Association between intraoperative carotid blood flow reductions and postoperative delirium in older patients undergoing surgery: a prospective observational study

PURPOSE: Postoperative delirium (POD) is common among older patients undergoing surgery and is associated with impaired cerebral perfusion. In this study, we sought to investigate the relationship between intraoperative carotid artery blood flow changes and POD risk in older patients undergoing abdominal surgery. METHODS: We conducted a prospective observational analysis of patients older than 65 yr who underwent elective abdominal surgery in a single tertiary care hospital from September 2021 to May 2022. Common carotid artery (CCA) blood flow was continuously monitored intraoperatively using ultrasound vector flow imaging (VFI). We assessed the association between CCA flow changes and POD with multivariable logistic regression models. We explored additional models incorporating intraoperative mean arterial pressure (MAP) reductions to evaluate relative predictive performance. Postoperative delirium was assessed within 7 days postoperatively. RESULTS: Among 210 patients analyzed (from 242 screened), POD occurred in 41 (19.5%). In the primary analysis, longer intraoperative reductions in CCA blood flow > 40% from baseline were independently associated with increased POD risk (adjusted odds ratio [aOR] per 10-min increment, 2.24; 95% confidence interval [CI], 1.51 to 3.31; Bonferroni-adjusted P < 0.001), which remained robust in sensitivity analyses (aOR, 1.78; 95% CI, 1.45 to 2.19; Bonferroni-adjusted P < 0.001). In secondary analyses, prolonged CCA blood flow increases were associated with reduced POD (aOR, 0.58 per 10-min increment; 95% CI, 0.40 to 0.83; Bonferroni-adjusted P < 0.001). Common carotid artery flow reductions showed limited concordance with MAP-based hypotension (Cohen's κ ≤ 0.08). Models incorporating CCA flow showed better discrimination and calibration metrics for predicting POD than those based on MAP. CONCLUSIONS: In older patients undergoing abdominal surgery, persistent intraoperative CCA blood flow reductions > 40% from baseline were associated with an increased risk of POD Intermittent CCA flow measurement with VFI may help identify patients not identifiable through blood pressure monitoring alone. Nevertheless, because the results derive from an observational design with interval-based sampling, the findings should be interpreted with caution and warrant prospective validation.