Pedrini L, Tarantini S, Cirelli M R, Ballester A, Cifiello B I, D'Addato M
Institute of Vascular Surgery, University of Bologna, Italy.
Int Angiol. 1998 Mar;17(1):10-4.
This study aimed to evaluate the reliability of somatosensory evoked potentials (SEPs) in identifying clamping ischaemia during carotid surgery under general anaesthesia.
We reviewed the records of 196 consecutive carotid endarterectomies (CEA) performed under general anaesthesia, out of 1550 patients operated on between 1975 and 1993. SEPs were monitored after contralateral median nerve stimulation at the wrist in all patients. Moreover they received an intravenous bolus of 2500 IU of heparin and the stump pressure was measured. A completion angiography was performed in all patients. An intraluminal shunt was inserted when the amplitude of the N20-P25 SEPs complex decreased by more than 50% of pre-clamping value (pathologic SEPs) or when a preoperative CT-scan showed an ischaemic area in the contralateral hemisphere. In some patients the shunt was not inserted because of technical difficulties or because the pathological SEP complex decrease developed when the suture of the arteriotomy was almost complete.
As the preclamping amplitude (Ab) of N20-P25 was extremely variable, ranging from 0.9 and 7.5 microV, we adopted the ratio: deltaA=(At-Ab)/Ab (At=amplitude measured during clamping every 2 min at time t). Mean decrease of deltaA measured in the whole group ranged between 15% and 20%, but mean deltaA values in patients with pathological SEPs were around 60%. Even patients with positive CT-scans or with a back-pressure lower than 50 mmHg developed a mean deltaA decrease of about 20%. A pathological SEP was present in 50 patients, but developed in only 12 during the clamping trial. An intraluminal shunt was inserted in 22 cases; the other patients received pharmacological treatment with anaesthetic or vasoactive drugs. Among the patients with pathological SEPs, 3 presented postoperative symptoms related to carotid cross-clamping; only 1 of these was shunted but without SEPs normalisation. No patients with normal SEPs developed a postoperative neurological deficit, giving a reliability of 86.7%, a sensitivity of 100% and a specificity of 86.5%.
本研究旨在评估全身麻醉下颈动脉手术中体感诱发电位（SEP）在识别夹闭缺血方面的可靠性。
我们回顾了1975年至1993年间1550例接受手术的患者中连续196例在全身麻醉下进行颈动脉内膜切除术（CEA）的记录。所有患者均在手腕处对侧正中神经刺激后监测SEP。此外，他们接受了2500国际单位肝素的静脉推注，并测量了残端压力。所有患者均进行了血管造影。当N20 - P25 SEP复合波的振幅下降超过夹闭前值的50%（病理性SEP）或术前CT扫描显示对侧半球有缺血区域时，插入腔内分流管。在一些患者中，由于技术困难或在动脉切开缝合几乎完成时出现病理性SEP复合波下降，未插入分流管。
由于N20 - P25的夹闭前振幅（Ab）变化极大，范围为0.9至7.5微伏，我们采用了以下比率：deltaA =（At - Ab）/Ab（At =在时间t每2分钟夹闭期间测量的振幅）。全组测量的deltaA平均下降范围为15%至20%，但病理性SEP患者的平均deltaA值约为60%。即使CT扫描阳性或背压低于50 mmHg的患者，deltaA平均下降也约为20%。50例患者出现病理性SEP，但仅12例在夹闭试验期间出现。22例插入了腔内分流管；其他患者接受了麻醉或血管活性药物的药物治疗。在病理性SEP患者中，3例出现了与颈动脉夹闭相关的术后症状；其中只有1例进行了分流，但SEP未恢复正常。SEP正常的患者均未出现术后神经功能缺损，可靠性为86.7%，敏感性为100%，特异性为86.5%。
