Kritik Hastalık Miyopatisi Elektrofizyolojik Tanısında Stimulus - Birleşik Kas Aksiyon Potansiyeli Genlik / Alan / Süre Yanıt Eğrisi Çalışması

Abstract

Crtitical illness myopathy (CIM) and critical illness neuropathy (CIN), which are the most common causes of paresis acquired in the intensive care unit, are acquired neuromuscular dysfunction cases and asssociated with prolonged mechanical ventilation and hospitalization time, increasing costs, morbidity and mortality. Because of that CIM has a better prognosis, full recovery potential with rehabilitation and seen up to 100% in special intensive care unit populations, it’s early diagnosis is important. In nerve conduction studies, both CIM and CIN has decreased compound muscle action potential (CMAP) amplitude (CMAPAmp) and there is also synchronous dispersion (prolongation) is seen in CMAP negative peak duration (CMAPDur) both at proximal and distal stimulaiton sites in CIM. In this study, because of that CMAPDur prolongation is not present or found to be at borderline level in some patients in electrophysiological diagnosis of CIM, we examined CMAPDur at submaximal stimulation intensities and aimed to develop new parameters for earlier and more sensitive and specific diagnosis of CIM occurence. The study is done by ulnar nerve stimulation and recording from ADM muscle in 11 patients who are diagnosed as CIM or CINM after electromyography and 12 healthy controls. The stimualtion intensities which are first CMAP recorded (UMin,) and maximum CMAP recorded (UMax,) are determined then (UMax – UMin) is divided into 4 equal parts which constitiute 4 stimulation intensities (U%20, U%40, U%60, U%80). At all different stimulation intensities CMAPAmp, CMAPDur and ratio of other 5 CMAPDur to maximum CMAPDur are calculated (MaxR_Dur_UMin, MaxR_Dur_U%20, MaxR_Dur_U%40, MaxR_Dur_U%60, MaxR_Dur_U%80). CMAPDur is prolonged as compared to healthy subjects in patient group in all intensities of stimulation but the most prominent difference was at UMin and U%20 intensities. More importantly, in our study there was no prolongation of CMAPDur in two patients at maximal stimulaion intensities. However, prolongation is detected at these two intensities in these patients. In patients CMAPDur was maximum at UMin and shortened, while in controls it was minimum at UMin and became longer as the stimulation intensity increased. In corcordance with this finding, in patients MaxR_Dur_UMin, MaxR_Dur_U%20 values was found to be statistically higher as compared to controls. CMAPDur prolongation which is diagnostic marker for CIM is found to be more prominent and has higher sensitivity at lower stimulaition intensities (UMin, U%20) compared to ones that are obtained in supramaximal stimulaiton intensities used in routine electrophysiologic studies. Considering, CMAPDur isn’t prolonged in some patients at supramaximal stimulaiton intensities in literature and our study, our finding increases the sensitivity of electrophysiologic diagnosis especially in the early period of CIM and very useful because it doesn’t require additional technical supply or time. This finding is thought to be originated from variable levels of reduction of different muscle fibers membrane excitability at different stimulation intensities in CIM and action potentials which belong to the these fibers causing electrical phase cancellation.