Department of Anesthesiology, Eye, Ear, Nose, and Throat Hospital, Fudan University, Shanghai, China.
Laryngoscope. 2012 Aug;122(8):1831-7. doi: 10.1002/lary.23286. Epub 2012 Apr 20.
OBJECTIVES/HYPOTHESIS: To evaluate mechanisms of discrepant responses to the nondepolarizing muscle relaxant rocuronium among normal and injured facial nerve-innervated orbicularis oris and tibial nerve-innervated gastrocnemius, and to provide information for the proper use of muscle relaxants to balance evoked electromyography (EEMG) monitoring and immobility in general anesthesia.
Randomized controlled study.
Right-sided facial nerve injury was induced by crush axotomy in 18 Sprague-Dawley rats. At different rocuronium concentrations, muscular tension amplitude (MTA) was determined in vitro for normal and injured facial nerve-innervated orbicularis oris and gastrocnemius; the number of unsaturated acetylcholine receptors (AChRs) at end plates was determined by (125) I-α-bungarotoxin staining followed with gamma spectroscopy. The morphological composition of muscle fibers was determined by histological examination.
Following rocuronium incubation, the percentage of MTA inhibition (MTAI%) of gastrocnemius was significantly higher than the corresponding values of orbicularis oris (P < .05), and the degree of saturation of AChR in gastrocnemius was significantly greater than that in orbicularis oris (P < .05). The baseline MTA and AChR density of injured-side orbicularis oris was significantly smaller than those of the normal side, whereas no significant difference was found regarding MTAI% and the degree of AChR saturation between the normal and injured side.
The affinity of AChR at end plates and different number of AChR per unit fiber cross-sectional area may be the mechanisms for differential sensitivities to neuromuscular blockers between facial nerve-innervated muscles and somatic nerve-innervated muscles. The lower EEMG responses in the impaired facial nerve-innervated muscles may result from the lower AChR density at end plates compared with the normal facial nerve-innervated muscles.
目的/假说：评估正常和损伤面神经支配的口轮匝肌和胫神经支配的腓肠肌对非去极化肌松药罗库溴铵反应不一致的机制，并为正确使用肌松药平衡诱发电肌电图（EEMG）监测和全身麻醉下的无动性提供信息。
随机对照研究。
在 18 只 Sprague-Dawley 大鼠中通过挤压切断右侧面神经诱导面神经损伤。在不同的罗库溴铵浓度下，在体外测定正常和损伤面神经支配的口轮匝肌和腓肠肌的肌肉张力幅度（MTA）；通过（125）I-α-银环蛇毒素染色后进行伽马能谱分析，确定终板上未饱和乙酰胆碱受体（AChR）的数量。通过组织学检查确定肌肉纤维的形态组成。
罗库溴铵孵育后，腓肠肌的 MTA 抑制百分比（MTAI%）明显高于口轮匝肌的相应值（P<0.05），并且腓肠肌的 AChR 饱和度明显大于口轮匝肌（P<0.05）。损伤侧口轮匝肌的基线 MTA 和 AChR 密度明显小于健侧，而正常侧和损伤侧的 MTAI%和 AChR 饱和度无明显差异。
终板上 AChR 的亲和力和单位纤维横截面积上的 AChR 数量的不同可能是面神经支配的肌肉和躯体神经支配的肌肉对神经肌肉阻滞剂敏感性不同的机制。与正常面神经支配的肌肉相比，损伤面神经支配的肌肉终板上 AChR 密度较低，可能导致 EEMG 反应较低。
