Guérit J M, Verhelst R, Rubay J, Khoury G, Matta A, Dion R
Clinical Neurophysiology Unit, Cliniques Universitaires St.-Luc, Brussels, Belgium.
Eur J Cardiothorac Surg. 1996;10(2):93-103; discussion 103-4. doi: 10.1016/s1010-7940(96)80130-8.
The usefulness of somatosensory evoked potential (SEP) monitoring as a means of preventing paraplegia in descending aorta surgery was evaluated in 47 consecutive cases operated on for isthmic (14 cases), thoracic (22 cases), or thoraco-abdominal (11 cases) repair. An aortic dissection was found in 11 cases (acute in 6). Somatosensory evoked potentials were obtained by unilateral left and right posterior tibial nerve (PTN) stimulation at the ankle and recordings were performed on four channels: peripheral nerve, lumbar spinal, brain-stem, and cortical recordings. Our experience led to the following current strategy: the establishment of atrio(aorto)-femoral(aortic) bypass (29 cases), proximal and distal aortic cross-clamping, aortic repair with reimplantation of the culprit artery(ies) as indicated by SEP alterations. Five types of SEP alterations were defined on the basis of the neural level involved: type I (27.7% of cases) = distal spinal ischemia due to proximal aortic cross-clamping in the absence of bypass; type II (21.3%) = PTN ischemia due to left common femoral artery cross-clamping; type III (12.8%) = segmental spinal ischemia due to the exclusion of critical feeding arteries; type IV (4.3%) = ischemia in the left carotid artery territory; type V (4.3%) = global brain hypoperfusion due to systemic hypotension. Forty-five patients survived the operation and could be tested for neurological dysfunction. Three patients presented a postoperative spinal cord deficit, but this deficit was already present preoperatively in one case, so that the actual incidence of a new paraplegia in our series was 2/45 cases (4.4%). One of the two cases was clearly a delayed paraplegia with SEP alterations appearing several hours after the operation. Somatosensory evoked potentials were evaluated on the basis of their sensitivity, specificity, and impact on the surgical strategy. Regarding SEP sensitivity, we did not encounter any unexpected immediate paraplegia, but the critical factor appeared to be the duration of SEP absence due to spinal cord ischemia, which, according to the literature, should never exceed 30 min; after a longer absence, SEP return does not guarantee neurological recovery. Somatosensory evoked potential specificity was also 100%, but only 58% of the abnormalities found were actually consequent to spinal cord ischemia, the rest of the abnormalities being consequent to peripheral nerve or brain ischemia. Finally, SEP monitoring had a significant impact on surgical strategy in 19% of the cases. It is concluded that distal aortic perfusion and multilevel SEP monitoring play a significant role in preventing paraplegia in descending aorta surgery.
在47例连续接受峡部（14例）、胸段（22例）或胸腹段（11例）降主动脉修复手术的患者中，评估了体感诱发电位（SEP）监测作为预防降主动脉手术中截瘫手段的有效性。11例患者发现主动脉夹层（6例为急性夹层）。通过在踝关节处单侧刺激左右胫后神经（PTN）获得体感诱发电位，并在四个通道进行记录：外周神经、腰段脊髓、脑干和皮层记录。我们的经验得出了以下当前策略：建立心房（主动脉）-股动脉（主动脉）旁路（29例），近端和远端主动脉阻断，根据SEP改变情况对罪犯动脉进行再植入的主动脉修复。根据所涉及的神经水平定义了五种类型的SEP改变：I型（占病例的27.7%）=在无旁路的情况下，近端主动脉阻断导致的远端脊髓缺血；II型（21.3%）=左股总动脉阻断导致的PTN缺血；III型（12.8%）=关键供血动脉被排除导致的节段性脊髓缺血；IV型（4.3%）=左颈动脉区域缺血；V型（4.3%）=全身低血压导致的全脑灌注不足。45例患者术后存活并可进行神经功能障碍检测。3例患者出现术后脊髓功能缺损，但其中1例术前就已存在该缺损，因此我们系列中新发截瘫的实际发生率为2/45例（4.4%）。两例中的一例明显为延迟性截瘫，SEP改变在术后数小时出现。根据SEP的敏感性、特异性及其对手术策略的影响对体感诱发电位进行了评估。关于SEP敏感性，我们未遇到任何意外的即刻截瘫情况，但关键因素似乎是脊髓缺血导致SEP缺失的持续时间，根据文献，该持续时间绝不应超过30分钟；SEP缺失时间更长后，其恢复并不保证神经功能恢复。SEP特异性也为100%，但发现的异常中只有58%实际上是由脊髓缺血导致的，其余异常是由外周神经或脑缺血导致的。最后，SEP监测在19%的病例中对手术策略有显著影响。得出的结论是，远端主动脉灌注和多水平SEP监测在预防降主动脉手术中的截瘫方面发挥着重要作用。
