Consciousness, Awareness & Cognitive Experiences During Cardiac Arrest
Approximately 10 percent of cardiac arrest survivors report positive psychological outcomes in conjunction with the perception of some level of cognitive experience or conscious awareness during their cardiac arrest. Since the advent of modern cardiopulmonary resuscitation (CPR), millions of people have been resuscitated. Among these are many survivors who have provided anecdotal reports of lucid, well-structured thought processes with memory formation from a period during their cardiac arrest (sometimes referred to by the scientifically imprecise term “near-death experiences”).1 In recent years, the accuracy of these reports has been supported by evidence from case studies, and more recently, large-scale prospective cardiac arrest studies.
Cardiac arrest survivors often describe these events in similar terms as a deeply transformative experience. Experiences range in depth and acuity, and may include auditory awareness, visual observation, and even verifiable reports of events, conversations, and activities that transpired during their own resuscitation. Many people report a sense of calm and comfort, a disconnection from time, and moments of great insight and perspective. Some describe the perception of experiencing family and friends who had previously passed away. Another common characteristic of these reports is the experience of conducting a “life review,” reflecting on and appraising the life lived and choices made thus far and finding new meaning to life centered on greater altruism and selflessness.2
Reports of the perception of cognitive experiences during cardiac arrest, as well as awareness during cardiac arrest, with or without explicit memories, pervade all cultures and nations, and have even been reported by children as young as three. This phenomenon is not uncommon: the few research studies that have rigorously examined these experiences indicate that nearly 40 percent3 of cardiac arrest survivors may report some perception of awareness during the event without detailed explicit memories, in addition to the 10 percent whose reports are consistent with what is often referred to as a near-death experience.
Analysis of the phenomenology of these experiences using standardized questionnaires that examine qualities and aspects of memories have shown that the memories of cardiac arrest survivors bear the characteristics of real memories, rather than those of imagined events.4 These experiences are deeply transformative, and appear to confer a strong protective psychological effect, in stark contrast to the significant cohort of cardiac arrest survivors who experience negative psychological outcomes.
The phenomenon of awareness during cardiac arrest is not well understood from a biological standpoint. In some rare cases, patients may even move and show transient signs of being visibly conscious. However, these instances typically do not represent a true cardiac arrest. For example, some people may have a beating heart but are so ill that their pulse is weak and impalpable by hand. Clinicians will thus start CPR, which strengthens the heartbeat and enables enough blood flow to reach the brain and body while CPR is underway for people to show visible signs of movement.
However, in a true cardiac arrest, when there is no heartbeat, even with CPR there is insufficient blood flow to the brain (around 20 percent) to meet the needs of brain cells. Consequently, seconds after cardiac arrest, brain function ceases as evidenced by brain stem reflexes and electrical activity in the brain. People also immediately lose any visible signs of consciousness and are deemed unconscious by all available clinical assessments.
However, cognitive activity and conscious awareness have been reported by 10 to 20 percent of people from the period of true cardiac arrest. Studies of cardiac arrest survivors’ experiences of awareness during a time when the brain is not functioning support the idea that—as with many other conditions that biologically mimic death, such as deep hypothermic circulatory arrest—even when people lose conscious awareness of the outside world and do not feel pain or discomfort, the entity of the human consciousness and mind may not become immediately annihilated once the heartbeat ceases.
Disorders of Consciousness
Another class of neurological consequences of cardiac arrest are the disorders of consciousness, which include coma and persistent vegetative state. These conditions are signs of significant brain injury and severely impaired consciousness. A significant proportion of patients whose hearts are restarted after cardiac arrest do not regain consciousness immediately, and may be comatose for hours, days, or much longer. Some of these patients may recover, though many die. Others may enter a minimally conscious state or a persistent vegetative state.
Patients who suffer from disorders of consciousness are either wholly unconscious and unresponsive to stimuli (coma) or unconscious, yet may reflexively respond to stimuli and display sleep-wake cycles and periodic limb or facial movements. Whether a person is comatose or in a vegetative state, they are unable to speak, eat, coordinate their movements, or otherwise interact. The well-publicized case of cardiac arrest survivor Terry Schiavo drew the world’s attention to the devastating decisions families and caregivers must make for loved ones in a persistent vegetative state.
Schiavo’s case, and countless others, highlight the need for greater understanding of the mechanisms of consciousness itself, which must be studied in order to prevent disorders of consciousness. The two areas of study are mutually reinforcing, and can be seen as two sides of the same coin: in order to prevent disorders of consciousness, researchers must study consciousness itself in people after cardiac arrest has occurred.
- Parnia S … Schoenfeld ER. AWARE—AWAreness during REsuscitation—a prospective study. Resuscitation. 2014. . Opens in a new tab.
- Parnia S … Fenwick P. A qualitative and quantitative study of the incidence, features and aetiology of near death experiences in cardiac arrest survivors. Resuscitation. 2001. . Opens in a new tab.
- Van Lommel P … Elfferich I. Near-death experience in survivors of cardiac arrest: a prospective study in the Netherlands. Lancet. 2001. . Opens in a new tab.
- Thonnard M ….Vanhaudenhuyse A. Characteristics of near-death experiences memories as compared to real and imagined events memories. PLoS ONE. 2013. . Opens in a new tab.