In this study, a western researcher showing who have already established consciousness in individuals believed to be in an unresponsive vegetative state are now approaching anaesthetized patients with similar inferences, hoping to find ways to better detect surgical consciousness and minimize the harm of this nightmare, when it does occur.
Mackenzie Graham looking at possible methods of detecting consciousness in anaesthetized patients and ways to mitigate trauma and harm when they do wake during a surgical procedure, unable to communicate their consciousness to medical staff. "With vegetative patients, the way we determine they are vegetative is with behavioural tests at the bedside.
We see if they respond to stimuli. If they don't, they get a diagnosis as vegetative. A long-time unresponsive participant's brain response during the same movie strongly resembled that of the healthy participants, suggesting not only was he consciously aware, but also, he understood the movie.
But these methods cannot be used to test consciousness in anaesthetized patients. These patients cannot demonstrate consciousness to medical staff and, when that awareness occurs in the middle of a surgical procedure, it can be a nightmare. The parallel between vegetative patients and anaesthetized patients spurred his and Naci's recent work, Graham explained.
"There's a connection between anaesthetised patients and vegetative patients, namely that both are behaviourally unresponsive and appear to be unconscious, but in both cases, they may not be," he said. "Anaesthesia patients don't move; we presume they are unconscious, but as many as 1-in-1,000, or more, are actually aware when they are receiving anaesthesia," he added.
Graham and Naci set out to explore methods that could detect consciousness in those undergoing surgery with a general anaesthetic, hoping also to extrapolate some lessons they learned from vegetative patients about minimizing harm, only in an anaesthesia context, Graham explained.
There are monitors that measure brain activity of anaesthetized patients, much like an fMRI is used to measure the brain activity of a vegetative patient. These monitors translate how deeply a patient is anaesthetized into a single number, ranging from 100 (wide awake) to 0 (no brain activity whatsoever). The "sweet spot" for anaesthesia is between 40-60, Graham said.
"Managing anxiety levels in patients while this is happening can help reduce the harm – while it's happening and long term. Because we've learned that patient communication is important in the vegetative context, even though they don't look aware or they're not responding, communicating with them could be very beneficial. The same thing is true in the anaesthesia context. We're just applying what we've already learned to a different population."
In further study, the goal is to find a common neural code is a signature, that signals awareness. If this works, surgery patients could wear an EEG hairnet and headphones, and a monitor could indicate the presence of higher level thought or information processing when awareness is present under anaesthesia.