The purpose of this studywas to determine the efect of dexmedetomidine on hemodynamic responses toDLT intubation compared to placebo and to assess the adverse efects related to dexmedetomidine. Sixty patients were randomly allocated to receive 0.7 µg/kg dexmedetomidine (n=30)ornormalsaline(n=30) 10 minutes before general anesthesia. Systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), heart rate (HR), and rate pressure product (RPP) between groups were recorded. During intubation and 10 minutes aterward (T1-T10), the mean SBP, DBP,MAP, HR, and RPP in the control group were signiicantly higher than those in the dexmedetomidine group throughout the study period except at T1.he mean diferences of SBP, DBP, MAP, HR, and RPP were signiicantly higher in the control group, with the value of 15.2mmHg, 10.5mmHg, 14mmHg, 10.5 beats per minute, and 2,462.8mmHg min−1. Four patients in the dexmedetomidine group and 1 patient in the control group developed hypotension, while 2 patients in the dexmedetomidine group had bradycardia. Prophylactic dexmedetomidine can attenuate the hemodynamic responses to laryngoscopy and DLT intubation with minimal adverse efects. his trial is registered with ClinicalTrials.gov NCT01289769.