Disorders of plasma sodium--causes, consequences, and correction

Practical document on the management of hyponatremia in critically ill patients

Hyponatremia is the most prevalent electrolyte disorder in Intensive Care Units. It is associated with an increase in morbidity, mortality and hospital stay. The majority of the published studies are observational, retrospective and do not include critical patients; hence it is difficult to draw definitive conclusions. Moreover, the lack of clinical evidence has led to important dissimilarities in the recommendations coming from different scientific societies. Finally, etiopathogenic mechanisms leading to hyponatremia in the critical care patient are complex and often combined, and an intensive analysis is clearly needed. A study was therefore made to review all clinical aspects about hyponatremia management in the critical care setting. The aim was to develop a Spanish nationwide algorithm to standardize hyponatremia diagnosis and treatment in the critical care patient.

Allostasis and the Clinical Manifestations of Mild to Moderate Chronic Hyponatremia: No Good Adaptation Goes Unpunished

When homeostatic regulatory systems are unable to maintain a normal serum sodium concentration, the organism must adapt to demands of a disordered internal environment, a process known as "allostasis." Human cells respond to osmotic stress created by an abnormal serum sodium level with the same adaptations used by invertebrate organisms that do not regulate body fluid osmolality. To avoid intolerable changes in their volume, cells export organic osmolytes when exposed to a low serum sodium concentration and accumulate these intracellular solutes when serum sodium concentration increases. The brain's adaptation to severe hyponatremia (serum sodium < 120 mEq/L) has been studied extensively. However, adaptive responses occur with less severe hyponatremia and other tissues are affected; the consequences of these adaptations are incompletely understood. Recent epidemiologic studies have shown that mild (sodium, 130-135 mEq/L) and moderate (sodium, 121-129 mEq/L) chronic hyponatremia, long thought to be inconsequential, is associated with adverse outcomes. Adaptations of the heart, bone, brain, and (possibly) immune system to sustained mild to moderate hyponatremia may adversely affect their function and potentially the organism's survival. This review explores what is known about the consequences of mild to moderate chronic hyponatremia and the potential benefits of treating this condition.

A novel scoring system for assessing the severity of electrolyte and acid-base disorders and predicting outcomes in hospitalized patients

Electrolyte and acid-base disorders are commonly seen in critically ill and other hospitalized patients. A scoring system is needed to assess the severity of electrolyte and acid-base disorders and to predict outcome in hospital patients. Herein, we prospectively enrolled a total of 322,046 patients, including 84,700 patients in the derivation cohort and 237,346 in the validation cohort, in a large, tertiary hospital in East China from 2014 to 2017. A points-scoring system of general electrolyte and acid-base disorders with a sum of 20.8 points was generated by multiple logistic regression analysis of the derivation cohort. Receiver operating characteristic curve analysis showed that the optimal cut-off value of 2.0 was associated with 65.4% sensitivity and 88.4% specificity (area under the curve: 0.818 (95% CI 0.809 to 0.827)) to predict hospital mortality in the validation cohort. On Kaplan-Meier survival analysis, the five intervals of risk score (Q1: 0 to 2.0; Q2: 2.1 to 2.5; Q3: 2.6 to 3.3; Q4: 3.4 to 4.5; and Q5: >4.5 points) showed differences in hospital survival (p<0.001). Elevated (delta) risk score >2 during hospitalization increased the risk of hospital death, while those with a delta risk score <0 and <−2 points had higher survival rates. This novel scoring system could be used to evaluate and to dynamically monitor the severity of electrolyte and acid-base disorders in hospitalized patients.

Determining Fractional Urate Excretion Rates in Hyponatremic Conditions and Improved Methods to Distinguish Cerebral/Renal Salt Wasting From the Syndrome of Inappropriate Secretion of Antidiuretic Hormone

Our evaluation of hyponatremic patients is in a state of confusion because the assessment of the volume status of the patient and determinations of urine sodium concentrations (UNa) >30–40 mEq/L have dominated our approach despite documented evidence of many shortcomings. Central to this confusion is our inability to differentiate cerebral/renal salt wasting (C/RSW) from the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), syndromes with diametrically opposing therapeutic goals. The recent proposal to treat most or all hyponatremic patients makes differentiation even more important and reports of C/RSW occurring without cerebral disease leads to a clinically important proposal to change cerebral to renal salt wasting (RSW). Differentiating SIADH from RSW is difficult because of identical clinical parameters that characterize both syndromes. Determination of fractional urate excretion (FEurate) is central to a new algorithm, which has proven to be superior to current methods. We utilized this algorithm and differences in physiologic response to isotonic saline infusions between SIADH and RSW to evaluate hyponatremic patients from the general medical wards of the hospital. In 62 hyponatremic patients, 17 (27%) had SIADH, 19 (31%) had reset osmostat (RO), 24 (38%) had RSW, 1 due to HCTZ and 1 Addison's disease. Interestingly, 21 of 24 with RSW had no evidence of cerebral disease and 10 of 24 with RSW had UNa < 20 mEqL. We conclude that 1. RSW is much more common than is perceived, 2.the term cerebral salt wasting should be changed to RSW 3. RO should be eliminated as a subclass of SIADH, 4. SIADH should be redefined 5. The volume approach is ineffective and 6. There are limitations to determining UNa, plasma renin, aldosterone or atrial/brain natriuretic peptides. We also present data on a natriuretic peptide found in sera of patients with RSW and Alzheimer's disease.

Educational intervention improves fruit and vegetable intake in young adults with metabolic syndrome components

The FRUVEDomics study investigates the effect of a diet intervention focused on increasing fruit and vegetable intake on the gut microbiome, and cardiovascular health of young adults with/at risk for Metabolic Syndrome (MetS). It was hypothesized the recommended diet would result in metabolic and gut microbiome changes. The 9-week dietary intervention adhered to the USDA Dietary Guidelines for Americans and focused on increasing fruit and vegetable intake to equal half of the diet. Seventeen eligible young adults with/or at high risk of MetS, consented and completed preintervention and postintervention measurements, including anthropometric, body composition, cardiovascular, complete blood lipid panel, and collection of stool sample for microbial analysis. Participants attended weekly consultations to assess food logs, food receipts, and adherence to the diet. Following intention-to-treat guidelines all 17 individuals were included in the dietary, clinical, and anthropometric analysis. Fruit and vegetable intake increased from 1.6 to 3.4 cups of fruits and vegetables (P < .001) daily. Total fiber (P = .02) and insoluble fiber (P < .0001) also increased. Clinical laboratory changes included an increase in sodium (P = .0006) and low-density lipoprotein cholesterol (P = .04). In the fecal microbiome, Erysipelotrichaceae (phylum Firmicutes) decreased (log2 fold change: −1.78, P = .01) and Caulobacteraceae (phylum Proteobacteria) increased (log2 fold change = 1.07, P = .01). Implementing a free living 9-week diet, with intensive education and accountability, gave young adults at high risk for/or diagnosed with MetS the knowledge, skills, and feedback to improve diet. To yield greater impact a longer diet intervention may be needed in this population.

Hyponatremia in children with respiratory infections: a cross-sectional analysis of a cohort of 3938 patients

Hyponatremia can be a life-threatening illness among hospitalized children. The aims of this study were to evaluate the incidence and risk factors of hyponatremia in 3938 children who were admitted to the Cheil General Hospital and Women’s Health Care Center with respiratory infections. Clinical data were collected, and multiplex RT-PCR analyses were done for various microorganisms. Hyponatremia was observed in 531 (13.5%) patients. The incidence of hyponatremia differed according to the respiratory tract infection (P < 0.0001) and microorganism (P = 0.001). In children with hyponatremia, the age at admission was significantly older (P < 0.0001), male gender was more frequent (P = 0.019), CRP was higher (P < 0.0001), and coinfection with multiple organisms was more common (P = 0.001) than in children without hyponatremia. In multivariate analyses, an older age at admission (P = 0.006), male gender (P = 0.004), and increased CRP (P < 0.0001) were independent risk factors. Sodium levels correlated negatively with WBC (P = 0.037), CRP (P < 0.0001), and number of hospital days (P = 0.020). The AUC values of age (0.586, P < 0.0001), CRP (0.599, P < 0.0001), and blood urea nitrogen (0.559, P < 0.0001) were all significant predictors of hyponatremia. This study is the first to show that the incidence of hyponatremia differs according to infecting microorganism and radiological findings.

Hyponatremia in Cirrhosis: Implications for Liver Transplantation

Hyponatremia in cirrhosis is defined as a serum sodium level ≤130 mEq/L and occurs in approximately 22% of patients with cirrhosis. The appearance of hyponatremia in patients with cirrhosis portends a poor prognosis before liver transplantation (LT), independent of the Model for End-Stage Liver Disease (MELD) score. With the development of the MELD-sodium score, the management of hyponatremia has become more relevant than ever before. Overcorrection of hyponatremia before LT or perioperatively can lead to the devastating neurologic condition known as osmotic demyelination syndrome, which is often irreversible and fatal. Therefore, the most important tenet of hyponatremia is to avoid correcting the serum sodium by ≥8 mEq/L in a 24-hour period. Treatment of hyponatremia is highly challenging. The vast majority of patients with cirrhosis have chronic hypervolemic hyponatremia. Fluid restriction increases serum sodium levels, but tolerance and compliance are significant barriers. Diuretic withdrawal is helpful but contributes to worsening fluid overload. There are limited data to support use of intravenous concentrated albumin solutions. The use of the arginine vasopressin antagonists ("vaptans") is contentious; however, they may have a limited role. Risk factors for intraoperative overcorrection of serum sodium include increased utilization of packed red blood cell and fresh frozen plasma transfusions, which are often unavoidable. Intraoperative management is evolving, and more data are needed in regard to the use of sodium-reduced continuous venovenous hemofiltration and the use of trishydroxymethylaminomethane (Tris) to avoid excess sodium rebound. A thorough discussion of the current treatment options before and during LT is given in this review.

Approach and management of dysnatremias in cirrhosis

Hypervolemic (dilutional) hyponatremia is the most common dysnatremia in cirrhosis, with a prevalence close to 50% in patients with ascites, while hypovolemic hyponatremia occurs in a minority of cases. Hyponatremia carries a poor prognosis, being associated with increased mortality and reduced survival after liver transplantation. Hypernatremia is rarer and is also associated with an adverse prognosis. Increased non-osmotic secretion of arginine vasopressin and altered renal tubular sodium handling due to impaired free water generation are the mechanisms leading to hypervolemic hyponatremia, while diuretic-induced fluid loss is the main cause of hypovolemic hyponatremia. Hypernatremia usually follows hypotonic fluid losses due to osmotic diuresis (glycosuria) or lactulose-induced diarrhea. The main clinical manifestations of dysnatremias are due to their effects on the central nervous system: astroglial cell hyperhydration follows hyponatremia-an abnormality that exacerbates ammonia neurotoxicity-while the opposite abnormality occurs with hypernatremia. Asymptomatic or mildly symptomatic hypervolemic hyponatremia is mainly managed by correcting of precipitating factors and non-osmotic fluid restriction. Severe, life-threatening hyponatremia requires hypertonic saline infusion, avoiding rapid and complete correction of serum sodium concentration to prevent neurological sequelae such as osmotic demyelination. V₂ receptor blockade by vaptans may be considered in patients with sustained hyponatremia waitlisted for liver transplantation. Diuretic withdrawal and plasma volume expansion are required in hypovolemic hypernatremia. Prompt recognition, removal of the precipitating factor(s) and non-osmotic fluid administration represent the mainstays of hypernatremia management. Rapid correction of long-standing hypernatremia can lead to cerebral edema and has to be avoided.

Cell Volume Control in Healthy Brain and Neuropathologies

Regulation of cellular volume is a critical homeostatic process that is intimately linked to ionic and osmotic balance in the brain tissue. Because the brain is encased in the rigid skull and has a very complex cellular architecture, even minute changes in the volume of extracellular and intracellular compartments have a very strong impact on tissue excitability and function. The failure of cell volume control is a major feature of several neuropathologies, such as hyponatremia, stroke, epilepsy, hyperammonemia, and others. There is strong evidence that such dysregulation, especially uncontrolled cell swelling, plays a major role in adverse pathological outcomes. To protect themselves, brain cells utilize a variety of mechanisms to maintain their optimal volume, primarily by releasing or taking in ions and small organic molecules through diverse volume-sensitive ion channels and transporters. In principle, the mechanisms of cell volume regulation are not unique to the brain and share many commonalities with other tissues. However, because ions and some organic osmolytes (e.g., major amino acid neurotransmitters) have a strong impact on neuronal excitability, cell volume regulation in the brain is a surprisingly treacherous process, which may cause more harm than good. This topical review covers the established and emerging information in this rapidly developing area of physiology.

A Case of Diabetic Ketoacidosis Presenting with Hypernatremia, Hyperosmolarity, and Altered Sensorium

Diabetic Ketoacidosis commonly presents with hyponatremia, but hypernatremia is a rare entity. We report a unique case of a 50-year-old woman admitted with altered sensorium with blood glucose 979 milligrams/deciliter, serum osmolarity 363 mOsm/kilograms, and serum sodium 144 milliequivalents/liter. Patient was given initial bolus of isotonic saline and continued on half isotonic saline for correction of hypernatremia along with insulin infusion therapy. Patient was successfully treated with intravenous fluids, insulin infusion, and the altered sensorium was resolved without any sequelae. This case illustrates a teaching point in the use of intravenous fluids for the treatment of Diabetic Ketoacidosis with hypernatremia.

Critical gaps in the medical knowledge base of eating disorders

Eating disorders are unique in that they inherently have much medical comorbidity both as a part of restricting-type eating disorders and those characterized by purging behaviors. Over the last three decades, remarkable progress has been made in the understanding and treatment of the medical complications of eating disorders. Yet, unfortunately, there is much research that is sorely needed to bridge the gap between current medical knowledge and more effective and evidence-based medical treatment knowledge. These gaps exist in many different clinical areas including cardiology, electrolytes, gastrointestinal and bone disease. In this paper, we discuss some of the knowledge gap areas, which if bridged would help develop more effective medical intervention for this population of patients.

Risk Factors and Outcomes of Rapid Correction of Severe Hyponatremia

BACKGROUND AND OBJECTIVES

Rapid correction of severe hyponatremia can result in serious neurologic complications, including osmotic demyelination. Few data exist on incidence and risk factors of rapid correction or osmotic demyelination.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In a retrospective cohort of 1490 patients admitted with serum sodium <120 mEq/L to seven hospitals in the Geisinger Health System from 2001 to 2017, we examined the incidence and risk factors of rapid correction and osmotic demyelination. Rapid correction was defined as serum sodium increase of >8 mEq/L at 24 hours. Osmotic demyelination was determined by manual chart review of all available brain magnetic resonance imaging reports.

RESULTS

Mean age was 66 years old (SD=15), 55% were women, and 67% had prior hyponatremia (last outpatient sodium <135 mEq/L). Median change in serum sodium at 24 hours was 6.8 mEq/L (interquartile range, 3.4-10.2), and 606 patients (41%) had rapid correction at 24 hours. Younger age, being a woman, schizophrenia, lower Charlson comorbidity index, lower presentation serum sodium, and urine sodium <30 mEq/L were associated with greater risk of rapid correction. Prior hyponatremia, outpatient aldosterone antagonist use, and treatment at an academic center were associated with lower risk of rapid correction. A total of 295 (20%) patients underwent brain magnetic resonance imaging on or after admission, with nine (0.6%) patients showing radiologic evidence of osmotic demyelination. Eight (0.5%) patients had incident osmotic demyelination, of whom five (63%) had beer potomania, five (63%) had hypokalemia, and seven (88%) had sodium increase >8 mEq/L over a 24-hour period before magnetic resonance imaging. Five patients with osmotic demyelination had apparent neurologic recovery.

CONCLUSIONS

Among patients presenting with severe hyponatremia, rapid correction occurred in 41%; nearly all patients with incident osmotic demyelination had a documented episode of rapid correction.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2018_06_05_CJASNPodcast_18_7_G.mp3.

Practical issues for the management of hyponatremia in oncology

Hyponatremia is common in cancer patients and has a negative impact on outcomes and survival. Both the diagnosis and treatment of hyponatremia are challenging. Easy-to-use, practical guidelines are needed. The aim of this article is to discuss practical issues related to the diagnostic workup and management of hyponatremia, with particular attention to complex patients, such as those affected by neoplastic diseases. Admittedly, these patients may present several comorbidities, which may cause sodium alterations. In addition, multidrug therapy may precipitate serum sodium fall. An algorithm for the diagnosis and treatment of hyponatremia was also developed, based on the discussion of the results of a questionnaire completed by the authors and of the published recommendations/guidelines on hyponatremia. The goal was to produce an algorithm that was as simple as possible but still comprehensive, without compromising information completeness. Many explanatory notes were added with the aim of guiding clinicians throughout the management of complex patients with hyponatremia, such as those with cancer. The resulting algorithm and supporting literature are presented.

Valacyclovir Neurotoxicity and Nephrotoxicity in an Elderly Patient Complicated by Hyponatremia

A 66-year-old women with no history of renal disease was admitted due to a coma and acute kidney injury with a serum creatinine level of 7.44 mg/dL which were ascribed to valacyclovir neurotoxicity and nephrotoxicity, respectively. She had received valacyclovir at a standard dosage for the treatment of herpes zoster and was finally discharged, having fully returned to her normal baseline mental status with a recovered serum creatinine level of 0.68 mg/dL. We feel that awareness of this pathology remains a challenge for physicians and therefore strongly recommend the further accumulation of experiences similar to our own. Our experience underscores the pitfalls of administering valacyclovir to elderly patients who barely appear to have a favorable renal function. Several concerns regarding the therapeutic management, including blood purification strategies, that emerged in this case are also discussed.

Terlipressin for variceal bleeding induces large plasma sodium fluctuations in patients without cirrhosis

Background

Terlipressin is used as pharmacological treatment for variceal bleeding. The drug's physiological effect favours hyponatremia, and rapid changes in plasma sodium (PNa) may cause brain injury. Cirrhosis patients seem to be largely protected against this effect but patients without cirrhosis may not be so.

Objective

The objective of this study was to examine whether terlipressin treatment of patients without cirrhosis leads to more serious fluctuations in PNa than in cirrhosis.

Methods

In a retrospective cohort design, during a 39-month period, 11 patients with prehepatic portal hypertension and no cirrhosis and 134 patients with cirrhosis received a minimum cumulative terlipressin dose of 4 mg during at least 24 hours for variceal bleeding. The groups' PNa changes were compared.

Results

During terlipressin, the non-cirrhotic patients developed a greater reduction in PNa [mean 8.3 (95% confidence interval (CI) 1.9-14.6) vs. 1.8 (1.0-2.7) mmol/l; p = 0.048], a lower nadir PNa [129 (123-135) vs. 133 (132-134) mmol/l; p = 0.06], and within 48 hours after terlipressin a greater increase in PNa [12.6 (3.4-21.7) vs. 2.3 (1.5-3.0) mmol/l; p = 0.03]. Severe (>10 mmol/l change) hyponatriemia or PNa rebound were seen in 27% of these patients but in only 4% of those with cirrhosis (p = 0.02). One non-cirrhotic patient developed permanent brain damage.

Conclusion

Terlipressin treatment of bleeding varices carries a high risk of potentially dangerous PNa fluctuations in patients with non-cirrhotic prehepatic portal hypertension.

Intensive care management of severe hypernatraemia in the context of group A streptococcal septicaemia

This case describes a 54-year-old woman with exudative eczema, who was admitted to the intensive care unit with a serum sodium concentration of 191 mmol/L, secondary to profound dehydration in the context of group A streptococcal septicaemia. Successful rehydration and electrolyte normalisation was achieved with continuous venovenous haemodiafiltration (CVVHDF), the replacement fluid of which was infused with hypertonic saline to limit the rate of sodium reduction. This case report comments on three areas of interest. First, hypernatraemia of this level is unusual. Second, the infusion of hypertonic saline into the replacement fluid of the CVVHDF filter is not common practice but successfully ensured a controlled reduction in serum sodium concentration while aggressively replacing a 9 L water deficit. Third, the notable physiological reserve demonstrated by the patient: despite an extraordinary serum sodium concentration in the context of overwhelming streptococcal septicaemia, she has made a full cognitive recovery.

Using Electrolyte Free Water Balance to Rationalize and Treat Dysnatremias

Dysnatremias or abnormalities in plasma [Na+] are often termed disorders of water balance, an unclear physiologic concept often confused with changes in total fluid balance. However, most clinicians clearly recognize that hypertonic or hypotonic gains or losses alter plasma [Na+], while isotonic changes do not modify plasma [Na+]. This concept can be conceptualized as the electrolyte free water balance (EFWB), which defines the non-isotonic components of inputs and outputs to determine their effect on plasma [Na+]. EFWB is mathematically proportional to the rate of change in plasma [Na+] (dPNa/dt) and, therefore, is actively regulated to zero so that plasma [Na+] remains stable at its homeostatic set point. Dysnatremias are, therefore, disorders of EFWB and the relationship between EFWB and dPNa/dt provides a rationale for therapeutic strategies incorporating mass and volume balance. Herein, we leverage dPNa/dt as a desired rate of correction of plasma [Na+] to define a stepwise approach for the treatment of dysnatremias.

High Prevalence of Renal Salt Wasting Without Cerebral Disease as Cause of Hyponatremia in General Medical Wards

BACKGROUND

The approach to hyponatremia is in a state of flux, especially in differentiating syndrome of inappropriate antidiuretic hormone secretion (SIADH) from cerebral-renal salt wasting (RSW) because of diametrically opposite therapeutic goals. Considering RSW can occur without cerebral disease, we determined the prevalence of RSW in the general hospital wards.

METHODS

To differentiate SIADH from RSW, we used an algorithm based on fractional excretion (FE) of urate and nonresponse to saline infusions in SIADH as compared to excretion of dilute urines and prompt increase in serum sodium in RSW.

RESULTS

Of 62 hyponatremic patients, (A) 17 patients (27%) had SIADH, 11 were nonresponsive to isotonic saline, and 5 normalized a previously high FEurate after correction of hyponatremia; (B) 19 patients (31%) had a reset osmostat based on normal FEurates and spontaneously excreted dilute urines; (C) 24 patients (38%) had RSW, 21 had no clinical evidence of cerebral disease, 19 had saline-induced dilute urines; 2 had undetectable plasma ADH levels when urine was dilute, 10 required 5% dextrose in water to prevent rapid increase in serum sodium, 11 had persistently increased FEurate after correction of hyponatremia and 10 had baseline urinary sodium < 20 mEq/L; (D) 1 patient had Addison disease with a low FEurate and (E) 1 patient (1.6%) had hyponatremia due to hydrochlorothiazide.

CONCLUSIONS

Of the 24 patients with RSW, 21 had no cerebral disease, supporting our proposal to change cerebral-renal salt wasting to renal salt wasting. Application of established pathophysiological standards and a new algorithm based on determination of FEurate were superior to the volume approach for determination of urinary sodium when identifying the cause of hyponatremia.

Treatment of Severe Hyponatremia

Patients with severe (serum sodium ≤120 mEq/L), symptomatic hyponatremia can develop life-threatening or fatal complications from cerebral edema if treatment is inadequate and permanent neurologic disability from osmotic demyelination if treatment is excessive. Unfortunately, as is true of all electrolyte disturbances, there are no randomized trials to guide the treatment of this challenging disorder. Rather, therapeutic decisions rest on physiologic principles, animal models, observational studies, and single-patient reports. European guidelines and recommendations of an American Expert panel have come to similar conclusions on how much correction of hyponatremia is enough and how much is too much, but there are important differences. We review the evidence supporting these recommendations, identifying areas that rest on relatively solid ground and highlighting areas in greatest need of additional data.

High Salt Intake Attenuates Breast Cancer Metastasis to Lung

Diet-related factors are thought to modify the risk of cancers, while the influence of high salt intake remains largely uncharacterized. Breast cancer is the most common cancer in women worldwide. In the present study, we examined the effect of salt intake on breast cancer by using a 4T1 mouse mammary tumor model. Unexpectedly, both the fitness and the survival rate of the tumor-bearing mice were improved by high salt intake. Similarly, high salt intake suppressed the primary tumor growth as well as metastasis to lung in mice. Mechanistically, high salt intake greatly reduced food intake and thus might exert antitumor effect through mimicking calorie restriction. Immunoblotting showed the lower proliferation marker Ki-67 and the higher expression of the tumor suppressor gene p53 in tumors of high salt intake mice. Importantly, high salt intake might induce hyperosmotic stress, which sensitized breast cancer cells to p53-dependent anoikis. Collectively, our findings raise the possibility that endogenous salt deposition might act as the first-line defense system against breast cancer progression as well as metastasis.

Recommendations for active correction of hypernatremia in volume-resuscitated shock or sepsis patients should be taken with a grain of salt: A systematic review

Background:

Healthcare-acquired hypernatremia (serum sodium >145 mEq/dL) is common among critically ill and other hospitalized patients and is usually treated with hypotonic fluid and/or diuretics to correct a “free water deficit.” However, many hypernatremic patients are eu- or hypervolemic, and an evolving body of literature emphasizes the importance of rapidly returning critically ill patients to a neutral fluid balance after resuscitation.

Objective:

We searched for any randomized- or observational-controlled studies evaluating the impact of active interventions intended to correct hypernatremia to eunatremia on any outcome in volume-resuscitated patients with shock and/or sepsis.

Data sources:

We performed a systematic literature search with studies identified by searching MEDLINE, Embase, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, ClinicalTrials.gov, Index-Catalogue of the Library of the Surgeon General’s Office, DARE (Database of Reviews of Effects), and CINAHL and scanning reference lists of relevant articles with abstracts published in English.

Data synthesis:

We found no randomized- or observational-controlled trials measuring the impact of active correction of hypernatremia on any outcome in resuscitated patients.

Conclusion:

Recommendations for active correction of hypernatremia in resuscitated patients with sepsis or shock are unsupported by clinical research acceptable by modern evidence standards.

Chloride imbalance is involved in the pathogenesis of optic neuritis in neuromyelitis optica

Chloride imbalance between the serum and the cerebrospinal fluid (CSF) has been recently shown to exist in the acute phase of neuromyelitis optica (NMO). In this report, we studied the relation between the quotient of chloride (Q_Cl) and the severity of optic neuritis (ON) in NMO patients. There was a positive correlation (R = 0.67; p < 0.05) between Q_Cl and the length of ON-lesion. The visual prognosis also showed a positive correlation with Q_Cl in the acute phase (R = 0.58; p < 0.05). These results support the theory that chloride imbalance between serum and CSF may trigger the ON in NMO spectrum disorders.

Hyponatremia, bone mineral density and falls in the elderly; Results from AHAP study

Background. Hyponatremia (HN) can be associated with osteoporosis, falls and bone fractures in the elderly. Recent researches demonstrated different results about the correlation of HN with bone mineral density and bone fractures.

Methods. This analytic research came from the AHAP project in northern IRAN. All people aged 60 years and over were included in the study. Individuals with severe comorbidities and then who had concurrent conditions which could have impact on bone mineral densities (BMD) such as long-term use of steroids, calcium and/or vitamin D supplements, bisphosphonates, calcitonin, thiazides and hormonal medications were excluded.

Results. One thousand and one hundred and thirteen older persons entered in the study. More than 10 percent of the participants had HN (serum Na+ level ≤ 137mEq/L). No significant difference has been observed between hyponatremic and nonhyponatremic individuals about their balance abilities; bone mineral density; incidence of falls and/or bone fracture during the previous 6 months; dependency in activities of daily living; and osteoporosis.

Conclusion. HN was not a prevalent problem in older adults who met the inclusion criteria of this research. No significant difference has been observed between HN and bone mineral density and falls in the elderly.

An experimental model for hypertensive crises emergencies: Long-term high-fat diet followed by acute vasoconstriction stress on spontaneously hypertensive rats

Currently, the prevention and treatment of hypertensive crises especially when it occurs with serious adverse outcomes have led to worldwide controversy. Despite of clinical possibilities of multiple agents, clinical failures still occur frequently. Therefore, early evaluations and observations of different therapies on appropriate animals should be emphasized. In the present study, an animal model for hypertensive crises emergencies was firstly established and experimentally testified. Five-month-male spontaneously hypertensive rat was consecutively fed with 60%-Kcal fat diet for four, six, and eight weeks with body weight and blood pressure monitored every two weeks, and then followed by an acute vasoconstriction stress of 5-min ice-bath treatment in the 4-h time interval of two adrenaline injections (0.8 mg/kg). Forty-four biochemical parameters were detected, covering hepatic and renal function, blood glucose and lipid levels, myocardial enzymes and energy metabolisms, blood coagulative and anti-coagulative system, oxidative stress and anti-inflammatory cytokine, blood viscosity, and RAAS system. Six tissues including heart, brain, liver, kidney, coronary arteries, and mesenteries were removed for pathological observations with hematoxylin-eosin staining. As a result, multi-organ dysfunctions in the heart, brain, liver, kidney, vascular endothelium, and blood system were testified in the modeling rats at weeks 6 and 8. In conclusion, severe consequences of this animal model were highly similar to those in hypertensive crises emergencies, which could be further utilized in the early intervention of hypertensive crises emergencies including the possible risk factors control and efficient therapies assessment. Impact statement In the late 90s, numerous reports predicted that 1-2% of hypertensive individuals would undergo hypertensive crises (HPC) and figures reached as high as 7% when no antihypertensive therapies were administrated. Currently, clinical failures appear frequently due to the improper or excessive medication regimen instead of the illness itself. Therefore, early evaluations and observations of HPC on appropriate animal models ahead of patients should be discussed and emphasized more widely. In the present study, an appropriate animal model for HPC emergencies was firstly established, in which the consequences of long-term high-fat diet feeding followed by an acute vasoconstriction stress on the spontaneously hypertensive rats were experimentally testified. The proposed model would have a wide application prospects in early intervention of HPC emergencies including the controls of possible risk factors and assessments of efficient therapies.

Dehydration is how you define it: comparison of 318 blood and urine athlete spot checks

Clinical medicine defines dehydration using blood markers that confirm hypertonicity (serum sodium concentration ([Na⁺])>145 mmol/L) and intracellular dehydration. Sports medicine equates dehydration with a concentrated urine as defined by any urine osmolality (UOsm) ≥700 mOsmol/kgH₂O or urine specific gravity (USG) ≥1.020.

Thirst

Our bodies are mostly water, and this water is constantly being lost through evaporative and other means. Thus the evolution of robust mechanisms for finding and consuming water has been critical for the survival of most animals. In this Primer, we discuss how the brain monitors the water content of the body and then transforms that physical information into the motivation to drink.

Fluid balance concepts in medicine: Principles and practice

The regulation of body fluid balance is a key concern in health and disease and comprises three concepts. The first concept pertains to the relationship between total body water (TBW) and total effective solute and is expressed in terms of the tonicity of the body fluids. Disturbances in tonicity are the main factor responsible for changes in cell volume, which can critically affect brain cell function and survival. Solutes distributed almost exclusively in the extracellular compartment (mainly sodium salts) and in the intracellular compartment (mainly potassium salts) contribute to tonicity, while solutes distributed in TBW have no effect on tonicity. The second body fluid balance concept relates to the regulation and measurement of abnormalities of sodium salt balance and extracellular volume. Estimation of extracellular volume is more complex and error prone than measurement of TBW. A key function of extracellular volume, which is defined as the effective arterial blood volume (EABV), is to ensure adequate perfusion of cells and organs. Other factors, including cardiac output, total and regional capacity of both arteries and veins, Starling forces in the capillaries, and gravity also affect the EABV. Collectively, these factors interact closely with extracellular volume and some of them undergo substantial changes in certain acute and chronic severe illnesses. Their changes result not only in extracellular volume expansion, but in the need for a larger extracellular volume compared with that of healthy individuals. Assessing extracellular volume in severe illness is challenging because the estimates of this volume by commonly used methods are prone to large errors in many illnesses. In addition, the optimal extracellular volume may vary from illness to illness, is only partially based on volume measurements by traditional methods, and has not been determined for each illness. Further research is needed to determine optimal extracellular volume levels in several illnesses. For these reasons, extracellular volume in severe illness merits a separate third concept of body fluid balance.

Plasma Calcium Concentration Modifies the Blood Sodium During Hemodialysis: Lessons from Hard Water Syndrome

Introduction. Extracellular sodium (Na+) concentration is maintained within a tight physiological range due to hormonal control, that mainly modulates thirst, Na+ and water renal excretion. Extra-renal regulation of Na+ and water homeostasis is only partially understood. Recently it has been debated whether the osmotically inactive Na+ storage is fixed or variable. Methods. In the present study, fourteen End-Stage Renal Disease (ESRD) patients treated by chronic hemodialysis underwent by accident to a sharp increase in plasmatic calcium (Ca+2) levels due to the failure of the water control system, leading to the so-called hard water syndrome. The levels of plasmatic Ca+2 after 1 hr of hemodialysis were correlated with urea, Na+, potassium (K+) and creatinine levels. Eleven ESRD patients treated with hemodialysis under similar conditions were used as controls. Results. The hard water syndrome resulted in hypercalcemia, while mean plasma levels of Na+, K+ and urea were not different compared to controls. Plasma creatinine levels were slightly but significantly higher that control. A correlation analysis on the measured variables has showed a positive correlation between plasma Ca+2 and Na+ levels (Pearson=0.428, p=0.032), and the absence of any correlation with K+, creatinine and urea concentration. Conclusions. Our study suggests that acute changes in plasmatic Ca+2 levels may affect Na+ concentration in the absence of renal function; it is possible that hypercalcemia may trigger Na+ release from the osmotically inactive storage. These data further support previous observations on the interplay of sodium and calcium at extrarenal sites.

Hyponatremia in the elderly: challenges and solutions

Decreased serum sodium concentration is a rather frequent electrolyte disorder in the elderly population because of the presence of factors contributing to increased antidiuretic hormone, the frequent prescription of drugs associated with hyponatremia and also because of other mechanisms such as the “tea and toast” syndrome. The aim of this review is to present certain challenges in the evaluation and treatment of hyponatremia in the elderly population and provide practical solutions. Hyponatremia in elderly subjects is mainly caused by drugs (more frequently thiazides and antidepressants), the syndrome of inappropriate antidiuretic hormone secretion (SIAD) or endocrinopathies; however, hyponatremia is multifactorial in a significant proportion of patients. Special attention is needed in the elderly population to exclude endocrinopathies as a cause of hyponatremia before establishing the diagnosis of SIAD, which then requires a stepped diagnostic approach to reveal its underlying cause. The treatment of hyponatremia depends on the type of hyponatremia. Special attention is also needed to correct serum sodium levels at the appropriate rate, especially in chronic hyponatremia, in order to avoid the osmotic demyelination syndrome. In conclusion, both the evaluation and the treatment of hyponatremia pose many challenges in the elderly population.

The neural basis of homeostatic and anticipatory thirst

Water intake is one of the most basic physiological responses and is essential to sustain life. The perception of thirst has a critical role in controlling body fluid homeostasis and if neglected or dysregulated can lead to life-threatening pathologies. Clear evidence suggests that the perception of thirst occurs in higher-order centres, such as the anterior cingulate cortex (ACC) and insular cortex (IC), which receive information from midline thalamic relay nuclei. Multiple brain regions, notably circumventricular organs such as the organum vasculosum lamina terminalis (OVLT) and subfornical organ (SFO), monitor changes in blood osmolality, solute load and hormone circulation and are thought to orchestrate appropriate responses to maintain extracellular fluid near ideal set points by engaging the medial thalamic-ACC/IC network. Thirst has long been thought of as a negative homeostatic feedback response to increases in blood solute concentration or decreases in blood volume. However, emerging evidence suggests a clear role for thirst as a feedforward adaptive anticipatory response that precedes physiological challenges. These anticipatory responses are promoted by rises in core body temperature, food intake (prandial) and signals from the circadian clock. Feedforward signals are also important mediators of satiety, inhibiting thirst well before the physiological state is restored by fluid ingestion. In this Review, we discuss the importance of thirst for body fluid balance and outline our current understanding of the neural mechanisms that underlie the various types of homeostatic and anticipatory thirst.

Sodium variability is associated with increased mortality in severe burn injury

BACKGROUND

Dysnatremias are associated with increased mortality in critically ill patients. Hypernatremia in burn patients is also associated with poor survival. Based on these findings, we hypothesized that high plasma sodium variability is a marker for increased mortality in severely burn-injured patients.

METHODS

We performed a retrospective review of adult burn patients with a burn injury of 15% total body surface area (TBSA) or greater from 2010 to 2014. All patients included in the study had at least three serum sodium levels checked during admission. We used multivariate logistic regression analysis to determine if hypernatremia, hyponatremia, or sodium variability independently increased the odds ratio (OR) for death.

RESULTS

Two hundred twelve patients met entry criteria. Mean age and %TBSA for the study was 45 ± 18 years and 32 ± 19%. Twenty-nine patients died for a mortality rate of 14%. Serum sodium was measured 10,310 times overall. The median number of serum sodium measurements per patient was 22. Non-survivors were older (59 ± 19 vs. 42 ± 16 years) and suffered from a more severe burn injury (50 ± 25% vs. 29 ± 16%TBSA). While mean sodium was significantly higher for non-survivors (138 ± 3 milliequivalents/liter (meq/l)) than for survivors (135 ± 2 meq/l), mean sodium levels remained within the laboratory reference range (135 to 145 meq/l) for both groups. Non-survivors had a significantly higher median number of hypernatremic (> 145 meq/l) measurements (2 vs. 0). Coefficient of variation (CV) was significantly higher in non-survivors (2.85 ± 1.1) than survivors (2.0 ± 0.7). Adjusting for TBSA, age, ventilator days, and intensive care unit (ICU) stay, a higher CV of sodium measurements was associated with mortality (OR 5.8 (95% confidence interval (CI) 1.5 to 22)). Additionally, large variation in sodium ranges in the first 10 days of admission may be associated with increased mortality (OR 1.35 (95% CI 1.06 to1.7)).

CONCLUSIONS

Increased variability in plasma sodium may be associated with death in severely burned patients.