Cardiac Arrest As A Model To Study Consciousness
Many critically ill patients' have recalled similar unusual experiences from their period of critical illness and resuscitation. These include having lucid, well-structured thought processes together with reasoning and memory formation. The recalled memories vary from images of bright lights and tunnels to the very interesting recollection of actual verified events from their period of resuscitation in which people describe a feeling of separation from their bodies and being able to watch themselves, as if from a vantage point above. Although initially largely anecdotal, recently, a number of independent studies have been carried out which support the occurrence of these reports. The first of these was a British study of cardiac arrest survivors, in which 11% reported the characteristically typical lucid well-structured thought processes, together with reasoning and memory formation. In a larger Dutch study 12% reported similar experiences to those from this study. In addition these patients' also reported being able to watch and recall in detail specific events from their cardiac arrest such as the removal of dentures. Two other recent independent studies carried out on cardiac care units in the US, have also reported that 10 and 20% of cardiac arrest survivors respectively reported the above phenomenon together with an ability to view events from a vantage point above. The consensus of opinion raised by the authors of these studies has been that the occurrence of lucid well-structured thought processes together with reasoning and memory formation as well as an ability to recall detailed accounts of events from the period of resuscitation is a scientific paradox. This is due to the fact that studies of cerebral physiology during cardiac arrest carried out in humans and animals have indicated that cerebral function is at best severely impaired and possibly even absent. Nevertheless, approximately 10% of survivors consistently report heightened activity of the mind and consciousness from this period. This paradox can be better understood by examining cerebral physiology during and after cardiac arrest.