Dysnatremia and 6-Month Functional Outcomes in Critically Ill Patients With Aneurysmal Subarachnoid Hemorrhage: A Prospective Cohort Study

Objectives: To investigate the association between plasma sodium concentrations and 6-month neurologic outcome in critically ill patients with aneurysmal subarachnoid hemorrhage.

Design: Prospective cohort study.

Setting: Eleven ICUs in Australia and New Zealand.

Participants: Three-hundred fifty-six aneurysmal subarachnoid hemorrhage patients admitted to ICU between March 2016 and June 2018. The exposure variable was daily measured plasma sodium.

Interventions: None.

Measurements and main results: Six-month neurologic outcome as measured by the modified Rankin Scale. A poor outcome was defined as a modified Rankin Scale greater than or equal to 4. The mean age was 57 years (± 12.6 yr), 68% were female, and 32% (n = 113) had a poor outcome. In multivariable analysis, including age, illness severity, and process of care measures as covariates, higher mean sodium concentrations (odds ratio, 1.17; 95% CI, 1.05-1.29), and greater overall variability-as measured by the sd (odds ratio, 1.53; 95% CI, 1.17-1.99)-were associated with a greater likelihood of a poor outcome. Multivariable generalized additive modeling demonstrated, specifically, that a high initial sodium concentration, followed by a gradual decline from day 3 onwards, was also associated with a poor outcome. Finally, greater variability in sodium concentrations was associated with a longer ICU and hospital length of stay: mean ICU length of stay ratio (1.13; 95% CI, 1.07-1.20) and mean hospital length of stay ratio (1.08; 95% CI, 1.01-1.15).

Conclusions: In critically ill aneurysmal subarachnoid hemorrhage patients, higher mean sodium concentrations and greater variability were associated with worse neurologic outcomes at 6 months, despite adjustment for known confounders. Interventional studies would be required to demonstrate a causal relationship.