How do they know you’re not awake?
AWARENESS DURING SURGERY
In cool, clinical language it’s known as “unintended intraoperative awareness with recall” — waking during surgery, unable to speak or move.
It’s estimated as many as one or two in every 1,000 people who receive general anesthesia experience it. People have described waking with their eyes taped shut and hearing surgeons say, “cut deeper,” or hands moving instruments inside their bodies and trying desperately to signal — with a shrug, a twitch — that they’re conscious.
Now, researchers are trying to reduce the rare but real nightmare phenomenon by applying what they’re learning from another group of patients who appear to lack consciousness but who are aware: people misdiagnosed as being in a vegetative state.
The goal, they say, is to minimize the harm to people of surgical awareness and find better ways to detect conscious thought in people believed to be entirely oblivious. No monitor exists now that can rule awareness out in 100 per cent of cases.
Some 20,000 to 40,000 people experience accidental awareness a year in the U.S. alone, the research team, which includes renowned Western University neuroscientist Adrian Owen, wrote in a recent issue of the journal Anesthesia & Analgesia. Sometimes the anesthetist simply gives too little anesthesia by error. Some patients are more resistant to the drugs and don’t respond in normal ways.
When it happens, people report hearing voices or the sound of equipment, feeling breathing tubes down their throat and, sometimes, searing pain. Many experience vivid flashbacks, nightmares and post-traumatic stress, and avoid anything that reminds them of the trauma, even lying flat.
In May, a Toronto woman who woke during surgery because of an anesthetist’s negligence and felt surgeons “ripping me apart” won Canada’s first malpractice ruling involving accidental awareness.
Frozen by paralytic drugs, “the patient had no way of indicating something was wrong,” the judge found.
It’s a similar scenario for the 13,000 to 53,000 people in the U.S. in a vegetative state — people that show no signs of awareness and are “behaviourally nonresponsive.”
Owen and his lab have for years been using brain scans to communicate with people considered all but dead. In 2011, they reported as many as 19 per cent of vegetative patients show signs of “covert” consciousness when their brain waves are measured using a cheap, portable bedside EEG. Of 16 vegetative patients in the study, three repeatedly showed appropriate brain activity responses when asked to imagine moving their right hand and wiggling their toes.
More recently, Western neuroscientists led by Lorina Naci, now a professor of psychology at Trinity College Dublin, used a short Alfred Hitchcock movie — Bang! You’re Dead! — to detect consciousness in a man who had been in a vegetative state for 16 years. While inside a special MRI scanner, the 34-year-old showed similar patterns of brain activity — with peaks and dips at identical points of the movie — as healthy volunteers shown the same eight-minute clip.
Naci and colleague Mackenzie Graham are now exploring how to adapt these techniques to detect when surgery patients have “awakened.”
Traditionally, in addition to checking for increased blood pressure, pulse and other vital signs, anesthesiologists look to see if a patient is sweating or tearing. But people can have none of those changes and still be aware.
More recently, monitors such as a device known as BIS, or bispectral index monitor, have been developed to measure brain activity to determine how deeply a patient is anesthetized. The monitor translates the information into a single number, from 100 (wide-awake) to zero (no brain electrical activity). Anesthesiologists aim for somewhere between 40 and 60.
However, two major studies have found cases of patients who reported awareness even though the bispectral readings said they were in the “safe ranges” and unconscious.
Naci said the monitors aren’t based on the latest understanding of neurobiological markers of conscious awareness gleaned from studies on vegetative state patients.
What’s needed, she believes, is a better way to detect higher order thoughts.
Anesthetized patients can’t watch movies. So, Naci is testing using audio stories — a five-minute segment from the beginning scenes of the 2008 thriller Taken.
In a paper under review, Naci tested the audio-only story on vegetative patients, looking at how different brain networks are engaged by the story, especially in regions linked to higher level thought and information processing.
The goal is to find a common neural code or “signature” to detect awareness.
“What we’re looking for is the natural engagement that happens in the brain when we’re listening to a complex and intriguing narrative,” Naci said.
Theoretically, surgery patients would be given an EEG hair net and a set of headphones.
“We would say, ‘we’re going to play this engaging story for you and all that we want you to do is to attend to the story as best you can,’ and that elicits a certain pattern of activation in their brain,” said Graham, a postdoctoral researcher at Western’s Brain and Mind Institute.
“Once they become unconscious, the pattern would be extinguished. Should they regain consciousness and start paying attention to the story, we’re going to see this pattern of activation in the brain, which is only possible if they’re conscious.”
THE PATIENT HAD NO WAY OF INDICATING SOMETHING WAS WRONG.