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Dr. Bob is Robert Hsiung, MD,
bob@dr-bob.orgShown: posts 1 to 5 of 5. This is the beginning of the thread.
Posted by Chris A. on March 17, 2000, at 15:19:35
Dear Cam,
What would be the objection of the anesthetist to using curare instead of succhinicholine for ECT? Would it be cost, unfamiliarity, protocol for procedure, side effects? I have just started Aricept and my pDoc is having me stop it 48 hours prior to my next treatment. It would be nice to have the donzepil fully on board for neuroprotection. My expert consultant had suggested using curare. My pDoc and I are both a bit shy, so sometimes we don't fully discuss what we should.
Thanks.Chris A.
Posted by Cam W. on March 17, 2000, at 20:10:49
In reply to Cam - Anesthestia for Ect, posted by Chris A. on March 17, 2000, at 15:19:35
Chris - Most docs stop drugs before ECT because many of them interfere with the induction of the seizures. The anesthesiologist may not want to use curare as it is a finicky drug to dose. This area of medicine is not my specialty and I am just guessing on this point. Ask your docs why they do not want to use curare, I'm sure if you are persistent they will give you the real answer. Sometimes it is best to allow a doc to use the drugs that he is familiar with. This way any complications can be dealt with without any delay. Hope this helps a little. - Cam W.
Posted by Chris A. on March 18, 2000, at 13:17:57
In reply to Re: Cam - Anesthestia for Ect, posted by Cam W. on March 17, 2000, at 20:10:49
Thanks!
If curare is finicky to use that is reason enough for me. We do this at six a.m. on Monday mornings which is not a nice hour to ask someone to try new tricks. I did remember not to take the Aricept today...
Thanks again,
Chris A.
Posted by Scott L. Schofield on March 18, 2000, at 13:55:01
In reply to Cam - Anesthestia for Ect, posted by Chris A. on March 17, 2000, at 15:19:35
> I have just started Aricept and my pDoc is having me stop it 48 hours prior to my next treatment. It would be nice to have the donzepil fully on board for neuroprotection. My expert consultant had suggested using curare. My pDoc and I are both a bit shy, so sometimes we don't fully discuss what we should.
Why did he suggest curare? Why not atropine?
The role of these drugs in ECT is not to produce anesthesia, but to temporarily paralyze the muscles so that they don't contract violently during the convulsive phase of post-shock brain activity. You could actually break bones if you don't.
My guess is that having Aricept (donzepil) in the body would exaggerate unpredictably the muscle-relaxant properties of succinylcholine. Muscles are controlled by nerves that use the chemical known as acetylcholine as a neurotransmitter. Succinylcholine is essentially fake acetylcholine, and is an agonist specific to the nicotinic receptor subtype found on motorneurons. Succinylcholine is therefore pro-cholinergic. It accomplishes its muscle-relaxant effect by overstimulating acetylcholine receptors and producing a state of constant depolarization of the nerves that control muscle contraction. These cholinergic nerves become temporarily "fried" and no longer send messages to the muscles to contract.
Donzepil, an acetylcholine cholinesterase inhibitor, is also pro-cholinergic. It tends to enhance cholinergic neurotransmission by preventing the break-down of acetylcholine, thus allowing levels to rise. This is similar to how an MAO-inhibitor works with the monoamines. Increasing the amounts of real acetylcholine plus adding fake acetylcholine (succinylcholine) may be dangerous, or at least have unpredictable effects.
Curare produces muscle relaxation by antagonizing, or blocking the nicotinic acetylcholine receptors. This produces a condition where the nerves remain understimulated and thus do not send messages to the muscle. Curare is anti-cholinergic. Because it binds more strongly to the receptors than does acetylcholine, it doesn't matter that the levels of acetylcholine are increased by donzepil.
I am really not sure why atropine is not being considered. It is used routinely in ECT. Your expert is probably very smart, though. He may be trying to prevent atropine-induced anticholinergic interference with the positive actions of donzepil in the brain. Atropine is an antagonist of the muscarinic subtype of acetylcholine receptor, as opposed to the nicotinic subtype that is affected by curare. Muscarinic receptors in the brain are critical to memory and cognitive function. This is why antidepressants with strong anticholinergic properties can impair these functions. The pro-cholinergic activity of donzepil tends to enhance memory and cognition. Perhaps donzepil would lose its neuroprotective effects (if it has any) if these receptors were blocked.
Sorry. I threw in too much crap. I hope what I wrote isn't too confusing.
Bottom line:1. Succinylcholine + donzepil = too strong.
2. Atropine (and similar drugs) = cancels out positive effects of donzepil
3. Curare = avoids 1 and 2.
4. Atropine serves the purpose.
4. I don't know enough about curare.
- Scott
I should probably get a life.
Posted by Chris A. on March 18, 2000, at 15:55:56
In reply to Anesthesia for ECT / Muscle Relaxants / Curare, posted by Scott L. Schofield on March 18, 2000, at 13:55:01
Scott,
Thanks - I appreciate the discussion. It encourages my brain cells to wake up. Donzepil does greatly inhibit the metaboloism of succinylcholine. Dr. Steven Dubovsky gave my local docs the suggestion of 1)using curare as the muscle relaxant or 2), discontinuing the Aricept long enough prior to the next ECT treatment to allow the plasma pseudocholinesterase activity to go back to normal. I did hear one of the anesthetists say they would have to "look it up," referring to using the curare in this situation, which makes me think it's not within their comfort zone. Perhaps they're looking for more of a muscle relaxant effect than atropine affords - I am extremely fine-boned and the density is not up to par. If my pDoc remembers that he has a good memory.I am feeling rather lame-brained right now and definitely didn't attend closely enough to biosynthesis and metabolism in school. We didn't have enough pharmacology. I won't tell you how long it's been since I worked at a paying job in nursing, either! I'll rehash this again at 6:00 a.m. Monday with my docs - great hour, great place (the recovery room).
Thanks,
Chris A.
This is the end of the thread.
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