An audit of hyponatraemia in a large UK university teaching hospital

Abstract

Background/ lntrod uction Hyponatraemia is the most commonly observed electrolyte abnormality in hospitalised patients. The many causes of hyponatraemia may be classified either by volume status or aetiology. Thorough history taking, clinical examination and investigation are necessary in order to accurately determine the cause of hyponatraemia and so formulate the most appropriate management plan. Methods Patienis with serum sodium<131mM were identified by daily automated search of the biochemistry database at Nottingham University Hospitals NHS Trust over a two week period (September 2012). Data regarding clinical history examination of volume status, investigations undertaken, diagnosed aetiology of hyponatraemia, length of hospital stay and treatment were extracted retrospectively from the medical notes using a linked anonymised system. Data analysis was performed using Microsoft Excel@ 2010 and results are given as mean +/-standard deviation.Results 75 patients were identified. Mean age was 76.0 (+/-13.0) and 53% were female. Mean serum sodium was 126.5 mM (+/-4.1), potassium 4.4 mM (+/-1.0), creatinine 1 1 6.8 ;rM (+t1 33), plasma osmolarity 270.1 osmol/Kg (+t 22.4). Mean urinary osmolarity was 362 +/-osmol/Kg (+/-141.7) and spot urinary sodium of 38.1 mM (+/-40.2).The average length of stay was 18.2 days (+l-26.11. 43% had recorded an examination of volume status.The aetiology of hyponatraemia was established in 37.3o/" of patients. 11 patients were recorded as having SIADH but in only two of these were investigations sufficient to substantiate this conclusion.