Zandbergen E G J, Koelman J H T M, de Haan R J, Hijdra A
Department of Neurology and Clinical Neurophysiology, D2-112 Academic Medical Centre, University of Amsterdam, P.O. Box 22660, 1100 DD, Amsterdam, The Netherlands.
Neurology. 2006 Aug 22;67(4):583-6. doi: 10.1212/01.wnl.0000230162.35249.7f.
Short latency somatosensory evoked potential (SSEP) (N20) is a good predictor of poor outcome in postanoxic coma. It has been suggested that the long latency response (N70) may increase the sensitivity of SSEPs for predicting poor outcome.
As part of a prospective cohort study in 407 adult patients unconscious 24 hours after cardiopulmonary resuscitation (CPR), N20 was recorded 24, 48, and 72 hours after CPR, and N70 was recorded at least once in 319 patients. Poor outcome was defined as death or persistent vegetative state 1 month after CPR.
Absent N20 had a 0% false positive test rate at all time intervals, with prevalence of poor test result varying from 37 to 48%. Addition of abnormal N70 (absent or delayed > 130 msec) with present N20 as poor test result added 21 to 28% to this prevalence, but at the cost of a false positive test rate of 4 to 15%. Good outcome could not be predicted reliably with either of the tests, as only 28% of patients with normal N20 and N70 had a good outcome.
Determination of presence or absence of the N70 in patients with postanoxic coma gives additional information about the likelihood of poor outcome, but it is not precise enough to base treatment decisions solely on its absence.
短潜伏期体感诱发电位（SSEP）（N20）是缺氧后昏迷预后不良的良好预测指标。有人提出，长潜伏期反应（N70）可能会提高SSEP预测预后不良的敏感性。
作为一项对407例心肺复苏（CPR）后24小时仍昏迷的成年患者进行的前瞻性队列研究的一部分，在CPR后24、48和72小时记录N20，并在319例患者中至少记录一次N70。预后不良定义为CPR后1个月死亡或持续植物状态。
在所有时间间隔内，N20缺失的假阳性率为0%，检测结果不良的发生率在37%至48%之间。将异常N70（缺失或延迟>130毫秒）与存在的N20作为检测结果不良相加，使该发生率增加了21%至28%，但代价是假阳性率为4%至15%。两种检测方法均无法可靠地预测良好预后，因为只有28%的N20和N70正常的患者预后良好。
确定缺氧后昏迷患者是否存在N70可提供有关预后不良可能性的额外信息，但仅根据其不存在来做出治疗决策还不够精确。
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