Mejia Jorge, Goffin Pierre, Reina Miguel A, Sala-Blanch Xavier
Anesthesiology, Hospital Clinic de Barcelona, Barcelona, Spain
Anesthesia and Intensive Care, CHC de Liège, Liège, Belgium.
Reg Anesth Pain Med. 2025 May 6;50(5):417-420. doi: 10.1136/rapm-2024-105294.
The test dose or hydrolocation technique allows rapid detection of spread location. Though its primary aim is to enhance safety in peripheral nerve blocks, evidence on the potential risks of an intraneural test aliquot is lacking. We conducted a cadaveric study to evaluate the risk of fascicular injury following a low-volume (<1 mL) intraneural injection of the median nerve.
Ten upper limbs from fresh unembalmed human cadavers were studied. In-plane ultrasound-guided intraneural injections of the median nerve were performed at mid, proximal, and distal locations using 1 mL of methylene blue and heparinized blood solution. Nerves were extracted and samples immersed in 10% buffered formalin for 4 weeks. Perpendicular 3 mm slices were obtained for H&E staining and light microscopy analysis. Our main objective was to assess the number of injured fascicles. Secondarily, we evaluated the pattern of intraneural spread. Fascicular injury was defined as the presence perineurium or axonal disruption and/or the presence of erythrocytes inside a nerve fascicle.
Thirty injections were performed in 10 median nerves. Sonographic swelling was confirmed in 100% of the cases. 352 histological sections were analyzed to assess study outcomes. The mean number of fascicles on each section of median nerve was 20±6 covering 49%±7% of the nerve area. No evidence of axonal disruption nor intra-fascicular erythrocytes was found in any of the analyzed sections.
Low-volume intraneural injections do not result in evident fascicular injury. Our findings support the use of a test dose in ultrasound-guided regional anesthesia.
试验剂量或液压定位技术可快速检测扩散位置。尽管其主要目的是提高周围神经阻滞的安全性，但关于神经内注射试验剂量潜在风险的证据尚不足。我们进行了一项尸体研究，以评估在正中神经内注射少量（<1毫升）药物后束状损伤的风险。
研究了10具未经防腐处理的新鲜人体尸体的上肢。使用1毫升亚甲蓝和肝素化血液溶液，在超声引导下经平面在正中神经的中部、近端和远端进行神经内注射。取出神经，将样本浸入10%的缓冲福尔马林中4周。获取垂直的3毫米切片进行苏木精-伊红染色和光学显微镜分析。我们的主要目的是评估受损束的数量。其次，我们评估了神经内扩散的模式。束状损伤定义为神经束膜或轴突中断和/或神经束内存在红细胞。
在10条正中神经上进行了30次注射。100%的病例超声检查证实有肿胀。分析了352个组织学切片以评估研究结果。正中神经每个切片上束的平均数量为20±6，覆盖神经面积的49%±7%。在任何分析的切片中均未发现轴突中断或束内红细胞的证据。
少量神经内注射不会导致明显的束状损伤。我们的研究结果支持在超声引导区域麻醉中使用试验剂量。
