右美托咪啶用于老年患者硬膜外神经阻滞镇静的半数有效剂量

The median effective doses of dexmedetomidine to induce adequate sedation in elderly patients undergoing epidural anaesthesia

目的 探讨右美托咪啶用于老年患者硬膜外神经阻滞镇静的半数有效剂量。方法 选择拟硬膜外神经阻滞下择期行下肢手术的老年患者75例，按随机数字表法分为五组：D1组（右美托咪啶0.2 μg/kg），D2组（右美托咪啶0.4 μg/kg），D3组（右美托咪啶0.6 μg/kg），D4组（右美托咪啶0.8 μg/kg），D5组（右美托咪啶1.0 μg/kg），每组15例。输注右美托咪啶完毕后20 min，以警觉镇静评分（OAA/S评分）≤ 3分为镇静有效，采用概率单位回归法计算右美托咪啶用于老年患者硬膜外神经阻滞中镇静的半数有效剂量（ED50）和95%有效剂量（ED95）及95% CI；比较五组平均动脉压（MAP）、心率、脉搏血氧饱和度（SpO2）和OAA/S评分的变化情况，比较五组低血压、心动过缓、低氧血症及过度镇静等并发症的发生率。结果 老年患者镇静的ED50为0.36 μg/kg，95% CI为0.27~0.44 μg/kg；ED95为0.94 μg/kg，95% CI为0.71~1.62 μg/kg。右美托咪啶输注后五组MAP、心率、SpO2和OAA/S评分不同程度下降，但以D4组和D5组变化更明显。D1组、D2组和D3组低血压、心动过缓和过度镇静的发生率明显低于D4组和D5组（2/15、5/15和8/15比14/15和15/15，1/15、6/15、7/15比13/15和14/15，0、0和1/15比5/15和7/15），D1组、D2组和D3组低氧血症发生率明显低于D5组（0、0和0比3/15和4/15），差异有统计学意义（P〈0.05）；D4组与D5组各并发症发生率比较差异无统计学意义（P〉0.05）。结论 右美托咪啶用于老年硬膜外神经阻滞镇静的ED50为0.36 μg/kg，95% CI为0.27~0.44 μg/kg；输注右美托咪啶大于0.8 μg/kg时，对老年患者呼吸循环影响明显，不良反应增加。

Objective To study the median effective doses （ED50） of dexmedetomidine to induce adequate sedation in elderly patients undergoing epidural anaesthesia.Methods Seventy-five elderly patients undergoing lower extremity operation under epidural anesthesia were selected, and the patients were divided into 5 groups according to the random digits table method with 15 cases each： D1 group （dexmedetomidine 0.2 μg/kg）, D2 group （dexmedetomidine 0.4 μg/kg）, D3 group （dexmedetomidine 0.6μg/kg）, D4 group （dexmedetomidine 0.8 μg/kg） and D5 group （dexmedetomidine 1.0 μg/kg）. After 20 min of dexmedetomidine injection, adequate sedation was defines as observer′s assessment of alertness/sedation score （OAA/S score） ≤ 3 scores. The ED50 and 95% effective dose （ED95） of dexmedetomidine and 95% CI in elderly patients undergoing epidural anaesthesia were calculated by probit regression method. The changes of mean arterial pressure （MAP）, heart rate, pulse oxygen saturation （SpO2） and OAA/S score among 5 groups were compared. The incidences of adverse effects such as hypotension, bradycardia, hypoxemia and excessive sedation were compared.Results The ED50 in elderly patients was 0.36 μg/kg （95% CI 0.27-0.44 μg/kg）; the ED95 was 0.94 μg/kg （95% CI 0.71-1.62 μg/kg）. After dexmedetomidine injection, the MBP, heart rate, SpO2 and OAA/S scores in 5 groups were decreased, but in the D4 group and D5 group the decreases were more significant. The incidences of hypotension, bradycardia and excessive sedation in D1 group, D2 group and D3 group were significantly lower than those in D4 group and D5 group： 2/15, 5/15 and 8/15 vs. 14/15 and 15/15; 1/15, 6/15, 7/15 vs. 13/15 and 14/15; 0, 0 and 1/15 vs. 5/15 and 7/15, the incidences of hypoxemia in D1 group, D2 group and D3 group were significantly lower than those in D5 group： 0, 0 and 0 vs. 3/15 and 4/15, and there were statistical differences （P〈0.05）. There were no statistical differences in incidences of adverse effects between D4 group and D5 group （P〉0.05）.Conclusions The ED50 of dexmedetomidine in elderly patients undergoing epidural anaesthesia is 0.36 μg/kg, （CI 0.27-0.44 μg/kg）. The incidences of adverse effects are increased when single-dose dexmedetomidine is more than 0.8μg/kg.