Cerebral metabolic rate of oxygen (CMRO(2)) in pig brain determined by PET after resuscitation from cardiac arrest.
AIM: To assess the regional vulnerability to ischemic damage and perfusion/metabolism mismatch of reperfused brain following restoration of spontaneous circulation (ROSC) after cardiac arrest. METHOD: We used positron emission tomography (PET) to map cerebral metabolic rate of oxygen (CMRO(2)), cerebral blood flow (CBF) and oxygen extraction fraction (OEF) in brain of young pigs at intervals after resuscitation from cardiac arrest. After obtaining baseline PET recordings, ventricular fibrillation of 10min duration was induced, followed by mechanical closed-chest cardiopulmonary resuscitation (CPR) in conjunction with i.v. administration of 0.4U/kg of vasopressin. After CPR, external defibrillatory shocks were applied to achieve restoration of spontaneous circulation (ROSC). CBF and CMRO(2) were mapped and voxelwise maps of OEF were calculated at times of 60, 180, and 300min after ROSC. RESULTS: There was hypoperfusion throughout the telencephalon at 60min, with a return towards baseline values at 300min. In contrast, there was progressively increasing CBF in cerebellum throughout the observation period. The magnitude of CMRO(2) decreased globally after ROSC, especially in cerebral cortex. The magnitude of OEF in cerebral cortex was 60% at baseline, tended to increase at 60min after ROSC, and declined to 50% thereafter, thus suggesting transition to an ischemic state. CONCLUSION: The cortical regions tended most vulnerable to the ischemic insult with an oligaemic pattern and a low CMRO(2) whereas the cerebellum instead showed a pattern of luxury perfusion.
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