全身麻醉药对短潜伏期体感诱发电位的影响

目的为术中进行体感诱发电位监测选择合适的全身麻醉药及剂量。方法将150例神经外科择期手术病人利用随机排列表分成静脉组和吸入组。静脉组90例,分为异丙酚(1．5mg/kg、2mg/kg、3mg／kg)、咪哒唑仑(0．2mg／kg、0．3mg／kg、0.4mg/kg)和依托咪酯(0．15mg／kg、0．3mg／kg、0．4mg／kg)9个组,每组10例,观察用药后对短潜伏期体感诱发电位(short latency somatosensory evoked potential,SLSEP)的影响;吸入组60例,分为安氟醚、异氟醚和地氟醚组,每组20例,按呼气末浓度0．3、0．5、0．75、1．0和1．5最低肺泡有效浓度(MAC)进行观察。观察指标为N14、N20和中枢传导时间(CCT)。结果静脉药中异丙酚能明显抑制N20波幅,但N14、N20的潜伏期和CCT的影响不明显,咪哒唑仑抑制N20波幅,延长N20的潜伏期和CCT,依托咪酯明显增大N20波幅,且病人已清醒睁眼时该作用仍未消退。吸入药均表现出对N20和CCT的影响,安氟醚在1．0MAC时出现波形消失,而异氟醚和地氟醚则在1．5MAC才出现该现象。结论在全身麻醉病人进行SLSEP监测时,全麻诱导时可选择依托咪酯,在全麻维持阶段,吸入麻醉药可选择异氟醚或地氟醚,浓度应控制在1．0MAC以下。

Effects of intravenous and inhalational anesthetics on short-latency somatosensory evoked potentials

OBJECTIVE: To choose suitable general anesthetics dosages when short-latency somatosensory evoked potentials (SLSEP) is monitored during operation. METHODS: 150 ASA I-II neurosurgical patients undergoing elective operations were randomly divided into intravenous anesthesia group of 90 patients and inhalation anesthesia group of 60 patients. The intravenous anesthesia group was further divided into 9 subgroups of 10 patients treated with different anesthetics of different dosages: propofol (1.5 mg/kg, 2 mg/kg, and 3 mg/kg), midazolam (0.2 mg/kg, 0.3 mg/kg, and 0.4 mg/kg), and etomidate (0.15 mg/kg, 0.3 mg/kg, and 0.4 mg/kg). The intravenous anesthetics were given and upper limb SLSEP was monitored continuously. The inhalation anesthesia group was further divided into enflurane, isoflurane and desflurane subgroups of 20 patients each. The inhalational anesthetics were given at the concentrations corresponding to the end-expiratory concentrations of 0 to 0.3, 0.5, 0.75, 1.0 and 1.5 MAC. The changes of N(14), N(20) and central conduction time (CCT) were recorded. In addition to SLSEP, EKG, NIBP, SpO(2), P(ET) CO(2) were monitored as well as end-tidal anesthetic concentration. During the experiment SpO(2) was maintained > 95% and P(ET) CO(2) was maintained at the range of 35 - 45 mmHg by mask oxygen or assisted ventilation. RESULTS: The intravenous anesthetic propofol significantly decreased N(20) amplitude and produced less effect on the latency of N(14), N(20) and CCT. Midazolam significantly decreased the N(20) amplitude and prolonged the latency of N(20) and CCT. Etomidate significantly increased the N(20) amplitude, and the change did not recover when the patients had opened their eyes 10 minutes after medication. All three inhalational anesthetics significantly decreased the N(20) amplitude and prolonged the N(20) latency and CCT. N(20) amplitude disappeared in some patients treated with enflurane when the end-expiratory concentration was 1.0 MAC, while disappeared in some patients treated with isoflurane and desflurane when the end-expiratory concentration was 1.5 MAC for these 2 drugs. CONCLUSION: When using SLSEP monitoring, the most suitable general anesthetic is etomidate during the induction stage and isoflurane and desflurane during the maintenance stage with the end-expiratory concentration below 1.0 MAC.