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1、Topic of the Day I(for Interns and CA-2s)Oct 26 - Discuss unilateral epidural block - explain this result形成单侧硬膜外阻滞的原因Discussion point.A unilateral anesthetic block may result from the administration of local anesthetic in the epidural space secondary to the plica mediana dorsalis, a connective tissu
2、e band in the epidural space that extends in a vertical direction between the ligamentum flavum and dura mater dividing the epidural space in half. 由于背正中皱襞的存在，在硬膜外腔注入局部麻醉药后可造成单侧阻滞。背正中皱襞作为连接黄韧带和硬膜的带状结缔组织在硬膜外腔垂直延伸，并把其一分为二。Oct 27 - Compare sympathetic, motor & sensory block of epidurals vs spinals比较硬膜外
3、麻醉和脊髓麻醉的交感、运动和感觉神经阻滞Discussion points.Epidural anesthesia results in sympathetic nerve blockade, sensory nerve blockade, and motor nerve blockade just as in spinal anesthesia. In epidural anesthesia, however, the levels of each are different than they are in spinal anesthesia. First, sympathetic ner
4、ve blockade is at a level equal to sensory nerve blockade, rather than the two to six segments higher that is seen in spinal anesthesia. Second, motor nerve blockade may average four segments lower than sensory nerve blockade, rather than the two segments seen in spinal anesthesia.The major site of
5、action of local anesthetics administered in the epidural space is at the spinal nerve roots. At the spinal nerve roots the dura mater is relatively thin, allowing for the easiest diffusion of local anesthetic through the dura mater to the nerves.There is often a delayed onset in anesthesia at the Sl
6、-S2 nerve root region during an epidural anesthetic. This may be due to the covering of these nerve roots with connective tissue, slowing the diffusion of local anesthetic to these nerve roots.The diffusion of local anesthetic from the epidural space to the subarachnoid space is a minor contributor
7、to the anesthetic effects of local anesthetic solutions in the epidural space. 正如脊髓麻醉一样，硬膜外麻醉亦可阻滞交感、感觉和运动神经。但是，各神经被阻滞的平面在硬膜外麻醉与脊髓麻醉中有所不同。首先，硬膜外麻醉中交感阻滞与感觉阻滞的平面相同，而脊髓麻醉中前者要比后者高26个节段。其次，硬膜外麻醉中运动阻滞平面平均比感觉阻滞平面低4个节段，而脊髓麻醉中前者比后者低2个节段。脊神经根是硬膜外腔注入的局部麻醉药的主要作用部位。脊神经根附近的硬膜相对较薄，使局部麻醉药容易经此扩散至神经而发挥作用。在硬膜外麻醉过程中，骶12
8、神经根支配区域的麻醉起效常有延迟。这可能是因为包裹这些神经根的结缔组织减慢了局部麻醉药向神经根的扩散。在硬膜外麻醉中，局麻药液从硬膜外腔扩散至蛛网膜下腔而产生的麻醉效果所占比例很小。Oct 28- Discuss potential side effects of epidural anesthesia硬膜外麻醉的潜在并发症Discussion points.The potential side effects of spinal anesthesia also apply to epidural anesthesia. Additional side effects of an epidur
9、al anesthetic that do not apply to spinal anesthesia include the risks of accidental dural puncture, local anesthetic toxicity, subdural injection, and epidural hematoma formation. The risk of epidural hematoma formation resulting from an epidural anesthetic is extremely low. Patients on anticoagula
10、nts are considered to be at the greatest risk, although the incidence is extremely low even in patients with bleeding abnormalities. There are multiple reviews in the literature of patients who received anticoagulation intraoperatively and postoperatively without any neurologic sequelae. Nevertheles
11、s, the American Society of Regional Anesthesia published their consensus statement titled Neuraxial Anesthesia and Anticoagulation in May 1998 with their recommendations on how epidural catheters should be managed in the perioperative period in the presence of anticoagulation. Accidental puncture of
12、 the dura mater during attempted localization of the epidural space can be recognized by the anesthesiologist by the appearance of cerebrospinal fluid in the hub of the epidural needle. The flow of cerebrospinal fluid from the large-bore needle is rapid and continuous. Cerebrospinal fluid is warm, d
13、istinguishing it from saline used for the loss of resistance technique for localization of the epidural space. Cerebrospinal fluid will also dipstick test positive for glucose.The accidental subarachnoid injection of the large volumes of local anesthetic intended for epidural anesthesia results in a
14、 rapidly evolving total spinal. The accidental subdural injection of the large volumes of local anesthetic intended for epidural anesthesia results in a slowly evolving total spinal. A subdural injection of local anesthetic may be difficult to recognize. The potential for local anesthetic systemic t
15、oxicity with epidural anesthesia is high because of the high doses of local anesthetic that must be given to produce epidural anesthesia, coupled with the numerous venous plexuses found in the epidural space that lend themselves to systemic absorption of the local anesthetic. Even so, blood levels o
16、f local anesthetic administered in the epidural space are rarely in the toxic range. The risk of systemic toxicity from the systemic absorption of local anesthetic administered in the epidural space is decreased by the addition of epinephrine to the local anesthetic solution. Epinephrine in the local anesthetic solutions slows the rate of systemic absorption of the local anesthetic in the epidural space.Epidural anesthesia result
