Also called: Syncope & Diabetes
Fainting, also known as syncope, is an unexpected and temporary loss of consciousness resulting from inadequate blood flow to the brain. Fainting is a symptom of an underlying cause or condition, not a disease in itself. It may be due to a minor, serious or unknown condition.
In people with diabetes, causes of fainting can include hypoglycemia (low glucose levels), severe hyperglycemia, nerve damage or heart conditions. All patients, especially those with diabetes, should inform their physician of any episodes of fainting or near-fainting as soon as possible after the event.
Various diagnostic tests can help determine the cause of fainting. These tests include glucose tests, a tilt table test, an echocardiogram, a Holter monitor, event monitor, cardiac catheterization and an electrophysiologic study. In addition, a CAT scan or an MRI may be used to evaluate possible neurologic causes.
Treatment for fainting depends on the underlying cause. When the cause is hypoglycemia or hyperglycemia, treatment will involve maintaining glucose levels within the recommended range.
Fainting (syncope) is a brief, sudden loss of consciousness, typically followed by a complete recovery. Fainting occurs when the brain is starved for oxygen because of temporary inadequate blood flow. It occurs most often when a person has low blood pressure and the heart cannot pump a normal supply of oxygen to the brain.
Fainting may be a symptom of an underlying disorder, such as a heart condition or stroke. In about a third of cases, however, episodes of syncope may prove impossible to explain. Episodes of fainting are more common with age, perhaps due to an increased prevalence of certain diseases or an inability to respond to stressors that would not have caused fainting at a younger age.
A person with diabetes may faint as a result of hypoglycemia (low blood glucose) or autonomic neuropathy. Low glucose (blood sugar) first affects the autonomic nervous system. As hypoglycemia goes untreated, the brain begins to suffer from this lack because the brain needs glucose for energy. Low blood glucose can also impair regulation of blood pressure, which can lead to low blood pressure.
Fainting may also be due to hyperglycemic emergencies that can result in diabetic coma, such as diabetic ketoacidosis or hyperosmolar hyperglycemic nonketotic syndrome (HHNS).
Because of its link to glucose irregularities and cardiovascular problems, it is important for anyone experiencing fainting to report the episode to a physician as soon as possible.
Other symptoms related to fainting
Before fainting, an individual will become unresponsive and “floppy.” Immediately prior to the incident, the following symptoms may appear:
- Low blood glucose (hypoglycemia)
- Low blood pressure (hypotension)
- Lightheadedness or dizziness
- Palpitations (fast pounding or “galloping” heartbeat)
- Feeling confused, disorientated or generally “strange”
- Feeling of warmth
- Rapid breathing (hyperventilating)
- Blurred vision
- Difficulty hearing
- Low pulse rate
Types and differences of fainting
Fainting (syncope) is a symptom of many underlying conditions or causes. The type of syncope may relate specifically to the condition, even though the root of the cause is not always understood. Types of syncope include:
- Vasovagal syncope (also vasodepressor syncope or neurocardiogenic syncope). Fainting caused by a rapid fall in blood pressure, often accompanied by a slow heart rate. This common type of fainting can occur from emotional stress, physical pain, standing quickly after lying down or sitting (orthostatic hypotension) or after a heavy meal. When the terms fainting and syncope are used by themselves, it is generally referring to vasovagal syncope.
- Syncope anginosa. Fainting spells that are accompanied by angina. Angina is a type of chest pain caused by a lack of oxygen to the heart (cardiac ischemia) due to coronary artery disease.
- Carotid sinus syncope. A sudden loss of consciousness caused by compression of the carotid sinus, a blood vessel in the neck. It can be caused by turning the head to one side or wearing clothing or jewelry too tight on the neck. This is sometimes called carotid sinus syndrome.
- Defecation syncope. Fainting spells that occur during or immediately after a bowel movement. It can be caused by a condition of the gastrointestinal tract, cardiovascular disease, cerebrovascular disease or orthostatic hypotension.
- Hysterical syncope. Fainting caused by hysteria, acute anxiety or emotional distress.
- Cough syncope. Sudden loss of consciousness after an episode of coughing. Laryngeal syncope is brief and follows a tickle and coughing in the back of the throat. Tussive syncope follows deep coughing episodes associated with chronic bronchitis.
- Micturition syncope. An abrupt loss of consciousness during urination. It most often occurs in men who strain to urinate because of conditions such as prostate enlargement (benign prostatic hyperplasia, BPH). BPH is more common in men who are overweight and diabetic than those who are not.
- Swallow syncope. Fainting associated with swallowing. It may be related to disorders of the heart or esophagus but can also occur in healthy individuals.
- Syncope of unknown origin. As the name implies, this describes fainting for which a cause cannot be found (idiopathic). This applies to about a third of cases of fainting. In most of these cases, the syncope is a singular episode from which the patient recovers quickly and suffers no long-term damage. When injury does occur, it is usually due to falling during the faint.
Local syncope, despite its name, is not a loss of consciousness. It is when an area of the body becomes numb and/or white from lack of blood flow. “Local” refers to the fact that it is occurring in only a section of the body, usually the fingers or toes. It is associated with Raynaud syndrome, a vascular disorder caused by contraction of small arteries.
Potential causes of fainting
Fainting is not a disease itself, but rather a symptom of an underlying cause or condition. It may be due to harmless causes or to more serious conditions. However, in about a third of the cases, episodes of syncope may prove impossible to explain. Potential causes of fainting include:
- Hypoglycemia (low blood glucose), insulin shock (severe hypoglycemia) and other metabolic disorders
- Cardiovascular disorders, including low blood pressure, stroke, pulmonary arterial hypertension and many heart conditions
- Autonomic neuropathy
- Severe forms of hyperglycemia (high glucose) that can result in diabetic coma, such as diabetic ketoacidosis or hyperosmolar hyperglycemic nonketotic syndrome (HHNS)
- Sudden changes in body position, especially going from sitting or lying down to standing
- Certain medications (e.g., antihypertensives, opioids, anti-inflammatories) or medical procedures (e.g., injection, blood test, tilt-table test)
- Alcohol or drug abuse
- Emotional stress
- Heavy sweating
- Allergic reactions, such as an insulin allergy
- Insufficient diet
- Anemia (insufficient amount of red blood cells)
- Neurological disorders (e.g., seizures)
- Head injury
- Psychiatric disorders, including eating disorders
- Lung disorders
- Addison’s disease (insufficient production of adrenal hormones)
- Coughing or laughing
- Urination or defecation
Abnormal glucose levels, autonomic neuropathy, cardiovascular disorders and dehydration are major causes of fainting in people with diabetes. These conditions can affect the brain and nervous system and therefore may result in fainting.
Scientists recently discovered that severe, chronic fainting can be due to an autoantibody that impedes the autonomic nervous system. This condition has been resolved with a blood transfusion and medication that keeps more antibodies from forming.
Diagnosis methods for causes of fainting
The most important step for a physician in diagnosing syncope is to collect a medical history, followed by a physical examination. During the history, patients should be detailed about the fainting episode and include information about any previous episodes of fainting. It is also important to let the physician know about any medical conditions.
This information will help the physician decide what further tests should be ordered. A slower onset of fainting spells with prolonged or pronounced warning signals may indicate a metabolic problem, whereas a sudden incident points more to potential cardiac or circulatory problems. Whatever the cause, the physician will diagnose it as soon as possible so that potentially life-threatening conditions can be treated or avoided.
To make a diagnosis, the physician may order a number of tests. In patients with diabetes, a glucose test may be administered because low glucose (blood sugar) is a common cause of fainting in people with diabetes.
Another cause of fainting in people with diabetes is related to the autonomic nervous system. Tests used to diagnose autonomic neuropathy include nerve conduction velocity and electromyography.
Other tests that may be ordered include:
- Tilt table test. This test is used to assess a sudden drop in blood pressure with a widening of the blood vessels. Fainting that results from this change in blood pressure and blood vessels is called neurocardiogenic syncope. The tilt table test is conducted on a pivoting table. By securing the patient on his or her back to the tilt table, and then tilting the table upright, the factors leading to neurocardiogenic syncope may be simulated.
- Echocardiogram. This type of ultrasound uses sound waves to visualize the structures and functions of the heart. A moving image of the patient’s beating heart is played on a video screen, where a physician can study the heart’s thickness, size and function. It may reveal underlying cardiac conditions that could be causing the patient to faint.
- Holter monitor. This is an electrocardiogram (EKG) that is attached to a patient for 24 hours. It continuously records the heart’s electrical activity as the patient goes about the daily routine. Because of the relative rarity of fainting, this approach frequently fails to yield useful information.
- Event monitor. If a patient experiences symptoms only rarely, the Holter monitor may not pick up the pattern and thus may not alert the physician to the problem. The physician may therefore ask the patient to carry a different type of portable device called an event recorder or event monitor. Rather than monitoring the heart’s electrical activity continuously (as the Holter monitor does), an event recorder is used only when the patient is feeling symptoms. When symptoms occur, the patient activates the event recorder by pressing a button. Because these devices are “on-demand” rather than continuous, these recorders may be used for weeks or months. In certain cases, they may better reveal the pattern of symptoms.
- Electrophysiologic study. A thin tube (catheter) is inserted into a vein or artery (e.g., in the groin) and guided to the heart, where it can perform specific, essential measurements of the heart’s electrical activity and pathways. These measurements are particularly helpful in the diagnosis of heart rhythms that are particularly fast (tachycardias) or slow (bradycardias).
- CAT scan (computed axial tomography). Multiple x-rays are taken of the brain from a variety of angles. A computer is used to reassemble the views into cross–sectional images. It can provide clearer, more detailed information than single x-rays and can be used on a variety of tissues, including soft tissue, bone and blood vessels.
- MRI (magnetic resonance imaging). Magnetic fields and a computer produce high-resolution cross-sectional or three-dimensional images of the brain, heart and other structures. Images from an MRI scan are similar in many ways to those of a CAT scan, but MRI generally provides greater contrast between normal and abnormal tissues. It is done without x-rays or other forms of radiation.
- Electroencephalogram (EEG). A test that measures the brain’s electrical activity. It may be used to diagnose epilepsy, head injuries, infections, sleep disorders and other problems.
Treatment and prevention of fainting
Treatment will depend on the underlying cause of the fainting, as well as the patient’s age, symptoms and details surrounding the incident. In many cases, fainting is a one-time event that does not signal an underlying disease. In other cases, the underlying cause cannot be determined and treatments are aimed only at relieving symptoms. This often includes the use of medications to prevent blood pressure from dropping too low. However, if the cause of fainting is linked to diabetes, cardiovascular disease or other disease, the physician will treat these underlying causes.
Patients with diabetes benefit from keeping their glucose (blood sugar) within the range recommended by their physician. Controlling glucose is a primary treatment for autonomic neuropathy. When hypoglycemia (low blood glucose) or hyperglycemia (high blood glucose) is detected, patients should treat it promptly to avoid fainting and other complications. Diabetic patients are advised to ask their physician to create a sick-day plan for them, and to ask about carrying a glucagon kit in case of insulin shock (severe hypoglycemia).
By definition, fainting is unpredictable and unexpected. Yet, with proper personal care and medical attention, underlying conditions and damage may be detected early or prevented altogether. Some studies suggest that vasovagal syncope can be delayed or prevented by crossing one’s legs and tightening the abdomen, legs and buttocks. By causing more blood to be squeezed to the chest, blood pressure is increased, as is oxygen to the brain. Medical attention should be sought after any episode of fainting, particularly in patients with a history of heart disease.
Questions for your doctor about fainting
Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about fainting:
- What symptoms might I experience before an episode of fainting?
- What could be causing my fainting?
- Does my medical history suggest an underlying cause?
- Could any of my prescription or nonprescription drugs be a factor?
- Do I need any diagnostic tests? If so, what do they involve?
- What do my test results show?
- Do I have an underlying condition that needs to be treated?
- What are my treatment options?
- Do I need to be more careful about glucose monitoring and preventing hypoglycemia and hyperglycemia?
- Are there other ways I can prevent further episodes of fainting?