Module 4 Muscle relaxants

Question 1

Where does Ach bind on the post junctional membrane

Answer 1

It binds on the Nicotinic cholinergic receptors

Question 2

What is the enzyme that breaks down the Ach

Answer 2

Acetylcholinesterase

Question 3

What are the 3 compounds that block ACh binding

Answer 3

1. Mg
2. Aminoglycosides
3. Botox

Question 4

What are the 3 locations at which you can block a motor impulse and give an example for each

Answer 4

1. Motor nerve: Local anesthetics
   2.NMJ: IV muscle relaxants
2. Receptors inside the cells: Dantrolene

Question 5

What is the mode of action of a depolarising agents

Answer 5

They act as non competitive inhibitors binding to the nicotinic receptors and so causing depolarisation

Question 6

What is the mechanism of nondepolarizing agents

Answer 6

They bind to the nicotinic receptors but do not activate the receptors and so do not cause depolarisation of the membrane

Question 7

What is the effective dose 95

Answer 7

This is the dose that would cause muscle relaxation in 95% of people

Question 8

What are the 5 factors that make muscle relaxants more potent

Answer 8

1. Inhaled agents and aminoglycosides
2. Low K and Ca
3. Acidosis
4. Cold for depolarising and heat for non depolarising
5. Myasthenia gravis in nondepolarizing

Question 9

What are the surgical indications for muscle relaxants

Answer 9

1. Facilitate surgical access
2. If immobilisation of the field is required

Question 10

What are the anaesthetic factors that indicate muscle relaxants

Answer 10

1. Intubation
2. Controlled ventilation is required
3. Prone

Question 11

What are the patient factors that indicate for muscle relaxants

Answer 11

Critically ill patients

Question 12

What is the structure of sux

Answer 12

2 Ach molecules that are stuck together

Question 13

What is the most short acting muscle relaxant

Answer 13

Sux

Question 14

What is the enzyme that metabolises sux

Answer 14

Pseudocholineesteases

Question 15

What is a complication that can occur from sux and what causes it

Answer 15

Scoline apneoa: This is caused by a lack of the pseudocholinesterase

Question 16

What are some of the complications of sux

Answer 16

1. Histamine release
2. Anaphylaxis
3. Bradycardia
4. Muscle pain
5. Hyperkalemia

Question 17

What are the 2 main classes of non depolarising MR

Answer 17

Benylisoquilines: Curare based [All end in curium]
Aminosterids: [All end in ronuim]

Question 18

What is the dose of nondepolarizing agents based on

Answer 18

Lean body mass

Question 19

How are non depolarising agents metabolised

Answer 19

1. Hoffman degredation
2. Hepatic

Question 20

What patients can get Vecuronium and which cant

Answer 20

Can:
Cardiovascular
Renal
Asthma
Cant:
Liver

Question 21

Which patients can get Roc

Answer 21

Cardiovascular

Question 22

WHich patients can get Atracurium and which cant

Answer 22

Can
Renal and liver patients
Cant
Asthma

Question 23

What is the MOA of non depolarising reversal agents

Answer 23

They work by increasing the conc. of Ach this is because the non depolarising agents are competitive inhibitors and so the reversal agents inhibit acetylcholinesterase

Question 24

What is the MOA of neostigmine

Answer 24

Acetylcholinesterase inhibitor

Question 25

What is the side effect of neostigmine

Answer 25

It also inhibits the acetylcholinesterases at the muscarinic receptors

Question 26

What can be done to counter the effects of neostigmine

Answer 26

Give and anticholinergic for the muscurinic reseptors e.g. glycopyrralate or atropine

Question 27

What is needed to check the readiness for reversal

Answer 27

Peripheral nerve stimulator, it should have atleast 3 twitch present in a train of 4

Question 28

What are some of the signs of an inadequate reversal

Answer 28

Looks like a fish out of water Jerky respiration Tracheal tug Restlessness Inability to lift the head from the pillow Poor ability to cough

Question 29

What is the order of steps taken if the dose of reversal was inadequate

Answer 29

1. Exclude other causes e.g.hyper or hypocarbia and CVS 2. Maintain the ventilation 3. Reverse any specific causes 4. Check PNS 5. Give additional doses of neostigmine

Question 30

What is the MOA of sugammadex

Answer 30

It works by binding to rocuronium

Question 31

What are the 2 main benifits of sugammadex

Answer 31

1. It can be used at any time and there is no need to to wait until the patient is reversible 2. It does not affect the muscarinic receptors

Question 32

What does the binding of Ach cause on the postsynaptic neuron

Answer 32

It causes the influx of Na

Question 33

How is acetylcholine stored

Answer 33

As vesicles in the presynaptic motor axon

Question 34

Which is the most rapidly acting muscle relaxant

Answer 34

Sux

Question 35

How should suxamethonium be reversed

Answer 35

Waiting for pseudocholinesterase to break it down

Question 36

In which situation is suxamethonium contraindicated?

Answer 36

1. Drug allergies 2. Scoline apnoea 3. MH 4. Areas of hyperkalcemia e.g. renal failure, paralysis, crush and burns

Question 37

Which is the only non-depolariser that can be used for rapid sequence induction?

Answer 37

Rocuronium