硬膜外利多卡因对异氟醚和地氟醚MAC的影响

Effect of epidural Udocaine on minimum alveolar concentration of isoflurane and desflurane

目的 本研究以BIS>50作为指标来确定异氟醚和地氟醚的ED50值(MACBIS50),观察硬膜外利多卡因对异氟醚和地氟醚达到满意麻醉深度时用药量的影响。方法 48例患者随机分为两组:异氟醚组和地氟醚组,每组又随机分全麻复合硬膜外组和单纯全麻组(每组12例)。患者术前阿托品肌肉注射,全麻复合硬膜外组给予1.6％利多卡因10ml。全麻诱导采用咪达唑仑、芬太尼、异丙酚和维库溴铵,诱导插管后吸入异氟醚和地氟醚,待呼气末浓度(ET％)达到预定值并且稳定10 min后,记录相应的BIS值。采用上下波动法分别计算异氟醚和地氟醚MACBIS50,BIS值和呼气末浓度进行直线回归分析。结果MACBIS50全麻复合硬膜外组(异氟醚组0.77％、地氟醚组3.87％)和单纯全麻组(异氟醚组1.16％、地氟醚组5.18％)比较显著降低(P<0.01)。四组BIS和ET％均呈直线相关。结论硬膜外利多卡因可显著降低异氟醚(34％)和地氟醚(53％)维持足够麻醉深度的呼气末浓度,并保持BIS值和呼气末浓度的直线相关性。

Objective To determine the ED50 of isoflurane and desflurane in the presence and absence of epidural lidocaine using BIS value 50 as the criterion (MACBIS50 ) .Methods Forty-eight ASA I - II patients (26 male, 22 female) aged 18-70 years were randomly divided into isoflurane group ( n = 24) and desflurane group ( n = 24).Each group was further divided into 2 subgroups: general anesthesia group(GA, n = 12) and combined general-epidural anesthesia (CGEA, n = 12) . Patients with body weight over 110kg or under 50kg were excluded. The patients were premedicated with intramuscular atropine 0.01 mg·kg-1 . In CGEA subgroup epidural anesthesia was performed at T5-6 before induction of general anesthesia. A catheter was inserted into the epidural space in a cephalad direction for 3cm. A loading dose of 10ml of 1.6% lidocaine with 1:200 000 adrenaline was given after test dose followed by 5 ml 1.6% lidocaine every 40-60 min. General anesthesia was induced with fentanyl 1 μg·kg-1, propofol 0.5-1.0 mg·kg-1 and vecuronium 0.1-0.2 mg·kg-1 . The patients were intubated and mechanically ventilated (FiO2 = 100% , FGF = 2 L·min-1 , VT = 8-10 ml·kg-1, PET CO2 = 35 mm Hg) . Anesthesia was maintained with isoflurane or desflurane. The end-tidal concentration of isoflurane and desflurane was continuously monitored and BIS also. MACBIS50 was measured using up-and-down method. The initial concentration of anesthetic for isoflurane was 1.0% and for desflurane 5.0% . A steady state end-tidal concentration of isoflurane and desflurane was maintained for 10 min. When BIS value was < 50, the anesthetic concentration for the next patient decreased by 0.2% ( isoflurane group) or 0.5% (desflurane group) ; when BIS value was > 50 the anesthetic concentration for the next patient increased by the same amount. Results MACBIS50 of isoflurane in GA subgroup was 1.16% and in CGEA subgroup 0.77% . MACBIS50 of desflurane in GA subgroup was 5.18% and in CGEA subgroup 3.87% . There was linear correlation between BIS value and end-tidal concentration in each subgroup. Conclusion Epidural lidocaine significantly reduces the end-tidal concentration of isoflurane and desflurane for adequate depth of anesthesia. A linear correlation is maintained between BIS and end-tidal concentration.