A group of British researchers believe they have found a certain brain activity that marks the point when patients go under when anesthetized. This newfound information may help spare patients the experience of becoming aware of their own surgery. According to co-author Katie Warnaby, a research fellow at the University of Oxford in the United Kingdom, this may change the way anesthetics are administered globally.
Although doctors believe that this so-called “accidental awareness” is rare, one survey of anesthesiologists suggests that one in 15,000 patients experience it. However, another estimate suggests that 20,000 to 40,000 patients in the U.S. become aware of their surgery while under anesthesia yearly.
According to Dr. Russell McAllister, an associate professor of anesthesiology at Texas A&M Health Science Center College of Medicine, one needs to understand different levels of awareness. “For a patient under light or deep sedation, it would not be uncommon to experience recall of certain events during the procedure. For a patient under general anesthesia, it is not a common event.” However, accidental awareness can be a horrific event for patients who might experience intense pain of surgery. Apparently, some patients report lasting emotional scars and some exhibit symptoms of post-traumatic stress disorder.
Sixteen patients who were given propofol (anesthetic drug) were administered EEG tests and functional MRI scans to determine brain activity. Warnaby notes, “We were trying to pinpoint the changes that occur in the brain that lead to anesthetic-induced loss of consciousness.” They focused on a particular range of brain waves known as slow waves. They discovered that these slow waves reached a maximum before the anesthetic dose had finished rising. Additionally, the slow waves began increasing when the patient became unresponsive and reached a maximum later in time. These findings suggest that EGG readings could be used to monitor whether a patient is in deep sleep.
According to Warnaby, “There isn’t much evidence that the current method is that much better than traditional monitoring at reducing awareness during surgery.” Nevertheless, she believes a system could be developed to better monitor a patients state that is comparable in cost to methods currently in use. This may also prevent lawsuits after a patient has become aware of their surgery.
The current study has a drawback in that it looks at one kind of anesthesia. More often, combinations of drugs are used. McAllister notes, “the best monitor for preventing awareness under anesthesia is an experienced and vigilant anesthesia provider. Additional monitors can provide useful information that can guide an anesthetic. However, the research regarding reliability of these monitors thus far have not indicated that they should be a standard of care”.
The researchers will have to continue with their studies to see how patients are effected when other drugs are used during surgery such as painkillers. For more information, the study is available in Science Translational Medicine (Oct. 23 issue, 2013).