Somatosensory evoked potentials in moderate hyperthermia]

The effects of moderate whole-body hyperthermia on the cervical and cortical somatosensory evoked potentials (SEP) were studied in healthy male subjects, aged 22-32 years. They were immersed in hot water and heated to a median rectal temperature of 39.0 degrees C. Serial SEPs to median nerve stimulation were recorded during cooling at intervals of 0.1 degrees C. The general wave form and the amplitudes did not systematically change. For a 1 degrees C drop there was a median latency increase of 2.6-3.7% in cervical and 1.5-7.4% in cortical SEP components. In individual cases significant latency delays of cervical N13 and cortical N20 could already be observed at differences of 0.2 degrees and 0.5 degrees respectively. All other components showed significant latency changes at temperature intervals of 0.6 to 0.8 degrees C.     

The repeat reliability of somatosensory evoked potentials

The test-immediate-retest reliability of latency and amplitude values of cervical and cortical somatosensory evoked potentials (SEP) to median nerve stimulation was assessed in 86 normal subjects aged 15 to 71 years. In addition to the stability of data between repeat trials within one test session the standard errors of measurement and the interpretable differences for SEP measures were calculated according to measurement theory. The study revealed retest correlations rtt greater than 0.80 for all latency measures of the cervical and cortical SEPs and all cortical amplitude parameters. The highest stability was found for the latency measures of the cervical components P10, N11, N13, the cortical components P16 and N20 and for the amplitude N20/P25.     

The effect of temperature, mean arterial pressure, and cardiopulmonary bypass flows on somatosensory evoked potential latency in man

Median nerve somatosensory evoked potentials were recorded in 21 patients undergoing cardiac surgical procedures utilizing cardiopulmonary bypass, in order to establish the effects of hypothermia, reductions in mean arterial pressure, and alterations in cardiopulmonary bypass flows on evoked potential latency. Induction and maintenance of anesthesia with fentanyl caused a significant prolongation of latency of the first cortical peak. Temperature changes were linearly correlated with changes in latency for peaks recorded from Erb's point (r = -0.843, p less than 0.01) and the contralateral cortex (r = 0.843, p less than 0.01). There was no significant effect of mean arterial pressure or cardiopulmonary bypass flow reductions on latencies under the conditions of this study. Our results emphasize the importance of monitoring peripheral and first cortical peak latencies in evaluating somatosensory evoked potentials. It is suggested that peak latency prolongations beyond those predicted by temperature alterations may be indicative of hypoperfusion.     

脑白质疏松症患者的脑诱发电位研究

目的 探讨脑白质疏松症(Leukoaraiosis，LA)患者脑诱发电位改变的特点及其对LA的诊断价值。方法对40例脑白质疏松症合并脑梗死(LA CI)患者及40例单纯脑白质疏松症患者进行体感诱发电位(sEP)，脑干诱发电位(BAEP)及视觉诱发电位(VEP)检查，并与40名同年龄组健康人对照。结果LA CI组患者SEP、BAEP及VEP异常率分别为80％、63％及60％。SEP各波潜伏期、BAEP除Ⅰ波外各波潜伏期及波间期、VEP的P100波潜伏期和对照组相比差异均有显著性意义。而单纯LA组患者SEP、BAEP及VEP异常率分别为35％、30％及45％，SEP仅P15及％波潜伏期、VEP的P100波潜伏期和对照组相比差异有显著性意义。而BAEP和对照组相比，差异无显著性意义。结论SEP、BAEP及VEP联合检查，可反映LA患者皮层、皮层下及脑干功能的损害，并对判断LA患者白质疏松范围，LA严重程度有一定的意义。     

Influence of high-dose opioid anesthesia on posterior tibial nerve somatosensory cortical evoked potentials: Effects of fentanyl,sufentanil, and alfentanil

The effects of high doses of fentanyl (group F), sufentanil (group S), and alfentanil (group A) on posterior tibial nerve somatosensory cortical evoked potentials were studied in 30 patients scheduled for elective valve replacement surgery. Anesthesia was induced with either fentanyl, 75 μg/kg, sufentanil, 5 μg/kg, or alfentanil, 125 μg/kg. The lungs were ventilated with oxygen/air. A bolus dose of fentanyl, 25 μg/kg, was given 30 minutes after induction of anesthesia in group F. Anesthesia was maintained with a continuous infusion of sufentanil, 5μg/kg/h, in group S, or alfentanil, 500 μg/kg/h, in group A. Latencies of the peaks of the primary cortical complex (P1, N1, 132) increased by 1 to 2 ms after induction of anesthesia, although this was significant (P < 0.01) only for P1 and N1 in groups F and S. N2 latency increased significantly (P < 0.01) by 6 to 10 ms in all groups. P1-N1 amplitude did not change after induction of anesthesia. N1-P2 amplitude decreased significantly (P < 0.01) to 60%–70% of preinduction values in groups F and S. P2-N2 amplitude decreased significantly (P < 0.01) to 60%–70% of preinduction values in all groups. P1, N1 and P2 latencies did not change significantly from the post-induction values in the period preceding cardiopulmonary bypass (75 ± 16 minutes) in groups F and S. In group A significant changes were observed only for N1 and P2 latency (P < 0.01). During this period there was a further gradual increase in N2 latency and amplitudes remained stable, except P1-N1 amplitude in group F, which decreased significantly (P < 0.05). A bolus dose of fentanyl, 25 μg/kg, given in group F at 30 minutes after induction of anesthesia did not change latencies and amplitudes. No significant differences in latency or amplitude were found at any time among the three study groups. It is concluded that anesthesia with high doses of fentanyl, sufentanil, or alfentanil is a suitable technique when intraoperative monitoring of posterior tibial nerve somatosensory cortical evoked potentials is indicated.     

Cerebral oxygen monitoring during neonatal cardiopulmonary bypass and deep hypothermic circulatory arrest

BACKGROUND: This study was undertaken to investigate the physiological effects of cardiopulmonary bypass (CPB) and deep hypothermic circulatory arrest (DHCA) on cerebral oxygen metabolism estimated by near-infrared spectroscopy (NIRS). METHODS: Ten newborn piglets (2.1 to 2.6 kg) were monitored with right frontal NIRS; the right jugular bulb was cannulated for intermittent sampling of jugular venous blood. All animals underwent CPB, cooling to a core temperature below 15 degrees C, 60 minutes of DHCA followed by subsequent reperfusion and rewarming. Continuously recorded NIRS data and intermittent jugular venous blood values were compared. RESULTS: NIRS performance was examined over the jugular venous oxygen saturation (SjvO2) range of 40 to 98 %, a linear correlation was found between SjvO2 and NIRS-derived regional cerebral oxygen saturation (rSO2) (r = 0.91, p < 0.001). A correlation was observed between the cellular oxidation NIRS-parameter cytochrome oxidase aa3 (CytOx) slope during the DHCA period in relation to rectal and nasopharyngeal temperature immediately before the onset of DHCA (r = 0.75 and 0.85, p < 0.001). CONCLUSIONS: This study suggests that NIRS-measured hemoglobin oxygenation parameters may reflect functional changes in cerebral hemodynamics and brain tissue oxygenation, while CytOx values represent related effects on intracellular oxidative metabolism.     

Determination of neurophysiological parameters of the aging CNS. I. Evoked potentials (author's transl)]

Somatosensory (SEP) and visual (VEP) evoked potentials were studied in 65 healthy subjects who ranged in age from 62-91 years and in 48 normal persons aged 18-38 years. The amplitudes and latencies of the different components of the evoked potentials were measured. The transmission of evoked potentials from the specific response area into different regions of the ipsi- and contralateral hemisphere were studied. The findings can be summarized as follows: The latencies of the SEP and VEP of aged subjects are significantly prolonged. The increase in latency is relatively slight for the first components, progressively higher for the following components. The amplitudes of the different components of the SEP and VEP are significantly increased in aged subjects. The modifications of the SEP-latencies and of the VEP-amplitudes are more important over the dominant hemisphere. In young subjects the SE are confirmed to the centro-parietal region. In aged persons the SEP spreads over the whole hemisphere. The hypothesis that the aging process involves the synaptic transmitter mechanisms at the cortical level is discussed in relation to the involvement of the latencies. The increase in amplitude of the evoked potentials could be explained by assuming that the inhibition - an essential property of the cortex - decreases during the aging process.     

Real-time imaging of human cortical activity evoked by painful esophageal stimulation

BACKGROUND & AIMS: Current models of visceral pain processing derived from metabolic brain imaging techniques fail to differentiate between exogenous (stimulus-dependent) and endogenous (non-stimulus-specific) neural activity. The aim of this study was to determine the spatiotemporal correlates of exogenous neural activity evoked by painful esophageal stimulation. METHODS: In 16 healthy subjects (8 men; mean age, 30.2 +/- 2.2 years), we recorded magnetoencephalographic responses to 2 runs of 50 painful esophageal electrical stimuli originating from 8 brain subregions. Subsequently, 11 subjects (6 men; mean age, 31.2 +/- 1.8 years) had esophageal cortical evoked potentials recorded on a separate occasion by using similar experimental parameters. RESULTS: Earliest cortical activity (P1) was recorded in parallel in the primary/secondary somatosensory cortex and posterior insula (approximately 85 ms). Significantly later activity was seen in the anterior insula (approximately 103 ms) and cingulate cortex (approximately 106 ms; P=.0001). There was no difference between the P1 latency for magnetoencephalography and cortical evoked potential (P=.16); however, neural activity recorded with cortical evoked potential was longer than with magnetoencephalography (P=.001). No sex differences were seen for psychophysical or neurophysiological measures. CONCLUSIONS: This study shows that exogenous cortical neural activity evoked by experimental esophageal pain is processed simultaneously in somatosensory and posterior insula regions. Activity in the anterior insula and cingulate-brain regions that process the affective aspects of esophageal pain-occurs significantly later than in the somatosensory regions, and no sex differences were observed with this experimental paradigm. Cortical evoked potential reflects the summation of cortical activity from these brain regions and has sufficient temporal resolution to separate exogenous and endogenous neural activity.     

60例成年人直肠电刺激脑诱发电位特点及结果分析

目的探讨正常人直肠电刺激脑诱发电位（CEP）的正常值及波形特征。 方法检查者将刺激电极经肛置入受试者直肠内,在头顶部Cz点放置记录电极,参考电极置于前额部Fz点,使用英国Oxford公司肌电诱发电位仪采样分析。 结果所有检测对象均记录有直肠电刺激脑诱发电位,各波参数范围分别是：P1波潜伏期（45.55±3.26）ms,N1波（101.71±15.71）ms,P2波（198.35±27.70）ms,P1/N1波幅（5.62±1.58）μV,N1/P2波幅（8.26±2.48）μV。直肠电刺激脑诱发电位各波潜伏期及波幅在性别、年龄分组间比较,差异无统计学意义。经一般线性回归分析发现,在控制年龄分组、性别后,波幅随BMI增加而降低,BMI每增加1 kg/m²,P1/N1波幅平均下降0.234 μV（P=0.011）,N1/P2波幅平均下降0.320 μV（P=0.027）。 结论直肠电刺激脑诱发电位提供了一种简单、有效的评估直肠到大脑皮层感觉神经通路的方法。本研究对了解功能性胃肠疾病中的脑肠互动作用具有重要价值。本研究的检测结果及其影响因素分析,可供后续临床研究借鉴。     

Intraoperative somatosensory evoked potentials as a prognostic factor of neurologic state after carotid endarterectomy

Somatosensory evoked cervical and cortical potentials (SEP) were analyzed under general anesthesia in 106 patients undergoing carotid endarterectomy. Cortical electrical silence occurred in 5 patients without an inlying shunt; all developed a new neurologic deficit postoperatively. Analysis of the SEP in these patients revealed progredient cerebral ischemia as indicated by an increase in central conduction time (CCT) and a decrease in amplitude of the primary cortical response N20P25 resulting in a complete loss of cortical SEP later on during the clamping period. In 6 patients the insertion of a shunt restored the deteriorated SEP, these patients and those with unchanged SEP after carotid clamping showed an uneventful postoperative recovery. Taking the presence or absence of N20P25 as the sole parameter, the sensitivity of this technique was 83%, specificity 99% and predictability 83%. A normal range for CCT and amplitude of N20P25 during anesthesia and criteria for shunt insertion were developed. The presented monitoring regimen appears to be rational and is based on current concepts of cerebrovascular physiology and pathophysiology.     

Correlation of visual evoked potentials with dementia in Parkinson's disease]

There has been some debate regarding abnormalities in visual evoked potentials (VEP) in Parkinson's disease (PD). To elucidate the mechanism causing abnormal VEP, we investigated the relationship between VEP and mental function in PD patients. Pattern reversal VEP was recorded in PD patients (n = 27) and age-matched control subjects (n = 14). PD patients consisted of two subgroups; PD without dementia (nD-PD; n = 17) and PD with dementia (D-PD; n = 10). Dementia was evaluated according to the criteria for dementia assigned in DSM III-R, and mental faculties were estimated by using the mini-mental state examination (MMSE). In pattern VEP recordings, P100 latency and amplitude were measured for each eye stimulated. No patient or control subject had impairment of corrected visual acuity or ophthalmological disease. There was no significant difference in age among the three groups (D-PD, nD-PD and control subjects). D-PD patients showed significantly prolonged P100 latency compared to nD-PD patients and control subjects (p less than 0.05). With respect to P100 amplitude, no significant difference was shown among the three groups. In PD patients, there was a rough correlation between P100 latency and MMSE score. No correlation was found between P100 amplitude and MMSE score. In control subjects, P100 latency did not correlate with advancing age. In PD patients, nD-PD patients showed a significant correlation between P100 latency and age, whereas D-PD patients presented no correlation. Abnormal VEP in PD has been mostly ascribed to dopaminergic deficiency in the retina.(ABSTRACT TRUNCATED AT 250 WORDS)     

电生理指标联合应用在颅内巨大动脉瘤手术中的作用

目的研究躯体感觉诱发电位(SEP)、脑电图、脑干听觉诱发电位(BAEP)联合应用在颅内巨大动脉瘤手术治疗中的影响及临床意义。方法分别对23例颅内巨大动脉瘤患者进行手术直接夹闭或动脉瘤孤立加旁路移植手术,同时行SEP、脑电图和BAEP实时监测,观察手术操作对其的影响。结果 23例患者行颅内巨大动脉瘤手术操作时,均不同程度引起SEP、脑电图和BAEP的变化。其中SEP的N20、P25潜伏期延长3～5 ms,波幅较术前降低50%;BAEP的Ⅰ、Ⅲ、Ⅴ波潜伏期延长0.7～1.0 ms,Ⅰ～Ⅲ、Ⅲ～Ⅴ波峰间期及Ⅰ、Ⅴ波幅电位较术前降低30%～50%以上。结论术中动态监测SEP、脑电图和BAEP的电位变化,可以提示颈动脉阻断后的脑灌注状态,对调整手术时间及手术方式具有重要的指导意义。     

Correlation between esophageal contraction amplitude and lower esophageal sphincter pressure in patients with nutcracker esophagus

Nutcracker esophagus (NE) is a primary esophageal motility disorder characterized by high-wave amplitude at the distal esophagus. The aim of this study was to analyze patients with NE and determine the relationship between distal esophageal contraction amplitude and lower esophageal sphincter (LES) pressure. Esophageal manometry tracings of patients with NE, defined as the presence of distal contraction amplitude of more than 182 mmHg after wet swallow, were analyzed. LES pressure was measured as the mean end-expiratory value. Spearman's correlation coefficient analysis was used to compare esophageal contraction amplitude with LES pressure. This comparison was also performed in patients with isolated hypertensive LES (HLES) and in subjects with normal manometry. Forty patients (25 female, 15 male; mean age 54 years) with NE were included in the study. Mean (SD) distal esophageal contraction amplitude was 230 (35.7) mmHg and mean LES pressure was 27.3 (5.7) mmHg. Esophageal contraction amplitude showed a positive correlation with LES pressure (r = 0.49, P < 0.01). In contrast, no correlation was found in patients with HLES (r = 0.21, P > 0.05) and in those with a normal manometric study (r = 0.18, P > 0.05). It is concluded that in patients with nutcracker esophagus a positive correlation exists between distal esophageal contraction amplitude and LES pressure, suggesting a diffuse hypertensive pattern involving smooth muscle at the distal esophagus and adjacent LES.     

Monitoring urinary bladder temperature

We evaluated bladder, rectal, and esophageal temperatures compared with nasopharyngeal temperatures in 12 patients who underwent cardiac surgery that required CPB. Changes in bladder temperature lagged behind those of esophageal and nasopharyngeal temperature during rapid cooling and rewarming. Changes in rectal temperature were the slowest. Bladder and rectal temperatures were similar after surgery. Monitoring bladder temperature represents the core temperature in a steady state.     

SEP monitoring during clonidine therapy of alcohol delirium]

In 12 patients with developing alcohol withdrawal syndrome after abdomino-thoracic surgical procedures who were treated with Clonidine, short latency somatosensory evoked potentials were recorded. Clonidine leads to a good sedation, anxiolysis and moderated the psychotic symptoms. However, there was no significant correlation between the Clonidine medication and the SEP results over the time of drug administration concerning the primary cortical response N20 and the following N20/P25 wave. Therefore, the short-latency SEP-recording cannot provide a reliable monitoring of the good sedative effect of Clonidine in alcoholic withdrawal. The SEP responses after Clonidine are like those of morphine and are thought to have a similar central mode of action.     

The effects of nimodipine on regional cerebral blood flow, brain water and electrolyte contents in rats with subarachnoid hemorrhage

Secondary cerebral ischemic injury is a major cause of mortality and disability from subarachnoid hemorrhage (SAH). In this study, the protective effects of nimodipine were investigated. Rat SAH models were divided into a sham-operated group, a saline-controlled, and a nimodipine-treated group by an endovascular piercing method. Nimodipine, 100 microg/kg BW was injected intraperitoneally 30 minutes before operation and was repeated every 6 hours. Dynamic changes in cortical regional cerebral blood flow (rCBF) using a laser Doppler flow-meter probe, and somatosensory evoked potentials (SEP) were estimated. Brain water content, sodium, potassium and calcium contents at different time points were determined. rCBF, latency of SEP, brain water and electrolyte contents did not statistically change in sham-operated rats. In saline-controlled rats, rCBF decreased immediately after SAH, and stabilized at low levels within 24 hours. The latency of SEP delayed gradually after SAH. Brain water and sodium increased, while potassium decreased at 6 hours and 24 hours. Brain calcium content increased significantly from 1 hour to 24 hours after induction of SAH. Extents of alterations of the above parameters caused by SAH in the nimodipine-treated group were less than those in the saline-controlled group, statistically. In conclusion, nimodipine partly prevents a decrease in cerebral blood supply and attenuates secondary cerebral ischemic injury after SAH.     

Selective shunting based on somatosensory evoked potential monitoring during carotid endarterectomy

Somatosensory Evoked Potentials (SEPs), to median nerve stimulation, were continuously monitored in 58 patients undergoing carotid endarterectomy A first group of patients was shunted routinely; in a second group the shunt was selectively applied when inadequacy of collateral circulation was suspected based on stump pressure values and SEP changes. Both amplitude and latency modifications of SEPs occurred during surgery; however no post-operative neurological deficit was seen unless there was a complete flattening of cortical waves, even a transitory one. Inadequate collateral circulation and embolic ischemia affected SEPs differently. While the latter produced a disappearance of all cortical waves, the former led first to a progressive flattening of later cortical waves and then of N20 as well. For values of stump pressure ranging between 20 and 50 mmHg SEPs were unchanged in some patients and altered in others. These findings may explain the controversies existing about the usefulness of stump pressure for predicting tolerance to carotid clamping.     

Cerebral evoked potentials

Cerebral evoked potentials (EPs) represent a new technique for the evaluation of afferent outflow from the gastrointestinal tract. We compared EPs obtained with distension of the distal and proximal esophagus. Responses were recorded with the balloon 5 cm proximal to the lower esophageal sphincter and 3 cm distal to the upper esophageal sphincter. Balloon stimulation resulted in cortical responses recorded by midline scalp electrodes (CZ, PZ, and OZ by the International 10–20 system) in normal volunteers. EP responses consisted of two negative (N1, N2) and one positive (P1) deflections. The proximal esophageal latency of N1 was shorter in all three leads. The latency to P1 was shorter with proximal stimulation in lead CZ only, and N2 latencies were not different. Amplitudes expressed as the difference between N1 and P1, and P1 and N2 were not different. When two sets of potentials several minutes apart from the proximal position were compared, a decrease in amplitude with the second set of stimulations was noted. Esophageal EP recording is a new technique that may provide information about the integrity and function of the sensory innervation of the esophagus.Supported in part by a research grant to Dr. DeVault from the American College of Gastroenterology.     

Automatic quantification of SEP for continuous patient monitoring

Parameters presently used to analyse evoked potentials such as amplitude and latency are based on well defined single components, the recognition of which may become arbitrary in severely altered responses. Furthermore, they ignore changes also present in the remainder of an evoked potential wave form. Hence, they are ill suited for monitoring comatose patients or patients during high risk surgery. Alternatively, crosscorrelation analysis may be employed yielding two parameters by comparing the SEP of the patient with a reference response: R, the correlation coefficient, a numerical measure of similarity of the two responses in terms of overall configuration and tau, indicating the time displacement of the main common components of the two signals. A "grand average" evoked potential (SEP) composed of the responses of age and sex matched healthy subjects or in perioperative monitoring the patient's own preoperative response might be used as a reference. By help of continuous averaging of the SEP these two parameters may be determined in real time allowing a more dynamic way of monitoring than by sequential averaging individual responses.     

Changes in somatosensory evoked potentials in carotid desobliteration. Diagnostic significance and possible consequences for therapy

The cerebral function of 55 patients with stenosis and occlusion of carotid arteries was monitored intraoperatively by serial examination of somatosensory cortical evoked potentials (SEP). In 40 uncomplicated operations no significant alteration of the SEP was detected. In 13 examination series, however, reversible abnormalities were noted. Furthermore, in two cases irreversible SEP loss was documented. The nature and temporal development of SEP alterations enabled differentiation of possible etiological factors. Bilateral abnormalities were indicative of global hypoxemia whereas acutely arising unilateral SEP loss suggested embolic occlusion of cerebral arteries. Intraoperative SEP monitoring therefore appears to be of diagnostical and differential diagnostical value and allows statements in respect to further intra- and postoperative treatment.