Slashdot Mirror
Scientists Change Our Understanding of How Anaesthesia Messes With the Brain (sciencealert.com)
schwit1 shares a report from ScienceAlert: It's crazy to think that we still don't quite understand the mechanism behind one of the most common medical interventions -- general anaesthetic. But researchers in Australia just got a step closer by discovering that one of the most commonly used anesthetic drugs doesn't just put us to sleep; it also disrupts communication between brain cells. The team investigated the drug propofol, a super-popular option for surgeries worldwide. A potent sedative, the drug is thought to put us to sleep through its effect on the GABA neurotransmitter system, the main regulator of our sleep-and-wake cycles in the brain. But anyone who's been "put under" will know that waking up from a general anesthetic feels rather different from your usual morning grogginess. On top of that, some people can experience serious side-effects, so scientists have been trying to figure out what else the drugs might be doing in the brain.
Using live neuron cell samples from rats and fruit flies, the researchers were able to track neurotransmitter activity thanks to a super-resolution microscope, and discovered that propofol messes with a key protein that nerve cells use to communicate with each other. This protein, called syntaxin1A, isn't just found in animal models - people have it, too. And it looks like the anesthetic drug puts the brakes on this protein, making otherwise normal brain cell connections sluggish, at least for a while. The researchers think this disruption could be key to how propofol allows for pain-free surgery to take place - first it knocks us out as a normal sleeping pill would, and then takes things up a notch by disrupting brain connectivity. The research has been published in Cell Reports.
Using live neuron cell samples from rats and fruit flies, the researchers were able to track neurotransmitter activity thanks to a super-resolution microscope, and discovered that propofol messes with a key protein that nerve cells use to communicate with each other. This protein, called syntaxin1A, isn't just found in animal models - people have it, too. And it looks like the anesthetic drug puts the brakes on this protein, making otherwise normal brain cell connections sluggish, at least for a while. The researchers think this disruption could be key to how propofol allows for pain-free surgery to take place - first it knocks us out as a normal sleeping pill would, and then takes things up a notch by disrupting brain connectivity. The research has been published in Cell Reports.
I friend of mine just had a colonoscopy and was laying on his side looking at a pattern on the wall just before being given propofol. He woke up looking at the same pattern and the Doc said everything was normal. He accused the Doc of haven't done anything and was conducting some fraud because he hadn't any sense any lapse in time. Propofol is like that.
Propofol also has a very short duration of action. The "fog of general anesthesia" is much more likely to be caused by the benzodiazepine sedatives that most will get prior to actual induction of anesthesia. Those benzos - classically, Valium (diazepam); today, usually Versed (midazolam) - are in the same class as Rohypnol (flunitrazepam, but famous as "roofies"). They're very good for treating acute anxiety, but they're also addictive, and seriously interfere with memory formation.
I'm an anesthesiologist, and unless someone is really climbing the walls with anxiety (not, actually, all that common), I don't give benzos. I give a solid dose of long-acting opioids right up front, and that's it. The only time I've ever had Versed, I got an eight-hour gap in my memory. Don't remember a thing. Rather obvious why it became popular as a "date-rape drug".
We do use propofol for colonoscopies, and it's a great drug for that, but most general anesthetics are conducted with gas anesthetics - they are cheaper and they are very easily monitored (we can easily see how much you're breathing in and out, and thus infer how likely you are to have any awareness). In most cases, propofol is used only to induce anesthesia - to make you unconscious so that you can be intubated. As soon as the breathing tube is in, the gas is turned on, and that's what you're waking up from. The advantage there is that, as with alcohol, people tend to get disinhibited before they lose consciousness. You don't want someone without a secured airway flailing around on the OR table (they might fall off). A slug of propofol takes them from conscious to comatose in a matter of seconds. By the time it wears off, the gas has kicked in.
We generally don't care if you stop breathing - it's sort of our thing to breathe for you. Consciousness requires a great deal more coordination than the simple breathing centers, though. The same reason explains why anesthetics make you lose vision as a sense before you lose hearing - it's a more processing-intensive sense.
As for cardiac rhythms, gas anesthetics are arrhythmogenic, but it's usually not a problem. Spinals - as are given for most cesarean sections - are more likely to produce slow heart rates, as they disable the autonomic nerves as well as the sensory ones. However, we have drugs for that.