无肌松药条件下七氟烷诱导时右美托咪定对瑞芬太尼维持最佳气管插管条件的半数有效血浆浓度的影响

目的:探讨无肌松药条件下七氟烷诱导时右美托咪定对瑞芬太尼维持最佳气管插管条件的半数有效血浆浓度(Cp50)的影响。方法:择期全麻手术患者45例，采用随机数字表法分为右美托咪定组（D组，n=21）和对照组（C组，n=24）。D组泵注右美托咪定0.6 μg/kg，持续时间15 min，C组泵注等量生理盐水。采用8%七氟烷肺活量法诱导，待眼睑反射消失后，维持呼气末七氟烷浓度（CETSev）为3%，同时瑞芬太尼靶控输注，初始血浆靶浓度分别设置为3 ng/mL（D组）和4 ng/mL（C组），并按照改良Dixon序贯法调整各组下一例瑞芬太尼的浓度(浓度梯度为0.2 ng/mL)，达到瑞芬太尼血浆靶浓度90 s后喉镜检查评估并行气管插管。比较两组的气管插管条件和血流动力学。结果:C组和D组瑞芬太尼维持最佳气管插管条件的Cp50分别为3.079 ng/mL（95% CI 2.898～3.240）和2.468 ng/mL（95% CI 2.239～2.630）。结论:在七氟烷诱导并无肌松药条件下，右美托咪定可使瑞芬太尼维持最佳气管插管条件的靶控Cp50降低19.8%。

Effects of dexmedetomidine on the median effective plasma concentration of remifentanil for excellent tracheal intubation during sevoflurane induction without neuromuscular blockade

AIM: To explore the effects of dexmedetomidine on the 50% effective plasma concentration (Cp50) of remifentanil for excellent tracheal intubation during sevoflurane induction without neuromuscular blockade. METHODS: Forty-five patients undergoing selective general anesthesia were randomly assigned into two groups: infusion of 0.6 μg/kg dexmedetomidine over 15 min (group D, n=21), saline group (group C, n=24)．For induction, 8% sevoflurane induction was immediately begun in vital capacity until the loss of eyelash reflex, with end-tidal sevoflurane 3% subsequently was maintained. And the initial doses of remifentanil target-controlled infusion were set at 3 ng/mL for group D and 4 ng/mL for group C, and were decreased or increased by 0.2 ng/mL in the next patient using the Dixon's up-and-down method based on the success or failure of intubation. Laryngoscopy and intubation were performed, 90 s after achieving the target concentration of remifentanil. Tracheal intubation conditions and hemodynamics were recorded and compared.RESULTS:In group C and group D, the Cp50 of remifentanil for successful tracheal intubation were 3.079 ng/mL（95% CI 2.898-3.240）and 2.468 ng/mL（95% CI 2.239-2.630), respectively. CONCLUSION:Dexmedetomidine contributes to the reduced Cp50 of remifentanil by 19.8% for excellent tracheal intubation during sevoflurane induction without neuromuscular blockade．