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Objective: Hyponatremia is associated with considerable morbidity and mortality, but causal links have been difficult to establish. Here, we describe the establishment and representativeness of the Stockholm Sodium Cohort (SSC), designed to study etiologies and outcomes of hyponatremia., Study Design and Setting: All residents of Stockholm County undertaking at least one serum sodium test between 2005-2018 were included in the SSC. Individual-level test results from over 100 laboratory parameters relevant to hyponatremia were collected and linked to data on demographics, socioeconomic status, healthcare contacts, diagnoses and dispensed prescription medications using national registers., Results: A total of 1,632,249 individuals, corresponding to 64% of the population of Stockholm County, were included in the SSC. Coverage increased with advancing age, ranging from 32% in children and adolescents (≤18 years) to 97% among the oldest (≥80 years). The coverage of SSC included the vast majority of patients in Stockholm County diagnosed with diabetes mellitus (93%), myocardial infarction (98%), ischemic stroke (97%), cancer (85%), pneumonias requiring inpatient care (95%) and deaths (88%)., Conclusion: SSC is the first cohort specifically designed to investigate sodium levels in a large, population-based setting. It includes a wide range of administrative health data and laboratory analyses. The coverage is high, particularly among elderly and individuals with comorbidities. Consequently, the cohort has a large potential for exploration of various aspects of hyponatremia., Competing Interests: Declaration of Competing Interest None declared., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Disturbances in serum sodium concentration (dysnatremia) are common following aneurysmal subarachnoid hemorrhage (aSAH), but its direct impact on outcomes is not well understood. This study aimed to examine the association between dysnatremia following aSAH and patient outcomes., Methods: A retrospective cohort study of consecutive patients with aSAH who were admitted to an academic referral center between 2015 and 2021 was performed. Multivariate logistic regression was used to test the association of dysnatremia and outcomes including modified Rankin Scale score at 3 months after discharge and vasospasm. Multiple linear regression was used to test the association of hospital length of stay and dysnatremia., Results: We included 320 patients with confirmed aneurysmal etiology (mean [SD] age = 57.8 [14.3] years; 61% female; 70% White). No independent associations were found between hyponatremia or hypernatremia and functional outcome or vasospasm. However, hospital length of stay was longer in patients with hypernatremia (7 more days; 95% confidence interval = 4.4-9.6, P < 0.001) independent of age, Hunt and Hess grade, modified Fisher score, delayed cerebral ischemia, and other hospital complications., Conclusions: Although dysnatremia may not directly impact functional outcome or vasospasm risk, hypernatremia may prolong hospital length of stay. Judicious use of hypertonic saline solutions and avoidance of unnecessary dysnatremia in patients with aSAH should be considered., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Background: The reported cumulative prevalence of hyponatremia (sodium <135 mmol/L) in bronchiolitis is 28%. However, sodium level was never measured by direct potentiometry, the method recommended by the International Federation of Clinical Chemistry and Laboratory Medicine. Aim of this study was to assess the prevalence of hyponatremia, measured by direct potentiometry, in infants with moderate-severe bronchiolitis., Methods: A prospective cross-sectional study was conducted in infants ≥1month and ≤24months of age with bronchiolitis., Results: 160 consecutive infants were enrolled. Hyponatremia was observed in 91 (57%) patients and occurred more commonly in infants ≤6 months than in older infant (P < 0.005)., Conclusion: The first study on sodium level measured by the direct potentiometry in infants with bronchiolitis points out that the prevalence of hyponatremia is two-fold higher than so far reported., (Copyright © 2017. Published by Elsevier Ltd.)

The assumption that sodium accumulation in the human body is always accompanied by water retention has been challenged by data showing that sodium can be stored nonosmotically. Here we investigated the contribution of nonosmotic sodium storage to short-term sodium homeostasis after hypertonic saline infusion in healthy individuals on a low-sodium diet. During four hours after infusion, we compared the observed changes in plasma sodium concentration and urinary cation excretion with changes that were calculated with the Adrogue-Madias and Nguyen-Kurtz formula, formulations widely implemented to guide the treatment of dysnatremias. We included 12 healthy non-smoking male individuals with normal blood pressure, body mass index, and kidney function. Right after infusion, the average observed plasma sodium change from baseline (3.5 mmol/L) was similar to the predicted changes by the Adrogue-Madias (3.3 mmol/L) and Nguyen-Kurtz formula (3.1 mmol/L). However, the observed plasma sodium concentration change after four hours (-1.8 mmol/L) was very different from the changes as predicted by the Adrogue-Madias (0.4 mmol/L) and the Nguyen-Kurtz formula (-0.9 mmol/L). Moreover, only 47% and 55%, respectively, of the expected sodium and potassium excretion were retrieved in the urine. Thus, healthy individuals are able to osmotically inactivate significant amounts of sodium after hypertonic saline infusion. Further research is needed to uncover factors that determine nonosmotic sodium storage., (Copyright © 2016 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Background: Hyponatremia is common in patients with subarachnoid hemorrhage, but its effect on outcomes remains contentious. Fluctuation in sodium has been reported to negatively affect perioperative outcomes in general surgical patients, but not specifically in patients with a subarachnoid hemorrhage. The primary aim was to describe the relationship between 1) hyponatremia and 2) sodium fluctuations during intensive care and neurologic outcome at hospital discharge., Methods: Adults with aneurysmal subarachnoid hemorrhage between January 2012 and September 2013 were retrospectively reviewed. Data were collected for admission to day 14 of intensive care or death. Severity of illness was assessed by Hunt and Hess grade and simplified acute physiology score. Hyponatremia was defined as any measurement <135 mEq/L. Sodium variability was categorized as a maximum change of <6, 6-12, or >12 mEq/L during intensive care. Neurologic outcomes at discharge were assessed by modified Rankin Scale. The relationship between sodium and outcome was assessed by ordinal logistic regression., Results: A total of 198 patients were included. After adjustment for Hunt and Hess grade, severity of systemic illness, patient age, surgical intervention, and whether or not the hyponatremia was treated with additional sodium, hyponatremia was not associated with worse neurologic outcomes. More patients with sodium variability of 6-12 and >12 mEq/L had cerebral infarction than those with variability <6 mEq/L and had modified Rankin Scale scores of 2-3 and 4-6, respectively (P = 0.001)., Conclusions: Sodium fluctuation, not hyponatremia, is associated with worse neurologic outcome in patients with aneurysmal subarachnoid hemorrhage. This is in contradistinction to current teaching and warrants further examination., (Copyright © 2016 Elsevier Inc. All rights reserved.)