What causes sudden fainting?

Fainting is an unconscious symptom caused by transient cerebral ischemia due to various reasons. It usually causes sudden dizziness, blurred vision, black eyes, and cold limbs. There are many reasons for sudden fainting, which may be cardiac ischemia, cerebrovascular disease, or autonomic nervous system dysfunction. Why do these diseases cause fainting? This article will help you resolve your doubts on this issue. Let’s take a look.

1. Causes

Cerebral perfusion pressure depends on systemic arterial pressure; therefore, any cause of decreased cardiac output or decreased peripheral vascular resistance can cause syncope. Common causes include:

1. Autonomic nervous system dysregulation and vasomotor disturbances

For example, when hypotension occurs in the upright position, cerebral blood supply disorders may cause syncope, which is more common in people with poor physical constitution. Urinating a large amount of blood at one time or coughing continuously may reduce the amount of blood returning to the heart and cause syncope.

2. Cardiogenic cerebral ischemia

This cause of syncope is the most serious and is often seen in severe fast or slow arrhythmias or cardiac arrest. It can occur in any body position, and severe ischemia may be accompanied by convulsions of the limbs and incontinence.

3. Cerebrovascular disease

This situation is mostly caused by sudden insufficient blood supply to the brainstem. Due to ischemia of the ascending activation system of the brainstem reticular formation, the normal state of consciousness cannot be maintained, and it should be called transient cerebral (posterior circulation) ischemic attack.

4. Others

Syncope can also occur in patients with hypoglycemia, severe anemia, and hyperventilation.

Clinical manifestations

The patient suddenly feels dizzy, dazed, blurred vision or black eyes, and weakness in the limbs. This is the precursor to syncope; then he loses consciousness and falls to the ground. He recovers within seconds to minutes and stands up and walks. Some patients may feel general fatigue within half an hour. In many cases, the patient collapses quickly instead of falling, does not lose consciousness, or if it happens repeatedly and the patient gains experience and squats in time, the symptoms will quickly disappear. When fainting, the heart rate slows down or speeds up, blood pressure drops, the face becomes pale, and cold sweats may occur. Syncope basically occurs when standing or sitting. If it occurs in a lying position, you should pay attention to whether you have cardiovascular and cerebrovascular diseases such as arrhythmia, transient ischemic attack or epilepsy.

2. Differential Diagnosis

It should be differentiated from vertigo. Fainting and vertigo are completely different symptoms. Syncope occurs when there is a loss of consciousness. When vertigo occurs, no matter how severe it is or how long it lasts, there should be no disturbance of consciousness.