Understanding capture detection.

Automatic capture detection systems are currently available in several cardiac pacing devices. All current systems use low-polarization electrodes and no beat to beat detection system is available for all types of electrodes. In addition the success ratio for currently available systems is not always 100%. Failure to detect capture reliably is often related to the behaviour of the electrode-tissue interface under different circumstances. Pacemaker electrodes can be considered electrochemical cells with complicated characteristics depending on time, temperature and electrical charge. This electrochemical cell is disturbed when a charge is transferred across the electrode-tissue interface during pacing. Several measures can be taken in order to minimise this disturbance or pace polarization artefact (PPA) including the use of high active surface area electrodes and application of tri-phasic pacing pulses. Another factor influencing detection of evoked potentials is the input circuit of the pacemaker affecting the PPA and the evoked response. Positive PPAs can be falsely interpreted as evoked potentials due to the undershoot of the second order filters applied in modern cardiac pacemakers. This paper explains the behaviour of the interface between the electrode and the cardiac tissue in combination with the pacemaker output circuits and input amplifiers under different circumstances.     

Differential modulation of the short- and long-latency somatosensory evoked potentials in a forewarned reaction time task.

OBJECTIVE: We investigated modulation of the short- and long-latency somatosensory evoked potentials (SEPs) in a forewarned reaction time task. METHODS: A pair of warning (auditory) and imperative stimuli (somatosensory) was presented with a 2 s interstimulus interval. In movement condition, subjects responded by grip movement with the ipsilateral hand to the somatosensory stimulation when the imperative stimulus was presented. In counting condition, they silently counted the number of imperative stimuli. The SEPs in response to the imperative stimuli were recorded. RESULTS: Frontal N30 and central N60 amplitudes were significantly smaller in the movement than in the counting or rest conditions. None of the short-latency components differed between the counting and rest conditions. In contrast to the short-latency components, P80 was significantly larger in the counting than in the rest condition, and showed a further increase from the counting to the movement condition. The N140 amplitude was significantly larger in the movement than the rest condition, but was not changed between the counting and the rest conditions. CONCLUSIONS: The attenuation of the frontal N30 and central N60, and the enhancement of the P80 and possibly the N140 resulted from the centrifugal mechanism. The present findings may show the different effects of voluntary movement on the early and subsequent cortical processing of the relevant somatosensory information requiring a behavioral response. SIGNIFICANCE: The present study demonstrated the differential modulation of short- and long-latency components of SEPs in a forewarned reaction time task.     

Correlation with age and sex of flash-evoked electroretinogram and retinal oscillatory potentials recorded with skin electrodes

Electroretinograms and retinal oscillatory potentials to full-field flash stimulation were recorded by dermal electrodes in a population of subjects (1 to 84 yrs) balanced for age and sex (119 females, 133 males), without evidence or history of ocular and/or relevant systemic diseases. The electroretinogram latencies and b-wave amplitude increased, while the a-wave amplitude decreased linearly with age. The oscillatory potential amplitude initially increased, to decrease approximately at the age of 50, with an inverted U-shaped distribution.Presented in part at the XXV ISCEV Symposium, Sarasota (Florida), April 26–30, 1987.     

碘杂环化合物对离体豚鼠心乳头肌动作电位和收缩力的作用

采用细胞内微电极记录技术,同步观察了3,6-[二甲氨基]-二苯并碘因甲酸盐(IHC-64)对豚鼠心乳头肌细胞动作电位和收缩力的作用。50μmol/L IHC-64抑制心肌收缩力,而不影响快反应动作电位。增加IHC-64浓度,动作电位0相最大峰值(APA)、除极速率(dp/dt_(max))和复极50％和90％时程(APD_(50)、APD_(90))被明显抑制。IHC-64抑制慢反应动作电位,提高细胞外钙浓度可拮抗这种抑制。结果提示,IHC-64主要抑制慢Ca~(2+)内流,同时也部分抑制快Na~+内流,它可能是一种新型B类钙通道阻滞剂。     

Motor blockade associated with continuous epidural infusion after abdominal hysterectomy: a randomized controlled trial comparing 0.1% ropivacaine-plus-fentanyl versus 0.2% ropivacaine-alone

We compared rates of motor blockade, analgesia, adverse effects and patient satisfaction of 0.1% ropivacaine+fentanyl versus 0.2% ropivacaine-alone in a randomized, controlled trial. Fifty-four women who had undergone abdominal hysterectomy were randomly allocated into two groups to receive an epidural block at L_1–2 or L_2–3: group R received 0.2% ropivacaine-alone and group RF received 0.1% ropivacaine plus 2 μg fentanyl/ml, both at 8 ml/h. Rescue analgesia was provided via a morphine-loaded PCA device. Motor blockade (using a modified Bromage scale), pain intensity (visual analogue scale (VAS)), morphine consumption, level of sensory blockade and adverse effects, were measured at 4, 8 and 21 h after infusion. Patient satisfaction with pain management was assessed at the end of the study. The rates of motor blockade were not different at 8 h after infusion but at 21 h, group RF had significantly less motor blockade than group R. There were no differences in VAS, level of sensory blockade, adverse effects and patient satisfaction. Morphine consumption at each measurement was comparable but the total amount used by group RF was less than group R (12 mg versus 20 mg, P=0.049). Therefore, 0.1% ropivacaine with fentanyl 2 μg/ml appears to offer advantages over 0.2% ropivacaine-alone.     

兔坐骨神经挤压伤的MRI与SEP对比研究

目的:探讨磁共振成像和体感诱发电位以及两者结合在坐骨神经急性挤压伤中的诊断价值。方法:24只兔按钳夹力的不同随机分为A、B两组,左后肢为损伤侧,右后肢为对照侧,建立坐骨神经急性挤压伤模型,于伤后1、2、4、8周行MR扫描,同时行双侧体感诱发电位检查。结果:损伤侧24条神经,有23条MR显示异常,诊断正确率95.8%,假阴性率4.17%(1/24);24条损伤侧坐骨神经,有22条SEP显示异常,诊断正确率91.6%,假阴性率8.3%(2/24)。MRI与SEP对神经损伤的正确诊断率无统计学差异(P>0.05)。MRI与SEP结合起来,24条损伤神经均显示异常,诊断正确率100%。结论:MR与SEP检查可无创、准确地判断神经损伤,两者结合可明显提高神经损伤的正确诊断率,重复性好,可作为神经损伤的较好诊断手段。     

单极法运动诱发电位的测定方法

目的 本文提出了利用常规肌电图机用电刺激器,采用单极法进行MEP测定的技术方法.方法 单极法:刺激器采用英产MS-6型肌电图机用电刺激器,通过两个自制直径为1.5cm分离的圆盘状电极经皮对大脑皮质及脊髓进行单次超强刺激.结果 单极法有49个肢体呈现为中枢性传导阻滞,阻滞率为40.83%.单极法有61个肢体呈现为中枢性传导阻滞和延迟,异常率为50.83%.结论 通过测定及统计分析表明,该方法具有以下优点:(1)刺激量小,病人易接受.(2)无需专用刺激嚣,经济实用易于推广.(3)定位性能可靠.(4)通过单、双极两种方法的阻滞率和异常率比较,说明单极法更敏感,更易检出异常者.     

65例多发性硬化患者的临床分析

目的总结多发性硬化(MS)患者的临床特点(精神情感障碍)以及脑脊液、诱发电位、影像学改变进行分析。方法回顾分析65例MS患者的有关临床和实验室资料。结果65例中,男17例,女48例;年龄16~68岁,平均(36.5±14.1)岁,男女比为1∶2.8。MS首发及常见症状为感觉异常、肢体无力、视力减退及括约肌功能障碍,病变部位以脊髓受累最多见,部分患者存在精神情感障碍。结论出现感觉异常有助于MS早期诊断,诱发电位及MRI有助于发现亚临床病变;括约肌功能异常多见,可能与脊髓受累较多有关;MS患者的精神情感应受人们关注。     

恢复后期脑卒中综合康复治疗与单纯药物治疗的对比研究

目的 :研究综合康复治疗对恢复后期脑卒中患者运动功能及日常生活能力 (ADL)的影响。方法 :将 92例恢复后期脑卒中患者 ,随机分为康复组 5 0例 ,对照组 4 2例 ,两组一般治疗相同 ,康复组同时配合康复护理、运动疗法、作业疗法和电疗等综合康复治疗 8周。结果 :采用Fugl-Meyer运动功能评分 (FMA)和修订的Barthel指数 (MBI)评分 ,康复组各项指标评分明显优于对照组 (P <0 .0 5 )。结论 :综合康复治疗对于恢复后期脑卒中患者运动功能的恢复有明显效果 ,提高了ADL水平。     

听觉诱发电位指数指导全凭静脉麻醉期间病人输注异丙酚的效果

目的探讨听觉诱发电位指数(AAI)指导全凭静脉麻醉期间病人输注异丙酚的效果。方法择期全麻下行腹腔镜胆囊切除术病人60例,ASAⅠ或Ⅱ级,随机分为2组(n=30):试验组(Ⅰ组)和对照组(Ⅱ组)。静脉诱导气管插管后,持续输注0．2μg·kg-1·min-1瑞芬太尼以维持合适的麻醉深度。Ⅰ组通过监测AAI调节异丙酚输注速率,使AAI维持在30以下,Ⅱ组根据病人血压及心率调节异丙酚输注速率,每5分钟增减0．01 mg·kg-1·min-1异丙酚。记录气腹前(T1)、气腹后(T2)、分离胆囊(T3)、腹腔冲洗(T4)、手术结束(T5)时2组的血压、心率、AAI和输注异丙酚的速率,同时记录2组异丙酚、维库溴铵、瑞芬太尼用量、术毕睁眼时间、应答时间和拔管时间。结果2组各时间点AAI差异有统计学意义(P<0．05),与Ⅱ组相比,Ⅰ组输注异丙酚速率以及总用量减少(P<0．05)。术后24 h随访病人均无术中知晓。结论AAI指导全凭静脉麻醉输注异丙酚用于腹腔镜胆囊切除术病人,可较好的控制麻醉深度,指导合理用药,避免病人术中知晓。