# Association between perioperative potentially inappropriate medication exposure levels and postoperative hospital length of stay among chinese older hospitalized patients: a retrospective cohort study

## TL;DR

This study finds that exposure to inappropriate medications before and during surgery is linked to longer hospital stays in older patients.

## Contribution

The study introduces Total-PIMs, a combined metric of preoperative and intraoperative PIM exposure, as a novel predictor of prolonged postoperative hospital stays.

## Key findings

- Combined preoperative and intraoperative PIM exposure (Total-PIMs) is a stronger predictor of prolonged hospital stays than individual exposure measures.
- Total-PIMs showed a linear dose-response relationship with prolonged postoperative hospital length of stay.
- The Charlson Comorbidity Index modified the association between Total-PIMs and prolonged hospital stays.

## Abstract

Potentially inappropriate medication (PIM) administration in geriatric surgical patients is increasingly prevalent in the perioperative period. The relation between the variation in PIM exposure and other key postoperative geriatric outcomes, such as postoperative hospital length of stay (POLOS), however, has seldom been reported, and current researches mentioning perioperative PIM concentrate on preoperative long-term home medications or postoperative prescriptions that may not be actually taken. We aimed to investigate whether the level and the change of short-term PIM exposure in the immediate perioperative period was associated with prolonged POLOS (pPOLOS).

We performed a retrospective cohort study of patients ≥ 65 years of age who underwent elective inpatient surgery at a tertiary academic hospital from July 2022 and March 2023. PIMs were defined using the Beers Criteria as suggested by the American Geriatrics Society. Stage-varying exposure variables were used to quantify cumulative PIM exposure levels during the preoperative (Pre-PIMs), intraoperative (Intra-PIMs), and even the entire perioperative stage period (Total-PIMs, represented by summing Pre-PIMs and Intra-PIMs) for each participant. A multivariable logistic model and restricted cubic spline model were applied to explore the association and dose-response relationship of PIM exposure with the risk of pPOLOS in the total population and subgroups.

196 (44.6%) of 439 participants had a prolonged postoperative length of stay. There was PIM exposure in 378 (86.1%) of the current cohort, analgesics were administered most frequently both preoperatively and intraoperatively albeit via quite different mechanisms of action. Total-PIMs demonstrated superior association with pPOLOS compared to isolated exposure measures, exhibiting greater precision (narrower confidence interval) despite a moderate effect size. This combined metric provided significantly better predictive accuracy (area under the curve=0.763; Delong’s test, P<0.01) and a visually distinct linear dose-response relationship, establishing Total-PIMs as a robust independent predictor of pPOLOS risk. In subgroup analysis, significant modification effects of Charlson Comorbidity Index on the association of Total-PIMs with pPOLOS risk were observed.

Combined exposure to Pre-PIMs and Intra-PIMs more independently indicates the risk of pPOLOS in older patients than its individual exposure. These findings could help clinicians to be aware of the possible vulnerability of elderly patients under continued preoperative to intraoperative exposure to PIMs, and highlight the potential value of medication optimization and deprescribing PIMs in the immediate perioperative setting.

The online version contains supplementary material available at 10.1186/s12877-025-06848-y.