The management of hyponatraemia at two district general hospitals in the UK

Euvolaemic hyponatraemia as a rare first presentation of chronic hypopituitarism

A man in his late 40s with no significant medical history presented with 2 weeks of lethargy, nausea and dizziness, alongside worsening headaches. Initial assessment revealed severe hyponatraemia and secondary hypothyroidism; urgent MRI pituitary was requested with a clinical suspicion of pituitary apoplexy. This demonstrated a likely cystic pituitary adenoma, with further testing revealing pituitary gland suppression, leading to a diagnosis of chronic secondary hypopituitarism. Initiating hormone replacement allowed substantial reported improvements in this patient's quality of life.A review of the patient's work-up revealed areas in which best practice was not followed. Cortisol measurements and paired urinary and serum osmolalities were initially not sent, nor results appropriately chased. A subsequent literature review identified that conformation with national and local guidelines on hyponatraemia management is poor. This patient's case, when combined with the literature review, provides evidence to support methods to increase educational awareness of an appropriate work-up of hyponatraemia among clinicians.

The contribution of undiagnosed adrenal insufficiency to euvolaemic hyponatraemia: results of a large prospective single-centre study

OBJECTIVE

The syndrome of inappropriate antidiuresis (SIAD) is the commonest cause of hyponatraemia. Data on SIAD are mainly derived from retrospective studies, often with poor ascertainment of the minimum criteria for the correct diagnosis. Reliable data on the incidence of adrenal failure in SIAD are therefore unavailable. The aim of the study was to describe the aetiology of SIAD and in particular to define the prevalence of undiagnosed adrenal insufficiency.

DESIGN

Prospective, single centre, noninterventional, observational study of patients admitted to Beaumont Hospital with euvolaemic hyponatraemia (plasma sodium ≤ 130 mmol/l) between January 1st and October 1st 2015.

PATIENTS

A total of 1323 admissions with hyponatraemia were prospectively evaluated; 576 had euvolaemic hyponatraemia, with 573 (43·4%) initially classified as SIAD.

MAIN OUTCOME MEASURES

(i) Aetiology of SIAD, defined by diagnostic criteria; (ii) Incidence of adrenal insufficiency.

RESULTS

Central nervous system diseases were the commonest cause of SIAD (n = 148, 26%) followed by pulmonary diseases (n = 111, 19%), malignancy (n = 105, 18%) and drugs (n = 47, 8%). A total of 22 patients (3·8%), initially diagnosed as SIAD, were reclassified as secondary adrenal insufficiency on the basis of cortisol measurements and clinical presentation; 9/22 cases had undiagnosed hypopituitarism; 13/22 patients had secondary adrenal insufficiency due to exogenous steroid administration.

CONCLUSIONS

In a large, prospective and well-defined cohort of euvolaemic hyponatraemia, undiagnosed secondary adrenal insufficiency co-occurred in 3·8% of cases initially diagnosed as SIAD. Undiagnosed pituitary disease was responsible for 1·5% of cases presenting as euvolaemic hyponatraemia.

SIAD: practical recommendations for diagnosis and management

Hyponatremia is the commonest electrolyte disturbance encountered in hospitalized patients, and the syndrome of inappropriate antidiuresis (SIAD) is the most frequent underlying disorder. There is a well-recognized relationship between hyponatremia and increased morbidity and mortality. Therefore, to provide appropriate treatment is critical to improve the clinical outcome related to SIAD-hyponatremia. There have been important advances in the treatment of SIAD over the last decade, leading to the publication of several clinical guidelines. In particular, the introduction of the vasopressin-2 receptor antagonists provides a potent pharmacological tool to target the underlying pathophysiology of SIAD. The evidence base recommendations of the available therapies for SIAD are discussed in this study. Fluid restriction is considered the first-line therapy by the recent published guidelines, but it is certainly ineffective or unfeasible in many patients with SIAD. We discuss a number of relevant points to the use of fluid restriction in this study, including the lack of good evidence-based recommendations to support its use. Conversely, the clinical efficacy of oral tolvaptan in SIAD supported by good quality randomized, placebo controlled, clinical trials. However, the cost of the therapy and the need for long-term safety data may limit its widespread use. Finally, new recommendations for the management of acute hyponatremia with a focus on the use of bolus therapy with 3 % hypertonic sodium chloride are described in this study.

Inpatient hyponatraemia: adequacy of investigation and prevalence of endocrine causes

This study assessed the effect of endocrine input on the investigation of hyponatraemia and examined the prevalence of endocrine causes of hyponatraemia. This single-centre, retrospective study included 139 inpatients (median age, 74 years) with serum sodium (Na) levels ≤128 mmol/l during hospitalisation at a UK teaching hospital over a three-month period. In total, 61.9% of patients underwent assessment of volume status and 28.8% had paired serum and urine osmolality, and Na measured. In addition, 14.4% of patients received endocrine input; 80% of these patients underwent full work-up of hyponatraemia compared with 5% of patients not referred to endocrine services (p < 0.001; relative risk, 15.86; 95% confidence interval, 7.17-31.06). The prevalence of adrenal insufficiency was 0.7%, but basal serum cortisol levels were not measured in around two-thirds of patients. Despite 26.7% of patients having abnormal thyroid function tests, no patient was diagnosed with severe hypothyroidism. More widespread provision of expert input should be considered.

Multicentre study of investigation and management of inpatient hyponatraemia in the UK

Purpose

Hyponatraemia is associated with significant morbidity and mortality. The objectives of this study were to evaluate the investigation and management of hyponatraemia and to assess the use of different therapeutic modalities and their effectiveness in routine practice.

Study design

This multicentre, retrospective, observational study was conducted at three acute NHS Trusts in March 2013. A retrospective chart review was performed on the first 100 inpatients with serum sodium (sNa) ≤128 mmol/L during hospitalisation.

Results

One hundred patients (47 male, 53 female) with a mean±SD age of 71.3±15.4 years and nadir sNa of 123.4±4.3 mmol/L were included. Only 23/100 (23%) had measurements of paired serum and urine osmolality and sodium, while 31% had an assessment of adrenal reserve. The aetiology of hyponatraemia was unrecorded in 58% of cases. The mean length of hospital stay was 17.5 days with an inpatient mortality rate of 16%. At hospital discharge, 53/84 (63.1%) patients had persistent hyponatraemia, including 20/84 (23.8%) with sNa <130 mmol/L. Overall 37/100 (37%) patients did not have any treatment for hyponatraemia. Among 76 therapeutic episodes, the most commonly used treatment modalities were isotonic saline in 38/76 cases (50%) and fluid restriction in 16/76 (21.1%). Fluid restriction failed to increase sNa by >1 mmol/L/day in 8/10 (80%) cases compared with 4/26 (15.4%) for isotonic saline.

Conclusions

Underinvestigation and undertreatment of hyponatraemia is a common occurrence in UK clinical practice. Therefore, development of UK guidelines and introduction of electronic alerts for hyponatraemia should be considered to improve clinical practice.

Initial approach to the hyponatremic patient

Hyponatremia with cerebral symptoms is a medical emergency in which treatment delay may prove fatal. However, controversy prevails over which treatment is the best. This paper presents a practical and unified approach based on a literature study of the physiology of plasma [Na(+) ], the brain's response and clinical and experimental studies. Experimental and clinical studies were thoroughly reviewed. The literature was identified through MESH and free text search in the databases PubMed, Embase and Cochrane, and references in the literature. Cerebral water homeostasis is pivotal in hyponatremia. Prompt, repeated boluses of 2 ml/kg 3% saline constitute a rational treatment of symptomatic hyponatremia. After the initial correction, concern is mainly with avoiding overcorrection and osmotic demyelination. Plasma [Na(+)] is determined by the external balances of water and cations. The water balance must therefore be carefully monitored to counter the dramatic increase in plasma [Na(+)] that may result from brisk diuresis. Definitive treatment of hyponatremia should be directed toward its etiology. This can be challenging and the clinical application of traditional classifications based on hydration is difficult. Therefore, a practical approach is proposed based on the mechanisms of impaired urine dilution.

CONCLUSIONS

The conflict between previously opposing standpoints is gradually giving way to an emerging consensus: Prompt bolus treatment of symptomatic hyponatremia with hypertonic saline. After the initial treatment, overcorrection must be avoided. Definitive treatment should be directed toward the nature of the underlying disorder. An approach based on the mechanism governing the impaired urine dilution has been proposed.