# Association between perioperative rate pressure product and postoperative delirium in geriatric patients with hip fracture

## TL;DR

High heart rate and blood pressure in elderly hip fracture patients at admission may predict post-surgery delirium, partly due to inflammation.

## Contribution

This study is the first to link admission rate pressure product with postoperative delirium in elderly hip fracture patients.

## Key findings

- Higher admission RPP is an independent risk factor for postoperative delirium.
- RPP's effect on delirium is partially mediated by preoperative IL-6 levels.
- RPP shows moderate predictive ability for delirium with an AUC of 0.727.

## Abstract

Postoperative delirium (POD) is a serious complication of elderly hip fracture patients, leading to deleterious outcomes and substantial healthcare burdens. Early predictors remain a critical imperative. Rate pressure product (RPP), a stress indicator, has not been studied in relation to POD.

This study aimed to investigate the relationship between RPP at admission and incidence of POD in elderly patients undergoing hip fracture surgery and to explore whether the effect of RPP on POD is mediated by inflammatory response.

This study was conducted on patients aged ≥65 years who underwent hip fracture surgery under spinal anesthesia. POD was diagnosed using the 3-Minute Diagnostic Interview for CAM-defined Delirium (3D-CAM). A comprehensive dataset including demographics, clinical parameters, Mini-Mental State Examination (MMSE) scores, and RPP. Preoperative plasma levels of IL-1βand IL-6 were quantified. To mitigate confounding biases, a propensity score matching (PSM) was performed. Logistic regression analyses were used to build a model predicting probability of POD. Receiver operating characteristic (ROC) curve analysis assessed the predictive utility of RPP. Mediation analysis was employed to further explore the relationship between RPP and POD.

From an initial pool of 468 elderly patients undergone hip fractures, the rigorous screening and matching process culminated in a final analytical cohort of 150 patients. Post-PSM, patients in POD group exhibited higher admission RPP (p < 0.001), and elevated preoperative plasma IL-6 levels (p < 0.001) compared with patients in non-POD group. The binary logistic regression pinpointed higher admission RPP (OR: 1.325, 95% CI: 1.098–1.599, p = 0.003) and elevated preoperative plasma IL-6 (p < 0.001) as potent and independent risk factors of POD. Admission RPP demonstrated a commendable ability to predict POD, yielding an AUC of 0.727 (95% CI, 0.639–0.815, p < 0.001). Moreover, the results of mediation analysis show that the effect of RPP at admission on POD may be partially mediated by preoperative plasma IL-6.

Elevated RPP at admission is a risk factor of POD in elderly patients undergoing hip fracture surgery and the effect of RPP at admission on POD may be partially mediated by preoperative plasma IL-6.