Nav: Home

UW study: Incidence of consciousness during surgery lower than previous estimates

December 15, 2016

MADISON, Wis. - An international study of 260 surgical patients found that, contrary to many previous studies, just more than four percent were conscious of the external world while under general anesthesia but before the start of surgery.

None of the patients who responded, however, remembered it afterward. The researchers also noted that there are no known long-term problems associated with the brief period of awareness captured in this study, and stressed this should not dissuade patients from having surgery that they need to improve their health.

Fortunately, this number is far lower than the approximately 37 percent who were identified in earlier studies, using a similar measurement technique, as reporting awareness of a stimulus while under general anesthesia.

The new research, led by Dr. Robert Sanders of the University of Wisconsin School of Medicine and Public Health, was published this week in the Online First edition of Anesthesiology, the peer-reviewed medical journal of the American Society of Anesthesiologists. The study was conducted at six sites around the world (Madison, Wis.; Ann Arbor, Mich.; Hamilton, New Zealand; Aachen, Germany; Liege, Belgium; and Groningen, The Netherlands.).

The researchers wanted to find out how often patients were responsive following intubation in routine practice.

To gauge awareness, the research teams used the "isolated forearm technique," in which patients are given a verbal command to move the hand of a tourniquet-isolated arm. This technique gives real-time information about whether the patient was conscious; it does not rely on memory. However, the researchers said their estimate of 4.6 percent could be considered conservative because some patients who are conscious may still fail to respond to the command even though they hear it.

"This was the first multi-institution collaboration investigating the use of the isolated forearm technique," said Sanders, assistant professor of anesthesiology at UW-Madison. "One key feature is that the anesthetic technique was left to the anesthesiologist's discretion. We wanted to look at consciousness in routine clinical practice."

In general, responders were younger than non-responders and they were more lightly anesthetized. The age range for the entire group was 18 to 88 years old.

"Although we view such consciousness during surgery as an important issue, we urge caution in the interpretation of these results," said Sanders. "We looked at a very brief 'snapshot' of the time patients spend under anesthesia. In addition, these patients likely had very different experiences from those who report being awake but unable to move or speak during surgery."

Sanders added: "Patients expect to be unaware of surgery or any external stimuli during general anesthesia, and we're keen to establish anesthetic techniques that ensure we meet that expectation."

The findings suggest that a single IV injection of anesthetic to drift patients to sleep may not always be effective in preventing patients from regaining consciousness following intubation. Sanders said in future research his team will look in greater detail at the variables that might result in patients becoming conscious and ways we can prevent this from happening.

University of Wisconsin-Madison

Related Anesthesia Articles:

Does general anesthesia increase dementia risk?
There are concerns that exposure to general anesthesia during surgery may contribute to an increased risk of Alzheimer's disease.
Cannabis use prompts need for more anesthesia during surgery, increases pain
Not only might cannabis users require more anesthesia during surgery than non-users, they may have increased pain afterwards and use higher doses of opioids while in the hospital, suggests first-of-its kind research being presented at the ANESTHESIOLOGY® 2020 annual meeting.
COVID-19 testing of children before anesthesia saves PPE
Universal COVID-19 testing of children who are having procedures requiring anesthesia promotes efficient use of personal protective equipment (PPE), according to research being presented at the ANESTHESIOLOGY® 2020 annual meeting.
How do we disconnect from the environment during sleep and under anesthesia?
A series of new studies by researchers at Tel Aviv University's Sackler Faculty of Medicine and Sagol School of Neuroscience finds, among other important discoveries, that noradrenaline, a neurotransmitter secreted in response to stress, lies at the heart of our ability to ''shut off'' our sensory responses and sleep soundly.
Scientists unveil how general anesthesia works
The discovery of general anesthetics -- compounds which induce unconsciousness, prevent control of movement and block pain -- helped transform dangerous operations into safe surgery.
Surgery with anesthesia not linked to indicator of Alzheimer's, Mayo study finds
Older adults who have surgery with general anesthesia may experience a modest acceleration of cognitive decline, even years later.
Choice of anesthesia may affect breast cancer metastases
A new study led by Stony Brook University Cancer Center researchers to be published in Nature Communications suggests that the choice of anesthesia may change the metastatic process of breast cancer by affecting the cytokine and microenvironment.
Is headache from anesthesia after childbirth associated with risk of bleeding around brain?
This study examined whether postpartum women with headache from anesthesia after neuraxial anesthesia (such as epidural) during childbirth had increased risk of being diagnosed with bleeding around the brain (intracranial subdural hematoma).
Music can be a viable alternative to medications in reducing anxiety before anesthesia
Music is a viable alternative to sedative medications in reducing patient anxiety prior to a peripheral nerve block procedure, according to a new Penn Medicine study.
In cases when patients under anesthesia experience anaphylaxis, hyperactive immune...
A study of 86 patients reveals how drugs used for anesthesia can induce life-threatening anaphylaxis (a dangerous type of allergic reaction) through an alternative immune pathway.
More Anesthesia News and Anesthesia Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: The Power Of Spaces
How do spaces shape the human experience? In what ways do our rooms, homes, and buildings give us meaning and purpose? This hour, TED speakers explore the power of the spaces we make and inhabit. Guests include architect Michael Murphy, musician David Byrne, artist Es Devlin, and architect Siamak Hariri.
Now Playing: Science for the People

#576 Science Communication in Creative Places
When you think of science communication, you might think of TED talks or museum talks or video talks, or... people giving lectures. It's a lot of people talking. But there's more to sci comm than that. This week host Bethany Brookshire talks to three people who have looked at science communication in places you might not expect it. We'll speak with Mauna Dasari, a graduate student at Notre Dame, about making mammals into a March Madness match. We'll talk with Sarah Garner, director of the Pathologists Assistant Program at Tulane University School of Medicine, who takes pathology instruction out of...
Now Playing: Radiolab

What If?
There's plenty of speculation about what Donald Trump might do in the wake of the election. Would he dispute the results if he loses? Would he simply refuse to leave office, or even try to use the military to maintain control? Last summer, Rosa Brooks got together a team of experts and political operatives from both sides of the aisle to ask a slightly different question. Rather than arguing about whether he'd do those things, they dug into what exactly would happen if he did. Part war game part choose your own adventure, Rosa's Transition Integrity Project doesn't give us any predictions, and it isn't a referendum on Trump. Instead, it's a deeply illuminating stress test on our laws, our institutions, and on the commitment to democracy written into the constitution. This episode was reported by Bethel Habte, with help from Tracie Hunte, and produced by Bethel Habte. Jeremy Bloom provided original music. Support Radiolab by becoming a member today at     You can read The Transition Integrity Project's report here.