Department of Clinical Sciences, College of Veterinary Medicine, Université de Montréal, St. Hyacinthe, Quebec, Canada.
Equine Vet J. 2021 Jan;53(1):167-176. doi: 10.1111/evj.13269. Epub 2020 May 26.
The effect of intrathecal anaesthesia of the carpal sheath on distal forelimb sensitivity in horses remains unknown.
To assess the effect of carpal sheath anaesthesia on skin sensitivity of the distal forelimb and to determine potential locations for desensitisation of palmar nerves.
In vivo experimental and descriptive anatomical studies.
Mepivacaine hydrochloride 2% (0.6 mg/kg) was injected unilaterally in the carpal sheath of 8 horses. Mechanical nociception of the distal forelimb was measured with a dynamometer and compared with the control limb at t t t t t t and t . Additionally, the carpal sheath of 10 pairs of cadaveric limbs was injected with latex and potential locations for anaesthetic diffusion to the neighbouring nerves were identified during longitudinal dissection (one limb) and in 3-cm-thick transverse cuts (opposite limb).
Six of 8 horses (75%) were completely desensitised at the level of both heel bulbs. Anaesthetic injection was not smooth in the 2 horses without desensitisation. Desensitisation started between 30 and 60 minutes in 67% of desensitised heel bulbs (8/12), and 50% (6/12) of them were still completely desensitised at 180 minutes. Cadaveric specimens revealed close proximity between the sheath and the medial palmar nerve as it travels inside the mesotenon of the digital flexor tendons in the carpal region and with both palmar nerves at the proximal metacarpal region.
Skin mechanical nociception does not necessarily correlate with deep pain but remains the main clinical tool used by practitioners to assess distal limb anaesthesia.
Intrathecal anaesthesia of the carpal sheath led to distal limb skin desensitisation through diffusion to the palmar nerves at 2 possible locations. Carpal sheath anaesthesia should be interpreted within 15 minutes following injection and anaesthetic blocks distal to the carpus should be delayed for more than 3 hours following carpal sheath anaesthesia.
鞘内麻醉对手腕部皮肤感觉的影响尚不清楚。
评估腕管麻醉对手部掌侧皮肤感觉的影响，并确定感觉神经阻滞的潜在位置。
体内实验和描述性解剖学研究。
在 8 匹马的腕管内单侧注射盐酸甲哌卡因 2%（0.6mg/kg）。使用测力计测量远侧前肢的机械痛觉，并与对照肢在 t 1 、 t 2 、 t 3 、 t 4 、 t 5 、 t 6 和 t 7 时进行比较。此外，在 10 对尸体肢的腕管内注入乳胶，并在纵向解剖（一侧肢体）和 3cm 厚的横切（对侧肢体）过程中确定乳胶向相邻神经扩散的潜在位置。
8 匹马中有 6 匹（75%）在两个足跟球水平完全脱敏。在没有脱敏的 2 匹马中，麻醉注射不顺利。在 67%的脱敏足跟球（12 个中的 8 个）中，脱敏开始于 30-60 分钟之间，180 分钟时 50%（12 个中的 6 个）仍完全脱敏。尸体标本显示，在腕管内，鞘与内侧掌侧神经非常接近，因为它在指深屈肌腱的中膜间穿行，在掌侧近侧掌骨区域与两个掌侧神经也非常接近。
皮肤机械痛觉不一定与深部疼痛相关，但仍然是临床医生用于评估远侧肢体麻醉的主要临床工具。
腕管内麻醉通过向 2 个可能的位置扩散到掌侧神经，导致远侧肢体皮肤脱敏。腕管麻醉后 15 分钟内应进行解释，腕管麻醉后 3 小时以上应延迟腕管以下的麻醉阻滞。
