How long does brain activity last after cardiac arrest?

Cardiac arrest is a catastrophic event in which the heart stops beating. This means that the body is deprived of the oxygen it needs to survive. The American Heart Association reports that more than 356,000 out-of-hospital cardiac arrests occur in the United States each year. Nearly 90% of them are fatal.

In addition to the high risk of death, a major concern is the effect of prolonged hypoxia on the brain and the damage that can occur within three minutes of cardiac arrest.

This article explores what happens when oxygen to the brain is cut off during cardiac arrest, and the common symptoms a person experiences when they wake up. It also looked at problems that arise when blood flow starts again in damaged tissue.

What happens during cardiac arrest

A person can quickly lose consciousness during cardiac arrest. This usually happens within 20 seconds after the heart stops beating. Without the oxygen and sugar it needs to function, the brain cannot transmit the electrical signals needed to maintain breathing and organ function.

This may lead to hypoxia hypoxia Injury (HAI). Hypoxia refers to partial lack of oxygen, while hypoxia refers to complete lack of oxygen. In general, the more complete the hypoxia, the more severe the damage to the brain.

With cardiac arrest, all parts of the brain that depend on blood flow are affected by its malfunction. The damage caused by lack of oxygen is called diffuse brain damage. The most vulnerable part of the brain is the temporal lobe, where memories are stored.

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In the event of cardiac arrest, cardiopulmonary resuscitation (CPR) must be started within two minutes.Three minutes later, the global brain ischemia– Lack of blood flow throughout the brain – may lead to progressively worsening brain damage.

By 9 minutes, severe and permanent brain damage can occur. After 10 minutes, the chances of survival are low.

Even if a person is resuscitated, 8 out of 10 people will be in a coma and suffer some degree of brain damage. Simply put, the longer the brain is deprived of oxygen, the worse the damage.

If you haven’t learned CPR recently, things have changed. You can usually find a two- to three-hour training session at your local community health center, or contact the Red Cross or American Heart Association office in your area.

recovery and symptoms

People are most likely to be resuscitated successfully in a hospital or other setting where a defibrillator can be used quickly. These are devices that send electrical pulses to the chest to restart the heart. These devices can be found in many workplaces, sports fields, and other public places.

When cardiac arrest is treated quickly, a person may recover with no signs of injury. Others may have mild to severe damage.

Memory is most severely affected by hypoxia, so memory loss is often the first sign of damage. Other symptoms, both physical and mental, may be apparent, and some may not be noticed until months or years later.

For those who are resuscitated and not in a coma, hypoxia may cause:

  • severe memory loss (amnesia)
  • Involuntary muscle contractions (spasms)
  • loss of muscle control
  • Incapacitation and fine motor control
  • incontinence
  • speech disorder
  • personality change
  • Lost in place, person or time

Some symptoms may improve over time. However, others may be persistent and require a person to receive assisted care for life.


About 90 percent of people who experience cardiac arrest outside the hospital—that is, at home, at work, or wherever it happens—will die. Even if the heart restarts and blood flow starts delivering oxygen to cells again, most people are still severely affected. These effects, such as memory loss or reduced mobility, get worse the longer the brain is deprived of oxygen.


People in a coma after cardiac arrest often have damage to different parts of the brain, such as:

  • cerebral cortex
  • hippocampus
  • cerebellum
  • basal ganglia

Even the spinal cord can sometimes be damaged. People who are in a coma for 12 hours or more often have lasting problems with thinking, movement and feeling. Recovery is often incomplete and slow, taking weeks to months.

Those most severely affected may end up in a vegetative state, more appropriately known as Unresponsive Waking Syndrome (UWS). A person with UWS may open their eyes, and voluntary movements may occur, but the person is unresponsive and unaware of their surroundings.

About 50% of people with UWS caused by traumatic brain injury regain consciousness. Unfortunately, those with UWS due to lack of oxygen usually do not.

reperfusion injury

Restoring blood flow through the body is called reperfusion. This is the key to rejuvenating a person and preventing or limiting brain damage. But when this happens, the sudden rush of blood to the area of ​​damaged tissue can cause harm.

This seems counterintuitive since restarting blood flow is the key goal. But the lack of oxygen and nutrients during cardiac arrest means that when blood flow is restored, it can put oxidative stress on the brain as the toxin overwhelms already damaged tissue.

The resulting inflammation and nerve damage can trigger a range of symptoms, including:

  • severe headache or migraine
  • Seizures
  • Weakness or paralysis on one side of the body
  • Blindness or blindness in one eye
  • Difficulty understanding what is heard or said
  • Loss of awareness to one side of the environment (half-spatial neglect)
  • Slurred or disorganized speech
  • dizziness or vertigo
  • double vision
  • loss of coordination

The severity of these symptoms is closely related to how long a person is away without oxygen. Other factors include any pre-existing conditions that affect the brain and cardiovascular system.


When the heart stops, the blood pumping through the body also stops. Brain damage will begin within minutes as the blood cells lack oxygen.

Cardiac arrest is often fatal outside of a hospital setting, but even those who are revived can have serious and lasting effects. It is important to act quickly to restart the heart and limit these catastrophic effects.

VigorTip words

From the moment the heart stops, all brain activity is thought to cease within about three to four minutes. So if someone suddenly falls down in front of you and stops breathing, every second counts.

Instead of wasting time putting the victim in the car and rushing to the hospital, call 911 and start manual CPR right away. You can buy enough time until paramedics arrive to restart the heart.

Frequently Asked Questions

  • How long can the brain survive without oxygen?

    It may take less than five minutes of oxygen deprivation for some brain cells to start dying. Brain hypoxia, or when the brain is deprived of oxygen, can cause brain damage and be fatal in a short period of time.

  • How long can a person be in a coma?

    Rarely are people in a coma for more than two to four weeks. However, there are also very rare people who are in a coma for years, even decades. The longer a person is in a coma, the greater the chance of brain damage.

  • What happens during cardiac arrest?

    During cardiac arrest, a person’s heart stops beating and they quickly lose consciousness. Their breathing stops and their organs stop working. Brain damage can get worse if CPR is not performed within two to three minutes of cardiac arrest. After nine minutes, brain damage is highly likely. Because blood and oxygen cannot reach the brain reliably, the chances of surviving cardiac arrest after 10 minutes are very low.

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