Patients awakening during surgery focus of study
In cool, clinical language it’s known as “unintended intraoperative awareness with recall” — waking during surgery, unable to speak or move.
It’s estimated that as many as one or two in every 1,000 people who receive general anesthesia experiences 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 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, in fact, 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.
Some 20,000 to 40,000 people experience accidental awareness a year in the United States alone, the research team, which includes renowned Western University neuroscientist Adrian Owen, writes 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. 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.
Owen and his lab have for years been using brain scans to communicate with people considered all but dead. In 2011, they reported that 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.
More recently, Western neuroscientists used a short Alfred Hitchcock movie to detect consciousness in a man who had been in a vegetative state for 16 years. While inside a special MRI scanner, the 34-yearold 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.
Lori Naci and colleague Mackenzie Graham are now exploring how to adapt these new 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. 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 has tested the audio-only story on vegetative patients, looking at how different brain networks are engaged by the story.