The Association of Selective Serotonin Reuptake Inhibitors with Delirium in Post-Operative Adults: A Secondary Analysis of a Post-Operative Dataset with Daily Severity of Illness Adjustment

Background: Postoperative delirium is a prevalent condition associated with increased mortality, difficulties with physical recovery from surgery and decreased long-term cognitive function, especially in older adults. Currently, there are no direct medical treatments for delirium. We recently found an association between SSRI administration and reduced delirium in a critically ill medical population. We sought to evaluate this association in a surgical population. SSRIs may provide a new treatment option for delirium; further exploration is warranted. We aimed to assess the association between selective serotonin reuptake inhibitors (SSRIs) and delirium in postoperative adults.

Methods: We undertook a secondary analysis of an existing cohort in a large Academic Medical Centre in the Southeast United States. Patients were adults (aged 18-99) requiring at least one night of hospital admission following a scheduled surgery, enrolled from July 2017 to September 2017. Our primary outcome was the incidence of delirium 24 hours after administration of an SSRI. Our exposure variable was any SSRI administration in the preceding 24 hours. We collected data on demographics, SSRI administration, overall severity of illness via the ASA grading system, and daily severity of illness via the Sequential Organ Failure Assessment (SOFA) score from the electronic medical record review.

Results: We collected data on 191 patients (mean age 56.8 years, SD +/- 16.7). One hundred ten (57.6%) were female, and 149 (78%) were White. Most patients, 183 (95.8%), were non-Hispanic. Twenty-eight (14.6%) were prescribed SSRIs at any point during the study period and 35 (18.3%) were delirious on day one. Unadjusted analysis demonstrated that patients receiving SSRIs had OR 1.60 for delirium the next day (p=0.41). After adjusting for age ASA, age, hospital LOS, and SOFA, patients receiving SSRIs had OR 1.44 for next-day delirium (p=0.48).

Conclusions: SSRIs administered in the postoperative period were not associated with delirium on the subsequent day. This finding conflicts with prior results from a critically ill population. The association of SSRIs with delirium requires further investigation.