Kawaguchi M, Shimizu K, Furuya H, Sakamoto T, Ohnishi H, Karasawa J
Department of Anesthesiology, Nara Medical University, Japan.
Anesthesiology. 1996 Nov;85(5):1176-83. doi: 10.1097/00000542-199611000-00027.
The clinical application of intraoperative motor-evoked potentials (MEPs) has been hampered by their sensitivity to anesthetics. Recently, to overcome anesthetic-induced depression of myogenic MEPs, multiple stimulus setups with a paired or a train of pulses for stimulation of the motor cortex were reported. However, the effects of anesthetics on MEPs induced by these stimulation techniques are unknown.
Bipolar electrical stimulation of the left motor cortex was carried out in 15 rats anesthetized with thiopental while the compound muscle action potentials were recorded from the contralateral hind limb. After recording of the MEP in response to the single-shock stimulation of the motor cortex, paired pulses (double pulses) or a train of three pulses (triple pulses) with an interstimulus interval of each pulse at 0.3, 0.5, 1.0, 1.5, and 2.0 ms were applied. After control MEP recording, isoflurane was administered at a concentration of 0.25 minimum alveolar anesthetic concentration (MAC), 0.5 MAC, 0.75 MAC, and 1.0 MAC, and the effects of isoflurane on the MEPs induced by single, double, and triple pulses were evaluated.
In all animals, distinct baseline MEPs were recorded. During the administration of 0.25 MAC and 0.5 MAC isoflurane, MEPs induced by stimulation with a single pulse could be recorded in 87% and 33% of animals, respectively, and MEP amplitude was significantly reduced in a dose-dependent manner. During the administration of 0.75 MAC isoflurane, MEPs after single-pulse stimulation could not be recorded in any animals. By stimulating with paired or triple pulses, the success rate of MEP recording and MEP amplitude significantly increased compared with those after single pulse before and during the administration of isoflurane. Both the success rate of MEP recording and MEP amplitude after double- and triple-pulse stimulation decreased significantly in a dose-dependent manner during the administration of isoflurane.
Application of double or triple stimulation of the motor cortex increases the success rate of MEP recording and its amplitude during isoflurane anesthesia in rats. However, these responses are suppressed by isoflurane in a dose-dependent manner.
术中运动诱发电位（MEP）的临床应用因其对麻醉剂的敏感性而受到阻碍。最近，为了克服麻醉剂引起的肌源性MEP抑制，有报道采用成对或一串脉冲的多种刺激设置来刺激运动皮层。然而，麻醉剂对这些刺激技术诱发的MEP的影响尚不清楚。
对15只硫喷妥钠麻醉的大鼠进行左侧运动皮层的双极电刺激，同时记录对侧后肢的复合肌肉动作电位。在记录对运动皮层单脉冲刺激的MEP后，施加成对脉冲（双脉冲）或一串三个脉冲（三脉冲），每个脉冲的刺激间隔为0.3、0.5、1.0、1.5和2.0毫秒。在对照MEP记录后，以0.25最低肺泡麻醉浓度（MAC）、0.5 MAC、0.75 MAC和1.0 MAC的浓度给予异氟烷，并评估异氟烷对单、双和三脉冲诱发的MEP的影响。
在所有动物中均记录到明显的基线MEP。在给予0.25 MAC和0.5 MAC异氟烷期间，分别有87%和33%的动物可记录到单脉冲刺激诱发的MEP，且MEP波幅以剂量依赖性方式显著降低。在给予0.75 MAC异氟烷期间，任何动物均未记录到单脉冲刺激后的MEP。通过成对或三脉冲刺激，与异氟烷给药前和给药期间单脉冲刺激后的情况相比，MEP记录成功率和MEP波幅显著增加。在给予异氟烷期间，双脉冲和三脉冲刺激后的MEP记录成功率和MEP波幅均以剂量依赖性方式显著降低。
在大鼠异氟烷麻醉期间，对运动皮层进行双刺激或三刺激可提高MEP记录成功率及其波幅。然而，这些反应会被异氟烷以剂量依赖性方式抑制。
