Background: Hyponatremia is the commonest electrolyte abnormality encountered in clinical practice. It is associated with increased mortality and prolonged length of stay. Errors in establishing the aetiology of hyponatremia can lead to inappropriate treatment with adverse outcomes. An accurate diagnosis requires a careful clinical and biochemical assessment. An audit was undertaken to determine current practice at University Hospitals Bristol.
Method: A comprehensive retrospective review of case notes and the laboratory database was conducted for all medical patients admitted between 1/1/13 and 31/3/13, presenting with a serum sodium <130 mmol/l. The following standards were used to benchmark quality of care: i) laboratory alerts for very severe hyponatremia, ii) the diagnostic approach as compared against the European Society of Endocrinology Guidelines, iii) communication of hyponatremia management on the discharge summary; and iv) the rates of re-admission/mortality.
Results: Thirty-eight cases of moderate (125130 mmol/l, n=19) or severe (<125 mmol/l, n=19), hyponatremia were identified. Local laboratory standards for alerting very severe hyponatremia were achieved in 83% (10/12). The aetiology of hyponatremia was determined in only 45%; glucose, TFTs, cortisol, and urine/plasma osmolalities were requested in 68, 50, 18, and 24% respectively. Where SIADH was suspected, 78% had an incomplete biochemical assessment. Only 42% of discharge summaries clearly communicated the diagnosis and management of hyponatremia. Coding data demonstrated that of patients coded hypo-osmolality and hyponatremia during this 3-month window, 29% died within 12 months, 25% were readmitted to hospital within 28 days, and 55% within 1 year.
Conclusion: Hyponatremia assessments in the acute setting are often incomplete. Incorrect evaluation and management may be associated with prolonged in-patient stay and increased re-admission rates in an already vulnerable group of patients with a high background mortality risk. Early specialist input, clarity of diagnosis, and robust communication across the healthcare community could improve outcomes, patient experience and be cost effective overall.