Cardiopulmonary resuscitation no relation death
Life support
The purpose of cardiopulmonary resuscitation (CPR) during cardiac arrest is ideally reversal of the clinically dead state by restoration of blood circulation and breathing. However, there is great variation in the effectiveness of CPR for this purpose. Blood pressure is very low during manual CPR, resulting in only a ten-minute average extension of survival. Yet there are cases of patients regaining consciousness during CPR while still in full cardiac arrest. In absence of cerebral function monitoring or frank return to consciousness, the neurological status of patients undergoing CPR is intrinsically uncertain. It is somewhere between the state of clinical death and a normal functioning state.
Patients supported by methods that certainly maintain enough blood circulation and oxygenation for sustaining life during stopped heartbeat and breathing, such as cardiopulmonary bypass, are not customarily considered clinically dead. All parts of the body except the heart and lungs continue to function normally. Clinical death occurs only if machines providing sole circulatory support are turned off, leaving the patient in a state of stopped blood circulation.Controlled
Certain surgeries for cerebral aneurysms or aortic arch defects require that blood circulation be stopped while repairs are performed.  This deliberate temporary induction of clinical death is called circulatory arrest.  It is typically performed by lowering body temperature to between 18 °C and 20 °C (64 and 68 °F) and stopping the heart and lungs. This state is called deep hypothermic circulatory arrest. At such low temperatures most patients can tolerate the clinically dead state for up to 30 minutes without incurring significant brain injury.
Longer durations are possible at lower temperatures, but the usefulness of longer procedures has not been established yet.Controlled clinical death has also been proposed as a treatment for exsanguinating trauma to create time for surgical repair.
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