Associations of Intraoperative Hypotension, and Perioperative Blood Pressure with Delirium after Noncardiac Surgery: A Retrospective Cohort Analysis

Background: Postoperative delirium is a common and serious complication following non-cardiac surgery. A possible precipitating factor may be perioperative hemodynamic changes, with subsequent changes in brain perfusion. This study aims to investigate whether intraoperative hypotension, perioperative average blood pressure, or blood pressure variability are associated with postoperative delirium. Methods: We conducted a retrospective cohort study analyzing adult non-cardiac surgery patients from a single academic center between 2018 and 2022. The primary exposure was intraoperative hypotension, defined as area under the curve of intraoperative mean arterial pressure (MAP) below 65 mmHg. Secondary exposures were intraoperative and postoperative time weighted average of MAP. The outcome was the incidence of postoperative delirium, assessed twice daily using the bCAM and CAM-ICU. Results: We included 38,940 non-cardiac surgeries. The incidence of postoperative delirium was 6.56%. In the primary analysis, we found no significant association between the intraoperative area under the curve of MAP <65 mmHg and postoperative delirium (OR 1.000, 95%CI 0.999-1.000, p=0.17). In the secondary analyses, association with intraoperative time weighted average MAP was linear, where increasing MAP was associated with lower delirium risk (OR 0.993, 95% CI: 0.990-0.996, p<0.001). Postoperatively, we identified one change point for time weighted average MAP at 88 mmHg – where increasing increments of MAP were associated with lower risk of delirium when MAP<88 mmHg (OR 0.995, 95%CI 0.992-0.998, p<0.001), but higher risk of delirium when MAP≥88mmHg (OR 1.022, 95%CI 1.019-1.027, p<0.001). Conclusion: Intraoperative hypotension and intraoperative average blood pressure were not associated with postoperative delirium. Postoperative higher average blood pressures demonstrated a statistically significant association with delirium; however, this finding lacks clinical relevance.