Effects of epidural diamorphine on the somatosensory evoked potential to posterior tibial nerve stimulation

We have studied the effects of the epidural administration of diamorphine 0.1 mg/kg at the L3-4 interspace on somatosensory evoked potentials in the cervical epidural space before corrective surgery for idiopathic adolescent scoliosis. A further eight patients in whom anaesthesia was maintained with a propofol infusion acted as a control group. Epidural diamorphine had no effect on the latency or amplitude of the evoked potentials. We conclude that epidural diamorphine is a suitable technique to use in scoliosis surgery because of its lack of effect on neurophysiological variables, although the potential respiratory problems need investigation.     

Effects of temperature on somatosensory evoked potentials during open heart surgery

Somatosensory evoked potentials (SEPs) have been found to be useful for early detection of brain ischemia during hypothermic cardiopulmonary bypass in cardiac surgery. However, the relationship between temperature and latency period remains unclear. We prospectively analyzed SEPs obtained during hypothermic cardiopulmonary bypass in 20 patients who had valvular replacement.
We concluded that i) a linear correlation was found between temperature and latency period during cooling and rewarming, ii) no hysteresis effect existed in cooling and rewarming, iii) there was a greater hypothermic effect on the synaptic transmission than on the conduction velocity, and, iv) age had also more profound effect on relationship between temperature and latency of SEPs.     

躯体感觉诱发电位在脊柱手术监护中的应用

目的 探讨躯体感觉诱发电位（SEP）在脊柱手术监护中的应用价值。方法 分析４５８例脊柱手术中SEP监护的结果,特征,适用范围,其中颈部手术275例,胸椎,腰椎部手术183例,刺激电极为手指、足趾的环状电极或腕、踝的表面电极,记录电极为头皮针电极。结果 大部分患者的肌电图改变在器质性改变的范围内。409例（89．3％）,术中SEP有波幅轻度下降,潜伏期轻度延长,术后又恢复后近手术开始时水平;32例（7．1％）,SEP波幅有一定程度的提高,潜伏期部分缩短;12例（2．6％）有术中SEP明显恢复;2例（0．4％）术中未见SEP明显改变,术后有功能障碍;3例（0．7％）,术中出现SEP的波幅明显下降,潜伏期轻度延长,术持恢复欠佳。结论 SEP在脊柱手术监护中的作用是肯定的,但有一定的局限性。     

齿状突骨折对枕颈部生物力学影响的实验研究

为比较齿状突骨折后对寰枕和寰枢关节的生物力学影响，对６具新鲜尸体的枕颈部骨韧带标本（Ｃ０～Ｃ３），通过截骨术复制成齿状突骨折Ⅱ型的模型，采用生物力学方法测量了寰枕及寰枢关节的三维运动范围。结果表明，齿状突骨折后对寰枕关节的三维运动几无影响，该关节仍保持正常的生理性运动范围，对寰枢关节的影响主要表现为后伸及侧屈运动范围增大，后伸运动范围由正常的２１．５０°增至４５．４２°，增加５２．７％，侧屈的运动范围由正常的７．２５°增至２０．８１°，增加６５．１％，与正常相比均有显著性差异（Ｐ＜０．０１）。实验结果提示，齿状突骨折所致的枕颈部不稳主要集中在寰枢关节     

Effects of hypothermia and sternal retractors on median nerve somatosensory evoked potentials

Background: Somatosensory evoked potentials (SEPs) are altered by hypothermia, which is often used during cardiopulmonary bypass (CPB). However, the effect of hypothermia on SEP amplitudes is unclear. Also, the sternal retractors used during open heart surgery are reported to cause brachial plexus distension and SEP changes. Methods: Median nerve SEPs under hypothermic CPB were studied in 29 elective patients scheduled for open heart surgery. In 23 patients who underwent left internal mammary artery (IMA) dissection, the effects of sternal retractors on cortical SEP before the initiation of CPB were investigated. Results: A latency shift of all SEP components was detected when nasopharyngeal temperature decreased from 35.7(SD 0.4)°C to 27.8(SD 0.25)°C. The mean cortical N₂₀ latency was increased by 39% (P< 0.0001), cervical N₁₃ by 33% (P < 0.0001), and peripheral N₉ by 27% (P <0.0001). The latency changes were reversible when normothermia was restored. The effect of hypothermia on SEP amplitudes was more complex. The mean amplitude of N₂₀ decreased from 2.7 μV to 2.2 μV (P < 0.05) and the amplitude of N₁₃ from 2.5 μV to 2.0 μV (P < 0.0001). In contrast, the N₉ component showed an increase from 1.4 μV to 2.1 μV (P <0.0001) during hypothermia. The sternal retractors did not cause significant cortical SEP amplitude changes during IMA dissection or sternotomy. Also, the latency changes were small, although significant (P < 0.05). Conclusion: Despite the moderate amplitude changes produced by hypothermia, SEPs can be successfully monitored during hypothermia. Theoretically, the different behaviour of amplitude in peripheral and cranial components of SEP during hypothermia is interesting. Hypothermia has a more profound effect on synaptic transmission, represented by the cortical N₂₀ latency, than on the peripheral nerve conduction velocity. Intraoperative monitoring of temperature is essential whenever SEPs are recorded. The sternal retractors were not responsible for the intraoperative SEP changes.     

Brain dysfunction following vasospasm evaluated by somatosensory evoked potentials

Summary Somatosensory evoked potentials (SEP) were recorded in 9 patients with vasospasm caused by subarachnoid haemorrhage.There was a correlation between SEP changes and clinical outcome evaluated one month after onset.And, evaluation of SEP changes under induced hypertension or infusion of dehydrates was available to study the nature of ischaemic brain dysfunction caused by vasospasm.Furthermore, this study suggests that the available period of induced hypertension may be short in cases with severe clinical outcomes.     

Effects of abdominal surgery on somatosensory evoked potentials during nitrous oxide-enflurane anesthesia

The effect of abdominal surgery on median nerve somatosensory evoked potentials (SEPs) was studied in 8 enflurane and nitorous oxide anesthesia (GOE) patients. We further compared the effect of epidural anesthesia. The first recording was done immediately prior to induction. Anesthesia was then induced with 5mg·kg^–1 i.v. of thiopental and maintained with 1.0% enflurane, 66% N₂O and 33% O₂. Before skin incision for abdominal surgery, the second recording was performed under GOE anesthesia and the third recording during surgery. Then 2% lidocaine was injected into the epidural space through a preinserted catheter, and after 15min the fourth recording was obtained. The latencies of peaks N1, P2 and N2 and the amplitudes of N1-P2 and P2-N2 were measured. The latencies of N1, P2 and N2 increased and the amplitudes of N1-P2 and P2-N2 deceased significantly after the induction of anesthesia compared with the control values. During abdominal surgery the latencies of N1 and P2 decreased and the amplitudes of N1-P2 and P2-N2 increased. After epidural anesthesia, however, the latencies of N1 and P2 increased and the amplitudes of N1-P2 and P2-N2 decreased significantly and returned almost to the values recorded under preoperative GOE anesthesia. These phenomena indicated that the excitations produced by surgical stimulation in nerve ending might have been transmitted to the central nervous system via spinal nerves and blocked by epidural anesthesia.(Kasaba T, Kosaka Y: Effects of abdominal surgery on somatosensory evoked potentials during oxide-enflurane anesthesia. J Anesth 5: 281–286, 1991)     

Etidocaine and extradural somatosensory evoked potentials after posterior tibial nerve stimulation

We have examined the effects of lumbar extradural administrationof 1% etidocaine 10 ml on somatosensory evoked potentials toposterior tibial nerve stimulation measured in the cervicalextradural space. Eight patients, anaesthetized with propofoland nitrous oxide, were studied before hysterectomy and a controlgroup received a similar anaesthetic and 0.9% sodium chloridesolution 10 ml in the lumbar extradural space. Etidocaine decreasedsignificantly overall amplitude of the evoked potentials andthe amplitudes of all peaks, between 30 and 50 min after extraduralinjection. The effects of etidocaine on spinal cord conductionwere greater than those found previously for lignocaine andbupivacaine, suggesting that it is the local analgesic of choicefor inhibiting afferent conduction.     

右美托咪定对特发性脊柱侧弯矫形术中体感诱发电位和运动诱发电位的影响

目的:研究右美托咪定（dexmedetomidine, Dex）对特发性脊柱侧弯矫形术中体感诱发电位（somatosensory evoked potentials, SEPs）和经颅电刺激运动诱发电位（transcranial electric motor evoked potentials, TCeMEPs）的影响...     

体感诱发电位量化监护在腰椎滑脱复位内固定术中的应用

目的在下腰椎滑脱复位内固定术中应用节段性皮神经刺激体感诱发电位(SEP)监护,最大限度复位滑脱、解除症状的同时,减少术后并发症.方法利用节段性皮神经刺激SEP技术对52例下腰椎滑脱复位内固定术前、术中监测和术后远期随访,对术后功能改善优良患者的术中电位变化情况进行回顾性研究,确定术中有效的监护指标,为手术监护提供参考.结果以患者术前麻醉后SEP指标值为基础,术中监测电位指标变化表现形式①滑脱复位后,若潜伏期缩短10%～15%或波幅增加＞40%,提示预后良好;②监测电位指标平稳,或潜伏期缩短＜10%,或波幅增加＜30%,可继续完成复位,术后可有部分功能恢复和症状改善;③复位过程中,监测电位指标出现暂时性波动,可在15～20 min内恢复到基础电位,应在电位出现波动时停止复位,术后仍可恢复部分功能和改善症状.④若术中监测电位潜伏期延长＞5%,或波幅降低＞10%,或部分成分消失或波形离散提示术后出现疼痛和运动障碍加重,术中应做必要调整.该方法术中监护指标改善与术后功能恢复状态符合率达93.75%.结论节段性皮神经刺激SEP是下腰椎滑脱复位内固定术中监护,指导减压、复位、固定的客观而有效的方法.     

皮层体感诱发电位及经颅电刺激运动诱发电位联合监护在脊柱畸形矫正术中的应用

目的:探讨脊柱畸形矫正术中皮层体感诱发电位(CSEP)及经颅电刺激运动诱发电位(TES-MEP)联合监护在脊柱畸形矫正手术中的应用。方法:对我院收治的脊柱畸形患者根据术中监护方法分为两组:A组37例,其中男25例,女12例,年龄13～42岁,平均26.1岁,术中进行CSEP及TES-MEP联合监护;B组29例,其中男10例,女19例,年龄13～20岁,平均15.8岁,单纯采用CSEP监护作为对照组。术中持续观察CSEP及TES-MEP波幅及潜伏期变化,出现波幅下降50%、潜伏期延长10%或刺激强度高于初始刺激强度100V仍未引出者,停止手术并对症处理,术后给予激素治疗。结果:A组术中出现CSEP异常者4例(10.8%),TES-MEP异常者19例(60%)。术中CSEP及TES-MEP均异常者4例(10.8%),无术中CSEP异常而TES-MEP正常者。2例(陈旧性结核并后凸畸形1例,陈旧性骨折并后凸畸形1例)术中合拢截骨平面时,TES-MEP波形均消失,但仅1例出现CSEP异常,经术中积极处理,至手术结束时波形仍未恢复至术前水平,术后均出现神经功能障碍。余35例患者术后无神经功能损伤(假阴性率0%)。B组9例(21%)术中出现CSEP波形异常,其中2例虽经减少矫形角度及激素冲击治疗,术后仍出现双下肢瘫,余术后未出现神经功能障碍。3例术中监护未见异常者,术后出现重度不可逆性脊髓损伤(假阴性率10%)。结论:CSEP结合TES-MEP联合监护能较可靠、准确的反映术中脊髓功能状态,可降低监护假阴性率,为手术治疗过程提供参考。     

The effect of tracheal intubation and surgical stimulation on median nerve somatosensory evoked potentials during anaesthesia

This study was designed to determine whether alterations in the median nerve somatosensory evoked potentials occur during the stimuli of tracheal intubation and skin incision. Twenty-two patients scheduled for elective surgery and who required tracheal intubation were studied. Median nerve somatosensory evoked potentials were recorded, analysed and stored approximately every 40 seconds. Anaesthesia was induced with thiopentone and vecuronium used for neuromuscular blockade; the trachea was intubated 2 minutes after induction. Fentanyl 1.5 micrograms/kg was administered subsequently. Evoked potential monitoring was continued until at least 2 minutes after surgical incision. Induction of anaesthesia was associated with an increase in evoked potential latency of 0.8 msec and reduction in amplitude of 1.7 microV. Small, statistically insignificant changes occurred between induction of anaesthesia and tracheal intubation. Surgical incision was accompanied by a statistically significant mean decrease in evoked potential latency of 0.5 msec and a statistically significant increase in evoked potential amplitude of 0.6 microV. The fact that surgical stimulation produced an activating effect on evoked potentials suggests that they may be used as a measure of the neurophysiological effects of anaesthesia.     

Anesthetic induction with thiopental: its effect on scalp topography of median nerve somatosensory evoked potentials

The effects on median nerve somatosensory evoked potentials (SEPs) of analgesic doses of fentanyl, meperidine or morphine and of sodium thiopental (STP) anesthesia (4 mg/kg) were tested in 36 surgical patients. We also explored changes in SEP components as a function of their scalp location. Before and after medication, responses were recorded from the scalp overlying the parietal cortex (ipsi- and contralateral to the stimulated arm) and the precentral (contralateral) cortex. None of the three opiates affected SEP latencies or amplitudes. The barbiturate increased the amplitudes of subcortical and early cortical components (N18, N20, P22, P25), whose latencies, however, were not significantly modified. The effect of STP on later SEP cortical components depended on their scalp topography: parietal N33 and P45 underwent significant changes in both latency and amplitude, whereas precentral N30 showed a significant amplitude increase only. Thiopental anesthesia produces clearer short-latency SEP recordings, from both parietal (components N20-P25) and precentral (P22, N30) areas.     

A rare case of a somatosensory evoked potentials recording during cardiopulmonary resuscitation

Background: Neuronal damage is a possible complication of cardiac surgery. To reduce the potential risk of postoperative neurological deficit, the functional state of affectedcentral nervous system pathways is monitored intraoperatively by recording evoked potentials (EPs). Apart from animal research, there is little clinical evidence of EPs recordingduring cardiac arrest and cardio-pulmonary resuscitation (CPR).
Methods: Both scalp (SCEPs) and spinal (SSEPs) short-latency somatosensory EPs were recorded as the response to theelectrical stimulation of the right median nerve during mitral valve replacement surgery. Evoked potentials were recorded before, during, and after sudden ventricular fibrillationfollowed by CPR.
Results: Preoperative control recordings of both SCEPs and SSEPs were in the normal ranges. During the first 4 min of cardiac arrest and resuscitation, all SCEPs waves disappeared, while the spinal component of the SSEPs was still recognizable. After CPR, all waves of both EPs recordings recovered completely. The patient woke from anesthesia without neurological deficits.
Conclusions: As expected, scalp-recorded EPs are more sensitive to the cardiac arrest than spinal EPs. Rapid and almost complete recovery of postoperative EPs, namely SCEPs, correlated well with normal neurological recovery.     

皮节体感诱发电位在术中评价腰骶神经根减压效果的价值

目的:探讨皮节体感诱发电位(dermatomal somatosensory evoked potentials,DSEP)术中评价腰骶神经根减压效果的适用指标及其临床价值.方法:2011年5月～2011年12月对46例以感觉障碍为主诉,经查体、腰椎MRI及术前DSEP检查证实存在单侧腰骶神经根(L5或S1神经根)受压而接受神经根减压手术的患者进行术中DSEP监测,男34例,女12例;年龄20～63岁,平均41.2岁.其中L5神经根受累36例,S1神经根受累10例,MRI显示为旁侧型椎间盘突出或神经根管狭窄.记录并比较麻醉后至减压前及减压后受累神经根的P40潜伏期和波幅,术中结合自发肌电(EMG)监测相应节段神经支配肌肉,作为可能出现即时神经根医源性损伤的预警.术前、术后采用VAS评分和ODI评估患者的临床疗效,比较术前、术后的VAS及ODI评分.结果:术中自发EMG均未提示神经根医源性损伤.减压后32例患者潜伏期延长＜0.1,14例潜伏期缩短,其中8例改善率≥0.1.根据潜伏期改善率分为三组:无改善组(改善率≤0)、改善组(0＜改善率＜0.1)以及明显改善组(改善率≥0.1),无改善组的VAS改善率显著低于其他两组(P＜0.05),明显改善组与改善组的VAS改善率无显著性差异(P＞0.05),术后6个月随访时三组之间的ODI改善率无显著性差异(P＞0.05).减压后所有患者P40波幅均无降低,其中明显改善(改善率≥0.5)37例,改善(0.3≤改善率＜0.5)4例,无明显改善(改善率＜0.3)5例,明显改善组术后VAS改善率显著性大于其他两组(P＜0.05);术后6个月随访时明显改善组和改善组的ODI改善率均显著性大于无明显改善组(P＜0.05),而前两组之间的ODI改善率无显著性差异(P＞0.05).P40波幅改善率与VAS改善率和病程之间存在相关关系(P＜0.05).结论:对于病史较短且有典型相应皮区感觉症状的单侧腰骶神经根压迫患者,减压术中受累神经根DSEP P40波幅改善率可预示患者术后临床症状的改善情况,可作为评估减压效果的指标.     

Isovolaemic haemodilution with hydroxyethylstarch has no effect on somatosensory evoked potentials in healthy volunteers

Background: An animal study in anaesthetized baboons demonstrated that somatosensory evoked potentials (SSEP) can be affected by extreme haemodilution. This might lead to misinterpretation and reduce the value of intraoperative SSEP monitoring when colloids are administered. In the present study the effect of haemodilution (HD) and subsequent retransfusion of autologous blood on SSEP was determined in healthy non-premedicated volunteers.
Method: Acute isovolaemic HD served as a model for blood loss immediately replaced with colloids. In 12 volunteers, 20 ml/kg·bw blood was withdrawn within 30 minutes and simultaneously replaced with 6% hydroxyethylstarch (HES). 30 minutes later, the autologous blood was retransfused within 30 minutes. Recording sites and parameters were: 1. Median nerve SSEP: cortical, cervical (C2), Erb's point; 2. Posterior tibial nerve SSEP: cortical, cervical (C2), lumbar (L1). In addition to SSEP latency and amplitude, median and tibial nerve central conduction times, spinal conduction time and nerve conduction velocity were determined. Serial SSEP measurements were made before, during and after HD and retransfusion every 15 minutes.
Results: HD consisting of a withdrawal volume of 1550±155 ml (mean±SD) induced a decrease in haematocrit from 42.0±3.1% to 29.6±1.6% (P<0.001). Following retransfusion, haematocrit increased to 35.0±2.1% (P<0.001). Neither HD nor retransfusion influenced SSEP parameters.
Conclusion: We conclude from our data that the therapy of blood loss up to 30% of estimated blood volume with HES does not affect SSEP monitoring as long as normovolaemia is maintained.     

咪唑安定对体感诱发电位的影响

目的：了解咪唑安定对体感诱发电位的影响。方法：选择３０例ＡＳＡＩ～Ⅱ级的脑外科手术病人，根据国际１０～２０系统，在Ｃ３或Ｃ４、ＦＰｚ（参考）和ＳＣ（第二颈椎棘突处）安放盘状记录电极，记录体感诱发电位。均分为三组按剂量（０．２ｍｇ／ｋｇ、０．３ｍｇ／ｋｇ和０．４ｍｇ／ｋｇ）静脉注射咪唑安定，连续观察皮层Ｎ２０、Ｐ２３和颈髓Ｎ１４电位的变化。结果：（１）用药后，皮层Ｎ２０和颈髓Ｎ１４电位的波幅降低，分别抑制到术前的６３．７５％和４８．７５％（Ｐ＜０．０５），苏醒后恢复到基础水平；（２）颈髓Ｎ１４、皮层Ｎ２０和Ｐ２３的潜伏期及中枢传导时间均无显著延长，（３）各剂量组间的ＳＥＰ变化无明显差别。结论：咪唑安定对ＳＥＰ一定程度的抑制作用临床意义不足，可用作ＳＥＰ监测时的静脉麻醉药。     

Usefulness of somatosensory evoked potentials in peripheral nerve surgery

Summary One of the limiting factors in the clinical advancements of peripheral nerve surgery is the lack of objective, non-invasive methods in the assessment of nerve function. Somatosensory evoked potentials (SEPs) are mainly used in experimental and clinical studies on the central nervous system. In experimental studies, SEPs have been recorded using intra-cranial and intra-cerebral electrodes. Our method used for a non-invasive, easily applicable technique was with subcutaneous needle-electrode. We assessed the normal function of the sciatic nerve of the rat, and the first recovery signs after division and suturing under microsurgery.