# The effect of intraoperative hypotension on postoperative delirium: a meta-analysis and systematic review

## TL;DR

This study finds that low blood pressure during surgery is linked to a higher risk of postoperative delirium, but results vary due to inconsistent study methods.

## Contribution

The study provides the first meta-analysis linking intraoperative hypotension to postoperative delirium risk in adult surgical patients.

## Key findings

- Intraoperative hypotension increases postoperative delirium risk in randomized trials (RR: 1.89) and observational studies (OR: 2.48).
- Defining hypotension by absolute thresholds or mean arterial pressure shows stronger associations with delirium (OR: 4.11 and 2.90, respectively).
- Study heterogeneity is largely due to differing definitions of hypotension, suggesting a need for standardized criteria.

## Abstract

Postoperative delirium (POD) is a common complication linked to poor outcomes, yet its relationship with intraoperative hypotension (IOH) remains unclear. The objective of this study was to clarify the association between intraoperative IOH and POD.

We searched four databases (PubMed, EMBASE, Cochrane Library, and Web of Science) from their inception to June 14, 2025. Randomized controlled trials (RCTs) and observational studies were included when IOH was incorporated as a predictive variable for POD in adult patients undergoing elective surgery under general anesthesia. Risk ratio (RR) and odds ratio (OR) were calculated using a random-effect model separately in RCTs and observational studies.

In total, thirty out of 1,261 studies were included for the systematic review, of which 18 studies were eligible for quantitative meta-analysis. The remaining 12 studies were excluded due to incompatible data formats: eight used continuous metrics, and four lacked extractable effect estimates. IOH was significantly associated with an elevated risk of POD in both RCTs (RR: 1.89, 95%CI: 1.31–2.74) and observational studies (OR: 2.48, 95%CI: 1.64–3.75). Subgroup analysis of observational studies revealed that IOH defined by absolute threshold (OR: 4.11, 95%CI: 2.05–8.24) and mean arterial pressure (MAP) (OR: 2.90, 95%CI: 1.56–5.39) was related to a higher risk of POD. This heterogeneity was further explored by meta-regression, which identified the threshold nature of the IOH definition as a significant source of heterogeneity and a key effect modifier (p = 0.048).

Our meta-analysis demonstrates a statistically significant association between IOH and increased risk of POD. However, substantial methodological heterogeneity across the included studies limits the robustness of these findings. The current evidence should therefore be interpreted as exploratory, highlighting the need for more standardized investigations in this field.

Identifier CRD42023424166.