Breathing and consciousness will cease within a few seconds of the heart stopping. Clinical death is reversible. Researchers believe there's a window of about four minutes from the moment of cardiac arrest to the development of serious brain damage.
The longest time someone has been cardiac arrest and successfully revived and fully recovered is 17 hours. The record is held by Velma Thomas from West Virginia US.
This means they will not regain consciousness or be able to breathe without support. A person who is brain dead is legally confirmed as dead. They have no chance of recovery because their body is unable to survive without artificial life support.
As the blood pools, patches appear on the skin within 30 minutes of death. About two to four hours postmortem, these patches join up, creating large dark purplish areas towards the bottom of the body and lightening the skin elsewhere. This may be less apparent on darker skin. This process is called livor mortis.
Muscle cells live on for several hours. Bone and skin cells can stay alive for several days. It takes around 12 hours for a human body to be cool to the touch and 24 hours to cool to the core. Rigor mortis commences after three hours and lasts until 36 hours after death.
What Happens One Hour After Death? At the moment of death, all of the muscles in the body relax (primary flaccidity ). The eyelids lose their tension, the pupils dilate, the jaw may fall open, and the joints and limbs are flexible.
The first visible change to the body—occurring 15 to 20 minutes after death—is pallor mortis, in which the body begins to pale. Pallor mortis occurs because blood stops moving through the capillaries, the smallest of the body's blood vessels.
For the first few minutes of the postmortem period, brain cells may survive. The heart can keep beating without its blood supply. A healthy liver continues breaking down alcohol. And if a technician strikes your thigh above the kneecap, your leg likely kicks, just as it did at your last reflex test with a physician.
Although death has historically been medically defined as the moment when the heart irreversibly stops beating, recent studies have suggested brain activity in many animals and humans can continue for seconds to hours.
A conscious dying person can know if they are on the verge of dying. Some feel immense pain for hours before dying, while others die in seconds. This awareness of approaching death is most pronounced in people with terminal conditions such as cancer.
This is where the heart spontaneously starts beating again at a normal rate following failed attempts at resuscitation. Velma's 17 hour is thought to be the world record for the longest time dead before coming back to life.
If CPR is initiated within: 0–4 minutes: unlikely to develop brain damage. 4–6 minutes: possibility of brain damage. 6–10 minutes: high probability of brain damage.
Normally there is no measurable, meaningful brain activity after the heart stops beating. Within two to 20 seconds the brain “flatlines.”
That record is held by Jeanne Louise Calment, also of France, who lived to be 122 years and 164 days old and died in 1997, according to Guinness World Records.
The Lazarus effect is when someone a healthcare provider has declared dead suddenly regains blood flow and appears to come back to life. The medical term for this phenomenon is “autoresuscitation,” which refers to the return of spontaneous circulation after cardiopulmonary resuscitation (CPR) has ended.
Your heart stops beating. Your brain stops. Other vital organs, including your kidneys and liver, stop. All your body systems powered by these organs shut down, too, so that they're no longer capable of carrying on the ongoing processes understood as, simply, living.
The brain and nerve cells require a constant supply of oxygen and will die within a few minutes, once you stop breathing. The next to go will be the heart, followed by the liver, then the kidneys and pancreas, which can last for about an hour. Skin, tendons, heart valves and corneas will still be alive after a day.
Agonal breathing or agonal gasps are the last reflexes of the dying brain. They are generally viewed as a sign of death, and can happen after the heart has stopped beating.
In time, the heart stops and they stop breathing. Within a few minutes, their brain stops functioning entirely and their skin starts to cool. At this point, they have died.
“First hunger and then thirst are lost. Speech is lost next, followed by vision. The last senses to go are usually hearing and touch.”
Visions and Hallucinations
Visual or auditory hallucinations are often part of the dying experience. The appearance of family members or loved ones who have died is common. These visions are considered normal. The dying may turn their focus to “another world” and talk to people or see things that others do not see.
Hearing may indeed be one of the last senses to lose function as humans die.
If the body feels warm and no rigor is present, death occurred under 3 hours before. If the body feels warm and stiff, death occurred 3-8 hours earlier. If the body feels cold and stiff, death occurred 8-36 hours earlier. If the body is cold and not stiff, death occurred more than 36 hours earlier.
Pupils dilate
When people die, their bodies relax. This impacts your eyes just as much as the rest of your body. As soon as the muscles that control your eye movement relax, the pupils dilate. This happens over a progression of several hours after death.
For approximately the first 3 hours after death the body will be flaccid (soft) and warm. After about 3-8 hours is starts to stiffen, and from approximately 8-36 hours it will be stiff and cold. The body becomes stiff because of a range of chemical changes in the muscle fibres after death.