| Many out-of-hospital cardiac arrests (CA) occur in the world annually. Despite advances in cardiopulmonary resuscitation and critical care, overall survival rate from out-of-hospital cardiac arrest remains poor. Cerebral ischemia and asphyxia following CA usually leads to severe neurological impairment which has been one of the leading causes of morbidity and disability. Clinical trials have proven that therapeutic hypothermia can be introduced to protect the brain against the ischemic brain injury following stoke or CA. Though the neuroprotective hypothermia has been reported, many underlying issues are still open for research, e.g. what's the optimal time to induce hypothermia after CA, how long the hypothermia should be administrated, and etc. To answer these questions, we need to find effective early real time predictors for the long-term functional outcome. Researchers have been using the quantitative electroencephalogram (qEEG) to monitor and detect the brain injury following CA. Recent experimental researches based on animal model have demonstrated that qEEG was associated with the long-term outcome of the therapeutic hypothermia in brain injury. Nevertheless, predictors within the first 6 hours for the long-term functional outcome have not been reported yet. In this thesis, we propose to use C0 complexity and information quantity (IQ) to analyze EEG signals and compare these two methods in monitoring and predicting neurological recovery after CA. The subjects in this study included 12 Wistar rats (250g), which were randomly assigned to 9-min asphyxia injury under hypothermia (33 , n=6) and normothermia (37 , n=6). The EEG of the first 6 hours and the neurodeficit scores (NDS) after 72 hours after CA were obtained for qEEG and behavior study respectively. By analyzing the qEEG with IQ and C0 complexity and their correlation with NDS, we obtained the following results:°C°C(1) The IQ and C0 complexity of EEG signals decreased significantly after 9-min asphyxia injury. After cardiopulmonary resuscitation (CPR), IQ and C0 complexity recovered gradually. The results showed that both IQ and C0 complexity were able to monitor and track the neurological recovery after CA.(2) According to the 72h NDS, the hypothermic group had lower mortality (16.7%) compared with the normothermic group (50.0%). In addition, rats that survived in hypothermic group had significant higher average NDS (60.6 9.7) than those in normothermic group (53.0 1.0). The results confirmed the neuroprotection of therapeutic hypothermia.±±(3) Both IQ and C0 complexity of EEG signals correlated well with the 72h NDS from the 4th hour after CA (IQ: Pearson > 0.85; C0 complexity: Pearson > 0.85). Therefore, both measures can predict the long-term (72h) neurological recovery following cardiac arrest within 4 hours.(4) It was shown there was no significant difference (P > 0.05) of IQ between hypothermic and normothermic groups during the first 6 hours of the experiment. However, significantly greater (P≤0.05) C0 complexity was observed in hypothermic group than that in normothermic group at the 4th hour. Such a statistic indicated the advantage of C0 complexity over IQ as an early predictor for the brain injury following CA.In conclusion, the most important contribution of this thesis is to introduce early predictors (<6hr) for monitoring the long-term functional recovery after CA. Particularly, the C0 complexity of EEG signals at the 4th hour correlated well with the 72h NDS, and there was significant difference of C0 complexity between hypothermic and normothermic groups. Since the first 6 hours following ischemia brain injury is critical for clinical intervention, the results of the paper indicate that the C0 complexity can be used as a potential tool as the predictor (4hr) of the neuroprotective therapeutic hypothermia, to our knowledge, which is the earliest predictor by far.
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