Investigation and management of severe hyponatraemia - cause for concern?
MSB Huda1, GV Gill1, D Wile2, K Skagen1, A Boyd1, ID Watson2 & C van Heynigen2
Hyponatraemia is a common biochemical abnormality associated with significant mortality. However, adequate investigation and accurate diagnosis are frequently lacking. We have evaluated the assessment and management of severe hyponatraemia in a large teaching hospital. Inpatients with a plasma sodium (pNa) <125mmol/L were identified prospectively by laboratory database, over a 6 month period. Notes were examined and data extracted. Data was also retrospectively reviewed by a consultant endocrinologist (GVG) and a revised diagnosis made (if possible). One hundred and four (104) patients with a pNa <125mmo/L were identified. Mean (+/-SD) age was 69+/-14, 52% were female, mean hospital stay was 16+/-12 days and overall mortality was 27%. Adequate investigations were rarely performed. All patients had pNa, plasma creatinine and glucose. However, only 28 (26%) had a plasma osmolality measured, 29 (27%) urine osmolality, 11 (10%) urinary Na, 8 (8%) plasma cortisol, and 2 (28) a short Synacthen test. Comparing the 'ward' and 'specialist review' diagnoses, there were significant discrepancies for 'no cause found' ( 49% vs 27%, p<0.001), SIADH ( 20% vs 33%, p=0.001 ), and alcohol (6% vs 11%, p<0.01). There was a non-significant difference in thiazides as a cause (13% vs 18%, p=0.15). Treatment was often given with no clear diagnosis. There was no intervention in 42%, fluid restriction in 36%, intravenous (I/V) saline 24% and both fluid restriction and I/V saline in 7%. Diuretic treatment was modified in 10%, I/V glucose changed to saline in 2% and single patients were given demeclocycline and DDAVP respectively. Of the 38 patients treated by fluid restriction, only 3 were given < 1 litre per day. In conclusion, severe hyponatraemia is a serious condition, but its investigation and evaluation is grossly inadequate. In view of this, an accurate diagnosis is frequently not made. Treatment patterns appear to be arbitrary and illogical, and sometimes potentially dangerous.