The operating theater fell silent as Robert Liston drew his knife and approached the unconscious man lying before him. The stakes were higher than usual. Liston, a venerated surgeon, was testing out a newfangled theory that had just arrived from Boston. There, Dr. John Warren had successfully removed a neck tumor from a patient using ether — an early form of anesthesia — to put him to “sleep.” Skeptical, Liston resolved to gauge its effectiveness himself. Moments before, an ether-soaked handkerchief had dispatched his patient, Frederick Churchill, to what appeared to be a peaceful slumber. And just 28 seconds later, Liston had removed the man’s virulently infected leg.

The two burly medical assistants who flanked him hadn’t moved a muscle, because there’d been no need for them to physically restrain a howling patient. The application of ether — which until that point was considered by many British medical professionals to be American nonsense, and was dismissed as a “Yankee dodge” — had kept Churchill out cold during the entirety of the operation. For one of the first times in human history, a surgeon had successfully operated on an anesthetized patient. “This Yankee dodge, gentleman,” Listom announced excitedly, brandishing his bloody instrument, “beats mesmerism hollow!”

Mesmerism, or hypnosis, was one of the creative methods with which anxious patients sought to fend off the searing torture of pre-anesthesia surgery. Before germ theory took hold and washing one’s hands became the norm, unruly filth and feculence was par for the course in a 19th century hospital. Surgery was seen as a last resort, and death was an expected result of a hospital stay. Patients unfortunate enough to undergo surgical procedures were cut into with little more than a draught of whiskey (or a swift thump to the noggin) to dull the agony. They often struggled to escape mid-surgery, so speed and strength were crucial skills for any surgeon worth his unwashed scalpel. The idea of a mechanism by which the pain of surgery could be dulled or eliminated altogether was regarded with great suspicion, and while Liston wasn’t the first to anesthetize a patient, it wasn’t until word of his experiment spread that medical professionals began to embrace ether, and later, chloroform, as an essential part of their toolkits. The butchering art, as surgery was once known, had been forever changed.

Thus was launched the modern era of anesthesia, the application of which has evolved from Liston’s hastily-applied ether-soaked rag to today’s complex, often inscrutable chemical cocktails. The art of sending a conscious person into a deep enough fugue state to allow for invasive surgical intervention is a delicate one, far removed from the excruciating butchery of old. Still, undergoing general anesthesia isn’t a walk in the park. During anesthesia’s scattershot early days, there was quite a large margin of error, and the sensation of going under itself was often a profoundly unpleasant experience. Many patients described it as a feeling of being buried alive. Generally, most surgery patients were not thrilled about it. Even now, while most people are able to inhale, count down slowly, and sink sweetly off into a twilight sleep, others undergo far more traumatic experiences. For some people, enough consciousness has remained for them to be haunted by memories of things said and done during surgery. Some, floating under light anesthesia, conjure feelings of disassociation. Some have woken up outright, unable to feel pain but otherwise aware. And an unlucky minority have been rendered paralyzed, seemingly out cold but fully conscious, horror-struck, and in agony as they watch themselves be sliced open.

Australian author Kate Cole-Adams was initially inspired to write her new book, Anesthesia: The Gift of Oblivion and the Mystery of Consciousness, after hearing about one of those terrible failures. Her friend Rachel Benmayor, whose general anesthetic failed mid-surgery, awoke during a cesarean birth, and lay there mute and lucid, feeling every stroke of the knife, thinking with great certainty that death was near. Though she came out of it alive, Benmayor was haunted by the experience, and speaking to her about the ordeal sparked Cole-Adams’ curiosity.

What happens to our memories — and is it possible to ‘remember’ things that happen while one is anesthetized? Is pain still pain if we don’t remember it?

Morbid as it may be to consider, the possibility of not waking up — or waking up profoundly altered — is there whenever someone breathes into that little mask. According to the Mayo Clinic, roughly one to two people per thousand report waking up under anesthesia, through a smaller percentage are likely to feel pain during the experience. Benmayor was part of that profoundly unlucky statistic alongside people like Carol Weiher, who has spoken extensively about the time in 1998 when she woke up during eye surgery. Though she was paralyzed, Weiher could feel the surgeon scoop out her right eyeball, and felt every snip as they severed her optic nerves. She says that she felt no pain, but the ordeal left her with significant psychological scars. Other people Cole-Adams interacts with throughout the book report similar experiences, though few as harrowing as Weiher’s. She discovers just how unwilling some anesthesiologists are to admit the possibility that someone may wake up while under their care. Whether it’s personal hubris or professional confidence, it does help to explain why this inexact science has yet to be perfected. How can you solve a problem that — apparently — doesn’t exist?

This is far from a modern problem. The nightmarish danger of waking up mid-surgery has dogged anesthesia since its very first public demonstration in 1845, when Horace Wells administered nitrous oxide to an obliging dental patient at the Massachusetts General Hospital who moaned in pain as his tooth was extracted, leading the audience to jeer “Humbug!” By 1846, Boston dentist William Morton had tried again at the same location, this time administering ether beneath the majestic glass-roofed operating theater. His gamble was a success, and the hospital renamed said surgical theater the Ether Dome in honor of the miracle. From there, ether made its way across the Atlantic to Robert Liston’s operating table, and then to the bedroom of bedroom of Queen Victoria, whose decision to use ether during the birth of her son Leopold popularized the practice. That initial false start hasn’t harmed the advance of anesthesia, but the fact that even highly-trained modern medical professionals still can’t quite shake the problems that preyed upon their Victorian predecessors shows just how far the field still needs to go until it overcomes its haphazard past.

Thanks to various technological advancements, we now have at least a general idea of what happens to our brains when we’re out cold. Widely-used methods like the BIS (bispectral index) and procedures like MAC (monitored anesthesia care) help us to monitor anesthesia levels, while the EEG (Electroencephalography) provides a visual document of electrical activity in the brain. Anesthesiologists have more or less worked out how to balance the varieties and amounts of mind-altering drugs they administer, which are typically comprised of three elements: “hypnotics” to aid unconsciousness, “analgesics” to control pain, and, commonly, a muscle relaxant, which keeps patients from squirming (as sort of an updated version of Liston’s brawny assistants).

The latter are a direct descendent of curare, a paralyzing chemical that was first used by South American tribespeople to poison the tips of their war arrows. The medical use of “flying death” was “discovered” and exported by Western explorers in the 16th century, but it wasn’t fully understood for another two hundred years. Curare was prized by surgeons for its ability to paralyze, but its use had one quite significant drawback: it didn’t actually dull the sensory nerves. That meant that those to whom it was administered as part of an early anesthetic cocktail certainly weren’t able to move, but if they were so unfortunate as to awake during the procedure, would be left unable to breathe but wholly able to feel every cut. After hearing about its effects, a shocked Mark Twain wrote, “The apparent insensibility it produces is accompanied by the most atrocious suffering the mind of a man can conceive.” As barbaric as that sounds, use of curare wasn’t officially discontinued until 1946, which means there are still people walking around right now who have been subjected to its waking nightmare. The past is still alive.

I was doing a combination of praying and pleading and cursing and screaming, and trying anything I could do but I knew that there was nothing that was working.

Despite these and other equally alarming details, Anesthesia: The Gift of Oblivion and the Mystery of Consciousness isn’t a horror story. While the book offers many illuminating glimpses into the history of anesthesia itself, Cole-Adams is more interested in the more uncomfortable where, and how, and even whos of the matter. She seeks to answer a primordial question of: What really happens to us when we’re under? Where does our consciousness go? What happens to our memories — and is it possible to “remember” things that happen while one is anesthetized? Is pain still pain if we don’t remember it?

Throughout the book, Cole-Adams interviews a number of anesthesiologists and patients whose individual stories contribute pieces to the puzzle. She attends conferences on the subject, observes surgical procedures, pages through the handful of scant but fascinating studies that tackle the subjects of memory and pain under anesthesia, and interrogates famed anesthesiologists in their cluttered offices. Throughout the journey, her findings remain inconclusive — the more she learns and listens, the more determined the secrets of the inexact science are to remain hidden. Weiher’s eyeball is only the tip of the iceberg, as it were.

Reading through harrowing, agonized stories like Benmayor’s — which continues to resurface throughout, serving almost as a personal lodestone for Cole-Adams’ quest — is not pleasant. Being forced to contend with the fact that something like this might happen to you, or to someone you love, is frightening. Facing down the idea of surgery is bad enough without being saddled with the chilling examples of “what ifs” that this book serves up on a sterilized platter, and learning how resistant some anesthesiologists still are to address the possibility of it happening is chilling, to say the least. The only time I’ve undergone surgery was when I was still a tiny infant, barely conscious to begin with; I came out of that with only a few scars of the physical variety, and — as far as I know — no lingering mental after-effects. It was only after reading this book that I realized how lucky I was.