【Abstract】Objective To observe the effects of dexmedetomidine hydrochloride on cadiovascular response to trachea extubation.Methods One hundred ASA Ⅱ or Ⅲ patients of both sexes aged 30-60 yr weighing standard body weight ±20% scheduled for gastrointestinal surgery under general anesthesiawere randomly divided into 2 groups(n=50 each):propofol group(group P) and dexmedetomidine hydrochloride group(group D).Into the postanesthetic recovery room,patients in group P were maintained with propofol in which plasma target concentration of propofol were set at 1µg∕ml.Patients in group D were injected respectively loading dose and maintenance dose of dexmedetomidine hydrochloride at the rate of 0.5μg/kg(10min infusion) and 0.5µg•kg-1•h-1.Patients in both group were discontinued at spontaneous breathing.BP,HR and cough response were recorded at preoperative(T0),immediately transferred to postanesthetic recovery room(T1),after administration 10min(T2), spontaneous breathing(T3),extubation(T4),after extubation 10min(T5).The end-tidal anesthetic concentration,spontaneous breathing time,call out eyes open time,extubation time,visual analog score and side effects were recorded.Results Compared with group P,SBP,DBP and HR were more stable at T4 in group D(P=0.001,P=0.002,P=0.001,P<0.05),SBP,DBP and HR were also stable at T5 in group D(P=0.034,P=0.021,P=0.001, P<0.05).Spontaneous breathing and call out eyes open time were significantly shortened(P=0.021,P=0.006,P<0.05).The cough response were significantly decrease(P=0.001,P<0.05)and VAS score were significantly decreased(P=0.001,P<0.05).Compared with T0,BP were significantly higher at T4 in group P(P=0.001, P<0.05),HR were significantly higher at T4 and T5 in group P (P=0.001,P<0.05).Conclusion Dexmedetomidine hydrochloride could efficiently prevent the adverse cadiovascular response to trachea extubation and improve the quality of extubation.