Time to loss of brain function and activity during circulatory arrest

Abstract Purpose Brain function during the dying process and around the time of cardiac arrest is poorly understood. In order to better inform the clinical physiology of the dying process and organ donation practices, we performed a scoping review of the literature to assess time to loss of brain function and activity after circulatory arrest. Materials and Methods Medline and Embase databases were searched from inception to June 2014 for articles reporting the time interval to loss of brain function or activity after loss of systemic circulation. Results Thirty-nine studies met selection criteria. Seven human studies and 10 animal studies reported that EEG activity is lost less than 30 seconds after abrupt circulatory arrest. In the setting of existing brain injury, with progressive loss of oxygenated circulation, loss of EEG may occur prior to circulatory arrest. Cortical evoked potentials may persist for several minutes after loss of circulation. Conclusion The time required to lose brain function varied according to clinical context and method by which this function is measured. Most studies show that clinical loss of consciousness and loss of EEG activity occur within 30 seconds after abrupt circulatory arrest, and may occur prior to circulatory arrest after progressive hypoxia-ischemia. Prospective clinical studies are required to confirm these observations.