Department of Neurology, Inselspital, Bern University Hospital and University of Bern, Switzerland.
Clin Neurophysiol. 2011 Apr;122(4):834-41. doi: 10.1016/j.clinph.2010.09.024. Epub 2010 Nov 1.
To test the hypothesis that muscle fibers are depolarized in patients with critical illness myopathy by measuring velocity recovery cycles (VRCs) of muscle action potentials.
VRCs were recorded from brachioradialis muscle by direct muscle stimulation in 10 patients in intensive care with evidence of critical illness myopathy (CIM). Two sets of recordings were made, mean 3.9 d apart, and compared with those from 10 age-matched controls.
Muscle supernormality was reduced in the patients by 50% compared with controls (P<0.002) and relative refractory period was increased by 59% (P<0.01). Supernormality was correlated with plasma potassium levels (R=-0.753, P<0.001), and the slope of this relationship was much steeper than previously reported for non-critically ill patients with renal failure (P<0.01).
The abnormal excitability properties indicate that the muscle fibers in CIM were depolarized, and/or that sodium channel inactivation was increased. The heightened sensitivity to potassium is consistent with the hypothesis that an endotoxin reduces sodium channel availability in depolarized muscle fibers.
VRCs provide a practicable means to monitor muscle membrane changes in intensive care and to investigate the pathogenesis of CIM.
通过测量肌肉动作电位的速度恢复循环（VRC）来检验危重病性肌病患者肌肉纤维去极化的假说。
对 10 名重症监护中存在危重病性肌病（CIM）证据的患者进行直接肌肉刺激，从肱桡肌记录 VRC。进行了两组记录，平均间隔 3.9 天，并与 10 名年龄匹配的对照组进行比较。
与对照组相比，患者的肌肉超常性降低了 50%（P<0.002），相对不应期增加了 59%（P<0.01）。超常性与血浆钾水平相关（R=-0.753，P<0.001），并且这种关系的斜率比以前报道的肾衰竭非危重病患者陡峭得多（P<0.01）。
异常的兴奋性特性表明 CIM 中的肌肉纤维去极化，和/或钠离子通道失活增加。对钾的敏感性增加与内毒素降低去极化肌肉纤维中钠离子通道可用性的假说一致。
VRC 提供了一种可行的方法来监测重症监护中的肌肉膜变化，并研究 CIM 的发病机制。
