The history of critical care medicine has demonstrated the enormous potential for medical innovation to improve our ability to reverse the process of death after cardiac arrest. Today, researchers at NYU Langone’s Parnia Lab build on this history to explore how a deeper understanding of cardiac arrest and its effect on the body, brain, and consciousness can inform new and more effective treatments.

Cardiac arrest occurs when any event or illness, including trauma, infection, heart attack, cancer, or poisoning becomes so severe that it disrupts the delivery of sufficient oxygen to meet the requirements of the heart muscle, which then causes the heart to stop pumping. The heart can also stop pumping if it suffers a sudden abnormal electrical malfunction. Much the way that a stroke occurs after there is a restriction of blood flow to a portion of the brain, the end result of cardiac arrest is akin to a global stroke: once the heart stops beating, oxygen is cut off from all the body’s organs, including the brain, and within seconds, respiration stops and brain activity comes to a halt.

From a biological perspective, cardiac arrest is synonymous with death by cardiorespiratory criteria, which is declared based on the absence of heartbeat and respiration and the loss of brain function. Deprived of blood flow and oxygen, the cells of the body begin their own process of death. Different cell types die at different rates. Contrary to previous notions that brain cells die within 5 to 10 minutes, evidence now suggests that if left alone, the cells of the brain die slowly over a period of many hours, even days after the heart stops and a person dies.

Paradoxically, it is the reintroduction of oxygen to deprived cells after the heart is restarted that causes the cells to suddenly die much more rapidly. The longer someone has been left without a heartbeat, the greater this cell injury process—as a result, someone with less than 5 minutes without blood flow to the brain has a much higher likelihood of recovery compared to someone who experiences 30 minutes without blood flow. Minimizing the amount of time that cells are deprived of oxygen is critical to halting the process of cell damage and death.