The impairment of excitation-contraction coupling in ICU-acquired weakness

Abstract

The impairment of excitation-contraction (E-C) coupling have been recognized as a possible mechanism of ICU-acquired weakness (ICUAW). Although it has been reported that an E-C coupling impairment in animal models of ICUAW and muscle biopsy pathology in ICUAW patients, there has been few evidence in vivo. We developed a novel method to measure E-C coupling using accelerometer in vivo. The tibial nerve was stimulated at the popliteal fossa using a supramaximal rectangular pulse to record compound muscle action potential (CMAP) from soleus muscles. Simultaneously, movement-related potential (MRP) was recorded by accelerometer attached at the base of hallux. The E-C coupling time (ECCT) was calculated by differences between soleus CMAP and MRP. The amplitude of MRP corresponded to maximal twitch force of the soleus muscle. We found some patients revealed prolonged ECCTs and decreased MRP amplitudes without changes of CMAP templates in very early stages of ICUAW. These results indicated that the impairment of E-C coupling might occur in very early stages of ICUAW. Furthermore, the later stages may include additional mechanisms involving the complex pathologies of ICUAW.