Originally published on Van Winkle's (May 2016)

At times, general anesthesia seems more like a spell than science, doesn't it? The mask comes down, a few deep breaths and we're out, placed in a reversible state of unconsciousness and perceptual unawareness that allows us to undergo surgery without pain or recall of the event. Whether going under for a tooth extraction or triple bybass, we’re in much deeper than sleep or meditation. Yet, our brain still functions. Considering we're can't feel a scalpel slice through our skin, are we able to dream? And if we do, what shape do they take in this in-between world? 

A fair amount of research has attempted to answer these questions with sometimes confounding conclusions. Before we get to those results, let’s consider how lucky we are to be living in an age when general anesthesia is relatively safe and available. Not so long ago, drilling skulls and setting bones took place with little more than herbs, opium and cannabis vapors to dull the pain.

It wasn’t until the late 1700’s that Joseph Priestly discovered the “airs of oxygen” and nitrous oxide that changed the way physicians approached sedation. In 1844, Dr. Horace Wells volunteered to inhale nitrous oxide during his tooth extraction, and though successful, his work was declared “humbug” by the medical establishment. It all changed two years later at the “Ether Dome” at Massachusetts General Hospital when the colorless (and extremely flammable) liquid was successfully used to knock a patient out during surgery. Soon thereafter the word “anesthesia”, from the Greek meaning "lack of sensation" was coined by Dr. Oliver Wendell Holmes.

General anesthesia has made great strides since Dr Holmes. Yet, according to Houston, TX-based anesthesiologist Dr. Michael Ho, the exact mechanism of today's general anesthesia is still unknown. It is widely thought to involve a disconnection between sensory input and higher center cerebral processing. One theory looks to the thalamus, the small structure that’s located in the center of the brain just above the stem. It conveys signals from the body to the cortex, the command center of consciousness.

“In order for a person to remain awake, the thalamus must continually stimulate the cortex,” said Dr. Ho of the theory. “No thalamic stimulation, no wakefulness and sleepiness passively results. Taking advantage of this normal pathway to consciousness, general anesthesia may work by inhibiting the thalamus, shutting off the thalamocortical switch — closing the thalamic gate —  thereby inducing unconsciousness.” 

What we do know is that the administration of anesthesia is very precise, and complicated method of, for lack of a better phrase, turning off the brain. Yet, some studies have shown that even in this deep state, roughly 5 percent of patients dream. According to others  the number might be as high as 22 percent.

If you’re female, young and dream frequently at home, then you’re more likely to dream during surgery. The sooner after surgery you’re asked, research has found, the higher the recollection of dreams. This, however,  is not a consistent finding.

In terms of specific anesthetic drugs, the use of the propofol (Michael Jackson’s preferred sleep inducer) and ketamine (used experimentally as an antidepressant) seem to be associated with more dreams. Administration of another type of drug called scopolamine has been associated with fewer reported dreams. 

Dreams under anesthesia are rather unextraordinary. They typically involve work, family and friends. A 2007 study in Australian hospital noted that dreams during operations under general anesthesia are pleasant and sometimes prompted by conversations overheard during surgery. Not surprisingly, patients who are anxious before an operation are more likely to report unpleasant dreams.

During the early days of anesthesia, sexual dreams captured the imagination of a population new to this medical breakthrough. A fictional dramatic story published in 1884 centered around the dreamlike romantic experiences of young female patients under dental sedation. Surgeons and dentists were accused of sexually assaulting patients during an investigation spanning the years 1849 to1888. According to a modern day analysis of these charges, however, a bit of hysteria may have played a part in how these cases were handled. In one situation, for example, a patient vividly described being sexually assaulted by the dentist during a tooth extraction even though the patient’s husband was present during the procedure and testified that nothing was amiss.

Sexy or quotidian, however, it’s odd to consider that even with the brain turned down to almost zero, it picks up enough information to create dreams. Some researchers, believe the most likely scenario is that we retrieve bits of conversations and remembered dreams during the recovery phase of our anesthesia, also known as “emergence,” or that for some reason we’re not as fully sedated as someone else with the same amount of drugs.

Of course dreaming isn’t the only unusual thing that happens under general anesthesia. One might experience  hallucinations or  “intraoperative awareness” — a state of paralysis during which you see yourself undergoing surgery but are unable to move or speak. The experience is rare, but unsettling: more than 20 percent of patients who experienced awareness during surgery, suffered from psychological stress many months afterwards.

Experts note that there may be some confusion on the patient’s part in this area, as some people will actually dream about their operation and don’t experience it in real time. There are unfortunate others who can verify what actually happened. According to Dr. Ho, however,  an exact analysis of an experience during anesthesia can be tricky.

“Both awareness and dreaming depend on subjective recollection, and their detection is subject to bias, both from the patient’s ability and willingness to recall, and the timing and design of the study,” he said.  “Even more confounding —  and bordering on the philosophical —  are the possibilities that in some cases what was reported as a dream was actually awareness and what was reported as awareness was actually a dream.”  

It is unknown how environmental stimuli shape the dreams — if music, meditation, or relaxation techniques before surgery can decrease their frequency or make them consistently pleasant. But it’s been reported that hearing a calming phrase such as “after being treated with this drug, you will have pleasant dreams” has been associated with reduction in the reports of unpleasant dreams.

As in life, sometimes all it takes is a few sweet words to make things better.