Suddenly, my eyes went dark and I almost fainted.

Most people have probably experienced this situation where suddenly everything goes dark in front of their eyes and they almost faint. Many people feel very scared after experiencing this situation. Because if you faint, it is likely that something more serious will happen, but although this phenomenon often occurs in the human body, most people do not know what causes it. Next, I will introduce to you the reasons why you suddenly feel dizzy and almost faint.

1. Transient cerebral blood insufficiency

This is the most common cause of syncope and is characterized by rapid onset, transient nature, self-limiting, and complete recovery. This condition usually has the following pathogenesis:

(1) Vasovagal syncope

This type of syncope is most common among young people who usually have no health problems. We encounter more female patients in particular.

The specific mechanism is: due to the increased excitability of the vagus nerve and the decreased excitability of the sympathetic nerve, the heart rate slows down and the peripheral blood volume decreases, the cardiac output decreases, the blood pressure decreases, and the brain lacks sufficient blood supply, causing the patient to lose consciousness. Common triggering factors include:

Standing for long periods of time.

Caused by emotional factors, such as fear, pain, fear of blood, fear of needles, etc.

Carotid sinus compression. It is most likely to occur in situations such as sudden head turning, tight collars, kissing, and playing.

This type of patient generally presents with pale complexion, sweating, nausea, hypotension, bradycardia, etc., and may lose consciousness for tens of seconds or minutes, which can be relieved by lying down and resting for a while. After syncope occurs, lying flat or raising the lower limbs can help increase the amount of blood returning to the heart and restore consciousness.

If you experience frequent syncope and suspect this is the cause, you can do an upright tilt test.

(2) Situational syncope

This type of syncope occurs under certain circumstances:

For example, urinary syncope is more common in men. It may be caused by stimulation of the vagus nerve through breath holding during urination and a decrease in abdominal pressure after urination.

When you sneeze or cough, chest pressure increases, venous return is obstructed, and cardiac output decreases, leading to insufficient cerebral perfusion and syncope.

Fainting may also occur during swallowing, defecation, abdominal pain, laughing, after exercise, and after meals.

(3) Postural hypotension

The main cause of the disease is changes in body position, such as suddenly standing up after squatting for a long time, sometimes causing dizziness. The mechanism of the disease is that when the body position changes, blood mainly stagnates in the lower limbs, and the blood vessels have poor contraction function, resulting in less blood return, which leads to a drop in blood pressure and insufficient blood supply to the brain.

When young patients experience this kind of condition, the main consideration is autonomic nervous system dysfunction. They should strengthen physical exercise on a regular basis and pay attention to whether they have anemia, especially women.

Patients who have been bedridden for a long time are also prone to orthostatic hypotension when they stand up suddenly. It is also easy to induce when taking alcohol or certain drugs. If elderly patients do not have the above reasons, they should also pay attention to getting up slowly, especially when getting up in the morning, sitting on the bed for a while, sitting by the bed for a while, and getting used to it.

This type of patient should be diagnosed through a supine and standing test, measuring blood pressure in the supine and standing positions respectively.

(4) Cardiac syncope

Syncope caused by cardiac reasons is often the most dangerous and carries a higher risk of sudden death. This is the target we need to focus on. These can be divided into two categories:

Organic heart disease. For example, valvular heart disease, hypertrophic obstructive cardiomyopathy, cardiac tumors or thrombi, pulmonary embolism, pulmonary hypertension, acute myocardial infarction, myocarditis, pericardial tamponade, etc. When cardiac output is reduced due to various reasons and cannot increase with the body's needs, syncope may occur. The main diagnostic method for these patients is cardiac ultrasound.

Heart arrhythmia. Slow or fast arrhythmias may lead to insufficient cardiac ejection and cause syncope. Fainting often occurs without warning, and recovery is rapid upon awakening. Some patients have no history of heart disease, and if they are not taken seriously, they may be in the most dangerous situation. Because their electrocardiogram is abnormal only when the disease occurs, an electrocardiogram after the symptoms have eased may not reveal the cause of the disease. At this time, dynamic electrocardiogram monitoring or cardiac electrophysiological examination is also needed.

(5) Brain-related syncope

Syncope may also occur in cases of transient vertebrobasilar artery ischemia or stroke, migraine, etc. Neurological examinations are needed: including CT, MRI, cerebrovascular examination, etc.

2. Hypoglycemia

Strictly speaking, hypoglycemia does not fall into the category of fainting, but the symptoms are similar and many people often cannot distinguish them together, so it is necessary to discuss them together.

This type of patient rarely develops a sudden illness and often shows obvious symptoms for a long time before fainting, such as sweating, hunger, palpitations, pale complexion, and inattention. After the onset of the disease, it is difficult to recover on its own. Glucose needs to be given intravenously, and those who are conscious can be given sugar water orally, and the symptoms will gradually ease.

This type of patients is often seen in patients with diabetes who take oral hypoglycemic drugs or use excessive amounts of insulin, or have other diseases such as insulinoma and chronic liver disease. Checking blood sugar after the onset of the disease can quickly determine the cause of syncope.

3. Epileptic seizures

Epileptic seizures are not strictly speaking fainting, but because the symptoms are often relieved by the time the patient is sent to the hospital for treatment, doctors are often unable to rule out transient loss of consciousness caused by such reasons. The main diagnostic clues are: whether there is a relevant family history; whether there is muscle force, spasm, convulsion, mental confusion or drowsiness during the attack; whether similar symptoms have recurred in the past. Further examinations such as EEG are needed.

4. Pseudosyncope

This is a "fainting" caused by psycho-psychological factors. The onset of the disease is often triggered by anger, excitement, quarrels, etc. There is no loss of consciousness during the onset of the disease, but the patient responds to external stimuli. This type of patient suffers from hysteria, has no physiological abnormalities, and all test results are negative. They can get better with suggestive treatment.

2. Is it necessary to go to the hospital for examination if fainting occurs?

If you are a young person who is in good health and goes to the hospital for regular physical examinations, then if you occasionally faint and can find a clear triggering factor, compare it with the triggering factors listed above, and consider that it may be vasovagal syncope, situational syncope, or orthostatic hypotension, and if it can completely improve on its own after the onset of the disease, you can observe it temporarily. If the disease recurs multiple times or some symptoms do not improve after onset, you should go to the hospital to find out the cause.

If you do not usually go to the hospital for a physical check-up, it is strongly recommended that you go to the hospital for a preliminary screening even if it is your first fainting episode. Because cardiac syncope can lead to sudden death, even if the clear cause of the disease cannot be found for the time being, cardiac risk factors must be ruled out first.

If you have discovered some chronic diseases that may cause fainting, it is very necessary to go to the hospital for examination and adjust the treatment plan in time when fainting occurs to reduce the recurrence of fainting.