异丙酚镇静对硬膜外麻醉患者大脑皮层不同区域的作用及对记忆的影响

Effects of propofol sedation on different areas of cerebral cortex and memory in patients during epidural anesthesia

目的探讨异丙酚镇静对硬膜外麻醉患者大脑皮层不同区域的作用及对记忆的影响, 分析内隐记忆消失时的脑电非线性参数近似熵界值。方法10例择期行腹部或下肢手术患者,采用硬膜外麻醉,术中持续输注异丙酚镇静,输注速率为6 mg·kg-1·h-1,监测异丙酚给药前后近似熵及近似熵脑电非线性地形图。应用分离加工测试方法,调查内隐记忆和外显记忆的成绩。常规监测血液动力学参数。结果与入室后相比,镇静后近似熵降低(P<0.05)。与镇静前相比,镇静后外显记忆和内隐记忆成绩均下降(P<0.05)。内隐记忆消失时数近似熵为0.55。通过近似熵脑电非线性地形图动态观察发现,异丙酚对大脑皮层各区域抑制顺序是:顶叶区、枕叶区→额叶区、颞叶区→全脑皮层;各脑区恢复顺序是:额叶区和颞叶区→顶叶区和枕叶区→全脑皮层。结论硬膜外麻醉患者应用异丙酚镇静,近似熵低于0.55时,内隐记忆消失。异丙酚对大脑皮层各区域的抑制和恢复有一定的规律。

Objective To investigate the effeets of propofol sedation on different areas of eerebral eortex and memory during operation performed under epidural anesthesia using EEG non-linear monitor and determine the critical value of approximate entropy, the EEG non-linear parameter, without implicit memory. Methods Ten ASA Ⅰ or Ⅱ patients of both sexes aged 42-56 yr weighing 59-73 kg undergoing eleetive abdominal or lower limb operation under epidural anesthesia were enrolled in the study. The patients were unpremedieated. After correct placement of epidural catheter was confirmed, a mixture of 2% lidoeaine and 0.3% tetraeaine 13-15 ml was injected via the eatheter. Propofol was then infused i.v. at 6 mg· kg^-1 · h^-1 for sedation. BP, HR and SpO2 were continuously monitored. The EEG non-linear monitor （ZN16E） was used. The sensors were plaeed on frontal （FP1 , FP2 ） , temporal （ T3 , T4 ）, parietal （ C3 , C4 ） and occipital （ O1 ,O2 ） regions. Approximate entropy and topographic map of approximate entropy were recorded before and during propofol infusion. Sedation scores （OAA/S, 1 = deep sleep, 5 = alert） were assessed during operation. The patients＇ explieit and implieit memory scores were estimated by Process Dissociation Procedure during anesthesia sedateon. Results The approximate entropy was signifieantly deereased during propofol sedation eompared to the baseline value before sedation. OAA/S score were maintained at 1 during operation. The explicit and implicit memory scores were significantly decreased during propofol sedation eompared to the baseline seores before anesthesia sedation（ P 〈 0.05）. The eritieal value of approximate entropy without implicit memory was 0.55. According to the topographic map of approximate entropy the sequence of inhibitory effect of propofol on the cerebral cortex was： parietal and oeeipital area → frontal and temporal area → the whole cortex. The sequence of recovery was： frontal and temporal area → parietal and oeeipital area → the whole cortex. Conclusion During propofol sedation of patients undergoing operation under epidural anesthesia approximate entropy should be kept below 0.55. The sequence of propofol inhibitory effect on cortex and recovery are in regular order.