What to Know About Coma (2024)

A coma is a state of deep unconsciousness in which a person is unresponsive for a prolonged time. Although comas have many possible causes, they all involve temporary or permanent harm to the brain, impairing a person’s awareness of their surroundings and their ability to respond to them.

In some situations, a medically induced coma may help prevent brain damage, improving the chances of survival and reducing the likelihood of long-term disability. This article describes the causes of coma, rating scales, and what to expect if your loved one has been diagnosed with a coma.

What Is a Coma Exactly?

A coma is a state of unconsciousness caused by altered brain function and can also be medically induced in certain situations as a method of protecting the brain. People who are diagnosed as being in a coma are unable to move and usually require respiratory support—such as intubation and mechanical ventilation.

A coma may last for days or longer before a person regains consciousness, but in some situations, a person may never recover from a coma.

The outcome of a coma depends on the severity and cause. Often, the medical cause is treated while a person is receiving respiratory and other support.

Types of Coma

Health conditions can lead to a coma in different ways.

Some of the categories include:

• Metabolic changes: Alterations in the body’s chemicals, such as potassium, calcium, magnesium, and glucose, can affect brain cell function, leading to changes in consciousness that could become permanent if the metabolic changes are not quickly corrected.
• Hypoxia: Diminished oxygen supply to the brain due to heart failure, lung failure, or severe blood loss can lead to impaired function or permanent damage to nerve cells throughout the brain.
• Toxin exposure: Medications, drugs, and chemical exposures known to alter brain function can cause a coma due to overdose or drug withdrawal—sometimes even with normal doses.
• Trauma: Physical injuries can lead to blood loss, bleeding in the brain, or brain swelling—rapidly affecting brain cell function and leading to loss of consciousness.

A coma can involve one or more of these physical changes.

What Is the Cause of a Coma?

Several medical conditions can affect a person’s level of consciousness, potentially causing a coma.

The most common causes of coma include:

• Traumatic brain injury: Any brain injury can cause swelling or bleeding in the brain. Additionally, the trauma may induce rapid chemical and fluid shifts, affecting brain function. Sometimes, people can have significant improvement after a traumatic brain injury, but when there is substantial bleeding or swelling, the damage may be permanent.
• Stroke: Impaired blood supply to an area of the brain causes a stroke, which can lead to brain swelling. A large stroke or brainstem stroke may impair consciousness, causing a coma.
• Brain tumor: Cancer in the brain can cause pressure on areas of the brain that affect consciousness, potentially causing a coma. In some instances, tumor removal can be curative.
• Lack of oxygen (hypoxia): A heart attack or severe lung disease may prevent sufficient oxygen from reaching the brain—leading to substantial damage.
• Increased pressure in the brain: Many medical conditions can cause pressure in the brain, such as a brain tumor, bleeding in the brain, or swelling from a stroke, cancer, or traumatic brain injury.
• Diabetes: Uncontrolled diabetes can cause extreme changes in blood glucose levels and chemical and mineral concentration—preventing healthy brain cell function.
• Infections: A brain infection or a severe infection in the body can impair a person’s level of consciousness.
• Toxins and drug overdose: Many different types of medications and drugs of abuse can have a rapid impact on the brain, potentially causing a coma.
• Medical complications: Liver failure, kidney failure, thyroid disease, and blood loss are some of the medical conditions that have the potential to cause a coma.

What Are the Signs of a Coma?

A coma may be diagnosed during a hospital stay or suspected during an emergency response. Often, a coma is diagnosed after a person has been in an unresponsive condition for several hours or longer.

First responders will often describe a person’s state of consciousness using the AVPU scale.

The AVPU scale is:

• Alert: This designation indicates that a person is alert and responsive.
• Verbal: This designation indicates that a person has a diminished level of alertness but can have some type of response to sound.
• Pain: This designation indicates that a person has a diminished level of alertness but has some type of response to pain.
• Unresponsive: This designation indicates that a person is not alert and not responsive to sound, touch, or pain.

Healthcare providers diagnose a coma based on a physical examination, diagnostic tests, and assessment of the medical history and recent situation.

How Doctors Determine Severity: The Glasgow Coma Scale

The Glasgow Coma Scale (GCS) assigns a severity number to a coma through assessment of physical movements, speaking, and movement. The scale can also help healthcare professionals track improvement, decline, or stability.

The scale provides a maximum possible score of 15, which correlates to a mild coma. The lowest score of 3 indicates a deep coma.

Scoring is based on:

• Eye opening: Rated from 1 (no eye opening) to 4 (eyes open spontaneously)
• Verbal response: Rated from 1 (no verbal response) to 5 (verbal response makes sense)
• Physical responses: Rated from 1 (no movement) to 6 (follows commands)

How Comas Are Diagnosed

When a person is diagnosed with a coma, healthcare providers work to identify the cause. Often, treatment involves medical stabilization to minimize the risk of permanent brain damage.

Diagnosis is based on:

• Medical history: This is the key feature for determining the cause of a coma and directing treatment. For example, the treatment would differ for a coma caused by a traumatic injury than for a coma caused by an infection.
• Physical tests: A physical examination can assess the level of consciousness and responsiveness and help evaluate the cause with clues such as neurological changes or bruises.
• Urine test: A urine test may detect evidence of drugs or medication that could impair consciousness.
• Blood tests: Metabolic problems and changes in organ function—such as liver, kidney, or lung disease—can be detected with blood tests.
• Electroencephalogram (EEG): This test examines brain activity through external wires placed on the scalp. It can identify certain patterns, such as seizures, sleep, brain death, and more.
• Lumbar puncture or spinal tap: In rare instances of coma, this procedure collects fluid from around the spinal cord with a needle. Examining the fluid can help diagnose some types of cancer and infections.
• Imaging scans of the brain: Usually, a brain scan, such as a brain computerized tomography (CT) or magnetic resonance imaging (MRI), can help in identifying structural brain changes, such as stroke, cancer, or traumatic injury.
• Electrocardiogram (EKG): This study examines the function of the heart and can detect evidence of heart failure or a heart attack.
• Other imaging tests: Depending on a medical history, other imaging tests may be ordered to visualize the structure of the kidney, liver, or lungs.

How a Coma Is Treated

Treatment depends on how long a person has been in a coma, the cause, and the likelihood of recovery. Often, particularly when there is a high chance of recovery, the person is cared for in the intensive care unit, where close medical monitoring and quick medication adjustments are possible.

Corticosteroids or diuretics (water pills) can reduce brain swelling. Additionally, support for breathing, blood pressure, and heart function is usually necessary to maintain survival and prevent further brain injury. Medication to help manage any ongoing infections or inflammatory conditions is sometimes necessary.

Coma has many potential complications, which include pneumonia (lung infection or inflammation), skin infections, urinary tract infections, dysregulated body temperature, bowel obstruction, seizures, and more.

After recovery from a coma, rehabilitation can help to strengthen breathing muscles and build muscle strength and control. Many coma survivors will also need speech and swallow therapy.

What’s the Outlook for Someone in a Coma?

Many people can recover from a coma. If your loved one is in a medically induced coma, they are more likely to have a full recovery because the coma-inducing medication can be reversed when they become medically stable.

If your loved one is in a comatose state due to a medical condition or a head injury, then the outlook and potential for recovery are highly variable based on their individual situation.

Coma Recovery

Recovery from a coma depends on many factors individual to the person and the cause of the coma.

Waking Up From a Coma

Waking up from a coma is usually a gradual process. There may be a delay of hours or days after medical causes are treated before a person starts to become more alert.

If your loved one is waking up from a coma, remain patient and anticipate a slow recovery.

Signs of Coming Out of a Coma

When a person is recovering from a coma, they may periodically open their eyes, begin to move, respond to touch or pain, or toss and turn in bed. They may also cough or try to pull out medical devices, such as intravenous (IV) catheters or breathing tubes.

The Ranchos Scale

The Rancho Los Amigos Cognitive Scale-Revised (RLAS-R) is more detailed than the AVPU scale or the GCS. This scale rates people on 10 levels, based on many factors, including responsiveness, eye movements, need for assistance, memory, cooperation, learning, and more.

Will You Remember Anything That Happened During the Coma?

People do not typically remember anything from when they were in a coma after recovering from one. This is because they are not alert or aware of their surroundings during a coma. Some people may have a slight recollection of the event that caused the coma—such as a car accident—but usually can’t remember most of the details.

What Are the Risk Factors for Comas?

A head injury is the most clear-cut risk factor for a coma. Additionally, health conditions that can lead to rapid alterations in metabolism can also cause a coma. Drug or alcohol use or withdrawal can lead to altered levels of consciousness that can be temporary, permanent, or life-threatening.

Health conditions that are associated with a risk of coma include heart disease, lung disease, cerebrovascular disease (a disease of the blood vessels in the brain), thyroid disorders, diabetes, liver, disease, and kidney failure.

Can You Prevent a Coma?

Prevention of traumatic brain injury is a crucial step for preventing a coma. This includes wearing a seat belt while in a moving vehicle or wearing a helmet for certain contact sports.

Additionally, managing underlying health conditions, such as diabetes or kidney disease, can help prevent metabolic changes that could lead to a coma. Taking care of stroke risk factors—like high blood pressure, high cholesterol, diabetes, and smoking—can all reduce the risk of a stroke-induced coma.

That said, there is no specific coma prevention strategy. Taking care of your health is the best way to prevent serious brain damage that could lead to unconsciousness.

Summary

A coma is a state of unresponsiveness. People can be diagnosed as being in a coma based on a physical examination, medical history, and diagnostic tests. Several health conditions are known to have the risk of leading to a coma. Many people can recover from a coma, depending on its severity and underlying cause.

If your loved one has been diagnosed with a coma, you need to know that this diagnosis has variable outcomes—and their prognosis relies on many factors. When your loved one is stabilized, their healthcare providers will discuss expectations and treatment plans with you.