Mortality predictors in severe hyponatraemia in emergency inpatients

Hyponatraemia, one of the most common electrolyte abnormality when severe (<120 meq/l), has poor prognosis and fatal outcome. Published data on identification of mortality predictors in severe hyponatraemia is however insufficient. The aim of the study was to determine the characteristics, causes and outcome of severe hyponatraemia (<120 meq/l) in hospitalised patients and to identify the mortality predictors. A retrospective case note review of patients (n=175) admitted in emergency ward of a tertiary care hospital during a period of 12 months having severely hyponatraemic (<120 meq/l) were undertaken. Both at the time of admission and those developing during their stay were included. Severe hyponatraemia was found to be common in elderly males. Aetiology was predominantly multifactorial (60.5%), and single aetiologies were mainly, congestive cardiac failure (9.7%), alcoholic liver disease (8.6%) and obstructive airway disease (7.4%). Overall mortality in study group was 25.7%. The mortality was found to be higher (30.8%) in patients developing severe hyponatraemia during hospitalisation as compared to that on admission (24.2%). Mortality was also found to be significantly (p<0.05) higher in patients whose sodium levels were not normalised after treatment. A strong relation between lowest sodium levels rather than admission sodium levels was seen. Severe hyponatraemia (<120meq/l) is a commonly encountered clinical problem, associated with a poor prognosis. The data suggest that outlook in severe hyponatraemia is governed by aetiology and by the serum sodium levels. Identification of mortality predictors should not be overlooked, as correct diagnosis of the aetiology and early recognition of risk factors is critical both to determine correct management and for better prognosis.