.73 [3.34] kg; P<.001; and trial B, 3.77 [3.59] vs 2.79 [3.46] kg; P<.001), whereas improvements in global clinical status were not different between groups. More patients receiving tolvaptan (684 [76.7%] and 678 [72.1%] for trial A and trial B, respectively) vs patients receiving placebo (646 [70.6%] and 597 [65.3%], respectively) reported improvement in dyspnea at day 1 (both trials P<.001). Edema at day 7 or discharge improved significantly with tolvaptan in trial B (P = .02) but did not reach significance in trial A (P = .07). Serious adverse event frequencies were similar between groups, without excess renal failure or hypotension. In patients hospitalized with heart failure, oral tolvaptan in addition to standard therapy including diuretics improved many, though not all, heart failure signs and symptoms, without serious adverse events. clinicaltrials.gov Identifier: NCT00071331
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              Mild chronic hyponatremia is associated with falls, unsteadiness, and attention deficits.

              The study objective was to determine the eventual consequences (falls, unsteadiness, and cognitive impairment) of mild chronic hyponatremia, which is generally considered as asymptomatic. In a case-control study, we focused on the incidence of falls among 122 patients (mean age 72+/-13 years) with asymptomatic chronic hyponatremia (mean serum sodium concentration [SNa] 126+/-5 mEq/L), who were admitted to the medical emergency department, compared with 244 matched controls. To explore the mechanisms of the excess of falls, we prospectively asked 16 comparable patients (mean age 63+/-15 years; SNa+/-2 mEq/L) to perform 8 attention tests and a gait test consisting of 3 steps "in tandem," in which we measured the "total traveled way" by the center of pressure or total traveled way. Thereafter, the patients were treated and tested again (50% of the patients were tested first with normal SNa to avoid learning biases). Epidemiology of falls: Twenty-six patients (21.3%) of 122 were admitted for falls, compared with only 5.3% of the control patients (adjusted odds ratio: 67; 95% confidence: 7.5-607; P <.001). The frequency of falls was the same regardless of the level of hyponatremia. Gait: The total traveled way by the center of pressure significantly increased in hyponatremia (1336+/-320 mm vs 1047+/-172 mm with normal SNa; P=.003). Attention tests: The mean response time was 673+/-182 milliseconds in hyponatremia and 615+/-184 milliseconds in patients with normal SNa (difference: 58 milliseconds, P <.001). The total error number in hyponatremia increased 1.2-fold (P=.001). These modifications were comparable to those observed after alcohol intake in 10 volunteers. Mild chronic hyponatremia induces a high incidence of falls possibly as the result of marked gait and attention impairments. Treating these patients might prevent a considerable number of hospitalizations.
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                Author and article information

                Journal
                CRD
                Cardiology
                10.1159/issn.0008-6312
                Cardiology
                S. Karger AG
                0008-6312
                1421-9751
                2008
                September 2008
                25 April 2008
                : 111
                : 3
                : 147-157
                Affiliations
                Wayne State University, Detroit, Mich., USA
                Article
                121596 Cardiology 2008;111:147–157
                10.1159/000121596
                18434717
                © 2008 S. Karger AG, Basel

                Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

                Page count
                Figures: 1, Tables: 2, References: 63, Pages: 11
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