Epidural anesthesia is the most commonly used method of pain relief during labor in the USA. It is estimated that more than 50% of women delivering in hospital use epidural anesthesia. Despite approximately 4 million births per year in the USA, serious neuro-logical complications resulting from this technique are exceptionally rare. One review of 27 000 cases showed an incidence of just 0.01%.
在美国硬膜外麻醉是最常用的分娩过程中缓解疼痛的方法。据估计, 超过50%的妇女在医院分娩应用硬膜外麻醉。尽管每年将近400万新生儿出生在美国，但是由于硬膜外技术导致的严重神经系统并发症却相当罕见。一项27000例的回顾性研究显示只有0.01%
The patient was a 22-year-old primiparous white woman, who presented at 40 weeks gestation with rupture of the membranes. She had previously been in good health and the pregnancy had been unremarkable, including thyroid function tests. She had no history of substance abuse. Blood tests and urinalysis on admission were normal apart from expected dilutional anemia.
病人是一个22岁的初产白人女性，妊娠40周，胎膜破裂。她以前一直处于良好的健康、正常的孕程，甲状腺功能试验也正常。她没有滥用药物的病史。血液检查和尿液分析入院时也正常，除了预期的稀释性贫血。
Intravenous (IV) oxytocin was started as standard procedure shortly after admission. Labor commenced 5½ h later. Analgesia was achieved by IV morphine sulphate via patient-controlled analgesia (PCA) and epidural lidocaine 1.5%.
入院后不久按照标准程序静脉注射催产素。在5½h后开始产程。麻醉通过静脉患者自控镇痛泵静注吗啡和硬膜外给予1.5%利多卡因。
During her 4 h labor, the patient received a total dose of 6 mg of morphine via PCA. Over the same time period, she received a total of 60 ml of a solution of lidocaine 1.5% (total dose of lidocaine 600 mg) with epinephrine 1:200 000. The placement was confirmed by lack of cerebrospinal fluid (CSF) leak from the catheter. No ‘test’ dose of lidocaine was administered.
在她4小时的分娩过程中，病人通过自控镇痛泵接受了总剂量为6毫克的吗啡。与此同时，她输注了总共有60毫升的溶液，由1.5%利多卡因（利多卡因总剂量600 mg）与1:200000肾上腺素混合。装置被证实没有脑脊液从导管泄漏，没有 给予“试验”剂量利多卡因。
At this time a decision to proceed to cesarean section was made because labor was not progressing. She was given an additional bolus of epidural lidocaine (5 ml=50 mg) prior to surgery. She became unresponsive shortly thereafter and no further analgesia was given. Her airway remained patent with regular breathing. The patient’s blood pressure (BP) and heart rate remained stable throughout the procedure, at 110–125/65–80 mmHg and 65–80 /min, respectively.
These readings were similar to those at admission and to those taken during clinic visits throughout her pregnancy. Supplemental oxygen was administered throughout surgery, which was completed within 20 min. The infant’s APGAR scores were 10.
在这个时候，由于产程没有进展，所以决定进行剖宫产。术前她硬膜外被给予一个追加剂量的利多卡因（5毫升= 50毫克）。此后不久，她变得没有反应，此时并没有给予进一步的镇痛。她的气道保持通畅伴有正常呼吸。病人的血压、心率术中保持稳定，在110–125 / 65–80 mmHg和65–80 /分钟。
这些生命体征读数和在入院的时候，和整个她的怀孕期间的诊所随访的数值是相近的。手术近20分钟，全程给予吸氧，新生儿Apgar评分分别为10.
A detailed neurological exam 1½ h later (6 h after starting the epidural) was performed while she remained in the recovery room. This showed the following:
· Eyes closed; pupils fixed and unreactive, measuring 5 mm;
· No response to pain (nail bed pressure);
· Absent corneal and oculocephalic reflexes;
· No movement of the eyes with cold caloric stimulation;
· Decreased muscle tone throughout;
· Diminished reflexes: biceps 1 ; Babinski’s reflex was absent; no other reflexes could be elicited;
· Regular, deep breathing at a rate of 12/min without support; no cyanosis was present.
一个详细的神经系统检查在1½小时后进行（硬膜外操作后的6小时），此时她仍然在苏醒室。体征如下：
双眼紧闭；瞳孔固定，测量在5毫米；
对疼痛无反应（按压甲床）；
没有角膜和眼脑反射；
眼球对冷热刺激没有运动反应；
全身肌张力降低（几乎无力）；
反射减弱：肱二头肌1 ；Babinski反射消失；其他病理反射阴性；
能进行自主、规律的呼吸，频率为12，无紫绀。
Within 30 min she began to recover. This was manifest initially by the return of all brainstem reflexes along with sensitivity to pain; muscle power recovered to at least 4 /5 throughout.
在30分钟内，她开始恢复。最初是明显的由脑干反射系统的恢复以及对疼痛的感知，全身肌肉力量恢复到至少4 到 5级。
Within another 30 min she could open her eyes when spoken to and was able to say her name and also “I feel very tired”; she could easily follow instructions, such as “squeeze my hand”. She remained drowsy, limiting a more detailed assessment of mentation. Her muscle tone remained decreased and reflexes at the knees and ankles remained absent. Power was at least 4 /5 throughout. She was moved to a ward for additional observation.
在另一个30分钟内，她可以睁开眼睛，说出她的名字，和“我觉得很累”；她可以轻松地听从指令，如“握紧我的手”。她仍然昏昏欲睡，限制了一个更详细的精神心理状态评估。她的肌肉紧张度仍然减低，膝盖和脚踝的反射缺失。全身肌力4 到5级。转至病房做进一步的观察。
Within another 4 h she had recovered fully. Blood tests, performed at coma onset and the following day, were unremarkable: complete blood count, comprehensive metabolic panel, magnesium, TSH, and blood cultures. An MRI of the brain was performed, which was entirely normal. She was discharged on post-operative day 2 without incident.
在另一个4小时内，她已经完全康复了。血液检查，在昏迷发生当天和第二天，未见异常：包括血常规、生化、镁、TSH、和血培养。头部核磁检查完全正常的。她在手术后2天正常出院。
This case is typical of the phenomenon known as “massive epidural”. The neurologic exam and the stages of recovery are described in more detail here than in previous reports. The MRI of the brain is also reassuring; we acknowledge that the test may have been unnecessary.
这个病例是典型“大量硬膜外（给药）”。神经系统检查和恢复阶段的情况比其他病例描述的更详细。大脑的MRI结果也是可靠的；当然我们承认，这个检查可能是不必要的。
We propose that the mechanism at work here is ‘sensory deafferentation dependent sedation’, leading to the impairment of brainstem transmission. In particular, the ascending reticular activating system (ARAS) * appears to require sensory input in order to continue to maintain alertness. This is a logical extension of the experimental work below, particularly that performed with volunteers undergoing epidural anesthesia while measurements were taken of brainstem function, as well as of sedation
我们认为它的机制就是“（感觉）传入神经阻滞从属性镇静”，导致脑干传导缺失。特别是，上行网状激活系统（ARAS）为了继续维持觉醒，似乎需要的感觉的传入。如下是一个回归性的扩展实验工作，主要对志愿者进行硬膜外麻醉，同时采取镇静状态下的脑干功能测量。
The use of morphine can be seen as a predisposing factor,although it is neither necessary nor sufficient to explain the depth of coma reached. If this were the case, we would have expected the patient to have ‘pinpoint’ pupils. The half-life of morphine IV in young adults is around 2 h; therefore, the initial dose of 2 mg given over the first hour would be expected to have almost completely worn off by the time coma developed
使用吗啡可以被视为一种诱发因素，尽管它是既不是必需的，也不足以解释达到昏迷的深度。如果是因为这样的话，我们会预计病人有“针尖样”瞳孔 。在年轻的成年人中静脉给予吗啡的半衰期约为2小时，因此，最初的在第一个小时给予的2毫克剂量，在昏迷发生的时候，预计已经几乎完全消耗了。
Epidural (as well as spinal) anesthesia has long been recognized to reduce the drug dosages necessary to achieve CNS sedation or coma (e.g., with thiopental, midazolam, isoflu-rane, sevoflurane, and propofol). Furthermore, the higher potency bupivacaine (vs. lidocaine) has been reported to reduce the dose of anesthetic necessary to maintain general anesthesia for surgery
硬膜外麻醉（以及腰麻）早已被认识到要以减少药物剂量（如硫喷妥钠、咪达唑仑，异氟烷，七氟醚，丙泊酚），来达到中枢镇静和昏迷状态。此外，更高的效力布比卡因（与利多卡因）已被报道，以减少必要的麻醉剂量，来维持全身麻醉手术。
The question has been raised as to whether the systemic absorption of epidural anesthesia may be responsible for some of its observed effects. Evidence against this comes from a randomized trial of lidocaine given via epidural or IV to patients recovering from surgery under standard inhalational anesthesia. Despite the higher systemic levels of lidocaine in the IV group, they recovered more slowly from coma
是否硬膜外麻醉药物的全身吸收可能是观察结果的原因。相反的证据来自一个随机试验吸入麻醉下手术给予硬膜外或静脉注射利多卡因的患者苏醒情况。虽然在静脉注射组有较高的全身水平的利多卡因，他们从昏迷中恢复得更缓慢。
A technique closely related to epidural anesthesia is spinal anesthesia. One authority has noted that “the only real differences are the site of injection and the volume of anesthetic used”. While there is more systemic absorption of local anesthetic from the epidural space (due to its rich venous plexus), this is likely to have little bearing on loss of sensory input
硬膜外麻醉密切相关的技术是椎管内麻醉。一个权威人士指出，“唯一的真正的区别是注射的部位和麻醉的使用量”。虽然有更多的局麻药从硬膜外腔吸收至全身（由于其丰富的静脉丛），这可能对感觉传入的损失影响不大。
Both epidural and spinal anesthesia have been studied in volunteers to clarify the mechanism responsive for the sedation seen with these techniques. To quantify alertness, these studies used techniques that have been recommended in the operating room. The use of these measures remains far from routine:
硬膜外和椎管内麻醉都在志愿者身上进行了研究，澄清用这两种技术对镇静反应的机制。为了量化觉醒程度，以下研究使用的技术已被推荐在手术室应用。然而还不是常规应用：
1.The bispectral index (BIS) is a measure derived from EEG. It is recommended in the British National Institute for Health and Care Excellence (NICE) Guidelines as an option during any type of surgery in patients at higher risk of awareness during surgery or of excessively deep anesthesia and in all patients receiving total intravenous anesthesia. A meta-analysis concluded that it aids “postoperative recovery from relatively deep anesthesia”
1.脑电双频指数（BIS）源自脑电测量。它被英国国家卫生与临床优化研究所（NICE）推荐作为一个选项，在任何类型的有较高的认知风险的手术患者或者麻醉过深和所有全凭静脉麻醉的患者。一个Meta分析得出结论认为，它对从相对较深的麻醉术后恢复有帮助。
2.Brainstem auditory evoked potentials (BAEPs) . In a randomized trial in cardiac surgery, these have been shown to reduce the dose requirement for anesthetic agents and the need for intraoperative vasopressors. Changes in the BAEP index has also been suggested to be more useful than BIS in monitoring the induction of anesthesia, particularly for ketamine
脑干听觉诱发电位（BAEPs）。在一个在心脏手术的随机试验中，这些已被证明，可以减少麻醉药物和术前升压药需要的剂量。脑干听觉诱发电位指数的变化也被认为在麻醉诱导中比BIS监测更有用的，特别是对氯胺酮麻醉。
In the epidural study, the only correlate of depth of sedation was BAEP wave III. This measures the electrical activity of the inferior colliculus, which receives input from the spinothalamic tracts and the medial lemniscus; when active, it increases cortical activity through its influence on ascending cholinergic and serotonergic pathways. It is thought to be a key anatomic mediator of the increased alertness that occurs with the startle reflex.
在硬膜外的研究中，唯一相关的镇静深度指标为BAEP 波III，它测量下丘神经元的电活动，它接受来自脊髓丘脑束和内侧丘系传入；当活跃时，通过提升胆碱能和血清素途径影响增加皮层的活动。它被认为是重要的调节结构，提高了惊跳反射发生的觉醒。
Referring again to Table 1, it is certainly striking that a number of these cases occurred soon after the injection of a small additional bolus of anesthetic. Comparison of doses is complicated by differing dosing regimens and durations of anesthesia. However, the common theme is that this bolus pushed already-sedated patients ‘over the edge’ into coma, by further decreasing spinal cord input, resulting in a corresponding loss of brainstem function.Our case is, clinically, the most closely observed to date; like coma from any cause, respiration is the last reflex to plete loss and recovery of the other brainstem reflexes appears to occur almost simultaneously.
再次提到表1，显着的是这些案例均在追加小剂量麻醉药后不久发生。剂量、不同给药方案和麻醉持续时间比较很复杂。然而，共同的主题是，这个追加通过进一步减少脊髓信号传入，导致相应的脑干损失功能，使已经镇静的患者从边缘进入昏迷。我们的情况是，临床上，最密切观察到的日期，像任何原因导致的昏迷，呼吸是最后消失的反射。其他脑干反射的完全丧失和恢复似乎几乎同时发生。
Our patient lost consciousness due to impaired sensory input.Why this occurs only rarely remains unclear. Spread to the subdural space has been suggested as a possible cause. The latter appears attractive theoretically – the slow rate of spread is consistent with the gradual clinical onset of symptoms. An alternative explanation, that some individuals are much more sensitive to this form of anesthesia, cannot be excluded; however, there are no reports of recurrent episodes in the same patient. Also, these individuals appear to be at no greater risk of other adverse reactions to medications.
我们的病人，由于感觉传入的受损，失去了意识。为什么这种情况只发生很少仍然不清楚。药物进入硬膜下腔被提出作为一个可能的原因。后者从理论上讲显得很有吸引力，缓慢的传播速度和临床症状是一致的。另一种解释，不能排除，一些人对这种形式的麻醉更敏感；但是，有没有报告在同一病人的重复发作。此外，这些人似乎没有对其他药物不良反应表现出更大的风险。
Regarding nomenclature: the terms “massive epidural” and “total spinal analgesia following epidural analgesia”, while of undoubted historical importance, do not emphasize the pathogenesis of this condition and may be puzzling for the non-specialist. We propose the term “(transient) coma due to loss of sensory input” as more descriptive and easier to understand for the general physician.
关于命名术语：“大量硬膜外（给药）”和“蛛网膜镇痛后的全脊麻醉”，当然无疑具有历史意义，不强调这种情况的发病机制，这可能令非专业的人员很难理解。我们建议的术语“由于感觉传入的缺失的（瞬态）昏迷”，对大多数一身来讲更具描述性，更容易理解。
This ‘coma due to loss of spinal sensory input’ may be encountered by any clinician caring for a patient undergoing epidural anesthesia. Once the phenomenon is recognized, we suggest that no further investigations are required; the patient and family may be reassured once the coma resolves.
这种“由于脊髓感觉传入的损失”可能被任何临床医生对病人行硬膜外麻醉时遇到。一旦这一现象被确认，我们建议，没有进一步的调查的必要，一旦昏迷恢复，病人和家人就可以放心。
来源：舒适化麻醉论坛
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