S20-3 The impairment of excitation-contraction coupling in ICU-acquired weakness

Introduction. The aim of this study is to elucidate the impairment of excitation-contraction (E-C) coupling in ICU-acquired weakness (ICUAW) using a unique electrophysiologic method in patients received the intensive care in ICU. Methods. We examined 13 patients with ICUAW and 11 normal controls. We performed successive recordings of electrophysiological tests after ICU admission. First, CMAPs of abductor hallucis muscle (AH) and sural SNAPs were recorded using a conventional method. In addition, the tibial nerve was stimulated at the popliteal fossa using a supramaximal rectangular pulse to record CMAPs from soleus muscle (SOL). Simultaneously, movement- related potential (MRP) was recorded using an accelerometer (SV1101; NEC, Tokyo Japan) taped at the base of hallux and calculated E-C coupling time (ECCT) based on the latency differences between soleus CMAP and MRP. Results. We recorded significantly decreased CMAP amplitudes in 6 AHs and 8 SOLs and significantly longer CMAP durations in 2 SOLs. Also, we recorded significantly decreased MRPs in 9 patients and significantly prolonged ECCTs in 10 patients. These abnormal findings were detected even in very short durations of ICU stay such as 2-3 days. The durations of ICU stay seemed to be correlated with involvement of CMAP amplitudes of AH/SOL, MRPs and ECCTs. Ten patients showed decreased SOL-CMAP amplitude concomitant with decreased MRP and/or prolonged ECCT in spite of preservation of SOL-CMAP duration. In addition, CMAP amplitudes of AH/SOL and MRP were significantly smaller in patients than in controls. Furthermore, CMAP durations of AH and ECCTs were significantly longer in patients than in controls. Conclusion. The E-C coupling may be impaired in the very early stages of CIM. Noninvasive measurement of MRP and ECCT is easy to perform, and may be useful to detect the impairment of E-C coupling in the early stages of ICUAW.