The physician's assistant was removing stitches from my head, one week after neurosurgery. Sitting upright, I suddenly got lightheaded, and the room began to fade away.
"I think I'm going to pass out," I matter-of-factly announced to my husband.
Faster than you can say "syncope," the medical term for fainting, I was out cold. When I regained consciousness moments later, I was still in the chair. My husband told me I had slumped backward and was unresponsive. Because I was recovering from serious surgery, an ambulance was called.
As soon as I was horizontal, feet elevated, the shaky feeling dissipated. By the time I was wheeled into the emergency room, my most acute symptom was embarrassment for causing so much commotion.
Like many first-time fainters, I was clueless about the mechanics of what had happened and how it could have been avoided. In short, however, I'd lowered my blood pressure, reducing blood flow to the brain and ultimately causing a brief loss of consciousness.
Medical experts are still unsure why some people go a lifetime without fainting, while others are prone to passing out. When someone faints, doctors become detectives to determine whether it's a benign event or a symptom of a serious problem.
"Fainting is a very complicated situation," said electrophysiologist Dr. Ramin Ashtiani, a Los Angeles spokesman for the American Heart Association. He said fainters account for 3 percent of emergency room visits and 6 percent of hospital admissions.
To understand why a person has fainted, doctors first make sure there are no underlying conditions, such as cardiac, neurological or metabolic problems. Diabetes, allergic reactions, viral infections and pregnancy complications must also be considered.
"The vast majority of fainting episodes are not dangerous, but they should always be checked out," said Dr. Carolyn Sachs, an associate professor and emergency room physician at the University of California, Los Angeles.
Sachs added that in an otherwise healthy person, falling is the main risk in a benign fainting episode.
Susie Elkind, 57, an Oakland, Calif., proofreader and copy editor, knows this from firsthand experience. When she fainted in her bedroom in September while ill with pneumonia, she crash-landed onto a table.
"I had black and blue marks on my backside," Elkind said. "It's a good thing I didn't hit my head."
One common reason for fainting is the vasovagal reflex.
The large vagal nerve descends from the spinal cord and has nerve endings throughout the body, including the neck, chest and abdomen. It is part of the autonomic nervous system, which regulates heart rate and blood pressure.
"The vasovagal reflex is mediated by this nerve. In certain sensitive individuals, exposure to shocking stimuli [pain, emotional distress, anxiety and fear] results in activation of the vagal nerve's action, which then causes a reduction in heart rate and blood pressure," said Dr. Sam S. Torbati, a physician in the emergency department of Cedars-Sinai Medical Center in Los Angeles.
As a result, the brain does not receive enough blood flow and the person can faint.
"It's a reflex that can be stimulated in scenarios when somebody has an intense reaction to either something that's perceived as being painful or actually may be painful," Torbati said.
For example, seeing the dentist approach with a big needle or having blood drawn can activate this reflex.
In healthy young people, severe emotional stress is the main producer of vasovagal fainting episodes. In addition to the vasovagal reflex, other fainting triggers in healthy people of all ages include: dehydration, low blood sugar, overheating, heavy sweating, standing in one position for too long, exhaustion, violent coughing or gagging. Some prescribed medications, including ones for high blood pressure and anxiety also can cause lightheadedness. And certain lifestyle choices, such as extreme dieting and alcohol and drug use may lead to syncope. (The common thread in these very different scenarios is that they can result in insufficient blood flow to the brain.)
"It's usually a combination of causes in an otherwise healthy person," said Torbati, adding that most people get some kind of warning that they are about to faint, usually "a hot, flushed feeling, they start to feel dizzy and they get nauseated." Other warning symptoms are visual and aural, with images and sounds fading out.
Experts stress the importance of reacting quickly to avoid getting injured if you feel you're about to faint: Immediately lie down with your legs elevated. If this is not possible, sit with your head between your knees.
Simple muscle-tensing exercises may be another way to ward off vasovagal syncope, according to a March 2006 presentation by Dutch researchers at the American College of Cardiology meeting in Atlanta. Their 14-month study of 223 frequent fainters found that leg-crossing, hand-gripping and arm-tensing exercises reduced episodes of fainting.
As for my swooning, I inadvertently made it happen. For starters, I did not eat enough before leaving the house, and I forgot to bring a water bottle. It was a very hot day and by the time I arrived at the medical office I was overheated, nauseated and dehydrated. Added to the mix was my anxiety, which probably triggered the vasovagal reflex as the stitches were removed. Sitting upright sealed the deal, with blood pooling in lower extremities, away from my brain.
At the emergency room, after doctors ruled out any serious problem, I was sent home with tips on how not to faint.
At the top of the list, for me anyway - lie down during a medical procedure.
Emily Dawes wrote this article for the Los Angeles Times.