Vasovagal reaction

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Vasovagal reaction: A reflex of the involuntary nervous system that causes the heart to slow down (bradycardia) and that, at the same time, affects the nerves to the blood vessels in the legs permitting those vessels to dilate (widen). As a result the heart puts out less blood, the blood pressure drops, and what blood is circulating tends to go into the legs rather than to the head. The brain is deprived of oxygen and the fainting episode occurs. The vasovagal reaction is also called a vasovagal attack. The resultant fainting is synonymous with situational fainting, vasovagal fainting, vasodepressor fainting, and Gower syndrome which is named for Sir William Richard Gower (1845-1915), a famous English neurologist.

Causes

Vasovagal response 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.

Typical triggers for vasovagal episodes include:

  • Prolonged standing or upright sitting
  • Standing up very quickly (Orthostatic hypotension)
  • Stress
  • P.O.T.S.(Postural Orthostatic Tachycardia Syndrome) a condition in which a change from a prone position to a standing position causes an abnormally large increase in heart rate, called tachycardia. Several studies show a decrease in cerebral blood flow decreased by half. Patients with POTS have problems maintaining equal blood pressure when changing position, i.e. moving from one chair to another or reaching above their heads. Many patients also experience symptoms when stationary or even while lying down.
  • Any painful or unpleasant stimuli, such as:
    • Trauma
    • Watching or experiencing medical procedures
    • High pressure on or around the chest area after heavy exercise
  • Arousal or stimulants, e.g. flogging, whipping, sexual orgasms, tickling, etc.
  • Sudden onset of extreme emotions
  • Lack of Sleep
  • Dehydration
  • Urination ("micturition fainting") or defecation, having a bowel movement ("defecation fainting")
  • 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 amphetamine
  • Violent coughing
  • Serotonin level / SSRI (Selective serotonin re-uptake inhibitors) - SSRIs are a class of compounds typically used as antidepressants in the treatment of depression, anxiety disorders, and some personality disorders.

Treatment

Treatment for vasovagal response focuses on avoidance of triggers, restoring blood flow to the brain during an impending episode, and measures that interrupt or prevent the trigger mechanism described above.

  • The cornerstone of treatment is avoidance of triggers known to cause the response in that person. However, a new development in psychological research has shown that patients show great reductions in vasovagal response through exposure-based exercises with therapists.
  • Because vasovagal response causes a decrease in blood pressure, relaxing the entire body as a mode of avoidance isn't favorable. A patient can cross his/her legs and tighten leg muscles to keep blood pressure from dropping so drastically before an injection.
  • Before known triggering events, the patient may increase consumption of salt and fluids to increase blood volume. Sports and energy drinks, as well as coconut water, may be particularly helpful.
  • Discontinuation of medications known to lower blood pressure may be helpful, but stopping antihypertensive drugs can also be dangerous. This process should be managed by an expert.
  • Patients should be educated on how to respond to further episodes, especially if they experience early symptoms/warning signs: they should lie down and raise their legs; or at least lower their head to increase blood flow to the brain. If the individual has lost consciousness, he or she should be laid down with his or her head turned to the side. Tight clothing should be loosened. If the inciting factor is known, it should be removed if possible (for instance, the cause of pain).
  • Wearing graded compression stockings may be helpful.
  • There are certain orthostatic training exercises which have been proven to improve symptoms in people with recurrent vasovagal response. A technique called "Applied Tension" which involves learning to tense the muscles in your torso, arms, and legs is effective for vasovagal response.
  • Certain medications may also be helpful:
    • Beta blockers (β-adrenergic antagonists) were once the most common medication given; however, they have been shown to be ineffective in a variety of studies and are thus no longer prescribed.
    • Other medications which may be effective include: fludrocortisone, midodrine, SSRIs such as paroxetine or sertraline, disopyramide, and, in health-care settings where a response is anticipated, atropine.
  • For people with the cardioinhibitory form of vasovagal response, implantation of a artificial permanent pacemaker may be beneficial or even curative.
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