School of Medicine, University of Dundee, Ninewells Hospital, Dundee, UK.
Sunnybrook Research Institute, Toronto, Ontario, Canada.
Br J Anaesth. 2021 Jul;127(1):153-163. doi: 10.1016/j.bja.2021.03.036. Epub 2021 May 15.
Nerve damage is consistently demonstrated after subepineural injection in animal studies, but not after purposeful injection in patients participating in clinical studies. There is a need to better visualise nerves in order to understand the structural changes that occur during subepineural injection.
We scanned the brachial plexuses of three anaesthetised pigs using micro-ultrasound imaging (55-22 MHz probe), inserted 21 gauge block needles into the radial, median, and axillary nerves, and injected two 0.5 ml boluses of saline into nerves at a rate of 12 ml min. Our objectives were to measure the area and diameter of nerves and fascicles, and to describe changes in nerve anatomy, comparing our findings with histology.
Images were acquired at 42 sites across 18 nerves in three pigs and compared dimensions (geometric ratio; 95% confidence interval; P value). As expected, the nerve cross-sectional area was greater in the proximal brachial plexus compared with the mid-plexus (2.10; 1.07-4.11; P<0.001) and the distal plexus (2.64; 1.42-4.87; P<0.001). Nerve area expanded after 0.5 ml injection (2.13; 1.48-3.08; P<0.001). Using microultrasound, subepineural injection was characterised by nerve and fascicle rotation, uniform, or localised swelling and epineural rupture. Micro-ultrasound revealed a unique pattern suggestive of subperineural injection after a median nerve injection, and good face validity with histology. Histology showed epineural trauma and inflammation to the perineurium.
We accurately identified fascicles and real-time structural changes to peripheral nerves using micro-ultrasound. This is the first study to visualise in vivo and in real-time the motion of nerves and fascicles in response to anaesthetic needle insertion and fluid injection.
动物研究中，经皮神经下注射后始终会出现神经损伤，但在参与临床研究的患者中经皮神经下注射后则不会出现。为了更好地观察神经，有必要了解在皮神经下注射过程中发生的结构变化。
我们使用微超声成像（55-22MHz 探头）对三只麻醉猪的臂丛神经进行扫描，将 21 号针插入桡神经、正中神经和腋神经，并以 12ml/min 的速度向神经内注入两 0.5ml 盐水射流。我们的目的是测量神经和束的面积和直径，并描述神经解剖结构的变化，将我们的发现与组织学进行比较。
在三只猪的 18 根神经的 42 个部位采集了图像，并比较了尺寸（几何比；95%置信区间；P 值）。如预期的那样，与中束（2.10；1.07-4.11；P<0.001）和远束（2.64；1.42-4.87；P<0.001）相比，近束臂丛神经的神经横截面积更大。注射 0.5ml 后神经面积增大（2.13；1.48-3.08；P<0.001）。使用微超声，皮神经下注射的特征是神经和束旋转、均匀或局部肿胀以及神经外膜破裂。微超声显示出一种独特的模式，提示正中神经注射后存在皮神经下注射，与组织学具有良好的表面真实性。组织学显示神经外膜创伤和神经外膜炎症。
我们使用微超声准确识别了束，并实时观察到外周神经的结构变化。这是第一项在活体和实时观察神经和束在麻醉针插入和液体注射时的运动的研究。
