Objective: Postoperative delirium (POD) increases postoperative morbidity, mortality, and health care costs. POD has many risk factors, such as old age, preoperative cognitive impairment, alcohol abuse, malnutrition, multiple comorbidities, and vascular disease. Risperidone has been reported as effective in POD prevention and treatment. This study investigated the effectiveness of risperidone in reducing the incidence of POD in vascular patients.

Materials and Methods: Patients undergoing vascular surgery were assigned randomly to two groups. Those in the risperidone group received sublingual disintegrating risperidone (1 mg) within one hour after surgery, while the placebo-group patients received a sublingual Listerine strip. All patients were evaluated for POD using the CAM-ICU twice daily for seven days, with the DSM-5 delirium criteria being used to confirm POD by a psychiatrist blinded to the group allocations. The possible risk factors for POD were recorded.

Results: The study unfortunately needed to be terminated early as supplies of orally disintegrating risperidone became unavailable in Thailand. Of the 35 participating vascular surgery patients, 17 were in the risperidone group, and 18 in the control. One patient (5.6%) in the former group and one individual (5.9%) in the latter were diagnosed with POD. The overall POD incidence was 5.7%. The groups demonstrated no statistically significant differences in baseline characteristics, possible risk factors, or lengths of hospital stay.

Conclusion: The study could not demonstrate the impact of orally disintegrating risperidone (1 mg) on the incidence of POD among vascular-surgery patients due to the very low incidence and inadequate sample size. Keywords: CAM-ICU, disintegrating risperidone, postoperative delirium, sublingual, vascular surgery