Tag Archives: bispectral index

Are you conscious?

Count down from ten…

Have you ever been put under general anaesthetic before surgery? I have, and when the anaesthetist asked me to count down from ten, I got as far as eight before I was out cold. The next thing I knew, I was waking up in the ward, tonsil free, and looking forward to a two-week diet of painkillers and ice cream. Most of us assume that when the drugs knock us out, that’s it; we feel nothing until the effects of the drugs wear off. But is this really the case?

Andrew Morley is an anaesthetist. He regularly sedates patients for minor surgery. For this, he uses a general anaesthetic drug called propofol at a low, or ‘sedative’, dose. Under these circumstances apparently some patients respond to pain while they’re under.

‘Patients do appear to experience pain from time to time during procedures under sedation – I take their response as a prompt and give them painkillers and top up their sedation. Afterwards they very often have no memory of the pain.’

This suggests that we may experience pain during surgery even when under sedation, but not remember it after. If you can’t remember pain, does it matter?

Psychologist Jackie Andrade thinks it does:

‘You may be aware during surgery but not completely remember it. Partial or “implicit” memories of these situations might lead to psychological stress and longer recovery times.’

Questions like this, and the incredibly rare cases where patients remember specific events of awareness during major surgery under general anaesthesia, have prompted researchers to come up with new ways to measure consciousness to ensure we really are out for the count, when it counts.
Meet fEITER, a portable scanner that can project a real-time video of the brain’s activity as it slides into unconsciousness. Once anaesthetists understand exactly what this activity means, this new invention might help them to understand more about their patients’ awareness.

Unfortunately, there are only two of these scanners in the world and the scientists couldn’t spare one for a whole year for Pain Less.

But we have managed to get our object-handling gloves on one of these…

This is called a BIS monitor. I’ll leave it to our expert anaesthetist Andrew to explain:

‘This machine continuously records the electrical activity on the surface of the brain. It then analyses these “brain waves” using a mathematical formula to come up with a number that reflects the likelihood of the patient being conscious. Some anaesthetists use the monitor to adjust the dosage of anaesthetic drugs to keep their patient unconscious. Others are sceptical about how effective machines are at monitoring consciousness.’

I’ll be back soon with more stories of success (or disappointment) from the object quest.