The brain begins to suffer permanent damage from lack of oxygen within 4 to 6 minutes after the heart stops, but significant brain activity and even consciousness can persist for seconds to over 10 minutes, with some studies even showing activity for up to an hour under specific circumstances like CPR, highlighting that brain cells die slowly and complex activity can continue briefly after cardiac arrest. Immediate CPR is crucial because this period is reversible, but irreversible damage occurs quickly, though the brain is more resilient than previously thought.
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.
Permanent brain damage begins after only 4 minutes without oxygen, and death can occur as soon as 4 to 6 minutes later. Machines called automated external defibrillators (AEDs) can be found in many public places, and are available for home use.
Brain dead patients look asleep, but they are not. They do not hear or feel anything, including pain. This is because the parts of the brain that feel, sense, and respond to the world no longer work. In addition, the brain can no longer tell the body to breathe.
Brain function does not die immediately after the heart stops finds study. According to new research, people can be aware that they are dead after their heart has stopped beating. This suggests that the brain and consciousness seems to work even after the body has stopped working.
Normally there is no measurable, meaningful brain activity after the heart stops beating. Within two to 20 seconds the brain “flatlines.”
Is cardiac arrest painful? Some people have chest pain before they become unconscious from cardiac arrest. However, you won't feel pain once you lose consciousness. People may experience chest pain after receiving CPR.
In principle, there is no upper limit to surviving on life support. Patricia LeBlack from Guyana has been on continuous kidney dialysis in London for 40 years and John Prestwich MBE died in 2006 at the age of 67, after 50 years in an iron lung.
Brain activity supports that a dying patient most likely can hear. Even if awareness of sound cannot be communicated due to loss of motor responses, the value of verbal interactions is measurable and positive. Patients appear comforted by the sounds of their loved ones (in person and by phone).
They might not remember this time, although sedated patients may be able hear you even if they do not respond.
The Last Stages of Life
Annie Shapiro (1913–2003) was a Canadian apron shop owner who was in a coma for 29 years because of a massive stroke and suddenly awakened in 1992. After the patients in the true story Awakenings, Shapiro spent the longest time in a coma-like state before waking up.
Active dying is the final stage of the dying process that lasts roughly three days. By definition, actively dying patients are very close to death, and exhibit many signs and symptoms of near-death. Actively dying patients are often unresponsive and their blood pressure often drops significantly.
Ventilators, often referred to as life support machines, are used in intensive care units for patients who cannot breathe on their own. Many of the sickest patients with COVID-19 need the assistance of a ventilator to survive.
Other researchers have proposed that the surge of electrical activity in the moments after cardiac arrest is just the final seizure of a dying brain, or have hypothesised that it's a last-ditch attempt by the brain to restart itself, like jump-starting the engine on a car.
Most heart attacks involve discomfort in the center of the chest that lasts more than a few minutes, or that goes away and comes back. It can feel like uncomfortable pressure, squeezing, fullness or pain. Symptoms can include pain or discomfort in one or both arms, the back, neck, jaw or stomach.
Three early warning signs of heart failure include persistent fatigue/weakness, shortness of breath (especially with activity or lying down), and swelling (edema) in your legs, ankles, and feet, often accompanied by rapid weight gain from fluid buildup, all signaling your heart isn't pumping efficiently enough. Other key indicators are a chronic cough (sometimes with pink mucus) and heart palpitations.
Much depends on your cause of death and whether you have access to pain medications. For instance, you may die suddenly and experience no pain at all. Often, dying bodies fight to survive. The survival instinct programmed into our bodies can feel painful without medications.
About 75% of your brain is water, making hydration crucial for sharp thinking, focus, and mood, as even mild dehydration (losing 2% of body water) can impair memory, concentration, and reaction time. The remaining part of the brain is mostly fat, and this water content is essential for creating neurotransmitters and supporting brain function.
There is no rule about how long a person can stay on life support. People getting life support may continue to use it until they either recover or their condition worsens. In some cases, it's possible to recover after days or weeks of life support, and the person can stop the treatments.
Some processes continue for minutes or even hours after clinical death. In fact, during the early stages following clinical death, the body enters a series of steps that scientists call "active dying," where certain chemicals are released and neuron activity spikes as the brain and body gradually shut down.
Studies indicate that hearing is the last of the senses to be lost. We therefore encourage you to continue to talk to the person even if they appear to be unconscious. You may also wish to hold or gently massage the person's hands or feet as a way of maintaining physical contact.
Hospice Isn't About Giving Up
It's not a place to speed up the process of dying. A doctor suggesting hospice does not mean they're giving up on providing care and medical treatment. It's end-of-life care, but this doesn't mean giving up hope. It means shifting focus from curative treatments to comfort and support.
But the body tries valiantly. The first organ system to “close down” is the digestive system.
These can be supplied by connecting the blood vessels that supply the brain with an artificial blood substitute or by immersing the blood in an artificial cerebro-spinal fluid and oxygenating that directly. Guinea pig, dog and monkey brains have all been kept alive for hours or even days after being removed.