square off怎么理解？

To begin, place the patient in the prone position with a pillow beneath the abdomen to increase the distance between transverse processes. Using fluoroscopy in the AP view, identify the T12 vertebral body for a splanchnic nerve block and the L1 vertebral body for a celiac plexus block, and square off the superior end plate. Then oblique the C-arm to the patients left side until the tip of the respective transverse process is aligned with the anterolateral border of the respective vertebral body. Of note, for vertebral body levels above L1, aim for an oblique angle ~15° to minimize risk of pneumothorax. For a splanchnic nerve block, the target location lies at the mid to lower third of the T12 vertebral body at the anterolateral margin; often the C-arm may need to be moved caudally to move the 12th rib out of the target location. For a celiac plexus block, the target location lies just cephalad to the transverse process of L1 at the anterolateral margin of the L1 vertebral body. Administer subcutaneous local anesthetic, and advance coaxially a 20- or 22-gauge spinal needle that is 12–18 cm long (some prefer to use an introducer advanced to the posterolateral intervertebral disc space followed by a 25-gauge spinal needle). During needle advancement con firm depth with intermittent lateral fluoroscopic views.At this point, please refer to the classic posterior approach for details on proceeding with a splanchnic nerve block and celiac plexus block. To perform a transaortic celiac plexus block, continue needle advancement while detecting for increased resistance during passage through the crus of the diaphragm until aortic pulsations are felt (typically ~3 cm anterior to the L1 vertebral body) [46]. At this point, using intermittent aspiration or continuous observation of blood flow, penetrate the aortic wall, and advance the needle until negative aspiration or blood flow ceases, indicating passage through the anterior wall of the aorta. After negative aspiration for blood, air, CSF, or lymph, inject contrast under realtime fluoroscopy in the AP and lateral view, and observe for optimal spread. Contrast should be confined to the midline and concentrated along the bilateral anterior surface of the aorta infiltrating around the celiac axis in AP view while having a preaortic T12–L2 spread that is often pulsating in the lateral view. At this point proceed with the test dose and then the desired medications as previously described in the classic posterior approach. Of note, make sure to frequently aspirate to confirm the needle tip has not slipped back into the aorta.

首先，患者俯卧位，腹下垫枕，以增加横突间距。在AP位透视下，确定内脏神经阻滞部位的T12椎体，腹腔神经丛阻滞部位的L1椎体，并对齐上终板。然后将C臂斜向患者左侧，直到横突的尖端与相应椎体的前外侧对齐。值得注意的是，对于L1以上的椎体节段，倾斜角度调整为15°以将气胸的风险降至最低。对于内脏神经阻滞，靶点位于T12椎体前外侧缘的中下三分之一处，C臂可能需要向尾端移动以将第12肋骨移出目标区域。对于腹腔神经丛阻滞，靶点正好位于L1椎体前外侧缘L1横突的头侧。皮下注射局麻药，并与X线束透视一致的方向推进长度为12～18cm的20或22号脊麻穿刺针（有些医生倾向于先使用引导器进入后外侧椎间盘间隙，然后使用25号脊麻穿刺针）。在进针时，间断行侧位透视以确定深度。有关内脏神经阻滞和腹腔神经丛阻滞的详细信息，请参考经典的后入路法。进行经主动脉腹腔神经丛阻滞时，应继续进针，同时感觉穿过膈肌脚时阻力是否增加，直到感觉到主动脉搏动（常在L1椎体前方约3cm）^[46]。使用间歇性抽吸或连续观察血流，穿透主动脉壁，进针至抽吸无回血或血流停止，表明穿过主动脉前壁。在回抽无血、空气、脑脊液和淋巴夜，在正侧位实时透视下注射造影剂，并观察是否为最佳扩散效果。造影剂应局限于中线，AP位上沿双侧主动脉前表面集中并围绕腹腔轴周围，同时在T12～L2主动脉前扩散，侧位图常呈搏动。此时继续注射试验剂量，然后按照之前在经典后入路法中描述的所需药物进行治疗。值得注意的是，需反复回抽以确保针尖未退回主动脉。

square off 什么意思？

• square off (打斗等时)摆好(架势)； 把 ... 做成方形