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AWARE Study Abstract

A number of recent studies have indicated that 10% of cardiac arrest survivors report memories and thought processes from their period of resuscitation. A small proportion of survivors have also described the ability to “see” and “hear” details of their cardiac arrest. Even though the significance and mechanisms that lead to these experiences are not fully understood, nevertheless their occurrence may have significant implications for establishing clinical markers1 of improved brain resuscitation, as well as long term psychological support of cardiac arrest survivors2. The occurrence of cognitive3 function during cardiac arrest also raises the possibility that patients may have received improved “cerebral resuscitation” leading to consciousness and the activity of the mind. Furthermore, the occurrence of such experiences in cardiac arrest survivors has also been shown to lead to long-term positive life enhancing effects.4

Through a variety of psychological5 and physiological tests as well as cerebral monitoring techniques6, we aim to conduct the first comprehensive study examining the relationship between the human mind, consciousness and brain during cardiac arrest. Specifically, we aim to study the relationship between consciousness and the quality of cerebral resuscitation (as measured through non-invasive monitoring of cerebral perfusion)6 and its outcome on neurological, emotional and cognitive morbidity7. Patients’ experiences and cognition will also be examined qualitatively immediately after their cardiac arrest as well as at regular intervals for a period of two years.

The tests of consciousness include the use of independent markers8 designed to objectively examine the validity of survivor’s claims of being able to “see” and “hear” during cardiac arrest as well as their underlying association with socio-cultural9 and cognitive parameters. We will also examine the relationship between cognitive function during cardiac arrest with clinical and physiological markers, the severity of cardiac arrest, as well as markers of the relative effectiveness of resuscitation. An understanding of the nature of human consciousness and mental processes during cardiac arrest and its relationship with brain perfusion may have significant implications for improving the acute management of cardiac arrest resuscitation as well as the long term psychological care of survivors.

1. In other words these experiences may serve as indices (markers) for improved brain resuscitation meaning that those patients having had these experiences may have had better cardio-pulmonary resuscitation, leading to a better brain blood perfusion (hence more oxygen) during their cardiac arrest. For example, in one study comparing physiological parameters such as arterial oxygen and carbon dioxide levels during cardiac arrest, it was observed that patients with cognitive function had higher oxygen levels, possibly due to improved ventilation during resuscitation.

2. It has been well demonstrated that the occurrence of cognitive states during cardiac arrest is associated with long term psychological benefits, hence the occurrence of these states could serve as a predictor for improved long term cognitive outcomes.

3. Cognitive: refers to the mental processes of knowing, formulating judgments, reasoning, perceiving and being aware.

4. Survivors who had experienced memories and consciousness during cardiac arrest have been observed to develop a positive transformational change in behavior by two years, as characterized by greater empathy and understanding for others, involvement in the family and less fear of death compared to cardiac arrest survivors without the experience (Parnia S, et al.; Resuscitation Feb 2001 48, 149-156).

5. Psychological testing: for example testing for the occurrence of depression and anxiety.

6. This can be done by using devices of cerebral oximetry. This device works by non-invasively transmitting and detecting harmless near infrared light through sensors that are placed on a patient's forehead. Just as with the commonly used pulse oximetry devices, which measure changes in the saturation of oxygen in peripheral blood, cerebral oximetry monitors changes in the saturation of oxygen within the cerebral cortex. This device thus has the potential to provide a real time indicator of cerebral oxygen levels and hence cerebral perfusion. To date there have only been limited studies of cerebral oximetry during cardiac arrest, which have indicated that this technique can provide a useful measure of cerebral oxygenation during cardiac arrest. Real time brain monitoring using cerebral oximetry may potentially provide an important and invaluable tool to guide physicians and nurses regarding the effectiveness of their resuscitation efforts as well as an independent clinical marker of improved mortality and outcomes.

7. It is important to understand that lack of oxygen during a cardiac arrest may lead to irreversible brain damage (hypoxic brain injury), which often leads to cognitive and emotional impairments as characterised by short and long term memory disorders as well as depression and posttraumatic stress disorder (PTSD).

8. The verification of memories relating to the resuscitation events or “veridical perception” includes the use of hidden objects that are normally not visible from a patient’s or their caregiver’s perspective unless viewed from a vantage point above. Typically these are images placed on a support hanging from the ceiling in a hospital ward, in a way that the images face upward, towards the ceiling. These objects will provide an independent objective marker of the claims of being able to “see” during cardiac arrest because they will only be visible by “someone” observing them from above.

9. Association: the sociocultural background may influence what the patient claims to have “heard” or “seen”.

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