Changes in serum sodium during an external ventricular drain weaning in patients with subarachnoid hemorrhage

Dysnatremia is a common complication following non-traumatic subarachnoid hemorrhage (SAH). Potential causes include induced hypernatremia and hyponatremia related to cerebral vasospasm or cerebral salt wasting syndrome. Based on bedside observations, this study is aimed to investigate the correlation between changes in serum sodium during an external ventricular drain (EVD) wean trial and wean trial outcomes.

A retrospective analysis was performed on a cohort of patients admitted with SAH from a large volume tertiary center. The cohort comprises patients admitted to the neuroscience ICU between 2012 and 2022 with subarachnoid hemorrhage complicated by obstructive hydrocephalus. The primary outcome was defined as successful wean if the EVD was removed at the end of a wean attempt or failed if the EVD was reopened or if a ventriculoperitoneal shunt was placed.

The cohort included 985 patients and consisted of 1,318 unique wean attempts, of which 790 were successful and 528 were unsuccessful. Patients with failed attempts had overall higher clinical and radiographic hemorrhage grades. Serum sodium concentration (mEq/L, mean ± standard deviation) on the day of wean initiation was 139.3 ± 8.5 in the successful wean group versus 140.7 ± 6.6 in the failed group (p < 0.001). During the first 3 days of the wean attempt, serum sodium decreased by 0.8 ± 7.8 mEq/L in the successful group compared with 1.5 ± 5.8 mEq/L in the failed group (p = 0.048). There was no statistically significant difference in the cumulative sodium intake before (up to 2 days) or during the wean attempt between the groups. In a multivariable mixed effect logistic regression analysis, the slope of the change in serum was associated with the wean attempt outcome (odds ratio [95% confidence interval] of 1.324 [1.174-1.506]). When cases with positive or negative sodium changes were analyzed separately, both were independently associated with outcome, with a higher rate of change associated with increased risk of failure.

Temporal changes in serum sodium during EVD wean attempts after subarachnoid hemorrhage may represent a new trigger for post-SAH dysnatremia. These changes are not directly explained by iatrogenic exposures. These hypothesis-generating findings warrant validation in prospective trials.