Anoxic vs. Hypoxic Brain Injuries

The human brain weighs about three pounds but uses 20% of the body’s oxygen supply. Oxygen is delivered to the brain by the circulation of blood. Consequently, any reduction in the amount of oxygen in the blood or interruption in blood flow to the brain can deprive the brain of oxygen.

• Anoxic brain injuries result from the brain being completely deprived of oxygen. In an anoxic situation—with no supply of oxygen at all—brain cells begin to die after just four minutes.
• Hypoxic brain injuries result from the brain receiving less oxygen than it needs.
• Wondering about the differences between anoxic versus hypoxic brain injury? Although cerebral hypoxia (decreased supply of oxygen to the brain) may not damage the brain as rapidly as cerebral anoxia (no supply of oxygen to the brain), the long-term effects can be just as devastating—or deadly.

Although there is a technical distinction between the terms cerebral anoxia and cerebral hypoxia, clinicians often use them interchangeably.

Cerebral anoxia and hypoxia are a category of acquired brain injury (ABI). The term traumatic brain injury (TBI) is used to distinguish brain injuries caused by a blow (or trauma) to the head from brain injuries with other causes (ABIs).

Regardless of their cause, brain injuries can have catastrophic effects. It is not uncommon for moderate or severe brain injuries to result in permanent disabilities or death. Because the brain is involved in virtually every aspect of our physical and psychological life—regulating vital organs, processing input from our senses, controlling movement, storing memories, governing behavior, and providing intelligence and higher reasoning—anoxic and hypoxic brain damage affect victims in many ways.

Causes of Anoxic and Hypoxic Brain Injury

When someone suffers a traumatic brain injury, there’s a direct cause-and-effect link between a trauma to the head and the brain injury. In contrast, anoxic and hypoxic brain injuries often result from something going wrong elsewhere in the body. Let’s take a look at how this happens.

Anoxic and hypoxic brain injury causes can be grouped in two ways:

1. Events that cut off or reduce blood supply to the brain (the technical term for this is hypoxic-ischemic brain injury, or HIBI)
2. Events that eliminate or decrease the amount of oxygen in the blood (known as hypoxic brain injury, or HBI)

Both types of events result in no oxygen (anoxia) or less oxygen (hypoxia) being supplied to the brain. However, patients generally have a better chance of recovery with events in the second group because the circulation of blood is maintained. As the blood circulates—even when it carries less or no oxygen—it can still deliver glucose (energy) to the brain and clear away toxins.

What Events Cut Off or Reduce Blood Supply to the Brain?

The most common event that cuts off blood supply to the brain is cardiac arrest—when the heart stops beating. Cardiac arrest, which quickly leads to severe anoxic brain injury, is usually caused by some kind of heart disease, such as a heart attack—when a blood clot blocks an artery that brings blood to the heart.

The second most common event that cuts off blood supply to the brain is a stroke. A stroke is similar to a heart attack in that it’s usually caused by a blood clot blocking blood flow to the brain (that’s why a stroke is sometimes called a “brain attack”). A hemorrhagic stroke is caused by bleeding in or around the brain due to a blood vessel bursting.

Although events that cut off or reduce blood flow to the brain most often result from cardiovascular disease, there are some instances where a car accident might trigger a hypoxic-ischemic brain injury:

• Cardiac arrest can be initiated by a blow to the chest, such as might occur in a car accident, leading to cerebral anoxia.
• Heavy bleeding caused by a car accident can lead to cerebral hypoxia because there is less blood circulating in the body.

What Events Eliminate or Decrease the Amount of Oxygen in the Blood?

A wide range of events can eliminate or decrease the amount of oxygen in the blood. Although hypoxic brain injuries are often secondary to other conditions in the body, there are also quite a few direct causes.

Hypoxic brain injuries may be caused by:

• Respiratory failure: Usually due to various lung diseases, including pneumonia and chronic obstructive pulmonary disease (COPD), which causes emphysema or progressive chronic bronchitis.
• Asthma attacks or anaphylaxis (severe allergic reactions): Usually triggered by food or environmental allergens.
• Anything that prevents someone from breathing: Examples include drowning, choking, or strangulation.
• Low atmospheric oxygen: Usually results from being at a high altitude.
• Smoke inhalation: Usually due to being trapped in a fire. Causes lungs and airways to swell up.
• Carbon monoxide poisoning: Carbon monoxide is an odorless gas that is given off by burning fuel—from gas furnaces, grills, wood fires, or a car’s exhaust. Carbon monoxide binds to the oxygen-carrying cells in the blood, preventing the blood from absorbing oxygen.
• Lung collapse: Caused by air in the chest cavity outside the lungs. It can be triggered by lung disease or by an injury like a broken rib.

A car accident may cause a hypoxic brain injury if there’s a vehicle fire, if carbon-monoxide-laden vehicle exhaust gets into the car, or if a blow to the chest or broken rib results in a collapsed lung.

Anoxic or Hypoxic Brain Injury From Drug Overdose

Drug overdoses can cause anoxic or hypoxic damage in two main ways: respiratory depression or cardiac arrest. In the former case, a drug overdose blocks signals to the brain that the body needs to breathe. In the latter case, a drug overdose initiates heart failure.

Symptoms of Anoxic and Hypoxic Brain Injury

Anoxic and hypoxic brain injury symptoms are extremely varied. Some symptoms are evident immediately, some may develop gradually, and others may not show up until days or weeks after the initial event that caused the injury.

We’ll break the symptoms down into short-term and long-term symptoms.

Short-Term Symptoms

It’s important to be aware of short-term symptoms so that you can recognize when you or someone you know needs immediate medical attention to prevent brain damage from hypoxia.

Short-term signs of hypoxia and anoxia include:

• Loss of consciousness (cerebral anoxia—caused, for example, by cardiac arrest—typically results in loss of consciousness within 15 seconds)
• Headache, dizziness, or light-headedness
• Confusion or problems with concentration or coordination
• A blue tint to the skin (caused by a lack of oxygen in the bloodstream)

If you get into a car accident, it’s important to monitor everyone involved for any of these signs of hypoxia and to seek a full medical evaluation as soon as possible.

Long-Term Symptoms

Because the brain is the body’s central processing unit, brain injuries can affect a broad array of bodily functions and daily activities. The long-term effects of hypoxic brain damage include:

• Disorders of consciousness: These include being comatose or being left in a vegetative state.
• Movement disorders: These include tremors, tics, and difficulty walking.
• Cognitive effects: The most common cognitive effect of hypoxia is memory problems. Other effects include being slow to process information, being unable to concentrate, or having trouble making decisions or solving problems.
• Behavioral effects: For example, after hypoxic brain damage, some people have less self-control and struggle with social situations.
• Emotional effects: People with HBIs may suffer from depression, anxiety, mood swings, and other mental health issues.

Recovery From Anoxic Brain Injury

Treatment for hypoxic and anoxic brain injury begins with treating the immediate cause of cerebral hypoxia or anoxia and stabilizing the patient so that they do not incur any further brain damage.

Anoxic and hypoxic brain injury recovery times vary widely depending on the injury’s severity. Some survivors of anoxic and hypoxic brain injuries make a full recovery; others—perhaps as many as 30%–60%—have some of the long-term symptoms listed above.

Experienced California Car Accident Attorneys

If you suffered an anoxic or hypoxic brain injury in a car accident caused by another driver’s negligence, you may have a long road to recovery. The Bakersfield car accident attorneys of Chain | Cohn | Clark have helped many car accident victims with traumatic or hypoxic brain injuries, and they can help you pursue an insurance settlement or lawsuit that can relieve you of financial pressure as you recuperate. 

Contact us today for a free consultation.