氧化亚氮麻醉诱导时听觉诱发电位指数、脑电双频指数和边缘频率的变化

Changes in auditory evoked potential index, bispectral index and 95% spectral edge frequency during induction of anesthesia with nitrous oxide

目的 评价听觉诱发电位指数（AAI）监测氧化亚氮麻醉深度的可行性。方法 选择16例ASAI～Ⅱ级、在全身麻醉下择期手术的成年病人。监测AAI、双频指数（BIS）和95％边缘频率（95％SEF）。用面罩吸氧去氮,5min后吸入氧气与氧化亚氮的混合气体,总流量为10L·min-1。呼气末氧化亚氮浓度分别为0％、10％、20％、30％、40％、50％、60％和70％时,依据OAA/S评分法评估镇静程度。对比分析不同呼气末氧化亚氮浓度和OAA/S评分时AAI、BIS和95％SEF的变化。结果随着呼气末氧化亚氮浓度的增加,病人镇静程度逐渐加深。AAI与呼气末氧化亚氮浓度和 OAA/S评分值显著相关（Spearman’s等级相关系数r=-0.739和0.837,P<0.01）。BIS和95％SEF诱导期无明显变化。意识消失前AAI值与意识消失后相比有显著性差异（P<0.05）。结论 AAI可用于监测氧化亚氮的麻醉作用。

Objective To evaluate the feasibility of using auditory evoked potential index(AAI) to monitor the depth of nitrous oxide anesthesia. Methods Sixteen ASAⅠ-Ⅱpatients aged 23-64 years, weighing 51-86 kg scheduled for elective surgery under general anesthesia were studied. Patients with psychoneural diseases and hearing disturbances were excluded. The patients were premedicated with phenobarbital sodium 0.1g and atropine 0.5mg. AAI, BIS, 95% SEF, BP, HR, SpO2 monitoring were started before induction of anesthesia. The patients were preoxygenated for 5 min using a close-fitting face mask and 100% O2 at l0L·min-1 . Inhalation of nitrous oxide was then started. Nitrous oxide concentration was gradually increased in increments of 10% from 0% to 70% . AAI, BIS and 95%SEF were recorded and observer's assessment of alertness/sedation (OAA/S) scores were measured at each 10% increment of end-tidal nitrous oxide concentration which was maintained for 5 min. The correlation between AAI, BIS, 95% SEF and OAA/S scores was analyzed. Results OAA/S scores and AAI decreased as the nitrous oxide concentration increased. AAI correlated closely with OAA/S scores and end-tidal nitrous oxide concentration (the coefficients of Spearman' s rank correlation γ = - 0.739, 0.837, P< 0.01) . BIS and 95% SEF changed little during induction of anesthesia. Conclusion AAI can be used to assess the depth of nitrous oxide anesthesia, whereas BIS and 95% SEF can not.