Questions – Skeletal Muscle Relaxants

00:01 Let's move on to do some questions on these drugs.

00:04 Case study number one, Mitch is a patient who was given a muscle relaxant.

00:10 During the administration of this relaxant, the patient had a slight drop in blood pressure and a slight increase in heart rate.

00:17 The patient did not have any twitching during induction.

00:21 Which of the following agents was likely used as a muscle relaxant? Was it A succinylcholine; B pancuronium; is it C tubocurarine; D baclofen or E dantrolene? Good you chose Pancuronium.

00:42 Now let's take a look at this answer.

00:44 Succinylcholine is a depolarizing agent.

00:47 Patients will often twitch during the first phases of injection.

00:51 These agents are not reversed by acetylcholinesterase inhibitors.

00:56 Tubocurarine is a very old drug.

00:58 It was used way back in the 20th century, in the beginning of the 20th century.

01:02 It has a similar action, though to pancuronium.

01:05 Baclofen is an antispasmodic agent with an action right at the spinal cord, so this probably isn't a good choice.

01:12 And finally, dantrolene acts directly on the muscle to prevent calcium release.

01:17 It is not commonly used outside the management of malignant hyperthermia.

01:22 Now talking about pancuronium, it can block muscarinic cholinergic receptors in the heart, which can cause tachycardia.

01:31 It will often drop the blood pressures initially.

01:34 The answer here is pancuronium.

01:39 Let's move on to another question.

01:41 So we're going to stick with Mitch, but we're going to just change the parameters of his treatment a little bit.

01:45 Mitch is a patient who was given a muscle relaxant.

01:48 During administration, the patient had a slight drop in blood pressure and a slight increase in the heart rate.

01:55 After surgery, he was given glycopyrrolate, which is an atropine-like compound, and pyridostigmine. Now, which of these agents could be potentiated by the pyridostigmine if given during the first phase of blockade? Is it A succinylcholine? Is it B pancuronium? Is it C tubocurarine? Is it D baclofen? Or is it E dantrolene? Okay. This time the answer is Succinylcholine.

02:30 Now Succinylcholine again.

02:32 I'll say this over and over again.

02:34 Succinylcholine is a depolarizing agent.

02:37 They will often twitch during the first phase of injection.

02:40 These agents are not reversed by acetylcholinesterase inhibitors during the first phase of blockade.

02:47 During phase one, pyridostigmine may actually increase the blockade.

02:52 That's because the succinylcholine is depolarizing the muscle alongside the increased acetylcholine remaining in the cleft.

03:00 Remember that acetylcholinesterase does not hydrolyze succinylcholine.

03:07 Now, it's important with that last question to recognize something.

03:11 Notice that the name of the patient is the same and the answers are the same.

03:15 But the answer, the choices of answers are the same.

03:19 But the answer itself was different.

03:21 This is a this is a strategy that exam makers will will use in year to year changes to the questions. So one year for example, the answer is pancuronium.

03:33 The next year the answer is Succinylcholine.

03:35 So if patients sorry, if students are just memorizing question answers, they will get the question wrong. So you do have to know what you're talking about when you're looking at them, even when you're looking at old exam questions.

03:47 Okay, let's move on to a different question.

03:50 Which of the following drugs can cause hyperkalemia and cardiac arrest in patients with spinal cord injury? A. Succinylcholine.

04:01 B. Pancuronium.

04:03 C. Tubocurarine.

04:05 D. Baclofen and E.

04:09 Dantrolene. Interesting.

04:14 The question again comes out with Succinylcholine.

04:17 Again, I'm going to say it succinylcholine is a depolarizing agent.

04:21 Muscle contraction may result in elevated potassium and elevated leakage of potassium from the muscle into the serum.

04:29 Patients who have acute or chronic spinal cord injury have no real resting tone, so depolarizing these muscles will therefore be more disruptive to the muscle, and more potassium is going to be released.

04:43 Spinal cord injury patients also have a tendency towards having more potassium rates released from their muscles through an unknown mechanism.

04:54 Let's move on to a different question.

04:56 A 15 year old woman with a history of epilepsy was burned during a house fire.

05:02 She's now being prepped for surgery.

05:05 Which of the following medications could could be used as a muscle relaxant, while at the same time increasing the seizure threshold? A diazepam.

05:17 Be baclofen c rocuronium, d tubocurarine and e succinylcholine.

05:29 Here's the answer.

05:30 Diazepam is a benzodiazepine, and once again it acts through the Gaba, a receptor, to enhance the inhibitory effects of Gaba in the brain, midbrain, and spinal cord.

05:42 It does this by facilitating the hyperpolarization of neuronal membranes, which leads to decreased membrane depolarization and increased inhibition of neuronal activity.

05:51 This results in increasing the seizure threshold, so the likelihood of seizures is reduced. So it's a great choice in this particular patient.

06:01 Okay. That's great.

06:02 You did some questions, you learned a little bit.

06:05 I hope this really helped.

06:07 Go write your exams and show them what you know.