00:01
Let's try a question. Mitch don't twitch.
Mitch is a patient who was given a muscle relaxant.
00:07
During administration, the patient had a slight drop in
blood pressure and a slight increase in heart rate.
00:13
The patient did not have any twitching during induction.
00:16
Question. Which of the agents was likely
used as a muscle relaxant?
Would it be succinylcholine? Would it be pancuronium?
Would it be tubocurarine? Would it be baclofen?
Or would it be dantrolene?
The best answer here is pancuronium.
00:35
Technically, you could say C, D and E are okay as well.
Let's take a look at the explanation.
00:41
So, succinylcholine is a depolarizing agent. The patient
will often twitch during that first phase of injection.
00:49
Once the first phase is finished, they don't twitch anymore.
They are not reversed by acetylcholinesterase inhibitors.
00:56
Tubocurarine is an old drug. It was used back in the 1900.
It's not really used much anymore.
01:02
It has a similar action to pancuronium though.
Baclofen is a great drug but it's an antispasmodic.
01:10
It has an action at the spinal cord. Now dantrolene,
once again, used in malignant hyperthermia,
it is not commonly used outside of that use.
01:20
Now, remember pancuronium can block muscurinic cholinergic
receptors in the heart, causing tachycardia.
01:27
And it may drop the blood pressure initially.
But really, these are minimal effects.
01:32
I've used pancuronium many times and I've never
had worrisome drops in my experience,
and I've never had worrisome in rise in heart rate.
There is small changes but they are not big.
01:43
So, the answer here is going to be pancuronium.
01:48
Let's go on to a different question. Mitch won't twitch now.
So, Mitch is a patient who was given a muscle relaxant.
01:55
During administration, the patient had a slight drop in
blood pressure and a slight increase in heart rate.
02:00
After surgery, he was given glycopyrrolate which is
an atropine-like compound, and pyridostigmine.
02:08
Which of these agents could be potentiated by the
pyridostigmine during the first phase of blockade?
Is it succinylcholine? Is it pancuronium?
Is it tubocurarine? Is it baclofen? Or is it dantrolene?
Good. So, this is not the kind of question that you'll get
on a exam. But I'm putting this question to you now
so that when you do questions like this on the exam,
it will be much easier.
02:38
I made this question harder. And let's go through the
answers so that you really understand the signs.
02:44
Succinylcholine is a depolarizing agent. These patients
often twitch during the first phase of injection.
02:52
They are not reversed by acetylcholinesterase inhibitors
during the first phase of blockade.
02:58
Now, during phase 1, pyridostigmine may actually increase
blockade because succinylcholine is depolarizing the muscle
alongside the increased acetylcholine in the cleft.
So in other words, they may have more twitching because
there's more depolarization because
there's more acetylcholine.
03:20
Now, one more piece of information I want to give you is
that acetylcholinesterase does not hydrolyze succinylcholine.
03:27
So, when succinylcholine is getting broken down, it's getting
broken down outside of the acetylcholinesterase pathway.
03:33
And therefore, that's why these agents don't
increase succinylcholine clearance.
03:42
Next question, which of the following drugs
can cause hyperkalemia and cardiac arrest
in patients with a spinal cord injury? Succinylcholine,
pancuronium, tubocurarine, baclofen or dantrolene?
Right, succinylcholine. Succinylcholine is a depolarizing
agent. Muscle contraction may result in potassium leakage
from muscle to serum. Patients with spinal cord injury have
no resting tone. And depolarizing these muscles will therefore
be more disruptive to the muscles,
and you may see more potassium being released.
04:24
Spinal cord injury patients also tend to have more potassium
release through another unknown mechanism on top of
what I just described.
04:36
Let's take a look at a patient who has epilepsy and burns.
A 15-year-old female with a history of epilepsy
was burned during a house fire.
She is being prepped for surgery.
04:47
Which of the following medications could be used
as a muscle relaxant while reducing seizure threshold?
Would it be A, diazepam? B, baclofen? C, rucoronium?
D, tubocurarine? Or E, succinylcholine?
Here's the answer, diazepam is a benzodiazepine,
and once again, it acts through the GABA A receptor
to cause less membrane depolarization in the brain,
the midbrain, and in the spinal cord.
05:21
What this does is it results in increased
seizure threshold and fewer seizures.
05:27
So, this is a great drug to use in this case.
The other agents that you probably have seen are
more for muscle relaxants, it's not really relevant here,
so this is why diazepam was the answer.
05:40
Alright, there you have it.
I'm sure that you'll do very well on your exams,
just keep in mind that succinylcholine isn't the only
depolarizing agent, and it is not reversed
by the acetylcholinesterase. And the other issue
that I want to make sure that you remember is
malignant hyperthermia, dantrolene, less than 1 minute.
Good luck.