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目的 研究不同剂量的右美托咪定对老年患者全身麻醉苏醒期QT间期的影响.方法 76 例老年患者(年龄65～80岁,ASA分级Ⅰ-Ⅱ)在全身麻醉下行腹部手术,随机分为右美托咪定1组(DEX1组,n＝19),右美托咪定2组(DEX2组,n＝20),右美托咪定3组(DEX3组,n＝17)和对照组(CON组,n＝20),DEX组和CON组在术毕前10 min内分别泵入0.4 μg/(kg?h)(DEX1)、0.6 μg/(kg?h)(DEX2)、0.8 μg/(kg?h)(DEX3)右美托咪定和同等容量生理盐水.观察并记录两组患者用药前(T1)、用药后1 min(T2)、5 min(T3)、10 min(T4)及拔管后(T5)的QT间期 、心率(HR)和平均动脉压(MAP)的变化,以及手术结束至睁眼、自主呼吸恢复、拔管的时间.结果 各组患者给药前与给药后1 min各指标差异无统计学意义(P＞0.05).与CON组比较,DEX组在T3~T5时段QT间期明显缩短(P＜0.05),MAP和HR在这一期间显著降低;DEX组插管前后比较,QT间期、MAP和HR相对平稳.CON组在T3～T5时段,QT间期显著延长,MAP和HR显著增加(P＜0.05).术毕至睁眼的时间及Ramsay评分,DEX3组与其他组比较差异有统计学意义(P＜0.05).结论 小剂量右美托咪定(0.4 μg/(kg?h)或0.6 μg/(kg?h))可以有效抑制老年患者全麻苏醒期拔除气管导管引起的QT间期延长,血流动力学更稳定,且不影响患者苏醒.“,”Objective To investigate the effects of different doses of dexmedetomidine on QT intervals in old patients during recovery period of general anesthesia. Methods 76 old patients undergoing abdominal operation (65～80 years old) were randomly divided into 4 groups: Group DEX1, Group DEX2, Group DEX3 and control group (Group CON). Dexmedetomidine 0.4, 0.6, 0.8 μg/(kg?h) and normal saline were infused over 10 min in groups DEX and CON at 10 min before the end of the operation. The QT interval, heart rate (HR), mean arterial pressure (MAP) were recorded at the time before dexmedetomidine infused (T1), 1, 5, 10 min after dexmedetomidine infused (T2, T3, T4) and the time of tracheal extubation (T5). Time of eyes opened, breathing recovery and extubation after surgery were recorded. Results There were no significant differences among QTc, MAP and HR at T1 and T2 among four groups (P＞0.05); QTc, MAP and HR in Group DEX decreased significantly at T3, T4 and T5. QTc prolonged significantly and MAP, HR were higher in Group CON (P＜0.05). The differences of the time of eyes opened, and extubation after surgery between Group DEX3 and other groups were statistically significant (P＜0.05). Conclusion 0.4 or 0.6 μg/(kg?h) dexmedetomidine intravenously infused before the end of the operation can inhibit the QT interval prolongation induces by tracheal extubation in old patients during recovery period of general anesthesia, which make haemodynamics of patients undergoing thyroidectomy stable.