Münte Sinikka, Schmidt Maren, Meyer Maren, Nager Wido, Lüllwitz Ekkehard, Münte Thomas F, Piepenbrock Siegfried
Department of Anaesthesia, Medical School of Hanover, Hanover, Germany.
Anesthesiology. 2002 Mar;96(3):588-94. doi: 10.1097/00000542-200203000-00013.
Unconscious processing of words during general anesthesia has been suggested after surgery with several tests of implicit memory. Patients can neither recall those words nor do they have explicit memories of other intraoperative events. It is unclear to what degree information is processed during general anesthesia and which tests are best suited to detect implicit memory. In the current study, a lexical decision paradigm not previously used to demonstrate implicit memory during anesthesia was used.
Sixty patients undergoing lumbar disc surgery were assigned to receive isoflurane infusion- or propofol infusion-based anesthesia combined with alfentanil infusions and a nitrous oxide-oxygen mixture. A control group of 10 medical students listened to tapes without receiving anesthesia. Two tapes, each containing a list of 30 low-frequency German nouns repeated for 15 min, were prepared, with half of the patients listening to tape A and the other half listening to tape B during the operation. Exposure time was 15 min from the time of skin incision onward. In the test phase, approximately 7 h later, words from lists A and B plus 60 nonwords were presented in random order by a computer program. Subjects were asked to indicate, by pressing one of two response buttons, whether the spoken word was or was not a legal German word (lexical decision).
A recognition test revealed chance recognition for words presented during anesthesia. Lexical decision responses, however, were slightly faster to primed (previously presented) words than to unprimed (not previously presented) words when the entire group of patients was tested, suggesting a small implicit memory effect, which barely failed to reach the significance level. When the two medication groups were tested separately, no significant implicit memory effect could be ascertained statistically. The effects of previous exposure were much more pronounced in the control group.
Balanced anesthesia techniques with isoflurane or propofol lead to only a minimal, statistically borderline implicit memory effect in the lexical decision paradigm.
在手术后通过几项内隐记忆测试表明，全身麻醉期间存在对单词的无意识加工。患者既无法回忆起这些单词，也没有对其他术中事件的外显记忆。目前尚不清楚全身麻醉期间信息被加工到何种程度，以及哪些测试最适合检测内隐记忆。在本研究中，使用了一种先前未用于证明麻醉期间内隐记忆的词汇判断范式。
60例接受腰椎间盘手术的患者被分配接受基于异氟醚输注或丙泊酚输注的麻醉，联合阿芬太尼输注和氧化亚氮 - 氧气混合气体。10名医学生组成的对照组在不接受麻醉的情况下听磁带。准备了两盘磁带，每盘磁带包含一份由30个低频德语名词组成的列表，重复播放15分钟，手术期间一半患者听磁带A，另一半听磁带B。从皮肤切开时起暴露时间为15分钟。在测试阶段，大约7小时后，计算机程序以随机顺序呈现来自列表A和B的单词以及60个非单词。要求受试者通过按下两个响应按钮之一来表明所听到的单词是否为合法的德语单词（词汇判断）。
一项识别测试显示，对麻醉期间呈现的单词的识别率为随机水平。然而，当对全体患者进行测试时，对启动（先前呈现过）单词的词汇判断反应比对未启动（先前未呈现过）单词的反应略快，表明存在较小的内隐记忆效应，但几乎未达到显著水平。当分别对两个用药组进行测试时，在统计学上无法确定显著的内隐记忆效应。先前暴露的影响在对照组中更为明显。
在词汇判断范式中，使用异氟醚或丙泊酚的平衡麻醉技术仅导致极小的、统计学上接近临界值的内隐记忆效应。
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