Fear of Needles and the Vasovagal Reaction
Do You Pass Out When Faced with a Needle?
As an anesthesiologist, I am sometimes called to place difficult intravenous lines (IVs). Quite often, the patient will warn me, "I'm a wimp with needles; I'll faint or get all sweaty and nauseous" or "I pass out at the sight of a needle". It is not unusual for the person saying this to look quite healthy, young, and often very strong. Not at all what I would all "wimpy."
So, what is it that makes these robust people so helpless when they need to have blood drawn or an IV placed? Is the tiny needle really so terrifying? Or is there another explanation?
Symptoms of Vasovagal Reactions
- Pale, cool, and clammy skin
- Visual changes (e.g., tunnel vision) or "seeing stars"
- Fainting or near-fainting
What is a Vasovagal Syncope?
As it turns out, these people are not weak. In fact, it seems to me that big, strong, muscular men in very good physical condition seem to suffer this fate disproportionately. I noticed this when I worked in an area where we treated a lot of marines. Those guys were merciless when it came to dealing with each other; however, they'd feel faint as soon as they saw a little needle.
I would then help the poor soul save face by explaining the vasovagal reaction, also called vasovagal syncope.
- Vasal refers to blood vessel or the circulatory system.
- Vagal refers to the vagus nerve, a part of the nervous system that helps regulate heart rate and blood pressure.
- Syncope (sink-oh-pee) means fainting.
Doctors also use the term "neurocardiogenic syncope" to be very specific, with neuro referring to the origin of the reaction in the nervous system, cardio meaning the effects are on the cardiac system, and syncope again to mean brief loss of consciousness.
How Do Vasovagal Reactions Happen?
Basically, vasovagal reactions (you don't have to actually pass out to have this) occur when something--a stimulus of some kind--causes an overreaction of the parasympathetic nervous system. When this part of the nervous system is stimulated, the heart rate slows and blood vessels dilate. Because less blood is able to flow back to your heart and then to your brain, several characteristic changes occur that may or may not end with a brief fainting spell before the body corrects itself.
In this case, the stimulus is the needle (and perhaps later, through a conditioned response, just the sight of the needle) puncturing the skin or the blood vessel. The (mostly) parasympathetic nervous system causes heart rate and blood pressure to drop, leading to the familiar symptoms. Normally, the sympathetic nervous system quickly counteracts these effects. During a vasovagal spell, however, the sympathetic action is too slow, allowing the parasympathetic effects to overwhelm the body. Luckily, the reaction is short and self-limited, usually requiring no treatment.
Viewing this as a battle between the parasympathetic and sympathetic nervous systems is quite oversimplified. There are actually complex interactions between these two parts of the autonomic nervous system that result in the reaction.
Basically, the reflexes that slow heart rate and dilate blood vessels causing low blood pressure predominate temporarily. The overall effect is the vasovagal reaction with the symptoms listed above.
Passing out while giving blood is pretty common due to both the needle and the removal of blood.
Treatment for Vasovagal Syncope
Because fainting can result from a variety of causes, serious origins must be ruled out. Repeated fainting or loss of consciousness under unusual circumstances will require a workup to rule out problems with the heart or nervous system.
If fainting is determined to be a result of vasovagal syncope, that is good news, relatively. This is because vasovagal reactions are usually not serious. They tend to resolve themselves and require no treatment unless they are very frequent.
Vasovagal reactions in response to needles, IVs, or blood draws are fairly common. If you have a history of these attacks, inform the person who is about to use the needle on you. This will help him or her prepare for inadvertent movement and protect both of you from injury. Also, you can have the procedure done in a lying-down position to decrease the likelihood that you will lose consciousness or be injured if you do.