Department of Neurology, Charité Universitätsmedizin Berlin, Charitéplatz 1, D-10117 Berlin, Germany.
Neurology. 2010 Mar 23;74(12):965-9. doi: 10.1212/WNL.0b013e3181d5a631.
Bilateral absent N20 responses of median nerve somatosensory evoked potentials (SEPs) reliably predict poor prognosis after cardiac arrest. However, the studies supporting this fact were carried out before hypothermia was established as standard treatment. Recent evidence suggests that hypothermia treatment affects the predictive value of clinical findings in cardiac arrest patients, raising the question whether the predictive value of N20 responses has changed as well.
We retrospectively studied 185 consecutive patients treated with hypothermia after cardiac arrest. SEP recordings were available for 112 patients. SEPs were classified as bilateral absent N20, pathologic N20, or normal. Baseline and follow-up information were obtained from our database.
We identified 36 patients with bilateral absent N20, 35 (97%) of whom had poor outcome. One patient had prolonged high amplitude peripheral SEP, but bilaterally absent N20 3 days after cardiac arrest and regained consciousness with normal cognitive functions and reproducible N20 responses. One further patient had minimally detectable N20 at day 3 and recovered consciousness and normal N20 responses on follow-up.
Our data indicate that recovery of consciousness and cognitive functions is possible in spite of absent or minimally present N20 responses more than 24 hours after cardiac arrest in a very small proportion of patients. N20 responses may recover beyond this time window. The predictive value of bilateral absent N20 responses needs to be reevaluated in larger prospective studies. Until these studies are available, decisions to stop therapy in cardiac arrest survivors should not be based on N20 responses alone.
正中神经体感诱发电位（SEP）双侧 N20 波消失可可靠预测心脏骤停后患者的不良预后。然而，支持这一事实的研究是在低温治疗确立为标准治疗之前进行的。最近的证据表明，低温治疗会影响心脏骤停患者临床发现的预测价值，这引发了一个问题，即 N20 波的预测价值是否也发生了变化。
我们回顾性研究了 185 例接受心脏骤停后低温治疗的连续患者。112 例患者可进行 SEP 记录。SEP 被分为双侧 N20 波消失、病理性 N20 波或正常。基线和随访信息从我们的数据库中获得。
我们发现 36 例患者双侧 N20 波消失，其中 35 例（97%）预后不良。1 例患者有延长的高振幅周围 SEP，但双侧 N20 波在心脏骤停后 3 天消失，意识恢复，认知功能正常，N20 波反应可重现。另有 1 例患者在第 3 天仅可检测到最小的 N20 波，随后意识恢复，认知功能正常，N20 波反应可重现。
我们的数据表明，尽管在心脏骤停后 24 小时以上存在双侧 N20 波消失或仅存在极小的 N20 波，但仍有一小部分患者可能会恢复意识和认知功能。N20 波可能会在此时间窗口之外恢复。双侧 N20 波消失的预测价值需要在更大的前瞻性研究中重新评估。在这些研究可用之前，不应仅基于 N20 波反应来决定是否停止对心脏骤停幸存者的治疗。
