Determination of the Median Effective Dose of Dexmedetomidine for the Prevention of Emergence Agitation in Geriatric Patients Undergoing Major Open Surgery With General Anesthesia: A Prospective, Double-Blinded, Dose-Response Trial

Dexmedetomidine can effectively decrease the incidences of emergence agitation (EA) in adult patients, but there are major side effects related to increased dose of dexmedetomidine. The purpose of this study was to determine the median effective dose of dexmedetomidine in the prevention of EA among geriatric patients undergoing major open surgery with general anesthesia. A total of 50 geriatric patients were enrolled in this study. Dexmedetomidine 0.5 mu g center dot kg(-1)center dot h(-1) continuous intravenous infusion was administered to the first patient. The next dose was increased or decreased by .05 depending on the response of the previous patient, according to the Dixon up-and-down method. An "effective" or "ineffective" response was determined based on the Riker sedation-agitation score (RSAS), we defined "effective" as RSAS<5, and "ineffective" as RSAS >= 5. The ED50 of dexmedetomidine in prevention of EA was .30 mu g center dot kg(-1)center dot h(-1) (95% CI, .27-.33) and the predicted ED95 was .42 mu g center dot kg(-1)center dot h(-1) (95% CI, .38-.51). The incidence of bradycardia was significantly increased in the group without EA compared to the group with EA (57.1% vs 13.6%, P = .002). The ED50 of dexmedetomidine in prevention of EA was .30 mu g center dot kg(-1)center dot h(-1) (95% CI, .27-.33) and the predicted ED95 was .42 mu g center dot kg(-1)center dot h(-1) (95% CI, .38-.51). Bradycardia was the main complication.