“A lot of people think anesthesia is an off switch, and then you turn it back on later,” said Boris Heifets, MD, PhD, Professor of Anesthesiology, Perioperative, and Pain Medicine at Stanford Medicine, Stanford CA. “There’s much more to it.”

A new observational study published in Anesthesiology makes that case: Heifets and other researchers found that dreaming under anesthesia may not just be common, but participants in the study reported simpler, more positive dreams than what they’d experience in normal REM sleep. The happier dreams were linked to more positive surgical experiences.

So what, exactly, is going on?

A Study Is Born

“We do know that anesthesia dreaming is actually pretty common, but so far it has just been an interesting phenomenon. For a long time, anesthesiologists tried to avoid dreaming because they thought it might reflect awareness,” explained Pilleriin Sikka, PhD, postdoctoral scholar in Heifets’ lab and first author of the study. “Our clinical anesthesiologist, Dr Harrison Chow, noticed [in his operating room (OR) experience] that patients who have dream experiences seem to be better off. They seem to recover faster and communicate better after surgery.”

This piqued Heifets’ interest. “When Harrison came to Stanford about 5 years ago, he was talking about how he was actually intentionally producing these states because they seem to be healing,” he said. “I’m an anesthesiologist, but I study psychedelics. When Harrison and I met up, and he was telling me about these dream states that patients have that lead to these therapeutic outcomes, that spoke so much to work that we had already been doing [with psychadelics] where we’re intentionally producing what sound like very similar states of consciousness in order to improve mental health outcomes.”

To increase the chances of study participants dreaming, researchers anesthetized patients undergoing elective, outpatient surgeries at Stanford Medical according to a five-element protocol.

Element one: Verbally priming the patient before anesthesia. “It’s well known that when you go to sleep if you tell yourself you’re going to try to remember your dreams, that generally you have higher rates of recalled dreams. We [told patients] ‘you may have them as you emerge and we may ask you questions,’” explained Heifets. 

The second element is the choice of anesthetic agents. For dream recall, propofol was the clear choice. “Propofol is safe, has few side effects, and is associated with faster recovery,” said Sikka. “That seems to be important because you come out more quickly, your memory works better, and your better able to capture whatever your experience was.”

Brain monitoring to guide emergence was the third key element. Researchers used an EEG monitor to observe brain activity under anesthesia. Toward the end of each procedure, anesthesiologists would “try to bring patients to a lighter plane of anesthesia without having them emerge from anesthesia,” said Heifets. 

Dreams most likely took place during this phase. “We don’t know for sure because we don’t have any specific markers of dreaming,” said Sikka. “I think it’s most logical that [dreaming] happens in the emergence phase. [This is] a brain state that is associated with dreaming because you need some activation in the cortical areas to have subjective experiences.”

Fourth, the most difficult part in a busy hospital, was to keep patients in the pre-emergent state for at least 10 minutes in an environment with minimal stimulation. “What we know from sleep dream research is that for you to remember dreams, you need to reduce interference [during awakening],” said Sikka

The fifth and “critically important” step, according to Heifets, was making sure to interview patients immediately after they emerged. “Meaning as soon as the participants are able to talk,” said Sikka. 

Surprising Results

Even after the stress of undergoing surgery, researchers found that the patients’ dreams they recorded had one big thing in common: They were overwhelmingly positive.

Of 452 patients interviewed, 69% reported dreaming and 86% of those had positive dreams. No one reported “very negative” dreams. Dreamers also reported higher sleep quality.

Sikka was pleasantly surprised. “They’re going for surgery,” she said. “It’s a crazy, stressful experience. It’s a traumatic experience. And so it’s a strange phenomenon.” 

Most patients dreamed about being outdoors, being with family and friends, or enjoying other pleasant experiences. Many dreamed about surgery and everything having gone well. 

By and large, the dreams were simple, short, pleasant, and related to their everyday life experiences, “which makes them really unique in that sense, considering this situation and considering that they’re different from [REM] sleep dreams,” said Sikka. 

The OR-Sized Obstacle

The researchers see big potential for a better experience for patients after surgery. “If we can improve patients’ experiences in this extremely traumatic and stressful situation, we should do that. And if it only requires a few extra minutes spent on pre-emergence, that’s a beautiful goal,” said Sikka.

But those 10 minutes are precious in an OR and not easy to come by.

“If you’re in a busy surgery center, they need to keep things moving, right? So the idea that you would wait 10 minutes and not try to shake [a patient] awake is a little foreign,” said Heifets.

But when they did? More than 90% of patients recalled their dream. 

“When we didn’t we were down closer to 70%, which is still pretty impressive,” he said.

Lisa Leffert, MD, physician-in-chief of anesthesiology at Yale New Haven Hospital, New Haven, Connecticut, and Bridgeport Hospital, Bridgeport, Connecticut, and Chair of Anesthesiology at Yale Medical School, sees the same potential — and the same hurdle (she was not involved in the research). “Letting [a patient] emerge naturally and how important this is, intuitively, it makes a lot of sense,” she said. “And then when you look at the realities of patient care and what that actually means to let each person emerge on their own timescale, from an efficiency standpoint, that’s very challenging.” 

Her colleague at Yale Medicine, Janna Helfrich, MD, who was also intrigued by the study, agreed. She hopes that can change. “Maybe in the future there might be a possibility to incorporate it into the workflow,” she said. “[You could] have another room where you can actually let the emergence happen naturally.”

“Patients are happier, they’re more alert, they seem to like the experience,” said Heifets. “These are pleasant dreams far and away. And we have to think about what the benefit is of having a pleasant recovery from anesthesia vs a fast recovery from anesthesia.”

Even More Interesting Potential

Anesthesia dreams may have further mental health benefits.

Sikka describes some case studies the team has from the OR where patients with prior posttraumatic stress disorder (PTSD) had dream experiences during surgery — and had impressive outcomes. “These anesthesia dream experiences were related to their traumatic experiences, but they were positive,” said Sikka. “Then they reported no PTSD symptoms and no nightmares after these dream experiences.”

The researchers are now working on a trial outside of the OR with PTSD patients, specifically trying to induce anesthetic dreaming to treat PTSD. “We’re focused really on people who have nightmares, or people who have intrusive, recurrent memories of traumatic events,” said Heifets. “These seem to be things that people might be able to work through.”

Beyond PTSD, the team hopes to find more ways to use their findings to create positive mental health outcomes for patients.

“I mean, some of the stories we heard: This 80-year-old woman dreamt of being 17 with her boyfriend at the shore,” said Heifets. “They were in this limitless blue ocean, just in the waves, and it just went on forever. Hearing about it made me want to be there. The fact that we may be able to control that experience and do it a little bit more reliably than just waiting for happenstance, that some night it’s just going to happen to you, to me is where the magic is.”

This study did not receive direct external funding. Support for this work was provided from institutional and/or departmental sources. The authors declared having no competing interests.