# Intraoperative hypotension and postoperative delirium among older high-risk patients undergoing major noncardiac surgery: a retrospective single-centre cohort study

## TL;DR

This study found that intraoperative hypotension was initially linked to postoperative delirium in older high-risk patients, but this link disappeared when accounting for improvements in care over time.

## Contribution

The study shows that the observed association between hypotension and delirium may reflect historical practice trends rather than a direct causal relationship.

## Key findings

- Intraoperative hypotension was initially associated with increased odds of postoperative delirium.
- The association disappeared after adjusting for the year of surgery and improvements in care.
- Both hypotension exposure and delirium rates declined over the study period.

## Abstract

Intraoperative hypotension has been associated with postoperative complications, but its relationship with postoperative delirium remains debated.

This single-centre retrospective cohort study included adults (≥60 yr) with ASA physical status score of 3 or 4 undergoing major noncardiac surgery, with documented Confusion Assessment Method assessments. Patients with a history of neurosurgery, stroke, dementia, or neurocognitive disorders were excluded. The primary exposure was the cumulative duration of a mean arterial pressure <65 mm Hg (minutes). The primary outcome was postoperative delirium within 7 days, diagnosed via Confusion Assessment Method. Multivariable logistic regression was used to assess the association between intraoperative hypotension and delirium, adjusting for confounders.

Among 5171 patients included from 2013–2024, 632 (11.8%) developed delirium. The median (Q1–Q3) duration of surgery and time with mean arterial pressure <65 mm Hg were 281 (199–430) min and 28 (9–61) min, respectively. In models adjusted for patient characteristics and perioperative factors, intraoperative hypotension was associated with increased odds of delirium (odds ratio per 60 min, 1.12; 95% confidence interval, 1.01–1.24; P=0.038). However, after adjusting for year of surgery, the association was attenuated and no longer statistically significant (odds ratio, 1.06; 95% confidence interval, 0.95–1.18; P=0.320). Both intraoperative hypotension exposure and delirium incidence declined significantly over the study period.

Although intraoperative hypotension initially appeared to be associated with postoperative delirium, this association was no longer significant when accounting for temporal improvements in perioperative care. Intraoperative hypotension may represent a marker of historical practice patterns rather than an independent causal driver of delirium.