Faculty Bibliography

To date there has been no reliable noninvasive real time monitoring available to determine cerebral perfusion during cardiac arrest. OBJECTIVES: To investigate the feasibility of using a commercially available cerebral oximeter during in-hospital cardiac arrest, and determine whether this parameter predicts return of spontaneous circulation (ROSC). METHODS: Cerebral oximetry was incorporated in cardiac arrest management in 19 in-hospital cardiac arrest cases, five of whom had ROSC. The primary outcome measure was the relationship between rSO(2) and ROSC. RESULTS: The use of cerebral oximetry was found to be feasible during in hospital cardiac arrest and did not interfere with management. Patients with ROSC had a significantly higher overall mean +/- SE rSO(2) (35 +/- 5 vs. 18 +/- 0.4, p<0.001). The difference in mean rSO(2) between survivors and non-survivors was most pronounced in the final 5 min of cardiac arrest (48 +/- 1 vs. 15 +/- 0.2, p<0.0001) and appeared to herald imminent ROSC. Although spending a significantly higher portion of time with an rSO(2)>40% was found in survivors (p<0.0001), patients with ROSC had an rSO(2) above 30% for >50% of the duration of cardiac arrest, whereas non-survivors had an rSO(2) that was below 30%>50% of their cardiac arrest. Patients with ROSC also had a significantly higher change in rSO(2) from baseline compared to non-survivors (310% +/- 60% vs. 150% +/- 27%, p<0.05). CONCLUSION: Cerebral oximetry may have a role in predicting ROSC and the optimization of cerebral perfusion during cardiac arrest.

Perhaps the biggest challenge facing neuroscience at the dawn of the 21st century is understanding the relationship between mind, consciousness and the brain. Editorials in recent years have highlighted the difficulties faced by cognitive neuroscience in attempting to answer questions regarding the nature, as well as the mechanism by which subjective experiences and our sense of consciousness may arise through neuronal processes. Current scientific views regarding the origin of consciousness vary widely and range from an 'epiphenomenon' arising from neuronal networks, to neuronal quantum processes, to a separate undiscovered scientific entity. Although there has been a lack of experimental studies to test these theories, recent studies have indicated that the study of the human mind during cardiac arrest may hold the key to solving the mystery of consciousness. Four published prospective studies of cardiac arrest survivors have demonstrated that paradoxically human mind and consciousness may continue to function during cardiac arrest. This is despite the well demonstrated finding that cerebral functioning as measured by electrical activity of the brain ceases during cardiac arrest, thus raising the possibility that human mind and consciousness may continue to function in the absence of brain function. In this article the broad theories for the causation of consciousness are reviewed as well as a novel method to study consciousness during cardiac arrest. This may provide a unique experimental method to determine the nature of human mind and consciousness as well as its relationship with the brain.

Very little is known about the dying process and in particular the state of the human mind at the end of life. Cardiac arrest is the final step in the dying process irrespective of cause, and is also the closest physiological model of the dying process. Recent studies in cardiac arrest survivors have indicated that although the majority of cardiac arrest survivors have no memory recall from the event, nevertheless approximately 10% develop memories that are consistent with typical near death experiences. These include an ability to 'see' and recall specific detailed descriptions of the resuscitation, as verified by resuscitation staff. Many studies in humans and animals have indicated that brain function ceases during cardiac arrest, thus raising the question of how such lucid, well-structured thought processes with reasoning and memory formation can occur at such a time. This has led to much interest as regards the potential implications for the study of consciousness and its relationship with the brain, which still remains an enigma. In this article, we will review published research examining brain physiology and function during cardiac arrest as well as its potential relationship with near death experiences during this time. Finally, we will explore the contribution that near death experiences during cardiac arrest may make to the wider understanding of human consciousness.