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Can freezing the body save lives? Explore the impact of hypothermia on clinical death!
Clinical death is a medical term used to describe the state of cessation of blood circulation and breathing, two factors necessary to maintain life. Asystole occurs when the heart stops beating and is known as clinical death. Although stopping blood circulation was often considered irreversible in the past, now with the development of CPR (cardiopulmonary resuscitation) and other first aid techniques, the definition of clinical death has also had a new interpretation.
After cardiac arrest, consciousness is usually lost within seconds; in dogs, brain activity ceases within 20 to 40 seconds. During this period, even if irregular breathing occurs, it is often misjudged by emergency personnel as not requiring CPR.
During clinical death, ischemic damage gradually accumulates in tissues and organs in the body. For most organs, if they can receive appropriate treatment after the blood circulation has stopped, they can still survive for a period of time. For example, even if the blood circulation of a limb not related to the heart is stopped in a warm environment for six hours, it is still possible to successfully reattach it. However, during this time, the brain's immune response appears more fragile.
Research shows that ischemic damage to the brain is faster, especially within three minutes after clinical death. The chance of complete recovery is extremely slim, and irreversible brain damage will soon occur. The most vulnerable cells in the brain, CA1 neurons in the hippocampus, will begin to suffer fatal damage after being deprived of oxygen for ten minutes. It is worth noting that even if the nerve cells have not yet died, they will still undergo a delayed death process several hours after recovery.
Some experiments have shown that post-resuscitation medication can prevent brain death even after 20 minutes of oxygen deprivation. And in some cases, even after brain damage, human neurons can be extracted and proliferated within hours of clinical death.
A key factor here is reperfusion injury, a complex process that occurs after blood circulation is restored. The impact of these processes on blood circulation has become the focus of current research. As hypothermia treatments are further explored, scientists are finding that lowering body temperature can significantly extend life after clinical death. In 1990, research by Peter Safa, a pioneer in resuscitation technology, found that lowering body temperature by three degrees helped patients double the time window after clinical death from five minutes to ten minutes.
This induced hypothermia technology is now being used in emergency medicine. Further research shows that the CPR process helps to expand the time window for recovery, thereby increasing the number of dogs recovering without brain injury.
Theoretically, when a person's body temperature is below 20°C, the survival rate for clinical death can exceed one hour. This study and cases show that "the definition of death in the future may need to be rethought."
In some specialized medical procedures, especially those for cerebral aneurysms or aortic arch defects, surgeons sometimes deliberately induce clinical death with circulatory arrest in order to maintain a safe operating environment during the repair process. This controlled clinical death, called circulatory arrest, usually lasts up to 30 minutes and involves relatively little risk of brain damage.
In the past, death has been considered a single event. However, modern medicine is more inclined to understand death as a series of physiological changes. In sudden clinical death, CPR is usually initiated to try to restore normal heartbeat and breathing, and this is considered a medical emergency. However, whether there is true resuscitation and whether a person is completely hopeless often inevitably involves vague judgments.
Ethical and legal issues related to this have triggered extensive discussions in many cases, such as some patients' religious beliefs leading to debates about whether to discontinue life-sustaining treatment. These situations often prompt the medical community to rethink how to appropriately treat clinical death and its consequences.
In this context, the concept of frozen bodies has once again become the focus. Does cryonics preserve the chance of future recovery? Could the impact of hypothermia on clinical mortality offer new hope for saving lives?
