Fainting (Syncope) Causes, Symptoms, Diagnosis, and Treatment on MedicineNet.com

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Fainting
(Syncope)

Medical Author: Benjamin C. Wedro, MD, FAAEM
Medical Editor: Melissa Conrad Stöppler, MD

Vasovagal Syncope

Medical Author: Benjamin C. Wedro, MD, FAAEM
Medical Editor: Melissa Conrad Stöppler, MD

Springtime is a new adventure for many first-year medical and nursing students. After a semester in the classroom, they are let loose to observe the real world. Invariably, the same scenario plays out.

All is well as they enter the operating room. The anesthesiologist is finishing putting the patient to sleep, and the student is set to observe an actual surgical procedure for the first time. The room is excessively hot to keep the patient warm on the table. The surgeon puts sterile drapes across the body, the bright lights are turned on, and the only noise is that of the ventilator breathing for the patient. The surgeon turns to the anesthesiologist, asks permission to begin and makes a long, slow incision into the body with the scalpel edge.

Meanwhile, the student's cool veneer begins to show cracks. The heat of the room has made sweat start to stream on the forehead. The lights start to blur, and voices in the room become distorted. The sickening nausea, the lightheadedness, vision fades to black, and all this is quickly followed by the sound of the firs- year student hitting the floor in a faint.

Introduction to fainting (syncope)

Fainting, "blacking out," or syncope is the temporary loss of consciousness followed by the return to full wakefulness. This loss of consciousness is accompanied by loss of muscle tone that can result in falling or slumping over. To better understand why fainting can occur; it is helpful to explain why somebody is awake.

The brain has multiple parts, including two hemispheres, the cerebellum, and the brain stem. The brain requires blood flow to provide oxygen and glucose (sugar) to its cells to sustain life. For the body to be awake, an area known as the reticular activating system located in the brain stem needs to be turned on, and at least one brain hemisphere needs to be functioning. For syncope to occur, either the reticular activating system needs to lose its blood supply, or both hemispheres of the brain need to be deprived of blood, oxygen, or glucose. For the brain to stop functioning, the flow of blood must be briefly disrupted to the whole brain or to the reticular activating system.

Fainting is not caused by head trauma, since loss of consciousness after a head injury is considered a concussion. However, fainting can cause injury if the person falls and hurts themselves, or if the faint occurs while participating in an activity like driving a car.

What causes fainting (syncope)?

Decreased blood flow to the brain can occur because 1) the heart fails to pump the blood; 2) the blood vessels don't have enough tone to maintain blood pressure to deliver the blood to the brain; 3) there is not enough blood or fluid within the blood vessels; or 4) a combination of reasons one, two, or three above.