右美托咪定对肢体缺血再灌注后患者肺换气的影响

Effects of dexmedetomidine on gas exchange following limb ischemia reperfusion in patients induced by tourniquet

目的:观察右美托咪定对上肢止血带诱发肢体缺血再灌注后肺换气的影响。方法:前臂或者手部需要止血带进行手术的患者40例,采用随机数字表法,将患者分成两组(n=20):对照组(C组),右美托咪定组(D组)。D组患者在完成肌间沟臂丛神经阻滞后静脉泵注右美托咪啶负荷剂量1μg/kg,持续10 min,随后以0.5μg·kg-^(1)·h^(-1)速率直到手术结束;C组患者相同方法静脉泵注等量生理盐水。待麻醉起效后上止血带,分别在上止血带即刻(T_0)、上止血带后1 h(T_1)、松止血带后0.5 h(T_2)、2 h(T_3)、6 h(T_4)和24 h(T_5)取动脉血进行血气分析和测定血浆超氧化物歧化酶(SOD)和丙二醛(MDA)浓度,记录动脉血二氧化碳分压(Pa CO_2)、动脉血氧分压(PaO_2),按照公式计算肺泡动脉血氧分压差(PA-a DO_2)、呼吸指数(RI)和动脉血/肺泡氧分压比值(a/A比值)。结果:与T0比较,两组患者T4时Pa O2、a/A比值下降,PA-a DO_2、RI比值上升,D组上升幅度比C组大。与T0比较,C组T_(3-5)时血浆MDA浓度升高、SOD浓度降低,D组仅在T_4时血浆MDA浓度升高、SOD浓度降低,MDA浓度增加幅度明显低于C组,SOD浓度降低幅度明显低于C组。结论:右美托咪定改善肢体缺血再灌注后患者的肺换气功能,其可能的机制是右美托咪定可以增加体内氧自由基清除剂(SOD)从而减少体内脂质过氧化反应(MDA),减少肢体缺血再灌注过程中脂质过氧化损伤。

AIM： To investigate the effect of dexmedetomidine on gas exchange following limb ischemia reperfusion in patients induced by tourniquet. METHODS： Forty patients undergoing forearm or hand operation were randomly divided into 2 groups： control group（ C group） and dexmedetomidine group（ D group）. In D group,a dexmedetomidine intravenous infusion was started immediately after the interscalene brachial plexus anesthesia at a dose of 11 μg/kg for 10 min, followed by 0.5 μg·kg-^（1）·h^（-1）until the end of the operation.The equivalent volume of saline was infused in the control group. Arterial blood samples were collected immediately before using tourniquet（ T_0）,1 h after using tourniquet（ T_1） and 0. 5 h（ T_2）,2 h（ T_3）,6h（ T_4） and 24 h（ T_5） after ending using tourniquet for blood gas analysis and detection of MDA and SOD. Record Pa CO_2 and Pa O_2,and calculate PAa DO_2,RI and a /A ration according to formula. RESULTS： Compared with T_0,Pa O_2 and a / A ration was decreased, while PA-a DO_2 and RI was increased in T_4,but the change in group C were less than that in D group. Compared with T_0,SOD level was decreased and MDA was increased in T_（3-5） of C groups,but only T_4 of D group. Compared with C group,SOD level was increased and MDA was decreased in T_（3-5） of D groups. CONCLUSION：Dexmedetomidine improve gas exchange following limb ischemia reperfusion in patients induced by tourniquet,which possible mechanism was increasing oxygen free radical scavenger（ SOD） to reduce lipid peroxidation（ MDA） in body,reducing lipid peroxidation damage induced by limb ischemia reperfusion.