Dysnatremia in a changing climate: A global systematic review of the association between serum sodium and ambient temperature.

OBJECTIVE: Both hyponatremia and hypernatremia have been reported to occur more frequently with higher ambient temperatures, although the underlying mechanisms are not well understood. Global temperatures are rising due to climate change, which may impact the incidence of dysnatremia worldwide. We aimed to identify, collate and critically appraise studies analyzing the relationship between climate measures (outdoor temperature, humidity) and serum sodium concentrations. DESIGN: Systematic review, reported in accordance with PRISMA guidelines. METHODS: MEDLINE and Embase were searched with relevant key terms. Studies assessing the effect on serum sodium measurement of elevated temperature or humidity versus a comparator were included. RESULTS: Of 1466 potentially relevant studies, 34 met inclusion criteria, originating from 23 countries spanning all inhabited continents. The majority (30 of 34, 88%) reported a significant association between outdoor temperature and dysnatremia, predominantly lower serum sodium with increased ambient temperature. Humidity had a less consistent effect. Individuals aged above 65 years, children, those taking diuretics and antidepressants, those with chronic renal impairment or those undertaking physical exertion had increased vulnerability to heat-associated dysnatremia. The risk of bias was assessed to be high in all but four studies. CONCLUSIONS: Higher ambient temperature is consistently associated with an increased incidence of hyponatremia. We infer that hyponatremia presentations are likely to rise with increasing global temperatures and the frequency of extreme heat events secondary to climate change. Evidence-based public health messages, clinician education and reduction in fossil fuel consumption are necessary to reduce the expected burden on healthcare services worldwide.

Hypernatremia and intercalated disc edema synergistically exacerbate long-QT syndrome type 3 phenotype.

Cardiac voltage-gated sodium channel gain-of-function prolongs repolarization in the long-QT syndrome type 3 (LQT3). Previous studies suggest that narrowing the perinexus within the intercalated disc, leading to rapid sodium depletion, attenuates LQT3-associated action potential duration (APD) prolongation. However, it remains unknown whether extracellular sodium concentration modulates APD prolongation during sodium channel gain-of-function. We hypothesized that elevated extracellular sodium concentration and widened perinexus synergistically prolong APD in LQT3. LQT3 was induced with sea anemone toxin (ATXII) in Langendorff-perfused guinea pig hearts (n = 34). Sodium concentration was increased from 145 to 160 mM. Perinexal expansion was induced with mannitol or the sodium channel ß1-subunit adhesion domain antagonist (ßadp1). Epicardial ventricular action potentials were optically mapped. Individual and combined effects of varying clefts and sodium concentrations were simulated in a computational model. With ATXII, both mannitol and ßadp1 significantly widened the perinexus and prolonged APD, respectively. The elevated sodium concentration alone significantly prolonged APD as well. Importantly, the combination of elevated sodium concentration and perinexal widening synergistically prolonged APD. Computational modeling results were consistent with animal experiments. Concurrently elevating extracellular sodium and increasing intercalated disc edema prolongs repolarization more than the individual interventions alone in LQT3. This synergistic effect suggests an important clinical implication that hypernatremia in the presence of cardiac edema can markedly increase LQT3-associated APD prolongation. Therefore, to our knowledge, this is the first study to provide evidence of a tractable and effective strategy to mitigate LQT3 phenotype by means of managing sodium levels and preventing cardiac edema in patients.NEW & NOTEWORTHY This is the first study to demonstrate that the long-QT syndrome type 3 (LQT3) phenotype can be exacerbated or concealed by regulating extracellular sodium concentrations and/or the intercalated disc separation. The animal experiments and computational modeling in the current study reveal a critically important clinical implication: sodium dysregulation in the presence of edema within the intercalated disc can markedly increase the risk of arrhythmia in LQT3. These findings strongly suggest that maintaining extracellular sodium within normal physiological limits may be an effective and inexpensive therapeutic option for patients with congenital or acquired sodium channel gain-of-function diseases.

Association Between an Increase in Serum Sodium and In-Hospital Mortality in Critically Ill Patients.

OBJECTIVES: In critically ill patients, dysnatremia is common, and in these patients, in-hospital mortality is higher. It remains unknown whether changes of serum sodium after ICU admission affect mortality, especially whether normalization of mild hyponatremia improves survival. DESIGN: Retrospective cohort study. SETTING: Ten Dutch ICUs between January 2011 and April 2017. PATIENTS: Adult patients were included if at least one serum sodium measurement within 24 hours of ICU admission and at least one serum sodium measurement 24-48 hours after ICU admission were available. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: A logistic regression model adjusted for age, sex, and Acute Physiology and Chronic Health Evaluation-IV-predicted mortality was used to assess the difference between mean of sodium measurements 24-48 hours after ICU admission and first serum sodium measurement at ICU admission (Δ48 hr-[Na]) and in-hospital mortality. In total, 36,660 patients were included for analysis. An increase in serum sodium was independently associated with a higher risk of in-hospital mortality in patients admitted with normonatremia (Δ48 hr-[Na] 5-10 mmol/L odds ratio: 1.61 [1.44-1.79], Δ48 hr-[Na] > 10 mmol/L odds ratio: 4.10 [3.20-5.24]) and hypernatremia (Δ48 hr-[Na] 5-10 mmol/L odds ratio: 1.47 [1.02-2.14], Δ48 hr-[Na] > 10 mmol/L odds ratio: 8.46 [3.31-21.64]). In patients admitted with mild hyponatremia and Δ48 hr-[Na] greater than 5 mmol/L, no significant difference in hospital mortality was found (odds ratio, 1.11 [0.99-1.25]). CONCLUSIONS: An increase in serum sodium in the first 48 hours of ICU admission was associated with higher in-hospital mortality in patients admitted with normonatremia and in patients admitted with hypernatremia.

Diagnosis and Management of Disorders of Body Tonicity-Hyponatremia and Hypernatremia: Core Curriculum 2020.

Overall body fluid concentration is regulated within a narrow range by the concerted action of the hypothalamic-pituitary axis to influence water intake through thirst and water excretion via the effect of vasopressin, or antidiuretic hormone, on renal collecting duct water permeability. Sodium is the principal extracellular cation; abnormalities in overall effective body fluid concentration, or tonicity, manifest as disturbances in serum sodium concentration. Depending on its severity and chronicity, hyponatremia can lead to significant symptoms, primarily related to central nervous system function. Failure to correct hyponatremia can lead to permanent neurologic damage, as can over rapid correction. It is thus essential to stay within specific limits for correction, particularly for chronic hyponatremia. Hypernatremia also leads to central nervous system dysfunction, although goals for its correction rate are less well established. This Core Curriculum article discusses the normal regulation of tonicity and serum sodium concentration and the diagnosis and management of hypo- and hypernatremia.

Increased mortality risk associated with serum sodium variations and borderline hypo- and hypernatremia in hospitalized adults.

BACKGROUND: This study aimed to evaluate short-term and long-term mortalities in a cohort of unselected hospitalized patients with serum sodium concentration ([Na+]) variations within and outside of reference range. METHODS: All adult patients admitted to the Mayo Clinic, Rochester, MN, USA from January 2011 to December 2013 (n = 147358) were retrospectively screened. Unique patients admitted during the study period were examined. The main exposure was serum [Na+] variation. Outcome measures were hospital and 1-year all-cause mortalities. RESULTS: A total of 60944 patients, mean age 63 ± 17 years, were studied. On admission, 17% (n = 10066) and 1.4% (n = 852) had hypo- and hypernatremia, respectively. During the hospital stay, 11044 and 4128 developed hypo- and hypernatremia, respectively, accounting for 52.3 and 82.9% of the total hypo- and hypernatremic patients. Serum [Na+] variations of ≥6 mEq/L occurred in 40.6% (n = 24 740) of the 60 944 patients and were significantly associated with hospital and 1-year mortalities after adjusting potential confounders (including demographics, comorbidities, estimated glomerular filtration rate, admission serum [Na+], number of [Na+] measurements and length of hospital stay). Adjusted odds ratios for hospital and 1-year mortalities increased with increasing [Na+] variations in a dose-dependent manner, from 1.47 to 5.48 (all 95% confidence intervals >1.0). Moreover, in fully adjusted models, [Na+] variations (≥6 mEq/L) within the reference range (135-145 mEq/L) or borderline hypo- or hypernatremia (133-137 and 143-147 mEq/L, respectively) compared with 138-142 mEq/L were associated with increased hospital and 1-year mortalities. CONCLUSION: In hospitalized adults, [Na+] fluctuation (≥6 mEq/L) irrespective of admission [Na+] and borderline hypo- or hypernatremia are independent predictors of progressively increasing short- and long-term mortality burdens.

Tolvaptan-induced hypernatremia related to low serum potassium level accompanying high blood pressure in patients with acute decompensated heart failure.

BACKGROUNDS: Tolvaptan significantly increases urine volume in acute decompensated heart failure (ADHF); serum sodium level increases due to aquaresis in almost all cases. We aimed to elucidate clinical factors associated with hypernatremia in ADHF patients treated with tolvaptan. METHODS: We enrolled 117 ADHF patients treated with tolvaptan in addition to standard therapy. We examined differences in clinical factors at baseline between patients with and without hypernatremia in the initial three days of hospitalization. RESULTS: Systolic (p = 0.045) and diastolic (p = 0.004) blood pressure, serum sodium level (p = 0.002), and negative water balance (p = 0.036) were significantly higher and serum potassium level (p = 0.026) was significantly lower on admission day in patients with hypernatremia (n = 22). In multivariate regression analysis, hypernatremia was associated with low serum potassium level (p = 0.034). Among patients with serum potassium level ≤ 3.8 mEq/L, the cutoff value obtained using receiver operating characteristic curve analysis, those with hypernatremia related to tolvaptan treatment showed significantly higher diastolic blood pressure on admission day (p = 0.004). CONCLUSION: In tolvaptan treatment combined with standard therapy in ADHF patients, serum potassium level ≤ 3.8 mEq/L may be a determinant factor for hypernatremia development. Among hypokalemic patients, those with higher diastolic blood pressure on admission may be carefully managed to prevent hypernatremia.

Regional Citrate Anticoagulation versus No-Anticoagulation for Continuous Venovenous Hemofiltration in Acute Severe Hypernatremia Patients with Increased Bleeding Risk: A Retrospective Cohort Study.

PURPOSE: This study was aimed at evaluating the efficacy and safety of regional citrate anticoagulation (RCA) versus no-anticoagulation continuous venovenous hemofiltration (CVVH) in acute severe hypernatremia patients with increased bleeding risk. MATERIALS AND METHODS: Acute severe hypernatremia patients with high bleeding risk who underwent CVVH in our center between January 2011 and October 2017 were considered as candidates. Patients who were <18 years old, with hypovolemic hypernatremia, and had systemic anticoagulation were excluded. The included patients were divided into RCA and no-anticoagulation groups according to their anticoagulation strategy during CVVH and matched by age, sequential organ failure assessment scores, and vasopressor dependency. RESULTS: Of the 64 included patients, no-anticoagulation and RCA were employed for CVVH in 23 and 41 patients, respectively. The serum sodium reduction rate (RRSeNa) was not significantly different between the no-anticoagulation and RCA groups (p = 0.729). Compared to no-anticoagulation, RCA significantly prolonged the circuit survival time (15 h [4.1-23.9] vs. 51 h [21.3-80.7], p = 0.001). The incidence of filter failure was 65.2% (15/23) in the no-anticoagulation group and 2.4% (1/41) in the RCA group (p < 0.001), respectively. In the matched cohort, the RRSeNas were not different between the 2 groups (p = 0.569), and the filter lifespan was significantly longer in the RCA group as well (p < 0.001). CONCLUSION: RCA might be safe and effective for acute severe hypernatremia patients who underwent CVVH treatment. Further prospective, randomized, control trials are warranted to obtain robust evidences.

The prognostic importance of serum sodium levels at hospital discharge and one-year mortality among hospitalized patients.

BACKGROUND: The optimal range of serum sodium at hospital discharge is unclear. Our objective was to assess the one-year mortality based on discharge serum sodium in hospitalized patients. METHODS: We analyzed a cohort of hospitalized adult patients between 2011 and 2013 who survived hospital admission at a tertiary referral hospital. We categorized discharge serum sodium into five groups; ≤132, 133-137, 138-142, 143-147, and ≥148 mEq/L. We assessed one-year mortality risk after hospital discharge based on discharge serum sodium, using discharge sodium of 138-142 mEq/L as the reference group. RESULTS: Of 55 901 eligible patients, 4.9%, 29.8%, 56.1%, 8.9%, 0.3% had serum sodium of ≤132, 133-137, 138-142, 143-147, and ≥148 mEq/L, respectively. We observed a U-shaped association between discharge serum sodium and one-year mortality, with nadir mortality in discharge serum sodium of 138-142 mEq/L. When adjusting for potential confounders, including admission serum sodium, one-year mortality was significantly higher in both discharge serum sodium ≤137 and ≥143 mEq/L, compared with discharge serum sodium of 138-142 mEq/L. The mortality risk was the most prominent in elevated discharge serum sodium of ≥148 mEq/L (HR 3.86; 95% CI 3.05-4.88), exceeding the risk associated with low discharge serum sodium of ≤132 mEq/L (HR 1.43; 95% CI 1.30-1.57). CONCLUSION: The optimal range of serum sodium at discharge was 138-142 mEq/L. Both hypernatremia and hyponatremia at discharge were associated with higher one-year mortality. The impact on higher one-year mortality was more prominent in hypernatremia than hyponatremia.

Hypernatremia at admission predicts poor survival in patients with terminal cancer: a retrospective cohort study.

BACKGROUND: Although palliative care providers, patients, and their families rely heavily on accurate prognostication, the prognostic value of electrolyte imbalance has received little attention. METHODS: As a retrospective review, we screened inpatients with terminal cancer admitted between January 2017 and May 2019 to a single hospice-palliative care unit. Clinical characteristics and laboratory results were obtained from medical records for multivariable Cox regression analysis of independent prognostic factors. RESULTS: Of the 487 patients who qualified, 15 (3%) were hypernatremic upon admission. The median survival time was 26 days. Parameters associated with shortened survival included male sex, advanced age (> 70 years), lung cancer, poor performance status, elevated inflammatory markers, azotemia, impaired liver function, and hypernatremia. In a multivariable Cox proportional hazards model, male sex (hazard ratio [HR] = 1.53, 95% confidence interval [CI]: 1.15-2.04), poor performance status (HR = 1.45, 95% CI: 1.09-1.94), leukocytosis (HR = 1.98, 95% CI: 1.47-2.66), hypoalbuminemia (HR = 2.06, 95% CI: 1.49-2.73), and hypernatremia (HR = 1.55, 95% CI: 1.18-2.03) emerged as significant predictors of poor prognosis. CONCLUSION: Hypernatremia may be a useful gauge of prognosis in patients with terminal cancer. Further large-scale prospective studies are needed to corroborate this finding.

Copeptin and its role in the diagnosis of diabetes insipidus and the syndrome of inappropriate antidiuresis.

Copeptin is secreted in an equimolar amount to arginine vasopressin (AVP) but can easily be measured in plasma or serum with a sandwich immunoassay. The main stimuli for copeptin are similar to AVP, that is an increase in osmolality and a decrease in arterial blood volume and pressure. A high correlation between copeptin and AVP has been shown. Accordingly, copeptin mirrors the amount of AVP in the circulation. Copeptin has, therefore, been evaluated as diagnostic biomarker in vasopressin-dependent disorders of body fluid homeostasis. Disorders of body fluid homeostasis are common and can be divided into hyper- and hypoosmolar circumstances: the classical hyperosmolar disorder is diabetes insipidus, while the most common hypoosmolar disorder is the syndrome of inappropriate antidiuresis (SIAD). Copeptin measurement has led to a "revival" of the direct test in the differential diagnosis of diabetes insipidus. Baseline copeptin levels, without prior thirsting, unequivocally identify patients with nephrogenic diabetes insipidus. In contrast, for the difficult differentiation between central diabetes insipidus and primary polydipsia, a stimulated copeptin level of 4.9 pmol/L upon hypertonic saline infusion differentiates these two entities with a high diagnostic accuracy and is clearly superior to the classical water deprivation test. On the contrary, in the SIAD, copeptin measurement is of only little diagnostic value. Copeptin levels widely overlap in patients with hyponatraemia and emphasize the heterogeneity of the disease. Additionally, a variety of factors lead to unspecific copeptin elevations in the acute setting further complicating its interpretation. The broad use of copeptin as diagnostic marker in hyponatraemia and specifically to detect cancer-related disease in SIADH patients can, therefore, not be recommended.

Potassium conservation is impaired in mice with reduced renal expression of Kir4.1.

To better understand the role of the inward-rectifying K channel Kir4.1 (KCNJ10) in the distal nephron, we initially studied a global Kir4.1 knockout mouse (gKO), which demonstrated the hypokalemia and hypomagnesemia seen in SeSAME/EAST syndrome and was associated with reduced Na/Cl cotransporter (NCC) expression. Lethality by ~3 wk, however, limits the usefulness of this model, so we developed a kidney-specific Kir4.1 "knockdown" mouse (ksKD) using a cadherin 16 promoter and Cre-loxP methodology. These mice appeared normal and survived to adulthood. Kir4.1 protein expression was decreased ~50% vs. wild-type (WT) mice by immunoblotting, and immunofluorescence showed moderately reduced Kir4.1 staining in distal convoluted tubule that was minimal or absent in connecting tubule and cortical collecting duct. Under control conditions, the ksKD mice showed metabolic alkalosis and relative hypercalcemia but were normokalemic and mildly hypermagnesemic despite decreased NCC expression. In addition, the mice had a severe urinary concentrating defect associated with hypernatremia, enlarged kidneys with tubulocystic dilations, and reduced aquaporin-3 expression. On a K/Mg-free diet for 1 wk, however, ksKD mice showed marked hypokalemia (serum K: 1.5 ± 0.1 vs. 3.0 ± 0.1 mEq/l for WT), which was associated with renal K wasting (transtubular K gradient: 11.4 ± 0.8 vs. 1.6 ± 0.4 in WT). Phosphorylated-NCC expression increased in WT but not ksKD mice on the K/Mg-free diet, suggesting that loss of NCC adaptation underlies the hypokalemia. In conclusion, even modest reduction in Kir4.1 expression results in impaired K conservation, which appears to be mediated by reduced expression of activated NCC.

Novel Risk Score Efficiently Prevents Tolvaptan-Induced Hypernatremic Events in Patients With Heart Failure.

BACKGROUND: It has been 7 years since tolvaptan was approved in Japan for the indication of heart failure in patients with volume overload; the drug can be used in patients with normonatremia. Hypernatremia was identified as a significant adverse event to be prevented.Methods and Results:We compiled and analyzed data from 3,349 patients over 5 years to identify patients at high risk of hypernatremia with tolvaptan treatment. The incidence of hypernatremia, defined as serum sodium ≥150 mEq/L, was 3.65%. Baseline serum sodium concentrations, serum potassium concentrations, blood urea nitrogen : creatinine ratio, initial tolvaptan dose, and age were identified as risk factors for hypernatremia. A hypernatremia risk score was developed using the odds ratios for these factors. The high-risk population was defined as patients with a risk score ≥17.80. CONCLUSIONS: To prevent the occurrence of hypernatremic events in patients taking tolvaptan, we recommend a very low starting dose (i.e., 3.75 mg/day) in patients identified as being at high risk of hypernatremia using our new scoring process.

Hypernatremia and acute pancreatitis in chronic kidney disease: back to the salt mines. Questions.

BACKGROUND: Acute pancreatitis can be a life-threatening complication in patients with chronic kidney disease (CKD), especially in kidney transplant recipients. CASE DIAGNOSIS/TREATMENT: The patient was 7 years old when he received renal transplantation for CKD secondary to posterior urethral valves. Two years later, he presented with severe necrotizing pancreatitis (Ranson's score 5, Balthazar's score 8). Viral and genetic testing came back negative; pancreatitis was attributed to the patient's treatments (prednisone, trimethoprim-sulfamethoxazole, and everolimus). Twenty days later, necrotized pancreatic cysts had formed. Two drains were surgically inserted into the abdomen, and continuous cyst lavage was started with normal saline solution. Two days later, blood tests revealed severe hypernatremia and hypokalemia. We suspected unwanted peritoneal dialysis had occurred because of the high sodium chloride content and the absence of potassium in the normal saline solution being used for cyst lavage. We switched to a peritoneal dialysis solution for the lavage, leading to complete correction of hydroelectrolytic disorders. CONCLUSION: Acute pancreatitis is a frequent and potentially severe complication in CKD patients. It should be suspected in the presence of nonspecific symptoms, such as abdominal pain or vomiting. Rigorous monitoring of electrolytes is also mandatory for managing CKD patients with acute pancreatitis.

[Study of diagnostic value of natremia in a cohort of patients with hypercalcemia]. / Etude de la valeur diagnostique de la natrémie dans une cohorte de patients hypercalcémiques.

INTRODUCTION: Hypercalcemia is a common pathological condition in clinical practice. The two most common causes are primary hyperparathyroidism and cancer. SIADH is often encountered in cancer cases and is the most common cause of hyponatremia. The aim of this study is to evaluate serum sodium levels in a cohort of patients with hypercalcemia and consider its predictive value in determining the origin of this hypercalcemia. MATERIALS AND METHODS: We performed a retrospective study on a series of 15.284 blood tests among adult patients with hypercalcemia. After selection, the study population had 151 patients. We studied mainly serum sodium and etiology of hypercalcemia in our population. RESULTS: We observed a statistically significant association between the presence of hyponatremia and the neoplastic etiology of hypercalcemia. This association persisted after exclusion of patients under treatment with loop diuretics. Conversely, there was no association between hypernatremia and cancer-related hypercalcemia. Among 151 patients with hypercalcemia, 16 presented hyponatremia and 7 with hypernatremia. SIADH was the main cause of hyponatremia. We performed univariate and multivariate logistic regression showing the association between the presence of cancer and the presence of hyponatremia. CONCLUSION: Our study shows that there is an association between the presence of hyponatremia and neoplastic origin of hypercalcemia. Besides, the association described between hyponatremia and cancer is not faulted by the presence of hypercalcemia, a potential cause of acquired nephrogenic diabetes insipidus.

INTRODUCTION: L'hypercalcémie est une condition pathologique courante en pratique clinique. Les deux causes les plus fréquentes sont l'hyperparathyroïdie primaire et le cancer. Le syndrome de sécrétion inappropriée de l'hormone antidiurétique (SIADH) est souvent rencontré dans les cas de cancer, et constitue la cause la plus fréquente d'hyponatrémie. Le but de cette étude est d'évaluer la natrémie dans une cohorte de patients atteints d'hypercalcémie et d'apprécier sa valeur prédictive dans la détermination de l'origine de cette hypercalcémie. Matériel et méthode : Nous avons réalisé une étude rétrospective sur une série de 15.284 analyses sanguines chez des patients adultes hypercalcémiques. Après sélection, la population de l'étude comptait 151 patients. Nous avons étudié principalement la natrémie et l'étiologie de l'hypercalcémie au sein de notre population. Résultats : Nous avons observé une association statistiquement significative entre la présence d'une hyponatrémie et l'étiologie néoplasique de l'hypercalcémie. Cette association persistait après l'exclusion des patients sous traitement par diurétiques de l'anse. Par contre, il n'existait pas d'association entre l'hypernatrémie et l'origine cancéreuse de l'hypercalcémie. Sur 151 patients hypercalcémiques, 16 étaient hyponatrémiques et 7 étaient hypernatrémiques. Un SIADH représentait la cause principale des cas d'hyponatrémie. Nous avons réalisé une régression logistique uni- et multivariée montrant l'association entre l'existence d'un cancer et la présence d'une hyponatrémie. CONCLUSION: Notre étude montre qu'il existe une association entre la présence d'une hyponatrémie et l'étiologie néoplasique de l'hypercalcémie. Par ailleurs, l'association classiquement décrite entre hyponatrémie et cancer n'est pas prise en défaut par la présence d'une hypercalcémie, cause potentielle de diabète insipide néphrogénique acquis.

ENaC activity in the cortical collecting duct of HKα1 H+,K+-ATPase knockout mice is uncoupled from Na+ intake.

Modulation of the epithelial Na+ channel (ENaC) activity in the collecting duct (CD) is an important mechanism for normal Na+ homeostasis. ENaC activity is inversely related to dietary Na+ intake, in part due to inhibitory paracrine purinergic regulation. Evidence suggests that H+,K+-ATPase activity in the CD also influences Na+ excretion. We hypothesized that renal H+,K+-ATPases affect Na+ reabsorption by the CD by modulating ENaC activity. ENaC activity in HKα1 H+,K+-ATPase knockout (HKα1-/-) mice was uncoupled from Na+ intake. ENaC activity on a high-Na+ diet was greater in the HKα1-/- mice than in WT mice. Moreover, dietary Na+ content did not modulate ENaC activity in the HKα1-/- mice as it did in WT mice. Purinergic regulation of ENaC was abnormal in HKα1-/- mice. In contrast to WT mice, where urinary [ATP] was proportional to dietary Na+ intake, urinary [ATP] did not increase in response to a high-Na+ diet in the HKα1-/- mice and was significantly lower than in the WT mice. HKα1-/- mice fed a high-Na+ diet had greater Na+ retention than WT mice and had an impaired dipsogenic response. These results suggest an important role for the HKα1 subunit in the regulation of purinergic signaling in the CD. They are also consistent with HKα1-containing H+,K+-ATPases as important components for the proper regulation of Na+ balance and the dipsogenic response to a high-salt diet. Such observations suggest a previously unrecognized element in Na+ regulation in the CD.

Sodium supply influences plasma sodium concentration and the risks of hyper- and hyponatremia in extremely preterm infants.

BACKGROUND: Hyper- and hyponatremia occur frequently in extremely preterm infants. Our purpose was to investigate plasma sodium (P-Na) concentrations, the incidence of hyper- and hyponatremia, and the impact of possible predisposing factors in extremely preterm infants. METHODS: In this observational study, we analyzed data from the EXtremely PREterm (< 27 wk.) infants in Sweden Study (EXPRESS, n = 707). Detailed nutritional, laboratory, and weight data were collected retrospectively from patient records. RESULTS: Mean ± SD P-Na increased from 135.5 ± 3.0 at birth to 144.3 ± 6.1 mmol/l at a postnatal age of 3 d and decreased thereafter. Fifty percent of infants had hypernatremia (P-Na > 145 mmol/l) during the first week of life while 79% displayed hyponatremia (P-Na < 135 mmol/l) during week 2. Initially, the main sodium sources were blood products and saline injections/infusions, gradually shifting to parenteral and enteral nutrition towards the end of the first week. The major determinant of P-Na and the risks of hyper- and hyponatremia was sodium supply. Fluid volume provision was associated with postnatal weight change but not with P-Na. CONCLUSION: The supply of sodium, rather than fluid volume, is the major factor determining P-Na concentrations and the risks of hyper- and hyponatremia.

Associations of dysnatremias with mortality in chronic kidney disease.

BACKGROUND: Hyponatremia and hypernatremia are associated with death in the general population and those with chronic kidney disease (CKD). We studied the associations between dysnatremias, all-cause mortality and causes of death in a large cohort of Stage 3 and 4 CKD patients. METHODS: We included 45 333 patients with Stage 3 and 4 CKDs followed in a large healthcare system. Associations between hyponatremia (<136 mmol/L) and hypernatremia (>145), and all-cause mortality and causes of death (cardiovascular, malignancy related and non-cardiovascular/non-malignancy related) were studied using Cox proportional hazards and competing risk models. RESULTS: Dysnatremias were found in 9.2% of the study population. In separate multivariable Cox proportional hazards models using baseline serum sodium levels and time-dependent repeated measures, both hyponatremia and hypernatremia were associated with all-cause mortality. In the competing risk analyses, hyponatremia was significantly associated with increased risk for various cause-specific mortality categories [cardiovascular (hazard ratio, HR 1.16, 95% confidence interval, CI: 1.04, 1.30), malignancy related (HR 1.48, 95% CI: 1.33, 1.65) and non-cardiovascular/non-malignancy deaths (HR 1.25, 95% CI: 1.13, 1.39)], while hypernatremia was significantly associated with higher non-cardiovascular/non-malignancy mortality only (HR 1.36, 95% CI: 1.08, 1.72). CONCLUSIONS: In those with CKD, hyponatremia was associated with all-cause mortality, cardiovascular, malignancy and non-cardiovascular/non-malignancy-related deaths. Hypernatremia was associated with all-cause and non-cardiovascular/non-malignancy-related deaths. Further studies are needed to elucidate the mechanisms of differences in cause-specific death among CKD patients with hyponatremia and hypernatremia.

Serum sodium and mortality in a national peritoneal dialysis cohort.

BACKGROUND: Sodium disarrays are common in peritoneal dialysis (PD) patients, and may be associated with adverse outcomes in this population. However, few studies of limited sample size have examined the association of serum sodium with mortality in PD patients, with inconsistent results. We hypothesized that both hypo- and hypernatremia are associated with higher death risk in a nationally representative cohort of US PD patients. METHODS: We sought to examine the association of serum sodium over time and mortality among 4687 adult incident PD patients from a large US dialysis organization who underwent one or more serum sodium measurements within the first 3 months of dialysis over January 2007 to December 2011. We examined the association of time-dependent and baseline sodium with all-cause mortality as a proxy of short- and long-term sodium-mortality associations, respectively. Hazard ratios were estimated using Cox models with three adjustment levels: minimally adjusted, case-mix adjusted, and case-mix + laboratory adjusted. RESULTS: In time-dependent analyses, sodium levels <140 mEq/L were associated with incrementally higher death risk in case-mix models (ref: 140 to <142 mEq/L); following laboratory covariate adjustment, associations between lower sodium and higher mortality remained significant for levels <136 mEq/L. In analyses using baseline values, sodium levels <140 mEq/L were associated with higher mortality risk across all models (ref: 140 to <142 mEq/L). CONCLUSIONS: In PD patients, lower time-dependent and baseline sodium levels were independently associated with higher death risk. Further studies are needed to determine whether correction of dysnatremia improves longevity in this population.

Prevalence of pseudonatremia in a clinical laboratory - role of the water content.

BACKGROUND: Sodium concentration is a frequently used marker to discriminate between differential diagnoses or for clinical follow-up. Pseudonatremia, as a result of indirect ion-selective electrode (ISE) measurements in automated chemistry analyzers, can lead to incorrect diagnosis and treatment. We investigated whether the estimated water content, based on total protein and lipid concentrations, can be used to reduce diagnoses of pseudonatremia. METHODS: Indirect and direct ISE measurements of sodium were compared in blood samples from intensive care unit (ICU) (n = 98) and random non-ICU patients (n = 100). Differences between direct measurements using whole blood and lithium-heparin plasma were also determined. Water content, estimated by a linear combination of total protein and lipid concentrations, was used to correct indirectly measured sodium concentrations. The prevalence of pseudonatremia was evaluated in the ICU patient group. RESULTS: An absolute difference of 3 mmol/L was observed between direct measurements using lithium-heparin plasma and whole blood, with higher concentrations in plasma. Additionally, we observed that differences between indirect and direct measurements displayed a linear relationship with the estimated water content. The prevalence of pseudohypernatremia after indirect measurements (32%) was reduced when measurements were corrected for water content (19%). CONCLUSIONS: In critically ill patients, sodium concentrations should be preferably measured by direct measurements. Whole blood is the preferred material for these measurements. For routine sodium analyses in other patients, correction using the estimated water content appears promising in reducing the prevalence of pseudohypernatremia by indirect measurements.

Association between borderline dysnatremia and mortality insight into a new data mining approach.

BACKGROUND: Even small variations of serum sodium concentration may be associated with mortality. Our objective was to confirm the impact of borderline dysnatremia for patients admitted to hospital on in-hospital mortality using real life care data from our electronic health record (EHR) and a phenome-wide association analysis (PheWAS). METHODS: Retrospective observational study based on patient data admitted to Hôpital Européen George Pompidou, between 01/01/2008 and 31/06/2014; including 45,834 patients with serum sodium determinations on admission. We analyzed the association between dysnatremia and in-hospital mortality, using a multivariate logistic regression model to adjust for classical potential confounders. We performed a PheWAS to identify new potential confounders. RESULTS: Hyponatremia and hypernatremia were recorded for 12.0% and 1.0% of hospital stays, respectively. Adjusted odds ratios (ORa) for severe, moderate and borderline hyponatremia were 3.44 (95% CI, 2.41-4.86), 2.48 (95% CI, 1.96-3.13) and 1.98 (95% CI, 1.73-2.28), respectively. ORa for severe, moderate and borderline hypernatremia were 4.07 (95% CI, 2.92-5.62), 4.42 (95% CI, 2.04-9.20) and 3.72 (95% CI, 1.53-8.45), respectively. Borderline hyponatremia (ORa = 1.57 95% CI, 1.35-1.81) and borderline hypernatremia (ORa = 3.47 95% CI, 2.43-4.90) were still associated with in-hospital mortality after adjustment for classical and new confounding factors identified through the PheWAS analysis. CONCLUSION: Borderline dysnatremia on admission are independently associated with a higher risk of in-hospital mortality. By using medical data automatically collected in EHR and a new data mining approach, we identified new potential confounding factors that were highly associated with both mortality and dysnatremia.