Endocrine Abstracts

Introduction: Hyponatraemia is the most common electrolyte disorder in hospitalised patients and is associated with significant morbidity and mortality.

Methods: This retrospective study included all inpatients with serum sodium (sNa) ≤128 mmol/l at any point during hospitalisation at a teaching hospital over a 3-month period (1st March 2013 to 31st May 2013). Demographic, clinical and laboratory data obtained from patients’ case notes and laboratory information system were reviewed with the aim to study the investigation of hyponatraemic inpatients.

Results: 139 patients (69 males and 70 females) with a mean age (±S.D.) of 70.2±16.1 years were identified over this 3-month period. The median length of hospital stay was 12 days and the inpatient mortality rate was 17.3%.

61.9% of patients had their volume status assessed. The proportion of patients having appropriate laboratory investigations was: 38.1% for serum osmolality, 37.4% for urine osmolality, 35.2% for urine sodium concentration, 61.1% for thyroid function tests, 31.6% for serum cortisol. Only 28.8% of patients had paired serum and urine osmolality and sodium measured.

Patients with sNa ≤125 mmol/l (n=87) were four times more likely to have paired serum and urine osmolality and sodium checked and six times more likely to have serum cortisol measured than patients with sNa 126–128 mmol/l (n=52). Patients under the care of medical specialities were more likely to have the appropriate tests than patients under surgical specialities.

Only 20 patients (14.4%) were referred to endocrine services. 80% of these patients had complete clinical and laboratory assessment compared to 5% of patients not referred to endocrine services. The median time interval between onset of hyponatraemia and referral was 4 days and referred patients had on average two endocrine consultations.

Discussion: Hyponatraemia is frequently underinvestigated. Endocrine specialist input can facilitate the appropriate investigation of hyponatraemia.