Adequate oxygen is vital for the brain. Many factors can cause the brain to receive inadequate oxygen. When oxygen levels are significantly low for four minutes or longer, brain cells begin to die and after five minutes permanent anoxic brain injury can occur. Anoxic brain injury which is also called cerebral hypoxia or hypoxic-anoxic injury (HAI) is a serious, life-threatening injury; it can cause cognitive problems and disabilities. Some HAI injuries are due to a partial lack of oxygen; the term hypoxic means partial lack. Other HAI injuries are due to a complete lack of oxygen; the term anoxic means total lack. The greater the loss of oxygen, the more wide-spread and serious the injury will be.
The Brain's Dependance on Oxygen
The death of brain cells interrupts the brain’s electrochemical impulses and interferes with the performance of neurotransmitters—the chemical messengers which transmit messages within the brain. The neurotransmitters regulate body functions and influence behavior. For example, the neurotransmitters serotonin, dopamine, and norepinephrine help regulate moods, while the endorphins increase pleasure and control pain. The neurotransmitter acetylcholine plays an important role in memory.
Causes of Anoxic Brain Injury
There are four types of anoxia, but each can cause the same serious damage to the brain.
- Anemic anoxia. This form of anoxia results from blood that cannot carry sufficient oxygen to the brain. Some forms of lung disease can lead to insufficiently oxygenated blood, since the lungs are not processing oxygen sufficiently. While the blood flow to the brain is still adequate, the brain will not receive enough oxygen to perform vital functions. This can lead to slow deterioration of the patient’s overall condition. Chronic anemia, acute hemorrhage, and carbon monoxide poisoning can cause anemic anoxia.
- Toxic anoxia. This form of anoxia is caused by toxins in the system that prevent the blood’s oxygen from being used efficiently. For example, carbon monoxide poisoning can cause toxic anoxia.
- Stagnant anoxia. This condition is also called hypoxicischemic injury (HII). In HII, an internal condition blocks sufficient oxygen-rich blood from reaching the brain. Strokes, cardiac arrhythmia, and cardiac arrest can cause HII.
- Anoxic anoxia. This condition is caused when there is not enough oxygen in the air for the body to benefit with it. It can occur at high altitudes.
Common Causes of Anoxia
- Respiratory arrest
- Electrical shock
- Heart attack
- Brain tumors
- Heart arrhythmia
- Extreme low blood pressure
- Carbon monoxide inhalation
- Compression of the trachea
- Respiratory conditions which interfere with proper breathing
- Illegal drug use
Symptoms of Anoxic Brain Injury
Usually HAI will begin with a loss of consciousness or a coma, although this is not always the case. A coma resembles sleep, but the person will not wake up when called or stimulated in some way. After the initial unconscious period the person may lapse into a persistent vegetative state—the person is not comatose, but yet he or she will not respond to being stimulated; the persistent vegetative states is often called “wakeful unresponsiveness.”
If the person regains full consciousness, he or she may experience a wide-range of symptoms which resemble the symptoms seen after head trauma. The extent and type of symptoms depend on the amount of brain tissue damage and part of the brain where the injury occurred.
Cognitive Problems with Anoxia
- Short-term memory loss. Most people with HAI experience short-term memory loss; the problem is extremely common when a hypoxicischemic injury caused the HAI. The person cannot remember new information which has just been presented. The part of the brain responsible for learning new information is called the hippocampus and it is very sensitive to a lack of oxygen.
- Poorer performance in executive functions. The executive functions include judgment making, reasoning, and processing information. The person with HAI may become impulsive and indecisive. He or she may lack the ability to concentrate or to focus on more than one task.
- Anomia. This term means having difficulty using words or processing what words mean. The right word may not be remembered or a word may be placed out of context. Sometimes the opposite word is used; for example, a person wanting to say “sunny” may say “cloudy” instead. Common words may not be understood.
- Visual disturbances. The person with HAI may have trouble processing visual information. They may find it difficult to focus or they may reach for an object, but not be able to touch it because they are reaching in the wrong place. Rarely, HAI causes cortical blindness; the eyes are normal, but the brain cannot process visual information and so the person cannot see. Oddly enough people with cortical blindness may act as though they can see, even though they seem unable to identify objects, colors, or shapes; this because the damaged part of the brain is unable to realize that it is damaged.
Physical Problems with Anoxia
- A lack of coordination. This is called ataxia. The person’s gait may be wobbly; they may weave or stagger like someone who has had too much alcohol.
- An inability to do common tasks. This is known as apraxia. The person may be unable to remember the sequence of common tasks like brushing the hair or drinking from a cup.
- Movement disorders. The person may experience spasticity, rigidity, and myoclonus (muscle spasms). The patient may have involuntary movements, jerky movements, or trembling.
- Quadriparesis. The person may experience weakness in all four limbs.
- Headaches. Anoxic brain injury can also cause confusion, depression, hallucinations, delusions, personality changes (such as increased irritability), and the inability to concentrate.
Diagnosing Anoxic Brain Damage
Loss of consciousness is a serious medical emergency; call an ambulance if you are with someone who has lost consciousness. If you or someone you know are experiencing symptoms of anoxic brain injury, do not delay seeking medical help. Problems such as heart arrhythmias can cause significant lack of oxygen to the brain without inducing a lack of consciousness; the person may simply be extremely sleepy or fatigued.
Diagnostic tests for anoxic brain damage include:
- MRI (magnetic resonance imaging)—considered the gold standard for diagnostic tests; an MRI produces detailed cross-sections of the brain by using radio waves and magnets. The images are shown on a computer screen.
- CT or CAT scan (computerized axial tomography) — which uses x-rays and the computer to show detailed images of brain’s interior.
- The evoked potentials tests evaluate the patient’s response to visual, auditory, and sensory stimuli. Electrodes are places on the patient’s head to measure brain waves and the various stimuli are then presented.
- EEG (electroencephalogram)—Electrodes are placed on the head to measure the brain’s electrical activity.
- Blood tests, especially tests for arterial blood gases, since these determine the level of oxygen in the blood.
Prognosis for Anoxic Brain Damage
Recovering from anoxic brain damage is difficult. Many factors contribute to the degree and rate of recovery. The amount and kind of brain damage is a critical factor; anoxic brain injury can be mild, moderate, or severe. The length of time spent unconscious or in a coma, coupled with how much normal function is recovered within the first month of the injury can indicate the chance of long-term recovery. People who have experienced severe anoxic brain injury may remain in a coma or vegetative state.
Their chances of recovery may be minimal. Cases of moderate anoxic brain injury have a better outcome, but recovery may still take months or years. People with mild anoxic brain injury usually make a full or nearly full recovery, and are able to live lives that are relatively normal and symptom free.
Treatment of Anoxic Brain Injury
When treating anoxic brain injury, doctors first attempt to pinpoint the cause of the injury and treat it. For example, if lack of oxygen is due to a stroke, the first priority will be to treat the patient for stroke. If the problem is due to heart arrhythmia, steps will be taken to regulate and stabilize the heart’s rhythm. Efforts to stop further brain damage will be combined with treatments for the cause of the problem. Every effort will be made to restore normal oxygen availability to the brain. The patient will be kept cool in order to reduce further brain damage, because the brain can reach high temperature during oxygen deprivation.
Steroids may be given in an attempt to reduce brain swelling, since swelling can also damage the brain. Barbiturates may be given to reduce brain activity and allow the tissue time to recover. Sometimes people with anoxic brain injury have seizures. Anti-seizure medications will be used to control this problem. Severe seizures may be treated with anesthesia. In many instances, the patient must be put on a ventilator during the first phase of treatment. This is frightening for the family, but it can be a step taken to assure the proper level of oxygen will be maintained so that the patient has a chance of recovery. Of course, all involved must be prepared for the possibility of brain death (no brain activity, which means no chance of recovery).
The longer a person remains unconscious, the greater the chance of brain death. The medical team should keep the appropriate family members aware of exactly what is going on; do not hesitate to ask questions about every treatment. There are no “dumb questions.” Once the patient is stable and life-threatening injuries have been treated, the rehabilitation phase of treatment will follow. Generally, chances of recovery are better when rehabilitation can be started quickly, particularly with people over 25. As people age the muscles atrophy more quickly with bed rest, so it is important to begin movement as soon as possible.
During rehabilitation the patient and his or her family will work with a multidisciplinary staff including doctors, nurses, physical and occupational therapists, and other specialists to devise an individualized program designed to return the patient to the maximum level of function. The rehabilitation phase may include:
- Speech therapy
- Physical therapy
- Occupational therapy
- Recreational therapy
- Adaptive equipment training
Counseling the patient’s family and caregivers can help with rehabilitation by talking with all members of the rehabilitation team and making sure that they understand what the goals of therapy are. Love and emotional support is vital for the patient during this time. Taking care of someone with anoxic brain injury can be a physically and emotionally draining experience; the person’s physical needs may be taxing and they may not relate to you in the way they once did.
If you are taking care of a loved one with anoxic brain damage, make sure that you also take care of your own physical and emotional needs. A support network is important. Do not hesitate to tell family and friends what you need and do not hesitate to take advantage of support systems offered by the hospital or rehab center.
Preventing Anoxic Brain Damage
The best way to avoid the long-term effects of an anoxic Brain Injury is to avoid injury altogether. While accidents can happen, there are steps you can take to reduce the risk of anoxic brain damage to yourself and your loved ones:
- Make sure children under the age of three are not exposed to choking hazards.
- Chew your food slowly and carefully.
- Learn how to swim and teach your loved ones to swim. Make sure that small children who aren’t able to swim aren’t left alone in pool areas, bathtubs, or areas in which there is water. It only takes a couple of inches for a child who can’t swim to experience a near-drowning event.
- Learn CPR (cardiopulmonary resuscitation).
- Stay away from high-voltage electrical sources.
- Install carbon monoxide detectors in your home.
- Do not take illegal drugs, or abuse prescription drugs.
- Maintain your heart’s health by exercising regularly, eating right, and getting regular check-ups. Monitor your blood pressure.