Introduction: Significant hyponatraemia (serum sodium <128 mmol/l) is a potentially modifiable cause of prolonged hospital length of stay (LOS). By correcting euvolaemic hyponatraemia more rapidly than imposed fluid restriction, vasopressin receptor-2 antagonists may be useful adjuncts to existing treatments.
Aim: To explore the potential clinical utility of vasopressin antagonists by describing the frequency and nature of hyponatraemia typically encountered in UK acute practice.
Method: Seven day retrospective case note study of admissions to an ED-attached medical unit. Fluid-status determined by review of admission documentation (clinical examination and history) and serum biochemistry (urea>10 mmol/1). Significant cases categorised as hypovolaemic, euvolaemic or hypervolaemic and aetiology of hyponatraemia postulated. Documentation of investigations and subsequent plans for hyponatreamia correction recorded.
Results: 327 patients (55% female) with a mean age of 63.3 years (range 1699) were admitted. 324 (99%) had a biochemistry profile recorded and 44 (13.6%) were hyponatraemic (sodium<132 mmol/l). 28 (8.6%) were significantly hyponatraemic, presenting with falls or postural symptoms (23%), nausea or vomiting (20%) and dyspnoea (13%). Causes of hyponatraemia were; medication/diuretics (23%), infection (20%), malignancy (13%), diabetes / DKA (13%), liver disease (6%), and intra-cerebral vascular events (6%). Mean LOS for this group was 14.5 days and mortality was 9%. 86% of notes had evidence of a fluid-status assessment but only 8% specifically included plans for hyponatraemia correction. 10% had serum osmolarities and none had urine osmolarities performed. 13 patients had hypovolaemic, 8 euvolaemic and 1 hypervolaemic significant hyponatraemia (6 unclassified).
Conclusion: 23% of medical admissions have euvolaemic significant hyponatraemia. Documentation plans for correction of hyponatraemia are sparse and osmolarities rarely performed. Although detailed prospective studies and LOS outcome trials to establish the role of vasopressin antagonists in the management of hyponatraemia are warranted, greater attention should be paid to establishing the underlying cause and then correcting low sodium on acute medical units.
Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.
Funding: No specific grant from any funding agency in the public, commercial or not-for-profit sector.