What is a Coma?
A coma is a state of deep unconsciousness during which many of the body’s functions slow down considerably. A person in a coma does not move, communicate, or interact with their environment. Functions such as breathing rate, blood circulation, and metabolism may be altered, and brain activity decreases. However, people in comas retain the vital brain functions that keep their bodies alive.
Comas arise from a wide variety of underlying causes. Injuries, diseases, infections, drug overdoses, and oxygen deprivation are all common causes of coma. Treatment of the underlying condition is the standard course of action when a coma occurs.
Most people emerge from a coma in less than 2-4 weeks. A coma can last longer, however, and some patients eventually transition into a prolonged period of unconsciousness called a persistent vegetative state. The longer a person remains in a coma, the more likely significant, long-term complications are to result. If a person remains in a coma for a year or longer, recovery is unlikely.
Symptoms of Coma
Common symptoms of a coma include:
- Closed eyes, as if the patient is sleeping
- Reduced neurological reflexes, such as the pupils’ response to bright light
- No response to pain beyond reflex actions
- No response to touch or movement of limbs
- Depressed or irregular breathing rate
Persistent Vegetative State
A vegetative state is a coma-like state of unconsciousness that can result from an event that causes significant brain damage. A persistent vegetative state is a term generally applied to a vegetative state that lasts more than a month. In this state, the parts of the brain that regulate vital functions such as heart activity, breathing, and blood pressure continue to function. However, the parts of the brain responsible for thinking, communicating, and other higher functions stop working.
Some signs of a persistent vegetative state may look like signs of consciousness, but they are the only evidence of the brain’s lower-level functioning. These signs can include:
- Open eyes
- Eye movements
- Tearing or watering eyes
- Reflexive brain stem activities such as yawning, swallowing, or making guttural noises
- Startle reflex reactions to loud sounds or bright light
- Sleeping and waking cycles
- Limited, primitive movement of limbs
- Facial muscle activity that may look like a smile or frown
Despite these signs, patients in a persistent vegetative state do not communicate or respond to commands. They may react to some stimuli, but not in a purposeful, conscious way. For example, they reflexively respond to pain, but they do not take action to avoid it.
Recovery from a persistent vegetative state is unlikely, but in very rare cases, some improvement does occur.
Minimally Conscious State
A minimally conscious state resembles a coma in many ways, but it is characterized by the patient’s ability to interact with their environment in certain ways. Signs of a minimally conscious state include:
- Making eye contact
- Reaching for objects
- Responding to basic commands
- Responding with limited vocalization
Patients are more likely to recover from a minimally conscious state, but their recovery may be limited. The longer the state lasts, the more likely the patient is to experience a permanent loss of higher brain function. The likelihood of recovery tends to be higher when the underlying cause is a traumatic brain injury.
In some cases, doctors may intentionally induce a coma-like state in a patient. The coma is induced through the administration of a central nervous system depressant drug such as pentobarbital or thiopental. The goal of a medically-induced coma is generally to reduce strain on the body as it heals from the effects of an underlying condition. The technique can be used, for example, to reduce stress on the brain as it heals following trauma or to sedate a patient undergoing treatment for severe respiratory illness.
What Causes a Coma?
A coma can result from many different kinds of trauma to the brain. It often occurs when the brain is directly physically injured or is deprived of oxygen as a result of some underlying condition, such as an infection, disease, or cardiovascular event.
Common causes of coma include:
- Traumatic brain injury
- Heart attack
- Drug or alcohol overdose
- Oxygen deprivation from drowning or suffocation
- Infections, especially those that involve the brain and central nervous system (meningitis, encephalitis, etc.)
- Brain tumors
- Exposure to toxins, such as carbon monoxide or lead
- Chronic seizures
- Diabetes. Extremely high or low blood sugar levels can trigger a coma.
Are Comas Hereditary?
There is no known direct inherited risk that makes a person more likely to enter a coma. Some underlying conditions that can trigger a coma may have inherited risk factors. Conditions as diverse as stroke and substance abuse may be more likely to run in families, and those conditions can put an individual at risk of coma.
How are Comas Detected?
A coma is always an emergency situation. The underlying problems that cause comas are life-threatening, and quick action must be taken to prevent death or decrease the risk of permanent complications. If you’re with someone who experiences a loss of consciousness, particularly if they are suffering from any conditions that put them at risk of coma, seek emergency medical care immediately.
How are Comas Diagnosed?
In the case of a coma, doctors are not able to ask the patient questions about their medical history or the circumstances that led to the coma. Without this vital part of the diagnostic process, doctors rely on information from loved ones or caregivers, physical exams, laboratory tests, imaging scans, and measures of brain activity to assess the patient’s condition.
Diagnostic steps may include:
- Physical exam. This exam will measure the patient’s reactivity to stimuli such as pain, noise, and light. The doctor will look for reflexive eye movements and evaluate the patient’s breathing. The doctor will also look for signs of injury or trauma.
- Laboratory tests. These tests may include measurements of blood chemistry, electrolyte levels, and blood sugar levels. Tests may also look at indicators of thyroid, kidney, and liver function. Other tests may look for signs of exposure to toxins such as carbon monoxide.
- Lumbar puncture (spinal tap). This test will examine the patient’s spinal fluid for signs of infection or other abnormalities.
- Computerized tomography (CT) or magnetic resonance imaging (MRI) scans. These imaging exams can indicate signs of trauma, bleeding, or other damage to the brain.
- Electroencephalography (EEG). This test measures the brain’s electrical activity.
The results of these procedures may suggest the underlying cause of the coma and provide direction for treatment.
PLEASE CONSULT A PHYSICIAN FOR MORE INFORMATION.
How are Comas Treated?
Treatment for a coma first focuses on treating the underlying condition that caused it. When treatment for the underlying condition is underway and the patient has stabilized, treatment procedures can expand to include prevention of complications that may arise as a result of the coma itself. These procedures may include:
- Proactive therapies to prevent respiratory infections, bed sores, blood clots, and other complications
- Respiratory assistance
- Nutritional support
- Physical therapy to prevent degeneration of muscles and bones that can occur over the course of a prolonged coma
How do Comas Progress?
The outcome for coma patients varies widely depending on the underlying cause of the coma and the extent of brain damage that occurs. Some patients may emerge fully from a coma and not suffer severe long-term complications, but many will have to contend with a range of physical and/or cognitive problems.
Potential complications include:
- Physical or motor disabilities
- Intellectual or cognitive disabilities
- Psychological or mental-health complications
- Communication difficulties
Recovery from a coma is usually gradual, and the longer the coma lasts, the less likely a full recovery.
A prolonged coma carries the risk of life-threatening complications that may arise while the patient is unconscious, including:
- Pneumonia or other respiratory infections
- Blood clots
- Bed sores and other skin infections
- Bladder infections or other internal infections
How are Comas Prevented?
There is no way to prevent a coma, but the underlying conditions that can cause a coma may be preventable. If you are at risk, take steps to keep yourself healthy:
- If you’re diabetic, carefully monitor your blood sugar levels and be alert to the signs and symptoms of both high blood sugar (hyperglycemia) and low blood sugar (hypoglycemia).
- Maintain a healthy weight.
- Do not abuse drugs or alcohol, and take steps to treat any substance abuse disorder.
- Get plenty of exercise and maintain a healthy diet to decrease your risk of heart attack or stroke.
- Be alert to signs of infection, and seek prompt medical attention when they appear.
- Install carbon monoxide detectors in your home.
- Use proper protective equipment in cars and while engaging in risky activities.
Coma Caregiver Tips
Coping with stress when a loved one is in a coma is not easy for anyone, and it doesn’t get any easier during the recovery process after your loved one emerges from a coma. Keep these tips in mind as you navigate the situation:
- Be involved in your loved one’s treatment. Your loved one’s treatment will involve a team of healthcare professionals, and it will be difficult to keep up with everything that’s going on. The recovery process will have a better chance of being successful if you learn as much as you can and work effectively with the team to give your loved one the best possible care.
- Develop a plan with other family members and loved ones. Don’t try to make it through the situation on your own. Enlist the help of other family members, and develop a detailed plan for dealing with your loved one’s treatment and other affairs.
- Stay optimistic. Recovery after a coma is a long, gradual process that will be a mixture of triumphs and setbacks. Be prepared for the obstacles, and be ready to celebrate every success, no matter how small. Your loved one’s recovery will be easier for everyone if you remain focused and hopeful.
Coma Brain Science
Many studies have suggested that the brain is better able to recover when a coma or vegetative state is caused by a traumatic brain injury, rather than by oxygen deprivation to the brain (cerebral hypoxia). Recovery from a vegetative state is very unlikely if the state is caused by hypoxia and lasts longer than a month. When the cause is a brain injury, the chance of recovery remains higher until 12 months after the vegetative state begins.
There is also evidence that, in some patients, brain activity during a coma might be more complex than was previously thought. Research has shown that as many as 15% of patients in injury-induced comas showed brain activity when asked to respond to basic commands (such as being asked to raise a hand). The brain activity was similar to the activity in a normal brain when a healthy patient complied with the same request. However, the coma patients did not actually physically respond to the command, and it is unclear how much the patient was aware of the request. Follow up studies showed that those patients who exhibited this kind of brain activity had a better long-term recovery prognosis than those who didn’t.
Title: Multimodal Outcome CHAracterization in Comatose Cardiac Arrest Patients Registry and Tissue Repository (MOCHA)
Contact: David Greer, MD
Boston Medical Center
Cardiovascular disease remains the leading cause of death in the United States. Mortality rates of cardiac arrest range from 60-85% and approximately 80% of survivors are initially comatose. Of those who survive, 50% are left with a permanent neurological disability, and only 10% are able to resume their former lifestyle. The early prognosis of comatose patients after cardiac arrest is critical for the management of these patients, yet predicting outcomes for these patients remains quite challenging.
The primary study objective of MOCHA is to develop an accurate and reliable assessment algorithm for determining neurologic prognosis in patients initially unconscious (no eye-opening, GCS-M<6 and not following commands) post-cardiac arrest, using multiple prognostic modalities at standardized time points.
Title: REsting and Stimulus-based Paradigms to Detect Organized NetworkS and Predict Emergence of Consciousness (RESPONSE 2)
Principal investigator: Brian L Edlow, MD
Massachusetts General Hospital
The aim of this study is to assess the utility of advanced magnetic resonance imaging (MRI) and electroencephalographic (EEG) technologies for predicting functional outcomes in patients with severe traumatic brain injury (TBI).
Title: Decision Aid Feasibility Trial for Families of Critically Ill Stroke Patients
Stage: Not Yet Recruiting
Principal Investigator: Suzanne Muehlschlegel, MD, PhD
University of Massachusetts
Severe strokes, including large artery acute ischemic stroke and intracerebral hemorrhage, continue to be the leading cause of death and disability in adults in the U.S. Due to concerns for poor long-term quality of life, withdrawal of mechanical ventilation and supportive medical care with the transition to comfort care is the most common cause of death in severe strokes, but occurs at a highly variable rate. Decision aids (DAs) are shared decision-making tools that have been successfully implemented and validated for many other diseases to assist in difficult decision making. The investigators have developed a pilot DA for goals-of-care decisions for surrogates of severe, critically ill stroke patients. This was developed through qualitative research using semi-structured interviews in surrogate decision-makers of traumatic brain injury patients and physicians and adapted to severe strokes. The investigators now propose to pilot-test a DA for surrogates of critically ill severe stroke patients in a feasibility trial.