The term clinical death defines the condition where the blood circulation completely stops along with the breathing process. These two conditions are essential to maintain vital organs and sustain life. When the cardiac arrest occurs i.e. the heart stops beating within the regular pace it causes death. But the restriction of blood flow can be reversed with the help of CPR, epinephrine injections or defibrillation. Before the twentieth century, these situations resulted in death but now due to the latest technology, there are chances of resuscitation after cardiac arrest.
When a person experiences clinical death, he or she undergoes unconsciousness within a minute or few seconds. Brain activity is seen for 20-40 seconds which can be easily measured. During this period, the person might experience irregular gasping but this is not a critical key to show that CPR is non-essential. When a person suffers from clinical death, the organs and body systems suffer from ischemic injury where the blood stops flowing.
Most of the organs or tissues can survive this clinical death process for a considerable duration. The organs below the heart can survive for around 30 minutes except for the spinal cord which might suffer from injury. Limbs, bones, tendons and skin, all can survive without blood for 6-12 hours. But when we consider the brain, it suffers from ischemic injury at a very high rate when compared to other organs. If you avoid providing any special treatment to the brain, the brain damage or brain death might occur within 3-4minutes. However, when considering the normal circumstances, the brain death or damage to the brain occurs after a longer duration when the blood circulation to the heart and other organs is restored. When a person recovers from clinical death, the limiting factor that might affect the recovery is a brain injury.
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The brain functioning is immediately lost after clinical death but there is no specific duration. CA1 neurons are the vulnerable cells within the brain that are present in the hippocampus. These brain cells undergo immediate injury within 10 minutes when there is no oxygen supply. In resuscitation conditions, these cells do not die for hours. The death of these cells is reversible with a pharmaceutical measure within 20 minutes. Complete brain damage is seen after clinical death due to the complex physiological processes known as reperfusion injury. During this situation, the blood is restored to the entire body but certain processes interfere with normal blood circulation within the recovery period.
According to different studies, it is seen that reduced body temperature i.e. hypothermia can enhance the recovery period after clinical death with no brain damage. The reduction in body temperature and blood cell concentration along with increased blood pressure is highly effective after resuscitation for increased chances of recovery.
During CPR, the person is recovered from cardiac arrest and the breathing is regained but the neurological status of the person is still uncertain. It is unknown whether the person’s brain is in the functioning or unconscious state.
In the past days, death was considered simply as clinical death but now it is seen that completion of the death process occurs after a series of physiological reactions other than the cessation of heartbeat or breathing. Some studies show the haunting findings where the people suffering from cardiac arrest were able to see what was going on around them before they revived back to life as their brain kept on working. According to the study conducted by neurologists at Charité–Universitätsmedizin Berlin, it shows that our brain keeps on working for a few minutes even after the heart stops pumping blood or oxygen throughout the body. So, to end up now beware when you are declaring someone dead as they might still be alive and listening to what you are saying and doing!
Until Next Time,
Team doctor ASKY!