Chabal C, Jacobson L, Little J
Department of Anesthesiology, University of Washington, School of Medicine, Seattle 98108.
Anesth Analg. 1988 Jun;67(6):509-13.
Intravenous narcotics increase the latency of somatosensory-evoked potentials (SSEPS), which are decreased but not abolished by epidural local anesthetics. In addition, intrathecal narcotics decrease spasticity in patients with central nervous system disease. This study of the effects of intrathecal fentanyl on posterior tibial SSEPS and the monosynaptic H-reflex arc found that intrathecal fentanyl had no effect on the latency of SSEPS, indicating the effects of narcotics on SSEPS are likely to exist at a supraspinal level. H-reflexes were not affected, confirming the lack of effect on this spinal motor reflex. In the same group of patients, intrathecal lidocaine administered 1 week later completely abolished SSEPS and H-reflexes. Complete suppression of SSEPS corresponded to full motor blockade, but sensation to pain and temperature was already many dermatomes higher than the S1 level. Return of SSEPS occurred with return of motor but not sensory function, indicating the likelihood that SSEPS are carried at least in part by large A-fibers. The study shows that spinal narcotics neither affect the transmission of SSEPS nor decrease the H-reflex, a spinal motor reflex. In addition, changes in SSEPS after intrathecal lidocaine do not correlate with the level of surgical anesthesia.
静脉注射麻醉药会延长体感诱发电位（SSEPS）的潜伏期，而硬膜外局部麻醉药会使其潜伏期缩短但不会消除。此外，鞘内注射麻醉药可减轻中枢神经系统疾病患者的痉挛。这项关于鞘内注射芬太尼对胫后SSEPS和单突触H反射弧影响的研究发现，鞘内注射芬太尼对SSEPS的潜伏期没有影响，这表明麻醉药对SSEPS的作用可能存在于脊髓以上水平。H反射未受影响，证实了对该脊髓运动反射无作用。在同一组患者中，1周后注射的鞘内利多卡因完全消除了SSEPS和H反射。SSEPS的完全抑制与完全运动阻滞相对应，但疼痛和温度感觉已经比S1节段高出多个皮节。SSEPS随着运动功能而非感觉功能的恢复而恢复，这表明SSEPS至少部分由粗大的A纤维传导。该研究表明，脊髓麻醉药既不影响SSEPS的传导，也不降低H反射（一种脊髓运动反射）。此外，鞘内注射利多卡因后SSEPS的变化与手术麻醉水平无关。
