Vasovagal response

A vagal episode orvasovagal response orvasovagal attack^[1] (also called neurocardiogenic syncope) is a malaisemediated by the vagus nerve. When it leads to syncope or "fainting", it is called avasovagal syncope, which is the most common type of fainting.^[2] Vasovagal syncope is most commonly found in adolescents and in younger adults.^[3]

There are different syncopesyndromes which all fall under the umbrella of vasovagal syncope. The common element among these conditions is the central mechanism which may lead to the loss of consciousness. The differences among them are in the factors that trigger this mechanism.

Signs and symptoms

Episodes of vasovagal response are typically recurrent and usually occur when the predisposed person is exposed to a specific trigger. Prior to losing consciousness, the individual frequently experiences early signs or symptoms such as lightheadedness, nausea, the feeling of being extremely hot or cold (accompanied by sweating), ringing in the ears (tinnitus), an uncomfortable feeling in the heart, fuzzy thoughts, confusion, a slight inability to speak/form words (sometimes combined with mild stuttering), weakness and visual disturbances such as lights seeming too bright, fuzzy or tunnel vision, black cloud-like spots in vision, and a feeling of nervousness can occur as well. The symptoms last for a few seconds before the loss of consciousness (if it is lost), which typically happens when the person is sitting up or standing.

When sufferers pass out, they fall down (unless prevented from doing so) and, when in this position, effective blood flow to the brain is immediately restored, allowing the person to regain consciousness. If the person does not fall into a fully flat, supine position, and the head remains elevated above the trunk, a state similar to a seizure may result from the blood's inability to return quickly to the brain, and the neurons in the body will fire off and generally cause muscles to twitch very slightly but mostly remain very tense. Fainting occurs with a loss of oxygen to the brain.^[4]

The autonomic nervous system's physiologic state (see below) leading to loss of consciousness may persist for several minutes, so

• If sufferers try to sit or stand when they wake up, they may pass out again
• The person may be nauseated, pale, and sweaty for several minutes or hours

Cause

Vasovagal syncope occurs in response to a trigger, with a corresponding malfunction in the parts of the nervous system that regulate heart rate and blood pressure. When heart rate slows, blood pressure drops, and the resulting lack of blood to the brain causes fainting and confusion.^[5]

Typical triggers for vasovagal episodes include:^[6]

• Prolonged standing or upright sitting
• After or during urination (micturition syncope)
• Standing up very quickly (orthostatic hypotension)
• During or post-biopsy procedures.
• Stress directly related to trauma^[7]
• Stress
• Postural orthostatic tachycardia syndrome (POTS) Multiple chronic episodes are experienced daily by many patients diagnosed with this syndrome. Episodes are most commonly manifested upon standing up.
• Any painful or unpleasant stimuli, such as:
  • Trauma (such as hitting one's funny bone)
  • Watching or experiencing medical procedures (such as venipunctureor injection)
  • High pressure on or around the chest area after heavy exercise
• Severe menstrual cramps
• Sensitivity to pain
• Arousal or stimulants, e.g. sex, tickling, or adrenaline
• Sudden onset of extreme emotions
• Lack of sleep
• Dehydration
• Hunger
• Being exposed to high temperatures
• In health care, such as nursing care, digital rectal procedures (e.g.,digital disimpaction)
• Random onsets due to nerve malfunctions
• Pressing upon certain places on the throat, sinuses, and eyes (also known as vagal reflex stimulation when performed clinically)
• Use of certain drugs that affect blood pressure, such as cocaine, alcohol, marijuana, inhalants, and opiates^[8]
• The sight of blood^[9]
• Serotonin level / SSRI ^[10]
• Swallowing^[11]
• (Less commonly) Low blood sugar^[12]
• Time varying magnetic field ^[13] (e.g., transcranial magnetic stimulation)

credit and source: WIKIPEDIA