Evaluate post-resuscitation functional outcome with variance analysis of somatosensory evoked potentials

Abstract

INTRODUCTION: Electrophysiological signals, such as somatosensory evoked potentials (SSEPs), may serve the useful function of monitoring hypoxic-ischemic brain injury after Cardiac Arrest (CA). Conventional ensemble average (EA) method supplies the mean value of amplitude and latency of the SSEP waveforms, but in addition, the variance of latency may also contain instructive information about time-variant neurological abnormality. This paper utilizes second order blind identification (SOBI) technique to extract single trial SSEPs to preserve the critical variance information which would be diminished by the EA method. METHODS: Sixteen adult male Wistar rats were subjected to 7 or 9 minutes asphyxial CA (n=8 per group). The SSEPs from median nerve stimulation were monitored and recorded continuously for 4 hours after CA and then for 15 minute periods at 24, 48 and 72 h. Neurological outcomes were evaluated by Neurologic Deficit Score (NDS) at 72h post-CA. The SSEP signal was analyzed offline by Matlab with SOBI processing. RESULTS: The N10 feature of SSEP was compared between good (NDS 50) and bad (NDS<50) outcomes. The results show that the N10 detection rate was significantly increased (p<0.05) from 90 min post-CA. Statistical difference of the latency variance of the N10 between good and bad outcome groups existed at 24,48 and 72 h post-CA (p<0.05). CONCLUSIONS: This study demonstrates that N10 latency variance increased after hypoxic-ischemic injury and that our SOBI technique is to detect such change in SSEP signal. SSEP N10 peak latency variance is one of good neurological prognostication markers after cardiac arrest.