Stupor and Coma

Some disorders interfere with the delivery of needed substances to the brain or with the body’s ability to use them. Examples are

• A very low or very high blood sugar level (hypoglycemia or hyperglycemia)

• A very low level of oxygen in the blood, as occurs in respiratory (lung) failure or heart failure

• The sudden stopping of the heart’s pumping (cardiac arrest) or breathing (respiratory arrest)

Blood delivers oxygen and essential nutrients (such as fats, sugars, minerals, and vitamins) to the body's tissues. Thus, when blood flow to the brain is decreased, the brain is deprived of oxygen and essential nutrients. The brain may also be deprived of oxygen when the lungs are not functioning normally, as occurs in respiratory failure. The brain can be deprived of nutrients when a disorder (such as hypoglycemia) causes levels of nutrients in the blood to be low.

Having diabetes increases the risk of stupor or coma because diabetes can cause the blood sugar level to become too high or, when treatment is too aggressive, too low. When blood sugar levels are very high, people become dehydrated, causing the brain to function less well. When blood sugar levels are low, the brain is deprived of its main source of energy (sugar) and can malfunction or become damaged. Over time, diabetes damages the blood vessels and nerve cells in the brain. As a result, the brain may not get enough oxygen, and brain tissue may die.

Other disorders can cause cells throughout the body to malfunction. Often, brain cells are affected the most. These disorders include

• Liver failure

• Kidney failure

• An underactive thyroid gland (hypothyroidism)

• A very low or high body temperature (hypothermia or hyperthermia)

• Very low or high levels of calcium or sodium in the blood

• Thiamin deficiency

• Infections, such as sepsis, meningitis, and viral infections, including encephalitis, COVID-19, and severe acute respiratory syndrome (SARS)

Other common causes are disorders that affect the areas of the brain that control consciousness. These disorders include the following:

• A head injury may jar but not physically damage these areas, directly damage them, or indirectly damage them by causing bleeding (hemorrhage) in or around the brain.

• Strokes and tumors can also directly damage areas of the brain that control consciousness.

Any disorder that increases pressure within the skull (intracranial pressure) can impair consciousness. A mass in the brain, such as an accumulation of blood (hematoma), a tumor, or an abscess, can impair consciousness indirectly by putting pressure on the areas of the brain that control consciousness.

A structural abnormality can block the flow of cerebrospinal fluid in the brain, increasing pressure within the skull. Cerebrospinal fluid is the fluid that flows through the tissues covering the brain and spinal cord and fills the spaces within the brain. Some structural abnormalities are present at birth.

A large mass can push the brain against the relatively rigid structures inside the skull, damaging brain tissue. If the areas of the brain that control consciousness are affected, stupor or coma results. If the pressure is high enough, the brain may be forced through a small natural opening in the relatively rigid sheets of tissue that separate the brain into compartments. This life-threatening disorder is called brain herniation. Herniation can further damage brain tissue, making an already dire condition worse.

Having had a stroke or having another disorder that affects brain function makes the brain more susceptible to other disorders that can impair consciousness.

Commonly, consciousness is impaired by drinking too much alcohol or taking too much of certain medications or illicit drugs, such as sedatives and opioids (narcotics). In addition to making brain cells function slowly, alcohol and some medications and illicit drugs can damage brain cells indirectly. They can slow breathing so much that the oxygen level in blood becomes low enough to cause brain damage.

Taking several medications (to treat several disorders) is also a common cause, partly because taking several medications increases the risk of interactions between medications.

Overdoses of marijuana, including medical marijuana, sometimes causes the brain to malfunction, resulting in impaired consciousness and sometimes seizures.

Occasionally, taking certain antipsychotic medications results in an unresponsive state called neuroleptic malignant syndrome. This syndrome is characterized by muscle rigidity, fever, and high blood pressure, as well as changes in mental function (such as confusion and lethargy).

Occasionally, people who have a mental health disorder or those who are psychologically stressed may appear unresponsive. For example, people who learn that they have cancer or that their spouse is going to leave them may collapse and not respond when they are spoken to or touched. Yet, such people may be aware of what is happening around them, and their brain may be functioning normally.

Based on the results of the examination, doctors can usually determine how much a mental health disorder or psychological distress contributes to what appears to be impaired consciousness and whether the person is pretending.

Aging alone does not increase the risk of impaired consciousness. However, age-related changes make impaired consciousness in older adults a particular concern (see Essentials for Older Adults: Stupor and Coma). For example, some disorders that are more common among older adults (such as high blood pressure or diabetes) can increase the risk of impaired consciousness if another problem develops.

Common problems that can trigger impaired consciousness in older adults include

• Reactions to medications

• Dehydration

• Infections

• Development of a new disorder (such as stroke or heart failure) or worsening of a disorder they already have

Body temperature is checked. An abnormally high temperature may indicate infection, heatstroke, or an overdose of a substance that stimulates the body (such as cocaine or an amphetamine). An abnormally low temperature may indicate prolonged exposure to cold, an underactive thyroid gland, alcohol intoxication, a sedative overdose or, in older adults, infection.

Doctors examine the head, face, and skin for clues to the cause, such as the following:

• Black eyes, cuts, bruises, or leakage of cerebrospinal fluid (the fluid that surrounds the brain) from the nose or ears suggests a head injury.

• Needle marks suggest an overdose of a substance, such as heroin.

• Fever with a rash often suggests an infection, such as sepsis (a serious bodywide response to a bloodstream infection) or a brain infection.

• Certain odors on the breath suggest diabetic ketoacidosis or consumption of a poison or large amounts of alcohol.

• If people have bitten their tongue, seizures may be the cause.

A thorough neurologic examination is done. This examination helps doctors determine

• How severely consciousness is impaired

• Whether the brain stem is functioning normally

• What part of the brain is damaged

• What the cause may be

If people are unconscious, doctors try to rouse them first by speaking to them, then by touching their limbs, chest, or back. If these measure do not work, doctors use stimuli that cause discomfort or pain, such as pressure on a nail bed or a pinch. If people open their eyes or grimace when a painful stimulus is applied or if they purposefully withdraw from it, consciousness is not severely impaired. If people can make sounds, the cerebral hemispheres are functioning to some degree. If the eyes open, some parts of the brain stem are probably functioning.

Doctors sometimes use a standardized scoring system, such as the Glasgow Coma Scale, to help track changes in a person's level of consciousness. This scale assigns points based on responses to stimuli. Eye movement, speech, and movements are evaluated. This scale is a relatively reliable, objective measure of how unresponsive people are.

Abnormal breathing patterns can provide clues to which parts of the brain are malfunctioning.

Checking responses to painful stimulation can help determine whether parts of the brain and spinal cord are malfunctioning. When coma is present, using painful stimuli may trigger unusual body positions. For example, the head may be tilted back with the arms and legs extended (called decerebrate rigidity). Or the arms may be flexed with both legs extended (called decorticate rigidity). This test helps identify the area of the brain that is not functioning normally.

Limpness of the entire body and no movements in response to pain are the worst possible response. They indicate severe dysfunction in the central nervous system (brain and spinal cord). However, if muscle tone and movements return, the cause may be a reversible one, such as a sedative overdose.

Automatic reflexes in specific parts of the body are checked by maneuvers, such as striking the joints with a reflex hammer. Doctors check for differences in the strength of reflexes in different parts of the body. This information sometimes helps them identify which areas of the brain are not functioning normally.

All automatic reflexes are normal if unresponsiveness is caused by a mental health disorder that does not impair consciousness.

The eyes also provide important clues about how well the brain stem is functioning and what may be impairing consciousness. Doctors check the position of the pupils, their size, their reaction to bright light, their ability to follow a moving object (in people who are alert and awake), and the appearance of the retina. Normally, pupils widen (dilate) when light is dim and become smaller (constrict) when light is shined on them. However, the pupils may not respond normally to light in people in a coma. How the pupils respond to light or whether they respond helps doctors determine the cause of the coma.

To accurately evaluate the person, doctors need to know whether the person takes a medication to treat glaucoma, which can affect pupil size, and they usually need to know whether the person’s pupils are normally different sizes.

Doctors also examine the inside of the eye with an ophthalmoscope for signs that the pressure within the skull is increased.

If findings suggest that the pressure within the skull is increased, doctors do imaging tests immediately to check for swelling, bleeding, a structural abnormality that blocks the flow of cerebrospinal fluid, or a mass in the brain (such as a tumor, an accumulation of blood, or an abscess). If imaging test results indicate increased pressure, doctors may drill a small hole in the skull and insert a device into one of the fluid-filled spaces (ventricles) in the brain. This device is used to reduce the pressure and monitor it during treatment.

The person’s response to certain maneuvers can help doctors determine whether the brain stem is functioning normally:

• Rotating the head and observing eye movements.

• If the person is unconscious, gently flushing ice-cold water into one ear, then the other ear and observing eye movements (called caloric testing)

Caloric testing is done only if people are unconscious and doctors cannot check eye movements any other way. If people are conscious, flushing ice-cold water into their ear can cause severe vertigo, nausea, and vomiting.

These tests provide further clues about the possible cause of stupor or coma.

Blood levels of substances including sugar, electrolytes (such as sodium), alcohol, oxygen, minerals (such as magnesium), and carbon dioxide are measured. High levels of carbon dioxide may indicate that the person's breathing is impaired and that mechanical ventilation is required. Red and white blood cell counts are determined. Blood tests to check liver function and kidney function are done.

Urine is analyzed to determine whether any commonly used or suspected toxic substances are present. Samples of blood and urine may be sent to a laboratory to be cultured (to grow any microorganisms present) to check for infections.

Doctors measure the oxygen level in blood with a sensor placed on a finger (called pulse oximetry). They also measure levels of oxygen, carbon dioxide, and sometimes other gases in a sample of blood withdrawn from an artery (arterial blood gas tests). These tests are done to check for heart and lung disorders.

Other laboratory tests may be done, depending on which causes of coma doctors suspect.

Electrocardiography (ECG) is done to check for heart disorders, which may reduce blood flow to the brain. Chest x-ray may be done to check for lung disorders, which may reduce the amount of oxygen in the blood.

If no cause has been quickly identified, computed tomography (CT) or magnetic resonance imaging (MRI) of the head is done to check for a mass, bleeding, swelling, or other structural brain damage.

If the cause is unclear after imaging tests or if meningitis or bleeding between the layers of tissue covering the brain (subarachnoid hemorrhage) is possible, a spinal tap (lumbar puncture) may be done to withdraw a sample of cerebrospinal fluid. The fluid is examined and analyzed to check for various causes. CT or MRI of the head is typically done before the spinal tap to determine whether pressure inside the skull (intracranial pressure) is increased—for example, by a tumor or bleeding within the brain (intracerebral hemorrhage). If pressure is increased, a spinal tap may be dangerous and should not be done. It could make the brain shift sideways and downward by rapidly reducing the pressure below the brain, and thus at least theoretically, cause or worsen brain herniation. However, herniation after a spinal tap is relatively uncommon. If intracranial pressure is increased, it is monitored continuously, and measures to decrease it are taken.

If doctors suspect the cause of impaired consciousness is seizures or if the cause is unclear after other tests are done, electroencephalography (EEG) may be done to check the brain’s electrical activity, which may be abnormal if the brain is not functioning normally. Occasionally, EEG indicates that the person is having seizures even though the limbs are not jerking (a disorder called nonconvulsive status epilepticus). Sometimes, when a person who has behavior or mental health problems appears unresponsive, EEG with video monitoring is done in the hospital. This test is done to determine whether brain function is normal. Results of the test can help doctors identify the problem and treat it appropriately.

If a person is rapidly becoming less alert and more difficult to arouse, immediate treatment is required, often before a diagnosis is made. This rapid deterioration in consciousness is considered a medical emergency.

The first steps in treatment, sometimes done by emergency medical personnel, are to check

• Whether the airway is open

• Whether breathing is adequate

• Whether pulse, blood pressure, and heart rate are normal (to make sure blood is reaching the brain)

If possible, any problems present are corrected.

People are treated first in an emergency department and then admitted to a hospital intensive care unit. In both places, nurses can monitor heart rate, blood pressure, temperature, and the oxygen level in the blood. Any abnormalities in these measurements are immediately corrected to prevent further damage to the brain. Oxygen is often given immediately, and a tube is inserted into a vein (an intravenous line) so that medications or sugar (glucose) can be given quickly.

If people have a very high or low body temperature, measures are taken to cool (heatstroke treatment) or warm them (hypothermia treatment). Any other disorders (such as heart or lung disorders), if present, are treated.

Blood pressure is closely monitored to make sure it is not too high or too low. High blood pressure can further impair consciousness and lead to other problems, such as stroke. Low blood pressure can impair consciousness because the brain does not get enough blood and oxygen.

The cause of stupor or coma is treated when possible.

For a low blood sugar level, glucose (a sugar) is immediately given intravenously. Giving glucose often results in instant recovery if the coma is caused by a low blood sugar level. Thiamin is always given with glucose because if people are undernourished (usually because of alcohol abuse), glucose alone can trigger or worsen a brain disorder called Wernicke encephalopathy.

If a head injury

If opioid

Rarely, when a person may have ingested certain toxic substances, illicit drugs, or medications within about 1 hour, doctors may insert a large tube through the person's mouth and into the stomach so that the stomach can be pumped. Pumping the stomach is done to identify its contents and to prevent more of the substances from being absorbed. Activated charcoal may also be given through the tube or through a smaller tube inserted through the nose (nasogastric tube). The charcoal prevents the stomach from absorbing more of the substances.

People in a deep stupor or a coma may require a breathing tube and mechanical ventilation. Mechanical ventilation is especially important if breathing is too slow or shallow or otherwise impaired (for example, because the brain is damaged or malfunctions) or if the person has very low blood pressure, vomiting, or a seizure.

The breathing tube is inserted through the mouth and into the windpipe (trachea)—called endotracheal intubation. Oxygen is delivered directly into the lungs through the tube. The tube also prevents people from inhaling stomach contents after vomiting. Before inserting the tube, doctors may spray the person's throat with a numbing spray or give the person a medication to prevent the muscles from contracting involuntarily (a paralytic medication). The tube is then attached to a mechanical ventilator.

Mechanical ventilation can cause agitation, which can be treated with a sedative.

If the pressure within the skull (intracranial pressure) is increased, the following measures may be taken to lower it:

• The head of the bed may be elevated.

• Mechanical ventilation may be used to help people breathe faster (called hyperventilation), particularly during the first half hour it is used. Breathing faster removes carbon dioxide from the lungs and reduces the level of carbon dioxide in the blood. As a result, blood vessels in the undamaged part of the brain narrow, and less blood reaches the brain. This measure quickly but temporarily lowers pressure within the skull (for about 30 minutes) and does not damage the brain further. Lowering the pressure for a time gives doctors time to start to treat the cause—for example, to do emergency brain surgery.

• Diuretics or other medications may be used to reduce fluids in the brain and rest of the body. Diuretics help eliminate excess fluid by causing the kidneys to excrete more sodium and water into urine.

• A sedative may be given to control excess involuntary muscle contractions or agitation caused by mechanical ventilation. These problems can increase pressure within the skull.

• Blood pressure is lowered if it is very high.

• Sometimes doctors insert a drain (shunt) into the ventricles of the brain to drain cerebrospinal fluid. Removing excess fluid can help lower pressure within the skull.

If other measures do not work, the following may be tried:

• When pressure within the skull is increased after a head injury or cardiac arrest, measures to lower body temperature may be tried. These measures may help some people who have had cardiac arrest. However, use of this measure is controversial.

• The skull may be opened surgically (craniectomy), creating more room for the swollen brain and thus reducing pressure on the brain. This treatment can prevent death, but it may not improve a person's ability to function.

People in a coma require comprehensive care. They are fed through a tube inserted through the nose and into the stomach (called tube feeding). Sometimes they are fed through a tube inserted directly into the stomach or small intestine through an incision in the abdomen. Medications may also be given through these tubes.

Many problems result from being unable to move (immobility), and measures to prevent them are essential (see Problems Due to Bed Rest). For example, the following can happen:

• Pressures sores: Lying in one position can cut off the blood supply to some areas of the body, causing skin to break down and pressure sores to form.

• Weak muscles: When muscles are not used, they waste away (atrophy) and become weak. People with muscle weakness may have trouble breathing on their own when they are taken off the ventilator.

• Contractures: Lack of movement can also lead to permanent stiffening and shortening of muscles (contractures) causing joints to become permanently bent.

• Blood clots: Lack of movement makes blood clots more likely to form in leg veins. The blood clots can break off, travel to the lungs, and block arteries there (called pulmonary embolism).

• Damage to muscles and nerves in the arms and legs: Lack of movement or lying in one position for a long time can put pressure on a nerve that runs close to the surface of the body near a prominent bone, such as a nerve in an elbow, a shoulder, a wrist, or a knee. Such pressure can injure the nerve. As a result, the muscles that the nerve controls function less well.

Pressure sores can be prevented by frequently repositioning the person and placing protective padding under parts of the body that are in contact with the bed, such as the heels, to protect them.

To prevent contractures, physical therapists gently move the person’s joints in all directions (passive range-of-motion exercises) or splint joints in certain positions. Starting physical therapy early can help people who have not been able to move recover function.

Preventing blood clots includes use of medications and compression or elevation of the person's legs. Moving the limbs, as occurs in passive-range-of-motion exercises, may also help prevent blood clots.

Because people cannot blink, their eyes may become dry. Eye drops can help.

If people are incontinent, care should be taken to keep the skin clean and dry. If the bladder is not functioning and urine is being retained, a tube (catheter) may be placed in the bladder to drain urine. Catheters are carefully cleaned and regularly examined to prevent urinary tract infections from developing.