Admission serum sodium and osmolarity are not associated with the occurrence or outcomes of acute respiratory distress syndrome in critically ill

Background: Previous studies suggested that hypernatremia or hyperosmolarity may have protective effects in lung injury. We hypothesized that hypernatremia and/or hyperosmolarity would prevent ARDS. 

Design: Retrospective cohort study of all admissions at medical, surgical, and multidisciplinary intensive care units in Mayo Clinic, Rochester from the year of 2009 to 2019. The occurrence of ARDS was identified using a validated computerized search strategy. The association between serum sodium/osmolarity and the occurrence of ARDS was analyzed using a multivariable logistic regression model. The relationship between serum sodium/osmolarity and outcomes of ARDS was analyzed using linear and logistic regression models. 

Results: Among 50,498 patients, the serum sodium level on admission did not have a significant association with the occurrence of ARDS, with an adjusted odds ratio of 0.95 [95% CI (0.86, 1.05)]. There was no significant association between calculated serum osmolarity and the occurrence of ARDS, with an adjusted odds ratio of 1.03 [95% CI (1.00, 1.07)]. 1560 patients developed ARDS during the ICU stay. Their serum sodium level and osmolarity level did not have a significant association with their outcomes. 

Conclusions: Admission serum sodium or serum osmolarity were not associated with the occurrence or outcomes of ARDS in ICU.