The mediating role of acute postoperative pain in the relationship between intraoperative dexmedetomidine and neuropsychiatric outcomes following gastrointestinal surgery in elderly patients: a multicenter observational study

The relationships among intraoperative dexmedetomidine administration, acute postoperative pain, and postoperative neuropsychiatric complications in elderly patients receiving gastrointestinal surgery remain incompletely characterized. This multicenter cohort study analyzed data from the Perioperative Database of Chinese Elderly Patients. The participants who underwent gastrointestinal surgery were divided into two groups: the dexmedetomidine group and the nondexmedetomidine group. The primary outcome was 30-day postoperative neuropsychiatric complications, whereas secondary outcomes included severe pain, surgery-related, respiratory, cardiovascular, and digestive system complications, and acute kidney injury. Propensity score matching balanced the baseline characteristics. Associations between dexmedetomidine and outcomes were assessed via univariate and multivariate logistic regression. Subgroup analyses and mediation analysis were used to evaluate the correlations and relationships among dexmedetomidine, postoperative pain, and neuropsychiatric complications. Multivariate regression was used to examine the dose‒response effects of dexmedetomidine. Of the 1388 eligible patients, 333 (24.0%) received intraoperative dexmedetomidine at a median dose of 30 μg (interquartile range [IQR]: 20–72 μg) or 0.5 μg/kg (IQR: 0.4–1.1 μg/kg). The dexmedetomidine group had significantly lower rates of neuropsychiatric complications (17.4% vs. 23.5%), surgery-related complications (7.8% vs. 13.7%), and digestive system complications (0.3% vs. 2.9%). Multivariate analysis indicated that dexmedetomidine was associated with reduced neuropsychiatric complications (OR: 0.641; 95% CI: 0.454 to 0.906, P = 0.012) and severe postoperative pain (OR: 0.591; 95% CI: 0.433 to 0.808, P = 0.001). Mediation analysis revealed an indirect effect through acute pain reduction (aOR -0.059, 95% CI -0.109 to -0.014, P=0.004), accounting for 13.0% of the total effect. Intraoperative dexmedetomidine was significantly associated with reduced postoperative neuropsychiatric complications in elderly gastrointestinal surgery patients. The reduction in severe pain may partially mediate the relationship between dexmedetomidine use and the lower incidence of neuropsychiatric complications. These findings suggest an association rather than proving causation and must be validated through randomized controlled trials.