Vasovagal syncope (VVS) is the most common cause of fainting, often called the common faint. This temporary loss of consciousness occurs when the nervous system overreacts to a specific trigger, leading to a sudden drop in both heart rate and blood pressure. The mechanism involves the vagus nerve, which slows the heart and causes blood vessels to widen, resulting in blood pooling in the lower extremities. This reduces blood flow to the brain, causing brief unconsciousness. While VVS is generally harmless, understanding its signs and knowing how to respond is important for preventing injury.
Recognizing Warning Signs and Immediate Response
Vasovagal syncope episodes are often preceded by warning signs known as the prodrome, which can last from a few seconds to a minute. Recognizing these symptoms quickly is the primary way to prevent a full faint and potential injury. Common sensations include lightheadedness, dizziness, nausea, and a warm, flushed feeling.
Visual disturbances are frequent, such as experiencing “tunnel vision” or a “gray out,” along with pallor (paleness of the skin). Profuse sweating and a cold, clammy feeling may accompany these symptoms. If a person recognizes these signs, the immediate action is to quickly assume a supine position, lying flat on the back.
Lying down helps restore blood flow to the brain and potentially aborts the episode. Elevating the legs above heart level, such as propping them on a chair, further enhances blood return to the core circulation. If lying down is not an option, the person should sit down immediately and place their head between their knees.
If the individual faints, a bystander should help them to the floor safely and elevate their legs. Once consciousness returns, the person should remain lying down for 10 to 15 minutes to allow blood pressure to normalize. Standing up too soon increases the risk of a second episode.
Lifestyle Changes for Prevention
Prevention focuses on long-term habits that manage blood volume and reduce sensitivity to triggers. Maintaining adequate hydration is a strategy, as low fluid intake reduces blood volume and increases susceptibility to a drop in blood pressure. Drinking plenty of water helps keep the circulatory system robust.
Increasing dietary salt intake, when advised by a healthcare provider, can be beneficial because sodium helps the body retain water, expanding blood volume. This volume expansion resists the blood pressure drop associated with a vasovagal episode. Individuals with existing hypertension should seek medical guidance before increasing sodium consumption.
Positional changes are crucial, particularly avoiding prolonged standing, especially in hot or crowded environments, which causes blood to pool in the legs. If standing is unavoidable, movements like shifting weight, flexing leg muscles, and crossing the legs promote venous return to the heart. Identifying personal triggers allows for proactive avoidance.
When to Seek Professional Diagnosis and Treatment
Fainting should always prompt a medical evaluation, especially after a first episode, to rule out more serious underlying cardiac or neurological conditions. A healthcare provider will begin with a thorough review of symptoms and medical history, including medications, and perform a physical exam. Diagnostic tools are then used, with an electrocardiogram (ECG) being a common initial test to check for heart rhythm abnormalities.
The Tilt Table Test is a specialized procedure that helps confirm a vasovagal diagnosis by monitoring heart rate and blood pressure while the patient is tilted upright. If non-drug preventative measures are insufficient for frequent episodes, a physician may recommend specific physical counter-pressure maneuvers. These maneuvers, like tensing the arms and legs or firmly gripping one hand with the other, are performed during the prodrome to temporarily increase blood pressure and prevent fainting.
For patients with recurrent, debilitating syncope, pharmacologic options are reserved for severe cases. Medications like fludrocortisone (which increases blood volume) or midodrine (which raises blood pressure) may be prescribed. Selective serotonin reuptake inhibitors (SSRIs) are also sometimes used to modulate the nervous system’s overreaction.