# Association between end-tidal sevoflurane concentration and postoperative cognitive dysfunction and pain sensitivity in elderly patients under general anesthesia

## TL;DR

Higher sevoflurane concentration during surgery in elderly patients is linked to better cognitive recovery and less postoperative pain, possibly due to changes in brain and pain markers.

## Contribution

This study identifies a link between sevoflurane concentration and reduced postoperative cognitive dysfunction and pain sensitivity in elderly patients.

## Key findings

- Higher sevoflurane concentration was associated with lower incidence of postoperative cognitive dysfunction and better cognitive scores.
- Elevated sevoflurane reduced pain sensitivity measures and altered levels of neurological and pain-related biomarkers.
- Multivariate analysis showed higher sevoflurane concentration and preoperative NGF levels were protective factors against cognitive dysfunction.

## Abstract

To analyze the association between end-tidal sevoflurane concentration and postoperative cognitive dysfunction (POCD) and pain sensitivity in elderly patients under general anesthesia.

A total of 121 elderly patients undergoing abdominal surgery were enrolled and divided into a low-concentration group (0.8–1.2 MAC, n = 61) and a high-concentration group (1.5–2.0 MAC, n = 60). End-tidal sevoflurane concentration, recovery parameters, Mini-Mental State Examination (MMSE) scores, POCD incidence, pain sensitivity (PSQ score, mechanical hypersensitivity areas and thresholds), and serum levels of neurological markers (NSE, ApoJ, NGF) and pain mediators (PGE2, 5-HT) were compared between groups. Pearson correlation and multivariate logistic regression were used to assess associations and influencing factors for POCD.

The high-concentration group had longer recovery times but a lower incidence of POCD (10.00% vs. 24.59%) and higher MMSE scores on postoperative days 1 and 3 (P < 0.05). Pain sensitivity measures were reduced in the high-concentration group on postoperative day 1, with lower PSQ scores, smaller mechanical hypersensitivity areas, and higher mechanical thresholds (P < 0.05). Compared to the low-concentration group, the high-concentration group exhibited significantly lower postoperative levels of NSE, ApoJ, PGE2, and 5-HT, and higher NGF levels (P < 0.05). End-tidal sevoflurane concentration positively correlated with MMSE scores, mechanical thresholds, and NGF levels, and negatively correlated with pain sensitivity measures, NSE, ApoJ, PGE2, and 5-HT (P < 0.05). Multivariate analysis identified age and preoperative elevations of NSE, ApoJ, PGE2, and 5-HT as risk factors for POCD, while higher sevoflurane concentration and preoperative NGF levels were protective factors (P < 0.05).

Higher end-tidal sevoflurane concentration is associated with improved postoperative cognitive function and reduced pain sensitivity in elderly patients, likely mediated by the modulation of neurological and pain-related biomarkers, serving as a protective factor against POCD.