Chavez V C Valencia, Baumann H, Biscoping J
Klinik für Anaesthesie und Operative Intensivmedizin, St. Vincentius-Kliniken gAG Karlsruhe, Germany.
Anaesthesist. 2010 Jan;59(1):23-9. doi: 10.1007/s00101-009-1661-6.
The influence of Trendelenburg positions and variations in spinal canal configuration on the spread of hyperbaric spinal anesthetics was examined in two models of the subarachnoid space.
Both models included simulations of the spinal cord, filum terminale and cerebrospinal fluid. Model I had a straight shape, thus omitting replications of lumbar lordosis and thoracic kyphosis. It allowed the evaluation of fluid dynamics and the spread of 0.5% hyperbaric bupivacaine and 4% hyperbaric mepivacaine in 0° (supine position), 5° and 10° head-down tilt positions. Model II included reconstructions of average adult spinal curvatures for closer analysis of the intrathecal spread of 0.5% hyperbaric bupivacaine in 0°, 5°, 10° and 15° head-down tilt positions. Concentration gradients within the artificial cerebrospinal fluid were calculated using a digital image processing technique. Data from both model investigations were compared to elaborate the effect of varying lumbar lordosis angles.
Model I: Only the 5° head-down tilt caused a significant difference in maximum spread of both local anesthetics. Model II: A 15° head-down tilt resulted in the local anesthetic solution spilling over lumbar lordosis and effusing into the thoracic areas. With increasing degree of head-down tilt, the local anesthetic solution was also detectable in ventral parts of the spinal canal cross-section.
Diffusion processes represent the decisive factor for distribution patterns of hyperbaric anesthetics in the supine position. Only the 5° head-down tilt demonstrated an influence of specific gravity. When tilted 10° head-down gravitation prevailed over differences in density. A 15° head-down tilt is a precondition for the mobilization of sacrally pooled local anesthetic. Data comparison of both model investigations showed that the extent of spread depends more on initial bidirectional distribution of the local anesthetic than on increasing flow rate due to the slope of lumbar lordosis.
在两个蛛网膜下腔模型中，研究了头低脚高位和椎管形态变化对高压脊麻扩散的影响。
两个模型均包括脊髓、终丝和脑脊液的模拟。模型I呈直线形状，因此省略了腰椎前凸和胸椎后凸的复制。它可以评估0°（仰卧位）、5°和10°头低脚倾斜位时0.5%高压布比卡因和4%高压甲哌卡因的流体动力学和扩散情况。模型II包括平均成人脊柱曲率的重建，以便更仔细地分析0°、5°、10°和15°头低脚倾斜位时0.5%高压布比卡因的鞘内扩散情况。使用数字图像处理技术计算人工脑脊液内的浓度梯度。比较两个模型研究的数据，以阐明不同腰椎前凸角度的影响。
模型I：仅5°头低脚倾斜导致两种局部麻醉剂的最大扩散有显著差异。模型II：15°头低脚倾斜导致局部麻醉剂溶液溢出腰椎前凸并渗入胸部区域。随着头低脚倾斜程度的增加，在椎管横截面的腹侧部分也可检测到局部麻醉剂溶液。
扩散过程是仰卧位时高压麻醉剂分布模式的决定性因素。只有5°头低脚倾斜显示出比重的影响。当头低脚倾斜10°时，重力作用超过密度差异。15°头低脚倾斜是动员骶部蓄积的局部麻醉剂的前提条件。两个模型研究的数据比较表明，扩散程度更多地取决于局部麻醉剂的初始双向分布，而不是由于腰椎前凸坡度导致的流速增加。
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