How anaesthesia works

Its a very important piece of modern medicine. If you think about what occurs when we do surgery,its a very traumatic insult to the body. Youre cutting people open,removing organs or possibly even transplanting them. The anaesthesiologist puts people into a condition where they can tolerate such extreme assaults.

Is anaesthesia like a coma?

Its a reversible drug-induced coma,to simplify. As with a coma thats the result of a brain injury,the patient is unconscious,insensitive to pain,cannot move or remember. However,with anaesthesia,once the drugs wear off,the coma wears off.

Anaesthesia was first demonstrated right here at Massachusetts General Hospital in 1846. Does that historical fact drive your research?

Theres quite a story to how that first public demonstration happened. Apparently,there was a social practice in that era called ether follies. People got together and they sniffed ether. At one of these,someone fell and cut himself,but felt no pain. And the story got out,which led a Boston dentist to start experimenting with ether for painless oral surgery. He brought the idea to the great surgeon John Collins Warren,and together they used it in an operation here to remove a neck tumour. Gentlemen,this is no humbug, Dr Warren declared after the successful procedure,meaning that this was the real thing and that it was going to change medicine. Before that,surgery was mostly butchery. The most successful surgeon was the one who could lop off a limb quickest. To this day,most inhaled anaesthetics are ether. Theyve been embellished a bit,but they are basically ether.

Is it true that we dont really know how anaesthesia works?

Its viewed as a mystery,and thats wrong. Its not a black box. Theres a lot that is actually known,and more is developing as neuroscience moves forward. Weve certainly known how to make anaesthesia safe. We watch the patient while he or she is under. We know whats normal in terms of heart rate,blood pressure,temperature,gases,etc. If things start to deviate from that,we intervene. Weve gotten very far by creating high standards for care while under anaesthesia.

In your research,youve been trying to figure out how anaesthesia actually works. How do you go about doing that?

Since 2004,weve been taking volunteers and giving them anaesthesia,though not in the midst of actual surgeries. As our subjects go under,we image their brains in functional MRI scanners and measure brain activities with EEG monitors. Before this technology was available,researchers had only looked at what happened to patients before and after anaesthesia. But with todays functional MRI,we can watch people lose consciousnesssee how the various parts of the brain change in activity. We can watch the transitions,what parts of the brain are turned on and off.

Were there ethical problems in designing a study where you rendered your subjects unconscious?

The way we overcame potential objections was by recruiting a unique set of study subjects. They were patients whod already had tracheostomiessurgical holes in their throat. We could place a tube into the hole and connect it to a breathing circuit. If anyone got into trouble while in the scanner,wed immediately be able to help them breathe.

Was there resistance to your doing the study?

Theres a large body of people in my field who feel that very little more progress needs to made because the process works well enough. My answer is that we could improve anaesthesia tremendously if we knew more neuroscience. This is a golden moment in neuroscience,and anaesthesiologistswho,after all,work with the brain every dayought to be part of it. Instead,people ignore whats happening over there and go,Its never been solved,people have been working on this since 1846,its fine as is,why bother? Theres a strange compliancy.

What has your research shown so far?

Under general anaesthesia,the brain is not entirely shut down. Certain parts are turned off; others are quite activenot only active, but there is a level of activity that is quite regular. Our observation is that it is this regular activity that prevents the brain from transmitting information and contributes to a state of unconsciousness. Its analogous to stopping communication down a phone line when transmission is blocked. You could block transmission another way: by sending a loud signal down the line so that that signal was the only thing you hear. So in some parts what we see is that activity is turned off,leading to unconsciousness. In other parts,we see activity that is more active than normal. This also leads to unconsciousness. In sum: the drugs alter the way the brain transmits information.CLAUDIA DREIFUS