Hogan Q H, Prost R, Kulier A, Taylor M L, Liu S, Mark L
Department of Anesthesiology, Medical College of Wisconsin, Milwaukee 53226, USA.
Anesthesiology. 1996 Jun;84(6):1341-9. doi: 10.1097/00000542-199606000-00010.
Although the cerebrospinal fluid (CSF) is the pathway of anesthetic delivery and the diluent for neuraxially administered drugs, little is known about its volume, including variability among individuals, longitudinal distribution, or influence of body habitus. Models made to investigate subarachnoid anesthetic distribution lack valid dimensions. CSF volume was measured in volunteers, and the effect of obesity and abdominal compression on CSF volume was evaluated using magnetic resonance imaging.
Low thoracic and lumbosacral axial magnetic resonance images of 25 healthy volunteers were obtained at 8-mm intervals by fast spin-echo sequence, which highlights CSF. A repeat image series was performed in 15 subjects during external abdominal compression. In two subjects, images were obtained without compression for the entire vertebral column. Dural sac and spinal cord areas were determined in a blinded fashion for each image using video/digital analysis. Area of the sac minus area of the cord constituted area of CSF and roots ("CSF/root"); this area multiplied by 8 mm resulted in CSF/root volume per section.
There is great interindividual variability in CSF/root volume. From the T11-T12 disc to the sacral terminus of the dural sac, the mean volume for all subjects is 49.9 +/- 12.1 ml (mean +/- SD; range 28.0-81.1 ml). This volume was significantly less in relatively obese subjects (42.9 +/- 9.5 ml) than in nonobese subjects (53.5 +/- 12.9 ml). Abdominal compression decreased CSF/root volume by 3.6 +/- 3.2 ml. Sections through intervertebral foramina showed the biggest decrease with abdominal compression, with a lesser change in sections with veins and no change in the absence of these anatomic features. Total vertebral CSF/root volume in two subjects was 94.84 and 120.01 ml, respectively.
CSF volume is widely variable between individuals. The decreased CSF volume that results from increased abdominal pressure, such as with obesity or pregnancy, may produce more extensive neuraxial blockade through diminished dilution of anesthetic. The mechanism by which increased abdominal pressure decreases CSF volume is probably inward movement of soft tissue in the intervertebral foramen, which displaces CSF.
尽管脑脊液（CSF）是麻醉药物输送的途径以及神经轴给药的稀释剂，但人们对其容量了解甚少，包括个体间的变异性、纵向分布或体型的影响。用于研究蛛网膜下腔麻醉分布的模型缺乏有效的尺寸数据。对志愿者的脑脊液容量进行了测量，并使用磁共振成像评估了肥胖和腹部压迫对脑脊液容量的影响。
通过快速自旋回波序列以8毫米的间隔获取25名健康志愿者的低胸段和腰骶段轴向磁共振图像，该序列突出显示脑脊液。在15名受试者进行腹部外部压迫期间进行了重复图像系列。在两名受试者中，获取了整个脊柱无压迫情况下的图像。使用视频/数字分析以盲法确定每个图像的硬脊膜囊和脊髓面积。硬脊膜囊面积减去脊髓面积即为脑脊液和神经根的面积（“脑脊液/神经根”）；该面积乘以8毫米得出每节的脑脊液/神经根体积。
脑脊液/神经根体积在个体间存在很大差异。从胸11 - 胸12椎间盘到硬脊膜囊的骶端，所有受试者的平均体积为49.9±12.1毫升（平均值±标准差；范围28.0 - 81.1毫升）。相对肥胖受试者的该体积（42.9±9.5毫升）明显低于非肥胖受试者（53.5±12.9毫升）。腹部压迫使脑脊液/神经根体积减少3.6±3.2毫升。椎间孔层面的减少最为明显，有静脉的层面变化较小，没有这些解剖结构特征的层面则无变化。两名受试者的整个脊柱脑脊液/神经根总体积分别为94.84毫升和120.01毫升。
个体间脑脊液容量差异很大。腹部压力增加（如肥胖或怀孕）导致的脑脊液容量减少可能通过减少麻醉药的稀释而产生更广泛的神经轴阻滞。腹部压力增加导致脑脊液容量减少的机制可能是椎间孔软组织向内移动，从而排挤脑脊液。
