Tissue Anoxia

Tissue anoxia is a life-threatening condition where organs and tissues are completely deprived of oxygen, potentially causing permanent damage within minutes if not treated immediately.

Table of contents

• What Is Tissue Anoxia?
• Types of Anoxia
• What Causes Anoxia?
• Signs and Symptoms
• Why Anoxia Is So Dangerous
• How Anoxia Is Diagnosed
• Treatment and Emergency Response
• Recovery and Long-Term Effects

What Is Tissue Anoxia?

Tissue anoxia happens when your body or specific organs completely lose their oxygen supply^[1]. This is different from hypoxia, which means that a part of your body doesn’t have enough oxygen. Anoxia is an extreme form of hypoxia—it represents a total absence of oxygen rather than just a shortage^[2].

When your body is harmed by a lack of oxygen, it’s called a hypoxic-anoxic injury^[1]. Anoxia usually results from hypoxia that has progressed to complete oxygen deprivation. The damage caused by partial or complete lack of oxygen supply is known as hypoxic or anoxic injury^[2].

Anoxia can affect any tissue or organ in your body, but the brain is the most vulnerable. The brain consumes much energy compared to its weight and size—it uses almost 20% of all the oxygen that enters the body even though it represents only about 2% of body mass^[4][3]. Because the brain is highly active and extremely sensitive to oxygen loss, cellular injury can begin within minutes if oxygen is not restored^[3].

Types of Anoxia

There are four main types of anoxia, each caused by different problems that prevent oxygen from reaching your tissues^[2][12]:

Anoxic anoxia (also called hypoxic anoxia) is caused by a lack of oxygen in the air you breathe, such as at high altitudes. When there isn’t enough oxygen in the air, less oxygen reaches your blood, and your tissues don’t get the oxygen they need^[2]. This type can also occur due to choking, strangulation, drowning, or airflow obstruction to the lungs caused by severe asthma^[12].

Anemic anoxia occurs when red blood cells lack the ability to carry enough oxygen. This can happen due to a reduction in hemoglobin (the protein in red blood cells that carries oxygen), a deficiency in red blood cells, or an alteration in hemoglobin’s capacity to carry oxygen^[2]. Health conditions frequently associated with anemic anoxia include lung disorders, chronic anemia, carbon monoxide poisoning, and severe blood loss^[2][12].

Stagnant anoxia (also called ischemic anoxia or hypoxic-ischemic injury) occurs when blood, although well-oxygenated, is not distributed properly to the tissues^[2]. This type is caused by conditions such as stroke, heart attack, cardiac arrhythmias, severe hypotension, or heart failure^[2][12]. Stagnant anoxia is probably the most frequent type and is more common among newborn babies^[12].

Toxic anoxia (also called histotoxic anoxia) occurs when toxic substances such as carbon monoxide, cyanide, narcotics, or alcohol are present in the body, restricting the delivery of oxygen to the tissue or preventing cells from using the oxygen properly^[2][12].

What Causes Anoxia?

Anoxia can occur whenever oxygen delivery to the brain or other organs is compromised. Oxygen delivery depends on blood flow to the tissue and the oxygen content of the blood^[3]. Many different conditions and events can lead to anoxia^[1]:

• Cardiac arrest (the most common cause in the United States)^[3]
• Heart attack or heart problems that reduce blood flow to organs^[1]
• Severe asthma attacks or other breathing difficulties that lower oxygen supply^[1]
• Pneumonia or other lung infections^[1]
• Stroke^[1]
• Near-drowning or choking^[1]
• Strangulation^[14]
• Carbon monoxide poisoning or smoke inhalation^[1][14]
• Drug overdose^[4]
• Severe anemia or significant blood loss^[1]
• Traumatic vascular injuries^[3]
• High altitude exposure where oxygen levels are low^[1][14]
• Anesthetic accidents^[14]

In the United States, cardiac arrest is the most common cause of hypoxic brain injury. According to data from the American Heart Association, over half a million patients suffer a cardiac arrest each year^[3].

Signs and Symptoms

The symptoms of anoxia may not always be obvious at first. Your brain can last a few minutes without oxygen before any symptoms appear. Sometimes, symptoms may be delayed and take several days or weeks to show up^[1].

Symptoms of anoxia depend on the duration of oxygen deprivation and the intensity of damage. The most vulnerable areas of the brain are the cerebral cortex (the outer layer of the brain responsible for thinking and processing), the hippocampus (important for memory), the basal ganglia (which control movement), and the cerebellum (which coordinates movement)^[2].

The first noticeable symptoms of anoxia can include^[1][2]:

• Mood and personality changes
• Memory loss or short-term memory problems
• Slurred speech or forgotten words
• Changes in judgment
• Trouble walking or moving your arms or legs normally
• Lack of attention, concentration, or coordination
• Weakness
• Feeling dizzy or disoriented
• Unusual headaches
• Trouble concentrating
• Hyperventilation and sweating

After your brain has been without oxygen for more than four to five minutes, other symptoms may become noticeable^[1][2]:

• Seizures
• Confusion and agitation
• Hallucinations
• Bluish discoloration of the skin around the lips, mouth, and fingertips (called peripheral cyanosis)
• Jerky contraction of muscles (called myoclonus)
• Passing out or suddenly losing consciousness

In severe cases of anoxia, the patient is often in a coma (a state of unconsciousness) for periods ranging from hours to days, weeks, or months^[14].

• Brain
• Heart
• Kidneys
• Body tissues

Why Anoxia Is So Dangerous

Oxygen is the body’s most essential nutrient. If you are deprived of oxygen, your body shuts down because it cannot function without oxygen. Oxygen promotes cell growth and allows for the removal of carbon dioxide from the body^[4].

Your cells need oxygen to produce energy and help your organs and tissues do their jobs. A complete lack of oxygen can be harmful or even deadly if it goes untreated^[1]. While some of your tissues can adjust to temporary dips in oxygen levels, prolonged anoxia can cause permanent organ damage. Brain and heart damage are particularly dangerous and can lead to death^[1].

Anoxia can be especially harmful to your brain. After about four to five minutes without oxygen, your brain can become permanently damaged. Without oxygen, your brain cells can die, and many of the functions that your brain controls can be affected^[1][2]. If oxygen deprivation persists beyond four minutes, brain cell death may occur, and permanent brain injury is likely if the oxygen supply is not restored within five minutes^[2]. Once the 15-minute mark is surpassed, it is possible that more than 95% of the brain tissue in that area is damaged^[12].

The longer your brain goes without enough oxygen, the more likely you may experience long-term complications, including death^[1]. Unfortunately, the vast majority of patients who experience a cardiac arrest do not survive until hospital discharge. Of those who do survive, the majority (50 to 83%) experience clinically significant cognitive symptoms^[3].

How Anoxia Is Diagnosed

If you or someone around you is experiencing any symptoms of hypoxia or anoxia, seek immediate emergency medical attention^[1]. Anoxia is a medical emergency, and the body needs a continuous supply of oxygen to function. A lack of oxygen can cause immediate damage to brain cells^[10].

Once a patient arrives at a hospital, healthcare professionals assess and stabilize the patient’s respiration and circulation to manage anoxia effectively^[10]. Medical evaluation may include physical examination and various tests to determine the cause and severity of oxygen deprivation.

Treatment and Emergency Response

The most important thing in treating anoxia is to get more oxygen into your body as quickly as possible^[1]. Emergency response and immediate medical attention are critical to prevent permanent organ damage and potential death.

Immediate Emergency Response

Cardiopulmonary resuscitation (CPR) is a crucial first step in managing anoxia. CPR helps maintain the circulation and oxygenation of vital organs, including the brain, during cardiac arrest, which can cause anoxic conditions^[10]. By maintaining blood flow and oxygenation to the brain after cardiac arrest, CPR can potentially reduce the severity of anoxic brain injury^[10]. However, CPR isn’t a cure—it’s a temporary measure intended to maintain enough blood flow to the brain until further medical help arrives^[10].

Once emergency medical services arrive, healthcare professionals take over. The focus is on establishing an adequate airway as soon as possible, using enough oxygen to saturate the blood, supporting the cardiovascular system as needed, and preventing or treating complications like pneumonia^[14]. Respiratory assistance may be necessary^[14].

Hospital Treatment

Treatment of anoxia consists of establishing an adequate airway, using enough oxygen to saturate the blood, and supporting the cardiovascular system^[14]. You’ll need to go to the hospital to get treatment for anoxia and to monitor your oxygen level. The most important goal is to get more oxygen into your body. You’ll receive oxygen through a small plug in your nose or through a mask that covers your nose and mouth^[1].

In severe cases, patients may require intensive care unit support. The focus shifts to stabilizing patients by managing body temperature and preventing or controlling seizures^[10]. When your life is in danger and other treatments aren’t working, you may need a machine to help you breathe^[1].

Hyperbaric Oxygen Therapy

One anoxia treatment that has shown positive outcomes for many patients is hyperbaric oxygen therapy (HBOT)^[4]. HBOT is a non-invasive treatment used to help reverse tissue damage, encourage stem cell mobilization, and decrease inflammation caused by anoxia. It works by increasing the flow of oxygen-rich blood and oxygen absorption rates in all parts of the body, including the brain, in a controlled setting^[4].

Recovery and Long-Term Effects

Depending on the severity of the injury, recovery may occur if the patient’s respiratory and cardiovascular systems can be supported properly^[14]. While some people are able to eliminate or reduce anoxia’s effects, others who have been cut off from oxygen for a significant period could experience permanent damage^[4].

As recovery proceeds, a variety of psychological and neurological problems may appear, which may persist for a time and may improve. These can include^[14]:

• Mental confusion
• Personality regression
• Memory loss and amnesia
• Hallucinations
• Persistent muscle spasms (myoclonus)

If someone survives an anoxic brain injury, they could still suffer from^[4]:

• Memory loss
• Speech and swallowing issues
• Personality changes
• Increased impulsive behavior

Long-term rehabilitation strategies are important for recovery from anoxic or hypoxic brain injury. The consequences associated with anoxia depend on several factors, including the duration of oxygen deprivation (the longer brain tissue has been without oxygen, the greater the damage), age (older people tend to experience more severe damage), existing health conditions before the event, and how quickly resuscitation was performed^[12].