science of us

Fainting Is a Pretty Weird Thing for a Body to Do

Photo: National Gallery of Art

Some people, to save lives, go to medical school for eons and take out exorbitant student loans. Me, I just lay on a cushioned platform for 15 minutes and eat Oreos. It’s why I’d always loved giving blood: It’s a lazy way to be a really good person. (Also: free unlimited cookies.)

But one day, my favorite good deed betrayed me. When I reached for the snack box after giving blood, I knew something was amiss: Voices became muffled, and a dark, fuzzy cloud fogged my eyes. I’ll never forget how everything disappeared — I could no longer see the bags of trail mix I’d reached out to grab. I raised my hand, a deeply ingrained impulse apparently, to ask a question about my state, but it was too late.

A minute later, I woke up facedown, surrounded by a puddle of urine and two irritated phlebotomists. I had passed out and peed myself on the floor of my once beloved bloodmobile. In my opinion, the nurses should have called a rescue helicopter and a trauma therapist, but instead they asked me to rest for only a few minutes before sending me on my way.

That was seven years ago, and I haven’t stepped a foot into a blood bank since. Fainting is terrifying: One minute I was about to chow on some cookies, and the next minute I was on the floor being stared at with pity by strangers. My brain shut down mid-thought like a phone dropping a call. I lost control of my body, even the ability to control one of my most basic functions.

I had some theories about why I lost consciousness — I thought the phlebotomist took out too much blood, so that my body could no longer operate. Or maybe my body went into shock, and needed a time-out. When I looked at the situation with some distance, I saw how crazy it is: We are all walking around with a spontaneous off button hidden somewhere inside, and yet have no idea what triggers it. Maybe if I figured that out, I could finally regain my confidence, go back, and start enjoying one of my favorite pastimes.

Fainting, formally, is known as syncope (sin-kuh-pee). It’s quite common: Half of all Americans faint at least once during their lifetimes. Fainting is simultaneously simpler and more complex than I’d expected. “It’s really due to one thing,” said Dr. Nicholas Tullo, a cardiac electrophysiologist who runs the New Jersey Center for Fainting. While there are many different triggers — emotional as well as physical — that can cause fainting, each results from the same condition: a lack of blood flow to the brain. “Without blood, your brain cells just shut down. It only takes four to ten seconds to completely lose consciousness.”

Without blood in my head, it made sense that I couldn’t eat cookies. The surprising part was that I could survive those moments without going brain dead. “There is no danger,” Tullo assured me, explaining that while fainting is the result of a problem — the lack of blood to the brain — it also results in the cure. When we become horizontal by falling to the floor, our brains fill back up with blood, because the fluid no longer has to fight against gravity to get there. (Of course, this is the case only if at the time you’re not, say, near the edge of a steep cliff.) “You recover almost immediately,” Tullo said. “Crazy enough, a lot of people even wake up feeling refreshed.”

But researchers still don’t understand why this happens. What causes that lack of blood to the brain in the first place? What scientists do know is that our brains hold many involuntary reflexes, such as breathing, digesting, temperature regulation, and blood pressure. Reflex syncope (also known as vasovagal syncope), the most common type of fainting, occurs when the brain sends out a wonky signal to lower the blood pressure and/or heartbeat. When blood pressure drops dramatically, blood can no longer make it all the way up to our brains — hence the loss of consciousness. “But why these reflexes go wrong,” Tullo said, “we really don’t know yet.”

So after donating blood, it wasn’t that I didn’t have enough blood left in my body or that I was in shock; it was that the blood I did have wasn’t distributed properly. It turns out that there are so many things that can cause fainting: dehydration, standing too long, a hot day, a claustrophobic environment. There’s even something called defecation syncope, which is the term for fainting if it happens while taking a crap — in this case, the brain, misreading a message sent from your colon, triggers this precarious blood-pressure drop.

“But it has to be a perfect storm,” Tullo said. “See, you’re dehydrated and you’re standing up and it’s hot and someone gives you bad news or you have some emotional stress — everything lines up, and that’s when you’ll faint.” Doing the same activity on a different day or under different circumstances rarely leads to the same outcome. “You can go ahead and give blood another time and it won’t happen again.”

Before Tullo and I finished up, I asked him one more thing.

“So how do you trust your body again?”

He was quiet for a moment. “I know it’s scary,” he said, “it’s always scary to lose control of your body, but know that you’ll always wake up again.” He also told me that, statistically speaking, I shouldn’t be too concerned about fainting again. After a fainting episode, one has a 40 percent chance that she will faint again in the next year, but if she doesn’t faint, then her chances drop to 17 percent for the year after that. This is because fainting often occurs in “clusters,” but as to why that is, we still don’t know. “Some people never faint again, but some do so several times a month,” he explained. “It’s one of those imponderables.” Considering that it’s been about 2,555 days since my one and only faint, this news was heartening.

A week later, I booked an appointment at a bloodmobile. When I arrived, I warned Donna, a petite middle-aged woman in a blue nursing uniform, about what happened the last time I donated. She didn’t seem fazed. “Some people, when they black out, can even have a bowel movement,” she said. I guess that’s life; people are always trying to one-up you.

Donna decided to take some extra precautions. She had me lie down and put cold wet towels around my neck. In order to keep me conscious, she exploited part of my thermoregulatory mechanisms — when a cold compress is used on the body, blood vessels will constrict in that area of the skin. Making my neck cold, she explained, would free up more blood to circulate in necessary areas like the brain.

From there, the experience was predictable, and soon enough, it was over. I rested for a few minutes. Then, cautiously, I stood up, wondering if my vasovagal reflex had been triggered. I stood still for a full minute. I went to the bathroom. I flushed the toilet. When I washed my hands, I was still standing upright! Donna, at that point, felt that I was in the clear, and let me go.

But before going home, I walked to the front of the bloodmobile and did what I’d aimed to do so many years before: sat down and indulged in three bags of mini Oreos.

From GROSS ANATOMY by Mara Altman, to be published on August 21, 2018 by G. P. Putnam’s Sons, an imprint of Penguin Publishing Group, a division of Penguin Random House, LLC. Copyright © 2018 by Mara Altman.

Fainting Is a Pretty Weird Thing for a Body to Do