Sudden cardiac arrest is a leading cause of death in the United States and is responsible for more than 300,000 deaths every year. For the last fifty years, the guidelines of cardiopulmonary resuscitation (CPR) have been the standards to revive cardiac arrest patients. However, the major components of CPR have not changed since its birth and the success rate of CPR remains unsatisfied (5-18%). My work presented in the dissertation mainly focuses on the role of oxygen during the resuscitation and post-resuscitation periods as well as correspondent mitochondrial functions. There are four parts in the dissertation. In chapter 2, a rat CPR model was used to demonstrate that oxygen is critical during resuscitation in order to achieve return of spontaneous circulation (ROSC). Additionally, there was no significant difference between the treatment groups (21% oxygen vs. 100% oxygen resuscitation) in terms of survival rates or neurological outcome. In chapter 3, mitochondrial functions were examined in the hearts undergoing 15 minutes of cardiac arrest and 10 minutes of CPR as compared to the hearts undergoing 25 minutes of cardiac arrest. The results suggest that, despite the inherent low oxygen delivery, CPR after prolonged cardiac arrest preserves heart mitochondrial function and morphology. It demonstrates the beneficial effects of CPR from a subcellular perspective for the first time. Preservation of mitochondrial function is reflected by improved mitochondrial respiration, electron transport chain (ETC) complex activities, and preservation of the ETC proteins. Meanwhile, complex I is the most sensitive ETC complex to ischemic injury and its activity is positively correlated with mitochondrial respiration.
In chapter 4, a rat cardiopulmonary bypass (CPB) model was done to study the effects of hyperoxygenation during the post-resuscitation period. After 25 minutes of normothermic cardiac arrest, hyperoxic reperfusion for one hour with CPB did show advantages compared to normoxic reperfusion in some aspects, including better systemic hemodynamics, less lactic acidosis and a small but significantly better cardiac relaxation. In addition, the benefits were also demonstrated by a better mitochondrial respiratory function. Finally, in chapter 5, a simplified method was developed to concentrate mitochondrial membrane complexes. It is a modified 2-D blue native/blue native PAGE (BN/BN-PAGE) which can be easily done with a mini-gel apparatus. Once completed, the concentrated protein complex in the gel strip is ready for SDS-PAGE or proteomic studies. Unwanted loss of protein complex is minimized, which is critical whenever the amount of mitochondrial sample is limited.