Management of hyponatraemia in older people: old threats and new opportunities

Prevention of Chronic Kidney Disease and Its Complications in Older Adults

In an era marked by a global demographic shift towards an aging society, there is a heightened prevalence of chronic kidney disease (CKD) among older adults. The burden of CKD spans from kidney-related complications to impacting psychological well-being, giving rise to depressive symptoms and caregiver burnout. This article delves into CKD prevention strategies within the context of aging, contributing to the discourse by exploring its multifaceted aspects. The prevention of CKD in the older adults necessitates a comprehensive approach. Primary prevention is centered on the modification of risk factors, acknowledging the intricate interplay of various comorbidities. Secondary prevention focuses on early CKD identification. Tertiary prevention aims to address factors contributing to CKD progression and complications, emphasizing the importance of timely interventions. This comprehensive strategy aims to enhance the quality of life for individuals affected by CKD, decelerating the deterioration of functional status. By addressing CKD at multiple levels, this approach seeks to effectively and compassionately care for the aging population.

Syndrome of Inappropriate Antidiuresis: From Pathophysiology to Management

Hyponatremia is the most common electrolyte disorder, affecting more than 15% of patients in the hospital. Syndrome of inappropriate antidiuresis (SIAD) is the most frequent cause of hypotonic hyponatremia, mediated by nonosmotic release of arginine vasopressin (AVP, previously known as antidiuretic hormone), which acts on the renal V2 receptors to promote water retention. There are a variety of underlying causes of SIAD, including malignancy, pulmonary pathology, and central nervous system pathology. In clinical practice, the etiology of hyponatremia is frequently multifactorial and the management approach may need to evolve during treatment of a single episode. It is therefore important to regularly reassess clinical status and biochemistry, while remaining alert to potential underlying etiological factors that may become more apparent during the course of treatment. In the absence of severe symptoms requiring urgent intervention, fluid restriction (FR) is widely endorsed as the first-line treatment for SIAD in current guidelines, but there is considerable controversy regarding second-line therapy in instances where FR is unsuccessful, which occurs in around half of cases. We review the epidemiology, pathophysiology, and differential diagnosis of SIAD, and summarize recent evidence for therapeutic options beyond FR, with a focus on tolvaptan, urea, and sodium-glucose cotransporter 2 inhibitors.

Serum sodium level is inversely associated with new-onset diabetes in hypertensive patients

BACKGROUND

Serum sodium level is associated with cardiovascular and endocrine health. Though decreased serum sodium is considered to be associated with reduced hypertension risk, some studies also found that it may increase the risk of diabetes. This study aimed to investigate the association of serum sodium with new-onset diabetes in hypertensive patients.

METHODS

Based on the annual health examinations from 2011 to 2016 in Dongguan City, Guangdong, China, hypertensive patients without diabetes at baseline were selected. Logistic regression and restricted cubic spline were used to evaluate the association between serum sodium level and new-onset diabetes. Subgroup analysis was also conducted.

RESULTS

A total of 4438 hypertensive patients with a mean age of 58.65 years were included, of whom 48.9% were male. During a median follow-up of 35.1 months, 617 (13.9%) of the subjects developed new-onset diabetes. Per 1-SD (3.39 mmol/L) increment of serum sodium was associated with a 14% lower risk of new-onset diabetes (odds ratio = 0.86; 95% CI: 0.78, 0.97; p = 0.01). The lowest quartile of serum sodium was associated with the lowest diabetes risk. The restricted cubic spline showed a linear inverse relationship (nonlinear p = 0.72). Across all the subgroups, the inverse association was consistent (p for interaction >0.05).

CONCLUSION

An inverse association of serum sodium with new-onset diabetes in hypertensive patients was observed.

Influence of Hyponatremia on Spinal Bone Quality and Fractures Due to Low-Energy Trauma

Background and Objectives: Hyponatremia is the most common electrolyte disorder in elderly and associated with increased risk of falls. Clinical studies as well as small animal experiments suggested an association between chronic hyponatremia and osteoporosis. Furthermore, it has been assumed that subtle hyponatremia may be an independent fracture risk in the elderly. Therefore, this study was designed to evaluate the possible influence of chronic hyponatremia on osteoporosis and low-energy fractures of the spine. Materials and Methods: 144 patients with a vertebral body fracture (mean age: 69.15 ± 16.08; 73 females and 71 males) due to low-energy trauma were treated in a level one trauma center within one year and were included in the study. Chronic hyponatremia was defined as serum sodium < 135 mmol/L at admission. Bone mineral density (BMD) of the spine was measured using quantitative computed tomography in each patient. Results: Overall, 19.44% (n = 28) of patients in the low-energy trauma group had hyponatremia. In the group with fractures caused by low-energy trauma, the proportion of hyponatremia of patients older than 65 years was significantly increased as compared to younger patients (p** = 0.0016). Furthermore, there was no significant gender difference in the hyponatremia group. Of 28 patients with chronic hyponatremia, all patients had decreased bone quality. Four patients showed osteopenia and the other 24 patients even showed osteoporosis. In the low-energy trauma group, the BMD correlated significantly with serum sodium (r = 0.396; p*** < 0.001). Conclusions: The results suggest that chronic hyponatremia affects bone quality. Patients with chronic hyponatremia have an increased prevalence of fractures after low-energy trauma due to a decreased bone quality. Therefore, physicians from different specialties should focus on the treatment of chronic hyponatremia to reduce the fracture rate after low-energy trauma, particularly with elderly patients.

Resistant hyponatraemia in a patient with follicular lymphoma and heart failure with reduced ejection fraction: a case report

Background

Hyponatraemia is a common problem in patients with heart failure. It can be difficult to treat, especially in the presence of the patient’s needs for diuresis and manipulation of the renin–angiotensin–aldosterone system (RAAS).

Case summary

This concerns a 74-year-old woman with follicular lymphoma and severe global left ventricular systolic dysfunction secondary to treatment with R-CHOP chemotherapy. She presented a difficult challenge in the management of her decompensated heart failure alongside hyponatraemia as low as 113 mmol/L. This was resistant to standard treatment. The resistance to usual measures necessitated treatment with Tolvaptan, a selective arginine vasopressin V2 inhibitor used to treat hyponatraemia in syndrome of inappropriate anti-diuretic hormone. This, along with a strict fluid restriction of 500 mL/day, resolved the patient’s hyponatraemia and enabled her discharge home on tolerated heart failure treatment. She has now remained stable for almost 12 months.

Discussion

The potential causes of hyponatraemia are discussed along with the role of Tolvaptan in its management.

Association between serum sodium level within normal range and handgrip strength in relation to hypertension status: a cross-sectional study

Serum sodium concentration within the normal range could act as an indicator of age-related changes such as decrease in muscle strength and impairment of capillary function. Since endothelial injury stimulates endothelial repair by enhancing CD34-positive cell production, the level of serum sodium may be inversely associated with that of circulating CD34-positive cells, thus indicating the degree of age-related endothelial injury. We conducted a cross-sectional study of 246 elderly Japanese men aged 60–69 years. Subjects were stratified by hypertension status because hypertension should act as a strong confounding factor for the analyses performed in this study. Serum sodium concentration was positively associated with handgrip strength in non-hypertensive subjects [standardized parameter estimate (β) = 0.29; p = 0.003], but not for hypertensive subjects (β = 0.01; p = 0.878), while it was inversely associated with circulating CD34-positive cell levels in non-hypertensive subjects [simple correlation coefficient (r) = − 0.28; p = 0.002] but not for hypertensive subjects (r = − 0.07; p = 0.454). For non-hypertensive elderly subjects, serum sodium concentration within the normal range is positively associated with handgrip strength and inversely associated with CD34-positive cells, thus partly indicating the degree of age-related endothelium injury. These associations could prove to be an efficient tool for clarifying the background mechanism governing the decrease in age-related muscle strength.

Prevalence of hyponatremia among older inpatients in a general hospital

PURPOSE

This study aimed to explore the incidence, clinical features, etiology, and mortality of hyponatremia in older inpatients and thus provide preliminary data for an epidemiological study.

METHODS

Hospitalized older patients diagnosed with hyponatremia at the First Medical Center of PLA General Hospital during January 2013-December 2016 were stratified by serum sodium concentrations into mild (130- < 135 mmol/L), moderate (125- < 130 mmol/L) and severe hyponatremia groups (< 125 mmol/L). Etiologies, medication histories, hospitalization times, and outcomes were analyzed.

RESULTS

During the indicated period, 4364 older patients with hyponatremia were hospitalized, including 2934 men and 1430 women with an average age of 84.6 ± 3.5 years (range 80-104 years). The prevalence of hyponatremia was 24.7%. An analysis of common primary diseases identified respiratory diseases as the most frequent (25.0%), followed by tumors (23.1%), cardiovascular diseases (19.9%), central nervous system diseases (8.9%), and orthopedic diseases (6.1%). PPIs (59.7%), loop diuretics (57.4%), potassium-preserving diuretics (29.5%), ACEIs/ARBs (20.0%), thiazide diuretics (12.5%), and NSAIDs (12.4%) were the drugs most commonly associated with hyponatremia. The in-hospital mortality rate was 11.7%. Aggravated hyponatremia led to a prolonged hospitalization time. Moreover, when compared with mild hyponatremia, moderate and severe hyponatremia were associated with significant increases in in-hospital mortality (ORs 1.89 and 2.66, respectively; 95% CIs 1.54-2.33 and 2.06-3.43, respectively; P < 0.01).

CONCLUSIONS

Hyponatremia is a common complication in hospitalized older patients and is caused mainly by respiratory diseases, tumors, and cardiovascular diseases. Given the correlation between the degree of hyponatremia and prognosis, the early and accurate identification and treatment of this condition can reduce the associated morbidity and mortality.

Is postoperative hyponatremia a real threat for total hip and knee arthroplasty surgery?

Postoperative hyponatremia (POH) is thought to be a fearsome complication of orthopedic surgery. Primary aim of this cohort study was to evaluate the incidence of POH and its clinical relevance in elective surgery, outlining differences between total knee arthroplasty (TKA) and total hip arthroplasty, looking for the presence of any risk factor commonly related to POH.Four hundred two patients that underwent total hip arthroplasty and total knee arthroplasty performed between 2016 and 2017 were retrospectively examined. Serum electrolytes, hemoglobin, hematocrit, glucose, and creatinine were evaluated preoperatively and at day 0-I-II from surgery. Age, sex, body mass index, comorbidities, drugs, surgery data, transfusions, postoperative symptoms, and length of stay (LOS) were determined. All surgeries were performed by the same equipe. Patients had the same perioperative management, excluded those that took thiazides, already at risk of POH.Patients were divided in 2 groups: group A, patients with normal postoperative natremia (294 patients) and group B, patients who developed POH (108, 26.9%); 66.7% of these developed POH within 24 hours postoperatively. In group B mean postoperative natremia was 133.38 (127.78-134.85) mmol/L. Two patients (1.8%) developed moderate hyponatremia, no severe hyponatremia was documented. Type of surgery, operation time, LOS, and presence of postoperative symptoms did not show statistically significant differences within groups. At multivariate logistic analysis chronic use of thiazides was the only variable associated to a decreased risk of developing POH (OR = 0.39; P = .03). Hemoglobin postoperative values (OR = 1.22; P = .03), the need of postoperative transfusion (OR = 2.50; P = .02) and diabetes (OR = 2.70; P = .01) were associated to an increased risk of POH.Although 26.9% of our patients exhibited POH, the onset of this disorder had no implication on postoperative symptoms and on LOS. Diabetes and transfusion are factors most often associated to POH.

Prevalence of mild hyponatremia and its association with falls in older adults admitted to an emergency geriatric medicine unit (the MUPA unit)

Background

Hyponatremia is the most common electrolyte disorder in older adults and it can increase morbidity and mortality. Approximately one in three older adults fall each year; mild chronic hyponatremia can predispose this group to injurious falls and fractures and serum levels of sodium can also influence bone health. Little is known regarding the association between mild chronic hyponatremia and injurious fall prevalence in elderly patients admitted to the Emergency Department (ED). Therefore, the present study investigated the link between mild hyponatremia and the risk of injurious falls in elderly patients admitted to the Emergency Geriatric Medicine Unit (The MUPA Unit).

Methods

This cross-sectional study was conducted over 4 months and included patients ≥75 years of age who were admitted to the MUPA Unit of University Hospital Center of Limoges (France). Sociodemographic factors, fall events, comorbidities, medications, and sodium levels were assessed (hyponatremia was considered as sodium level < 136 mEq/L). Additionally, the short Comprehensive Geriatric Assessment (short-CGA), the Frailty score on the Short Emergency Geriatric Assessment (SEGA), and the Katz Activity of Daily Living (ADL) scale were administered.

Results

Of the 696 cases included in the final analysis, the mean age was 86.1 ± 5.6 years and 63.1% were female. The prevalence of falls was 27.9% (95% confidence interval [CI]: 24.6–31.2%) and that of mild hyponatremia was 15.9% (95% CI: 13.2–18.6%). The prevalence rate of mild hyponatremia was 13.2% (95% CI: 10.1–16.3%) in patients without falls and 26.1% (95% CI: 19.8–32.4%) in patients admitted for falls. Mild hyponatremia was significantly associated with falls (P < 0.001) and the adjusted odds ratio (OR) was 3.02 (95% CI: 1.84–4.96).

Conclusions

Because mild hyponatremia might be a risk factor for injurious falls and ED admission, determination of sodium levels during basic biomarker assessment on ED admission could be an important component of fall prevention strategies for the elderly.

"Pleurex Desalination" in Malignancy-related Ascites: A Novel Mechanism of Hyponatremia

OBJECTIVE

Pleurex catheters are a form of palliative therapy for patients, offering relief from symptomatic ascites while also affording greater independence and flexibility; however, aggressive drainage can lead to significant total body sodium losses. We describe the course of patients with "Pleurex desalination," an under-appreciated cause of hypovolemic hyponatremia, highlighting its unique pathophysiology and providing recommendations on how to manage these complex patients.

PATIENTS AND METHODS

We included representative patients with "Pleurex desalination" who were evaluated and treated by the renal consult service at Brigham and Women's between 2017 and 2019.

RESULTS

We identified 3 patients who were hospitalized with "Pleurex desalination" and had complete data on serum and urine studies, as well as treatment course. We demonstrate that patients with "Pleurex desalination" were removing up to 1 to 2 L of ascitic fluid a day and were admitted with signs and symptoms of profound hypovolemia and hyponatremia. Patients worsened with administration of diuretics and salt restriction and improved with aggressive fluid resuscitation in the form of hypertonic saline, normal saline, and/or intravenous albumin.

CONCLUSION

"Pleurex desalination" is an under-recognized cause of hyponatremia; at-risk patients require close observation and periodic resuscitation with intravenous, volume-expanding fluids.

Sarcopenia as a potential cause of chronic hyponatremia in the elderly

Hyponatremia is the most frequent electrolyte disorder found in clinical practice, particularly in hospitalized elderly patients, where it is associated with fractures, falls, hospital readmission, prolonged hospital stay and increased mortality. Pathophysiologically, hyponatremia can be induced by the reduction in sodium or potassium body content, and/or the increase in water body content. Sarcopenia is an ageing-associated progressive and generalized loss of musculoskeletal mass and strength which leads to low physical performance, particularly in the frail elderly. Since muscle mass is the main potassium body store, this condition usually represents a reduced body potassium content. In the present article it is hypothesized that sarcopenia, as a cause of low potassium body content, could induce or co-induce hyponatremia, particularly in elderly individuals suffering from frailty phenotype.

Evidence for Effective Multiple K+-Current Inhibitions by Tolvaptan, a Non-peptide Antagonist of Vasopressin V2 Receptor

Tolvaptan (TLV), an oral non-peptide antagonist of vasopressin V₂ receptor, has been increasingly used for managements in patients with hyponatremia and/or syndrome of inappropriate antidiuretic hormone secretion. However, none of the studies have thus far been investigated with regard to its possible perturbations on membrane ion currents in endocrine or neuroendocrine cells. In our electrophysiological study, the whole-cell current recordings showed that the presence of TLV effectively and differentially suppressed the amplitude of delayed rectifier K⁺ (I_K(DR)) and M-type K⁺ current (I_K(M)) in pituitary GH₃ cells with an IC₅₀ value of 6.42 and 1.91 μM, respectively. This compound was also capable of shifting the steady-state activation curve of I_K(M) to less depolarized potential without any appreciable change in the gating charge of this current. TLV at a concentration greater than 10 μM also suppressed the amplitude of erg-mediated K⁺ current or the activity of large-conductance Ca²⁺-activated K⁺ channels; however, this compound failed to alter the amplitude of hyperpolarization-activated cation current in GH₃ cells. In vasopressin-preincubated GH₃ cells, TLV-mediated suppression of I_K(M) remained little altered. Under current-clamp condition, we also observed that addition of TLV increased the firing of spontaneous action potentials in GH₃ cells and further addition of flupirtine could reverse TLV-mediated elevation of the firing. In Madin-Darby canine kidney (MDCK) cells, the K⁺ current elicited by long ramp pulse was also effectively subject to inhibition by this compound. Findings from the present study were thus stated as saying that the suppression by TLV of multiple type K⁺ currents could be direct and independent of its antagonism of vasopressin V₂ receptors. Our study also reveals an important aspect that should be considered when assessing aquaretic effect of TLV or its structurally similar compounds.

Diagnosis and management of hyponatraemia in the older patient

Hyponatraemia (serum sodium concentration below 135 mmol/L) is the most common electrolyte disturbance and occurs commonly in older people. The causes can be complex to diagnose and treat and many published guidelines do not focus on the issues in an older patient group. Here, we are principally concerned with diagnosis and management of euvolaemic and hypervolaemic hyponatraemia in hospitalised patients over 70 years old. We also aim to increase awareness of hyponatraemia in residential aged care facilities and the community. Hyponatraemia can have many causes; in older people, chronic hyponatraemia can often be the result of medications used to treat chronic disease, particularly thiazide or thiazide-like drugs (such as indapamide) or drugs acting on the central nervous system. Where a reversible trigger (such as drug-induced hyponatraemia) can be identified, hyponatraemia may be treated relatively simply. Chronic hyponatraemia due to an irreversible cause will require ongoing treatment. Fluid restriction can be an effective therapy in dilutional hyponatraemia, although poor compliance and the burdensome nature of the restrictions are important considerations. Tolvaptan is an oral vasopressin receptor antagonist that can increase serum sodium concentrations by increasing electrolyte-free water excretion. Tolvaptan use is supported by clinical trial evidence in patients with hypervolaemic or euvolaemic hyponatraemia below 125 mmol/L. Clinical trial evidence also supports its use after a trial of fluid restriction in patients with symptomatic hyponatraemia above 125 mmol/L. The use of tolvaptan is affected by regulatory restriction of chronic therapy due to safety concern and the non-subsidised cost of treatment.

Hyponatremia Is Associated with Worse Outcomes from Fall Injuries in the Elderly

Background: Hyponatremia has been proposed as a contributor to falls in the elderly, which have become a major global issue with the aging of the population. This study aimed to assess the clinical presentation and outcomes of elderly patients with hyponatremia admitted due to fall injuries in a Level I trauma center. Methods: We retrospectively reviewed data obtained from the Trauma Registry System for trauma admissions from January 2009 through December 2014. Hyponatremia was defined as a serum sodium level <135 mEq/L, and only patients who had sustained a fall at ground level (<1 m) were included. We used Chi-square tests, Student t-tests, and Mann-Whitney U tests to compare elderly patients (age ≥65 years) with hyponatremia (n = 492) to those without (n = 2002), and to adult patients (age 20–64 years) with hyponatremia (n = 125). Results: Significantly more elderly patients with hyponatremia presented to the emergency department (ED) due to falls compared to elderly patients without hyponatremia (73.7% vs. 52.6%; OR: 2.5, 95% CI: 2.10–3.02; p < 0.001). Elderly patients with hyponatremia presented with a worse outcome, measured by significantly higher odds of intubation (OR: 2.4, 95% CI: 1.15–4.83; p = 0.025), a longer in-hospital length of stay (LOS) (11 days vs. 9 days; p < 0.001), higher proportion of intensive care unit (ICU) admission (20.9% vs. 16.2%; OR: 1.4, 95% CI: 1.07–1.76; p = 0.013), and higher mortality (OR: 2.5, 95% CI: 1.53–3.96; p < 0.001), regardless of adjustment by Injury Severity Scores (ISS) (AOR: 2.4, 95% CI: 1.42–4.21; p = 0.001). Conclusions: Our results show that hyponatremia is associated with worse outcome from fall-related injuries in the elderly, with an increased ISS, longer LOS, and a higher risk of death.

Prevalence of Hyponatremia in Elderly Patients with Hip Fractures: A Two-Year Study

OBJECTIVE

This study investigated the prevalence of hyponatremia in elderly patients (≥65 years old) with hip fractures.

SUBJECTS AND METHODS

All records containing clinical and laboratory data on the 334 elderly patients admitted to the San Giovanni di Dio e Ruggi d'Aragona Hospital of Salerno, Italy, with hip fractures during 2014 and 2015, were retrieved from the hospital database. Patients were divided into 4 groups, according to their sex and the type of hip fracture. Sodium serum concentrations were retrieved from the medical records. Hyponatremia was defined as the presence of at least 1 episode of hyponatremia during the hospital stay.

RESULTS

Of 334 elderly patients, hyponatremia was found in 64 (19%). The prevalence of hyponatremia was 18% (28/157) for female patients with extracapsular proximal femoral fracture, 22% (17/79) for female patients with intracapsular proximal femoral fracture, 20% (12/60) for male patients with extracapsular proximal femoral fracture, and 18% (7/38) for male patients with intracapsular proximal femoral fracture.

CONCLUSION

There was a high prevalence of hyponatremia in the elderly patients with hip fractures. Hence, serum sodium concentrations should be regularly assessed to prevent occurrence of hyponatremia.

Hyponatremia predicts mortality after stroke

Background

Hyponatremia, the commonest electrolyte imbalance encountered in clinical practice, is associated with adverse outcomes. Despite this, understanding of the association between hyponatremia and stroke mortality outcome is limited.

Aims

To investigate the association between admission serum sodium and mortality at various time-points after stroke.

Methods

Cases of acute stroke admitted to Norfolk and Norwich University Hospital consecutively from January 2003 until June 2013 were included, with mortality outcomes ascertained until the end of December 2013. Odds ratios or hazards ratios for death were constructed for various time-points (within seven-days, 8-30 days, within one-year, and over full follow-up).

Results

There were 8540 participants included (47.4% male, mean age 77.3 (±12.0) years). Point prevalence of hypernatremia and hyponatremia were 3.3% and 13.8%, respectively. In fully adjusted models controlling for age, gender, prestroke modified Rankin score, stroke type, Oxford community stroke project class, and laboratory biochemical and hematological results, the odds ratio (up to one-year)/hazards ratio (for full follow-up) for the above time-points were 1.00, 1.11, 1.03, 1.05 for mild hyponatremia; 1.97, 0.78, 1.11, 1.2 for moderate hyponatremia; 3.31, 1.57, 2.45, 1.67 for severe hyponatremia; and 0.47, 1.23, 1.30, 1.10 for hypernatremia. When stratified by age groups, outcomes were poorer in younger hyponatremic patients (aged <75 years).

Conclusion

Hyponatremia is prevalent in acute stroke admissions and is independently associated with higher mortality in patients <75 years).

Prognosis of hyponatremia in elderly patients with fragility fractures

BACKGROUND

Hyponatremia (serum sodium < 135 mmol/L) is the commonest electrolyte imbalance encountered in clinical practice. It is associated with multiple poor clinical outcomes including increased length of hospital stay, institutionalization and mortality. Prevalence of hyponatremia is higher in frail patient groups, and elderly patients with fragility fractures (EPFF) are particularly susceptible. This study aimed to establish the impact of hyponatremia on total length of inpatient stay (TLOS), need for inpatient rehabilitation and mortality in EPFF.

METHODS

Prospective observational study of consenting adults aged ≥ 65 years admitted with a fragility fracture to a university hospital between January 7, and April 4, 2013. Demographic and clinical data, length of hospital stay, discharge destination and any participant deaths were recorded. Prevalence of hyponatremia on admission and incidence of cases developing in hospital were reported. Basic demographic data and serum sodium results were included in multivariate linear regression models for TLOS. Difference in mortality rate and proportion of individuals discharged to inpatient rehabilitation between the hyponatremic and normonatremic group were tested using Chi-squared and Fisher's exact tests. Unadjusted odds ratios (ORs) and 95% confidence intervals (CIs) were also calculated.

RESULTS

Of 212 cases, 127 (60%) EPFF were recruited (mean age 79 years, 78% female). Of those not recruited, 66 had incapacity to consent and 19 refused participation. Thirty-three cases of hyponatremia were identified; point prevalence on admission was 13.4% and a further 12.6% developed hyponatremia during admission. There were no statistically significant differences in patient characteristics between the hyponatremic and normonatremic group. Hyponatremic participants had a 66.7% increased time from admission to surgery (P = 0.014) and a 51.5% increased length of index hospital stay (P = 0.006). Factors independently associated with increased TLOS were age (P = 0.03) and drop in sodium during admission (P < 0.001). Mortality rate and proportion of participants discharged to inpatient rehabilitation were higher in the hyponatremic group (OR 4.2 (95% CI: 0.9 - 19.8) and 2.2 (95% CI: 0.9 - 5.1), respectively), but figures did not reach statistical significance.

CONCLUSIONS

Hyponatremia is highly prevalent in EPFF, seen in 33/127 cases (26%), and is associated with increased length of index hospital stay. Drop in serum sodium during admission was independently associated with increased TLOS.

Hyponatremia: Special Considerations in Older Patients

Hyponatremia is especially common in older people. Recent evidence highlights that even mild, chronic hyponatremia can lead to cognitive impairment, falls and fractures, the latter being in part due to bone demineralization and reduced bone quality. Hyponatremia is therefore of special significance in frail older people. Management of hyponatremia in elderly individuals is particularly challenging. The underlying cause is often multi-factorial, a clear history may be difficult to obtain and clinical examination is unreliable. Established treatment modalities are often ineffective and carry considerable risks, especially if the diagnosis of underlying causes is incorrect. Nevertheless, there is some evidence that correction of hyponatremia can improve cognitive performance and postural balance, potentially minimizing the risk of falls and fractures. Oral vasopressin receptor antagonists (vaptans) are a promising innovation, but evidence of their safety and effect on important clinical outcomes in frail elderly individuals is limited.

Prevalence, incidence and etiology of hyponatremia in elderly patients with fragility fractures

INTRODUCTION

Hyponatremia (serum sodium<135 mMol/L) is the commonest electrolyte imbalance encountered in clinical practice. It is associated with multiple poor clinical outcomes including increased mortality, longer hospital stay, falls and fractures. Prevalence is higher in frail patient groups, and elderly patients with fragility fractures (EPFF) are particularly susceptible. Euvolemic hyponatremia due to syndrome of inappropriate anti-diuretic hormone (SIADH) is widely assumed to be the commonest cause. However, little is known about the epidemiology and etiology of hyponatremia in EPFF. This study established prevalence, incidence and etiology of hyponatremia in EPFF.

METHODS

Prospective observational study of consenting adults aged ≥65 years admitted with a fragility fracture to a university hospital between 7th January and 4th April 2013. Prevalence of hyponatremia on admission and incidence of cases developing in hospital were reported. Etiology of cases of hyponatremia was determined by consensus of an expert panel using pre-specified data collected daily.

RESULTS

127/212 (60%) EPFF were recruited (mean age 79 yrs, 78% female). Two participants withdrew mid-study. Of those not recruited, 66 had incapacity to consent and 19 refused participation. Point prevalence of hyponatremia on admission was 13.4% and a further 12.6% developed hyponatremia during admission. Hypovolemic hyponatremia was predominant (70%). 73% of cases were multi-factorial in etiology. The commonest potentially causative factors in cases of hyponatremia were thiazide diuretics (76%), dehydration (70%), proton pump inhibitors (70%), SIADH (27%) and mirtazapine (15%).

CONCLUSION

Hyponatremia is highly prevalent in EPFF, seen in 26% of cases. Dehydration and prescription of thiazide diuretics and proton pump inhibitors were the commonest potentially causative factors, not SIADH.

Bioelectrical impedance analysis is more accurate than clinical examination in determining the volaemic status of elderly patients with fragility fracture and hyponatraemia

OBJECTIVES

Management of hyponatraemia depends crucially on accurate determination of volaemic (hydration) status but this is notoriously challenging to measure in older people. Bioelectrical impedance analysis (BIA) provides a validated means of determining total body water (TBW), but its clinical utility in determining volaemic status in hyponatraemia has never been tested. This study assessed the utility of BIA in the clinical management of hyponatraemia in elderly patients with fragility fractures (EPFF), a group at high risk of hyponatraemia.

DESIGN

Prospective observational study of consenting patients ≥65 years with fragility fractures (N=127).

SETTING

University teaching hospital in Scotland.

PARTICIPANTS

Patients ≥665 years with fragility fractures with capacity to consent to participation.

MEASUREMENTS

BIA and standard clinical examination procedures (jugular venous distension, skin turgor, mouth and axillary moistness, peripheral oedema, capillary refill time, overall impression) were performed daily throughout each participant's hospital stay. Volaemic status of hyponatraemia was determined by an expert panel using clinical data (history, examination, nursing observations and laboratory tests) blinded to TBW readings. Cohen's kappa was calculated to assess the level of agreement between the expert panel and both BIA and standard clinical examination measures in determining the volaemic state of hyponatraemia.

RESULTS

26/33 (79%) cases of hyponatraemia had sufficient clinical information to allow determination of volaemic status by BIA. There was moderate level of agreement between BIA and the expert panel, kappa 0.52 (p<.001). All kappa values for standard clinical assessments of volaemic status neared zero, indicating nil to slight agreement.

CONCLUSION

BIA outperformed all aspects of the standard clinical examination in determining the volaemic status of hyponatraemic EPFF, suggesting it may be useful in clinical practice.

Prevalence of hyponatremia on geriatric wards compared to other settings over four decades: a systematic review

Aim of the study was to analyze temporal trends in prevalence of hyponatremia over four decades in different settings. A systematic review of the literature from 1966 to 2009 yielded prevalences of hyponatremia, with standard errors (SE) and pooled estimated means (PEM), calculated by year and setting (geriatric, ICU, other hospital wards, psychiatric hospitals, nursing homes, outpatients). 53 studies were included. Prevalence of hyponatremia was stable from 1976 to 2006, and higher on geriatric wards accept for ICU: e.g. PEM prevalence of mild hyponatremia (serum sodium <135 mM) was 22.2% (95%CI 20.2-24.3) on geriatric wards, 6.0% (95%CI 5.9-6.1) on other hospital wards and 17.2% (SE 7.0) in one ICU-study; for severe hyponatremia (serum sodium<125 mM) these figures were 4.5% (95%CI 3.0-6.1), 0.8% (95%CI 0.7-0.8) and 10.3% (SE 5.6). In nursing homes PEM prevalence of mild hyponatremia was 18.8% (95%CI 15.6-22.2). The higher prevalence on geriatric wards could partly be explained by age-related changes in the regulation of serum sodium. Other underlying factors can be the presence of multiple diagnoses and the use of polypharmacy.