Hyponatraemia is an important medical condition, relevant to all practitioners working in old age psychiatry. This has important clinical implications to ensure patients commenced on antidepressant medication are monitored for electrolyte imbalance.

To identify the incidence and key features of cases of hyponatraemia in consecutive referrals to a rural community Psychiatry of Old Age service (population 18,000 over 65)

Naturalistic study design, routine referrals to the service were reviewed between 1/4/10 to 30/9/2011 and considered for inclusion. All hyponatraemia cases were identified and recorded at the MDT meeting. Clinical case notes and/or correspondence reviewed, data collected on demographics, psychiatric, medical diagnoses, psychotropic and general medication.

796 referrals reviewed, 22 cases of hyponatraemia identified, (2.8%), 15 case notes available for review, 4 review letters (include key information required), 3 casenotes were missing and 2 did not meet inclusion criteria as outside the period of study. Of the 17 included (12 female, 5 male), mean age was 82.1, all widowed/ single, 94% diagnosis of depression, 5 dual diagnoses, Mean MMSE 26/30. 100% on psychotropic medication, (87% antidepressants, 58% SSRI's). Mean medication number was 9. 6/17 (35%) cases of hyponatraemia were judged to be directly related to SSRI medication.

Hyponatraemia is an important clinical outcome that should be looked for in vulnerable populations with complex medical and psychiatric morbidity. Although many potential causes for hyponatraemia, SSRI antidepressants should be monitored with regular electrolytes in at risk patients (older age, polypharmacy, medical co-morbidity).