主动脉转流防止脊髓损伤的研究

目的　探讨主动脉转流对主动脉阻断所致脊髓损伤的防止作用。方法　建立在小猪腹腔动脉开口以上阻断腹主动脉１ 小时和辅助主动脉转流的模型,观察术后动物出现并发症及组织病理学的改变,研究辅助主动脉转流重建肾上腹主动脉的效果。结果　阻断组１ 只小猪于术后死亡,另５ 只小猪术后都出现了下肢截瘫。阻断组术后截瘫评分明显低于转流组（ Ｐ＜ ０ ．０１） ,并能观察到明显的脊髓损伤的病理学变化。转流组和主动脉重建组的动物术后没有截瘫等并发症的发生。结论　当转流量达到腹主动脉近端原血流量的７０％ 时主动脉转流能较好地防止腹主动脉阻断１ 小时所造成的脊髓损伤。流量为主动脉近端原血流量的７０ ％ 是一个较好的远端主动脉灌注的个体化指标。     

体感诱发电位用于脊柱手术中脊髓功能的监测

目的评估体感诱发电位(SEP)用于脊柱手术中脊髓监测的可行性，以及皮质体感诱发电位(CSEP)与皮质下体感诱发电位(Sub—CSEP)监测的适应证。方法42例脊柱手术患者，年龄6～68岁，咪唑安定、丙泊酚及维库溴铵静脉诱导，安氟醚吸入维持麻醉．术中均应用CSEP和Sub—CSEP监测脊髓功能。结果CSEP受麻醉影响较大，Sub—CSEP波形稳定，全组7例诱发电位出现异常，其中3例与临床相符，4例为假阳性，无假阴性发生，准确率为90．5％。结论CSEP适于麻醉深度的监测，Sub—CSEP是脊柱手术中脊髓功能监测较为理想的方法。     

股静脉-股动脉转流在降主动脉重建术中的作用

目的：评价股静脉－股动脉转流在降主动脉人工血管重建术中的作用。方法：1999年12月至2001年6月间，在股静脉－股动脉转流下行降主动脉人工血管重建术12例为转流组；1994年6月至1999年8月15例降主动脉人工血管重建术为非转流组，比较两组在术后发生截瘫、内脏缺血、输血量和凝血功能异常等方面的差别。资料统计采用t检验或χ^2检验。结果：阻断时间超过60min者中，转流组的截瘫发生低于非转流组（P＜0．05）。转流组术后发生黄疸低于非转流组（P＜0．05），两组在术后肾功能异常上无明显差异（P＞0．05）。转流组输血量较非转流组明显减少（P＜0．01）。转流组术后凝血功能异常发生率低于非转流组（P＜0．05）。结论：股静脉－股动脉转流在预防降主动脉人工血管重建术后的截瘫发生、保护内脏功能、减少输血量和避免凝血功能异常等方面优于单纯阻断降主动脉，是一简便、安全的转流方式。     

主动脉转流压力控制对犬脊髓血流的影响

目的 评价主动脉转流压力控制对犬脊髓血流影响。方法 18条杂种犬随机分为转流1组、转流2组、阻断组(阻断主动脉30rnjn)，每组6条。转流1组控制脊髓灌注压为140mmHg、100mmHg、60mmHg、50mmHg；转流2组为40mmHg。同步记录脊髓灌注压、脊髓血流灌注量。术后3周进行神经功能评分及L3节段尼氏小体灰度半定量分析。结果 转流1组各压力点脊髓血流灌注量没有明显变化，转流2组有2条犬血流灌注量下降，阻断组则全部下降。转流1组无截瘫发生，转流2组有2条犬发生轻瘫，阻断组全部截瘫。结论 主动脉转流时脊髓灌注压50mmHg以上才是安全的，术前高血压者应适当提高脊髓灌注压水平。     

皮层体感诱发电位(CSEP)临护胸椎及胸椎管手术的临床研究

目的　通过开展皮层体感诱发电位 (CSEP)术中监护脊髓功能的临床研究 ,有效的预防医源性脊髓损伤 ,杜绝截瘫的发生。方法　 4 6例手术患者按 Frankel分级术前属 B级 6例 ,C级 14例 ,D级 15例 ,E级 11例 ,CSEP术中连续动态监测。监护临界值为 :D、E级患者术中波幅较麻醉后下降不超过 4 0 %。结果　 2 5例未达到监护临界值 ,术后无脊髓损伤。超过临界值发出警告 2 1例 ,其中 2 0例接受警告术后脊髓功能无损害 ,1例不顾警告继续手术 ,术后发生完全性截瘫。结论CSEP术中监护脊髓损伤准确可靠 ,值得推广应用。     

胸腹主动脉瘤手术的麻醉处理

胸腹主动脉瘤切除人造血管替换手术需高位阻断胸降主动脉,因而引起血流动力学的剧烈波动、阻断以下部位的代谢障碍和术后严重并发症(截瘫、肾衰等),麻醉处理颇有特点.现报道我院1998年完成的15例胸腹主动脉瘤手术的麻醉处理,探讨动脉转流、硬膜外阻滞以及脊髓保护措施在这类手术中的作用.     

皮层体感诱发电位监护在胸椎管狭窄症手术中的应用

目的：探讨皮层体感诱发电位（CSEP）监护在胸椎管狭窄症手术中的应用价值。方法：自2000年4月～2003年11月共有32例胸椎管狭窄症患者接受术中体感诱发电位监护，男21例，女11例，年龄38～75岁；其中单纯胸椎黄韧带骨化症13例，胸椎间盘突出症合并胸椎黄韧带骨化症10例，胸椎间盘突出症合并胸椎孤立后纵韧带骨化9例。单纯胸椎后路全椎板切除术4例，单纯后路全椎板截骨原位再植、椎管扩大减压术9例，全椎板截骨原位再植、环脊髓减压、椎管扩大减压成形术19例。术中均应用丹迪Key—Poim脊髓监护系统进行皮层体感诱发电位监护。结果：23例术中监护无异常，术后未出现神经系统并发症。其中12例患者术中即可见波形改善。4例术中出现波形异常，其中2例术后发生神经功能障碍。4例术中监护未见异常。术后症状加重，假阴性率12．5％。1例术中波形异常，但术后无脊髓损伤表现，假阳性率3.1％。结论：皮层体感诱发电位（CSEP）监护可及时发现术中危及脊髓的因素，但存在一定的假阳性或假阴性率。与其它监测方法合用可提高手术安全性。     

127例脊柱侧凸术中皮层体感诱发电位特点的分析

目的: 回顾分析 127例脊柱侧凸矫形手术术中皮层体感诱发电位的特点。方法: 127例脊柱侧凸手术采用皮层体感诱发电位监测, 电刺激胫后神经, 颅顶正中脑皮质足区放置表面记录电极。以基准线为判断基础, 当波幅下降超过 50%以上为阳性。结果: 在 127例监测中, 皮层体感诱发电位阳性者且与临床相符 3例。结论: 皮层体感诱发电位 (CSEP) 是目前首选的监测方法, 再组合皮层下诱发电位监测, 可进一步提高监测质量。     

颈胸椎手术中体感诱发电位监护的影响因素分析及准确性观察

目的探讨体感诱发电位监护在颈、胸椎手术中的应用价值,对其准确性及影响因素进行分析。方法颈、胸椎疾病患者采用皮层体感诱发电位（CSEP）及皮层下体感诱发电位（Sub-CSEP）术中监测,根据麻醉前、后及不同手术阶段体感诱发电位的变化与术后功能相结合,判断体感诱发电位（SEP）的准确性。结果麻醉因素引起的SEP波幅降低主要影响CSEP,双侧刺激均改变,但基本未达到手术预警标准值,而Sub-SEP变化不明显。手术高危操作侵及脊髓,SEP波幅降低主要影响高危操作的同侧,表现为同侧CSEP及Sub—CSEP波幅同时降低,并且降低幅度较大,达到预警标准值,而对侧CSEP及Sub-CSEP波幅变化不甚明显。其他非手术原因如低体温、局部冷盐水冲洗脊髓,引起SEP潜伏期延长,波幅变化不明显。失血过多致平均动脉压降低可引起SEP波幅降低,潜伏期变化不明显。局部低温及低血压引起的SEP改变,均未达到预警标准值。结论颈、胸椎手术中采用体感诱发电位监测排除各种干扰,可较准确地反映脊髓的生理或病理状况。     

颈椎手术中皮层体感诱发电位(CSEP)监护的临床研究

目的：通过开展皮层体感诱发电位（CSEP）术中监护脊髓功能的临床研究，有效的预防医源性脊髓损伤。杜绝截瘫的发生。方法：71例手术患者按Frankel分级术前属B级5例，C级24例，D级27例。E级15例，CSEP术中连续动态监测。作者经实验研究并结合临床提出CSEP术中监护临界值为，D、E级患者术中波幅较麻醉后下降不超过50%；B，C级患者术中波幅较麻醉后下降不超过40%，结果：39例未达到监护临界值，术后无脊髓损伤，超过临界值发出警告32例，其中31例接受警告术后脊髓功能无损害。1例不顾警告继续手术。术后发生完全性截瘫。结论：CSEP术中监护脊髓损伤准确可靠。值得推广应用。     

Cyclosporin A reduces delayed motor neuron death after spinal cord ischemia in rabbits

BACKGROUND: Spinal cord ischemia has varied etiologies, and in some cases, may develop into paraplegia. This is attributable to the vulnerability of spinal motor neurons to ischemia. We evaluated the potential of the immunosuppressant cyclosporin A for treatment of spinal motor neuron damage caused by ischemia. METHODS: Twenty-eight rabbits were randomized into four groups of 7 animals each: group A (cyclosporin A not administered), group B (2.5 mg/kg cyclosporin A), group C (25 mg/kg cyclosporin A), and group S (sham-operated). The spinal cord ischemia model was created by a 15-minute occlusion of the aorta just caudal to a renal artery with a balloon catheter. Administration of cyclosporin A began 30 minutes after restoration of blood flow. The spinal cords were removed after 7-day monitoring of neurologic function. Pathology specimens were prepared, and after staining them with hematoxylin-eosin, viable motor neurons in the ventral spinal cord were counted under light microscopy. RESULTS: At 7 days after reperfusion, recovery of motor function was seen at varying degrees in groups B and C, whereas all animals in group A continued to exhibit paraplegia. In group C, most of the animals recovered to the baseline level, before creation of the ischemia model. A significant difference in numbers of viable neurons was found in group A (cell count, 10.1 +/- 4.7) and group C (cell count, 22.2 +/- 8.0) (p < 0.05). Higher numbers of viable motor neurons corresponded to a greater recovery of motor function. CONCLUSIONS: These results suggest that cyclosporin A administration is effective against neuronal damage caused by spinal cord ischemia.     

The use of left heart bypass in the repair of thoracoabdominal aortic aneurysms: current techniques and results

The surgical repair of thoracoabdominal aortic aneurysms (TAAA) remains challenging. The prevention of spinal cord ischemic complications requires a multidisciplinary approach. The protective effect of left heart bypass (LHB), particularly regarding spinal cord ischemia, during the repair of extensive TAAA is evaluated here. Data from 1,250 consecutive patients who underwent the repair of extent I or extent II TAAA over a 16-year period was prospectively entered into a database. LHB was used in 666 (53.3%) patients. This group was retrospectively compared with 584 (46.7%) patients who had undergone surgery without the use of LHB. A total of 1,173 (93.8%) patients were 30-day survivors. Paraplegia or paraparesis developed postoperatively in 68 (5.5%) patients. In patients with extent I TAAA, paraplegia and paraparesis rates in the LHB cohort (9 of 290, 3.1%) and those without LHB (13 of 313, 4.2%) were statistically similar (P=0.866). The latter was observed despite the fact that longer clamp times were used in the LHB group. In patients with extent II TAAA, the LHB group had a statistically significant lower incidence of paraplegia or paraparesis (17 of 375, 4.5%) compared with the non-LHB group (29 of 259, 11.2%; P=0.019). In our experience, we identified LHB as protective for reducing the risk of postoperative paraplegia and paraparesis in patients who underwent the repair of extent I and extent II TAAA, the latter statistically significant.     

Immediate ischemic preconditioning based on somatosensory evoked potentials seems to prevent spinal cord injury following descending thoracic aorta cross-clamping.

OBJECTIve: Delayed ischemic preconditioning has demonstrated neuroprotective effects in spinal cord ischemia. We investigated the effects of immediate ischemic preconditioning based on somatosensory evoked potentials monitoring in a model of spinal cord injury due descending thoracic aorta occlusion in dogs. METHODS: Twenty-one dogs were submitted to spinal cord ischemia induced by descending thoracic aorta cross-clamping for 45 min. Control group underwent only the aortic cross-clamping (n=7), group A underwent one cycle of ischemic preconditioning (n=7) and group B underwent three equal cycles of ischemic preconditioning (n=7), immediately before the aortic cross-clamping. Ischemic preconditioning cycles were determined by somatosensory evoked potentials monitoring. Neurologic evaluation was performed according to the Tarlov score at 72 h of follow-up. The animals were then sacrificed and the spinal cord harvested for histopathology. RESULTS: Aortic pressures before and after the occluded segment were similar in the three groups. Ischemic preconditioning periods corresponded to a mean ischemic time of 3+/-1 min and a mean recovery time of 7+/-2 min. Severe paraplegia was observed in three animals in Control group, in four in group A and in none in group B. Tarlov scores of group B were significantly better in comparison to the Control group (P=0.036). Histopathologic examination showed severe neuronal necrosis in the thoracic and lumbar gray matter in animals who presented paraplegia. CONCLUSIONS: Immediate repetitive ischemic preconditioning based on somatosensory evoked potentials monitoring seems to protect spinal cord during descending aorta cross-clamping, reducing paraplegia incidence.     

Hypothermic regional perfusion for protection of the spinal cord during periods of ischemia

Ischemic spinal cord injury with resulting postoperative paraplegia is an inherent risk for operations on the thoracic aorta. The mechanism of injury is not clearly understood, and numerous adjuncts to avoid this complication have been suggested, with conflicting clinical results. A new technique of hypothermic regional perfusion of the spinal cord is described. Fifteen female pigs weighing 21 to 39 kg were used for the experiment. The control group consisted of 5 animals in which the thoracic aorta was clamped at the distal arch for 30 minutes. All of these animals sustained postoperative neurological damage. Eighty percent sustained postoperative paraplegia, and 20% had severe spasticity of the hind legs that precluded normal ambulation. The experimental group consisted of 10 animals in which hypothermic regional perfusion was performed for 30 minutes after cross-clamping of the distal arch. Perfusion cooling was followed by 30 minutes of ischemia in 5 animals and 45 minutes of ischemia in the remaining 5. All animals that underwent hypothermic regional perfusion were able to walk postoperatively, and no evidence of ischemic injury was found at postmortem examination of the spinal cords. This technique proved to be simple and effective in protecting the spinal cord for up to 45 minutes of ischemia in the experimental group. The clinical implications of this concept are promising for patients undergoing operations on the thoracic aorta.     

Left heart bypass during descending thoracic aortic aneurysm repair does not reduce the incidence of paraplegia

BACKGROUND: The preferred technique for spinal cord protection during surgical repair of descending thoracic aortic aneurysms (DTAAs) remains controversial. The purpose of this retrospective analysis was to determine if the use of left heart bypass (LHB) reduced the incidence of paraplegia in patients who underwent DTAA repair. METHODS: Over a 15-year period 387 consecutive patients underwent surgical repair of DTAAs using either the "clamp-and-sew" technique (341 patients, 88.1%) or distal aortic perfusion via a LHB circuit (46 patients, 11.9%). Data regarding patient characteristics, operative variables, and outcomes were retrieved from a prospectively maintained database. The impact of LHB on the frequency of paraplegia was determined using univariate and propensity score analyses. RESULTS: There were 17 operative deaths (4.4%) including 11 patients (2.8%) who died within 30 days. Paraplegia occurred in 10 patients (2.6%). On univariate analysis increasing age (p = 0.03), increasing aortic clamp time (p < 0.001), increasing red blood cell transfusion requirements (p = 0.01), and acute dissection (p = 0.03) were associated with increased incidence of paraplegia. Patients who received LHB had a similar incidence of paraplegia (2/46, 4%) compared with those treated without LHB (8/341, 2.3%; p = 0.3). Both matching and stratification propensity score analyses confirmed that LHB was not associated with reduced risk of paraplegia. CONCLUSIONS: On retrospective analysis the use of LHB during DTAA repair did not reduce the incidence of spinal cord injury. The "clamp-and-sew" technique remains an appropriate approach to DTAA repair.     

The effect of hyperemia on spinal cord function after temporary thoracic aortic occlusion

Nineteen mongrel dogs had 30 minutes of thoracic aortic occlusion to determine the effects that blockade of the renin-angiotensin system may have on preserving spinal cord blood flow and function during a period of temporary spinal cord ischemia. Cross-clamping of the thoracic aorta causes renal ischemia and activates the renin-angiotensin system with resulting increased production of angiotensin II. Angiotensin II is a potent peripheral constrictor and elevated levels may constrict collateral spinal cord circulation. At the time of aortic cross-clamping, 10 dogs received 100 mg/kg of MK422 (intravenous enalapril maleate), a converting enzyme inhibitor, and nine animals served as controls. The blockade of the renin-angiotensin system had no preserving effects on spinal cord flow as measured by microspheres and on spinal cord function as graded with the Tarlov scale. However, the paraplegic animals all had significantly increased lower thoracic and lumbar spinal cord flows 30 minutes after clamp release when compared with those animals that remained neurologically intact. In conclusion, marked hyperemia occurring after a period of hypoperfusion may lead to spinal cord edema and compartment syndrome with resulting paraplegia.     

Effect of the free radical scavenger MCI-186 on spinal cord reperfusion after transient ischemia in the rabbit

Objective: Paraplegia remains a serious complication of aortic operations. The production of free radicals during reperfusion after transient ischemia is believed to induce secondary spinal neuronal injury, resulting in paraplegia. The aim of the present study was to clarify the protective effect and method of administration of antioxidants on the neurological and histological outcome in the animal model for reperfusion injury after transient spinal cord ischemia. Methods: New Zealand white rabbits underwent surgical exposure of the abdominal aorta that was clamped for 15 minutes to achieve spinal cord ischemia. Group A animals received two 10 mg/kg doses of 3-methyl-l-phenyl-2-pyrazolin-5-one (MCI-186) at the time of release of the aortic clamp and 30 minutes later. In group B, MCI-186, 5 mg/kg, was given three times, at the time of aorta clamp release, 30 minutes and 12 hours later. In group C (control group), one dose of vehicle was administered. Neurological status was assessed using modified Tarlov’s score until 168 hours after operation. Spinal cord sections were examined microscopically to determine the extent of ischemic neuronal damage. Results: Groups A and B animals had better neurological function than group C (p(0.001). In contrast, group C animals exhibited paraplegia or paraparesis with marked neuronal necrosis. The number of surviving neurons within examined sections of the spinal cord was significantly greater in group B than in group C (p(0.001). Conclusion: In a 15-minute ischemia-reperfusion model using rabbits, systemic repetitious administration of MCI-186, a free radical scavenger, was found to have a protective effect on the spinal cord neurons both neurologically and histologically. We postulate that the drug minimizes the delayed neuronal cell death for reperfusion injury after transient ischemia by reducing the free radical molecules. Moreover, it was thought that we could protect delayed neuronal cell death more effectively by administering MCI-18612 hours later.