Hyponatremia in Elderly In-Patients

Introduction: Hyponatremia, the most common dyselectrolytemia, frequently occurs in elderly patients. Multiple aetiologies, association of comorbids play a major role in hyponatremia of elderly patients. Prolonged hospital stay and increased mortality are the consequences. Aim: To study the prevalence, common aetiologies, comorbids and clinical outcomes of hyponatremia in elderly in-patients. Materials and Methods: A prospective, observational study was conducted in a teaching hospital on 950 adults >= 60 years of age, admitted to the Post-graduate Department of Medicine, over a period of 12 months. Detailed history, clinical examination, outcomes, laboratory investigations, imaging studies, diagnoses and causes were recorded. For statistical analyses, histogram, Kolmogrove test for normality test and then Independent t-test, Wilcoxon rank sum test, Pearson's chi-square test, Fisher'sexact tests were used. Results: After excluding 32 patients of pseudo and hypernatremia, 440 patients (47.9%) had hyponatremia (s.Na+ level of <135 mEq/L) and 478 patients (52.0%) had normal sodium (135-145 mEq/L). The mean age of hyponatremic patients was 69.87 +/- 7.94 and 70 +/- 8.18 in normonatremic patients (p=0.815). The mean Na+ level was 122.08 +/- 8.68 mEq/L in hyponatremic patients and 138.05 +/- 2.71 in normonatremic patients. Hypovolemic hyponatremia was most frequent (42.0%). The leading aetiologies were diuretics (28.8%), acute renal failure (27.9%), and severe sepsis (15.2%) but 61.8% of patients with hyponatremia had multiple factors. Hypertension was the most common comorbid (63%) and presence of multiple comorbid was significantly associated with hyponatremia (p<0.001). Hyponatremic group, though hospitalised for longer period (p<0.001), higher mortality rate could not be established (p=0.699); not also with the severity of hyponatremia (p=0.06). Conclusion: Elderly patients are highly predisposed to hyponatremia and are often dehydrated. Presence of multiple comorbid is a risk factor. Hyponatremia prolongs the hospital stay but severity of underlying illnesses may rather accelerate the mortality rate.