The association between intraoperative hypotension and postoperative delirium- a retrospective cohort analysis

Background: Intraoperative hypotension might contribute to the development of postoperative delirium through inadequate cerebral perfusion. However, evidence regarding the association between intraoperative hypotension and postoperative delirium is equivocal. We therefore tested the hypothesis that in patients>70 years having elective non-cardiac surgery, intraoperative hypotension is associated with postoperative delirium. Methods: We conducted a retrospective cohort analysis of patients >70 years who underwent elective non-cardiac surgery in a single tertiary academic center between 2020 and 2021. Intraoperative hypotension was quantified as the area under a mean arterial pressure (MAP) threshold of 65 mmHg. Postoperative delirium was defined as a collapsed composite outcome including positive 4A's test during the initial 2 postoperative days, and/or delirium identification using the Chart-based Delirium Identification Instrument. The association between hypotension and postoperative delirium was assessed using multivariable logistic regression, adjusting for potential confounding variables. Several sensitivity analyses were performed using similar regression models. Results: In total, 2352 patients were included (median age 76 years, 1112 (47%) women, 1166 (50%) ASA score≥3, and 698 (31%) having high-risk surgeries). The median [IQR] intraoperative AUC of MAP<65 mmHg was 28 [0,103] mmHg^.min. The overall incidence of postoperative delirium was 14% (327/2352). After adjustment for potential confounding variables, hypotension was not associated with postoperative delirium. Compared to the 1^st quartile of AUC of MAP<65 mmHg, patients in the 2^nd, 3^rd, and 4^th quartiles did not have more postoperative delirium, with adjusted odds ratio (aOR) of 0.94 (95% confidence interval (CI) 0.64-1.36; P=0.73), 0.95 (0.66-1.36; P=0.78), and 0.95 (0.65-1.36; P=0.78), respectively. Intraoperative hypotension was also not associated with postoperative delirium in any of the sensitivity and sub-group analyses performed. Conclusions: To the extent of hypotension observed in our cohort, our results suggest that intraoperative hypotension is not associated with postoperative delirium in elderly patients having elective non-cardiac surgery.