Profound Hyponatremia: Prevalence, Underlying Disorders and Outcome in Tertiary Care Hospital

Background: Profound hyponatremia (<125 mmol/l) is a serious electrolyte disturbance often encountered in tertiary care setting and is associated with increased morbidity and mortality. Does hyponatremia per se or the underlying disorder contribute to increased mortality remains a controversial point. Clinical records of profound hyponatremia patients were explored with the aim of finding its cause and contribution of hyponatremia in final outcome.

Materials and Methods: All the inpatients with serum sodium ≤125 mmol/L were identified from laboratory data over a period of four months in a tertiary care hospital. Outpatients and cardiac patients were not included in the study. They were classified into three groups according to serum sodium levels in mmol/l (group I: 121-125, group II: 116-120, group III: ≤115). Clinical data was obtained from medical record office. Clinical diagnosis, extent of hyponatremia correction and mortality rates were studied.

Observations: One thousand and fifty patients were identified as having profound hyponatremia (sodium ≤125 mmol/l). Prevalence of profound hyponatremia was recorded as 6.35%. Majority of profound hyponatremic patients (70.54%) had sodium levels in range of 121-125 mmol/l. Very profound hyponatremia (≤115 mmol/l) was noted in 17.6% patients. Mortality rate was significantly higher than the general mortality rate of hospital during that period (8.83% vs 4.6%, p < 0.001). Mortality in group III was highest (12%) followed by patients in group-I (8.42%). Most common cause of hyponatremia was chronic liver disease (20.9%), followed by infectious disease (17.04%), chronic and acute renal disease (15.4%). Diabetes mellitus along with its complications and endocrinological cause were present in 12.1% patients. Other causes include malignancy (11%), neurological (7.04%), pulmonary and trauma (6.4% and 5.17% respectively). Some miscellaneous causes like burns, psychological, skin disease were also noted.

It was observed that patients died mainly because of underlying disease as in majority of subjects (75.72%) hyponatremia was corrected either fully or partially (Na≥ 130 mmol/l and Na ≥ 125 respectively) before demise.

Conclusion: High prevalence of hyponatremia was recorded in inpatients making it a common electrolyte disturbance. Underlying disease and severity of hyponatremia have a bearing on final outcome of patients.