Key PointsQuestionDoes perioperative administration of low-dose dexmedetomidine have a protective effect on posttraumatic stress disorder in patients with trauma undergoing emergency surgery?FindingIn this randomized clinical trial of 310 patients, posttraumatic stress disorder occurred in 14.1% of patients in the dexmedetomidine group and 24.0% of patients in the control group 1 month postoperatively.MeaningThe findings of this study support the perioperative use of dexmedetomidine for reducing the incidence of posttraumatic stress disorder in patients with trauma undergoing emergency surgery.