Hyponatremia causing factors and its association with disease severity and length of stay in COVID-19 patients: A retrospective study from tertiary care hospital

The coronavirus disease-2019 (COVID-19) infection has taken the world by storm within a few months. Evidence has suggested that patients with electrolyte imbalances at baseline may have a longer duration of hospital stay. We aimed to determine the factors associated with hyponatremia on admission in COVID-19 patients and its impact on the length of stay. We conducted a retrospective study including 521 patients who tested positive for COVID-19 and had their electrolytes checked on admission from June 2020 to October 2020. Patients with sodium <135 mmol/l were included in the hyponatremic group and were compared against normonatremic patients. The severity of COVID-19 was found to be more prevalent in the case group as compared to control (38.3% vs 29.2%; 21.1% vs 17.7%). Hyponatremic patients stayed more than 5 days in hospital (56.3% vs 46.5%), and stayed longer in special care (23.4% vs 20.0%) as compared to controls. Hyponatremic patients as compared to control were more likely to have diabetes (47.9% vs 30.0%), hypertension (49.0% vs 38.5%), ischemic heart disease (20.7% vs 15.4%), chronic liver disease (2.7% vs 1.2%), and chronic kidney disease (9.6% vs 3.8%). Upon matching on the age, the adjusted odds of hyponatremia in COVID-19-positive patients were 1.9 times among diabetic patients. Moreover, COVID-19-positive patients suffering from CKD had a higher risk of developing hyponatremia (OR = 2.3, 95% CI: 1.1-5.6). The risk of hyponatremia among COVID-19-positive patients is statistically higher in patients with 1 comorbidity (OR = 1.9, 95%CI: 1.3-3.4). Hyponatremia on admission can be used to forecast the length of hospital stay and the severity of illness in COVID-19 patients.