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Flashcards in Muscle Relaxants Deck (15)
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1
Q

What is the difference between a neuromuscular blocker and a centrally acting muscle relaxant?

A

Neuromuscular blockers act at the NMJ paralysing all striated muscle. Centrally acting muscle relaxants act on interneurones in the spine and weaken postural muscles

2
Q

Dantrolene MOA.

A

Interupts excitation-contraction coupling by preventing release of Ca2+ from the sarcoplasmic reticulum (antagonises ryanodine receptors)

3
Q

Botulinum toxin

MOA

A

Interferes with ACh release

4
Q

Why would we want to use muscle relaxants?

A
  1. Help surgical access
  2. Facilitate IPPV
  3. Balanced anaesthesia
  4. Endotracheal intubation
5
Q

What are the problems with muscle relaxant use during anaesthesia?

A

Unable to judge anaesthetic depth

Unable to fully ventilate patients lungs

6
Q

What is the order of paralysis in dogs?

A
  1. Facial expression
  2. Tail
  3. Distal limb/neck
  4. Proximal limbs
  5. Throat
  6. Abdominal wall
  7. Intercostals
  8. Diaphragm (fairly resistant)
7
Q

What is the MOA of peripherally acting nm blocking agents?

A

Compete with normal NMJ transmitter ACh at post-synaptic nicotinic ACh receptors

8
Q

Name the categories of Non-depolarising agents.

What is their MOA?

A
  1. Amino-steroids
    1. Vecuronium
    2. Rocuronium
  2. Benzylisoquinoliniums
    1. Atracurium
    2. Cis-atracurium

Block post-synaptics NACh recepts and prevent ACh from activating them

9
Q

Name the two depolarising agents.

Outline their MOA.

A
  • Succinylcholine
  • Suxamethonium

Firstly stimulate post-synaptic NACh receptors and then block them once the membrane becomes refractory

10
Q

Which parameters are used to assess degree of block?

A
  • Diaphragmatic movements - cleft in the capnograph
  • Jaw tone
  • Eye position
  • Eye reflexes and movement
11
Q

What is the gold standard for assessing degree of muscular block?

How can the twitch response be measured? (x4)

A

Apply electrical stimulus to a superficial nerve suppling a muscle where the twitch can be observed.

  1. Mechanomyography - m tension
  2. Acceleromyography - acceleration
  3. Electromyography - electrical response of muscle
  4. Phonomyography - sound of moving muscle
12
Q

Outline the different patterns of electrical stimulation often used during twitch response measurment.

A
  1. Single stimuli
  2. Train of four stimuli - TOF
  3. Two bursts of stimulation - DBS
  4. Tetanic
13
Q

Name three anticholinesterases and outline their mechanism of action.

Which are appropriate for reversal of muscle relaxants?

A
  1. Edrophonium - reversible
  2. Neostigmine - reversible carbamylation of enzyme
  3. Organophosphates - irreversible phosphorylation of enzyme
14
Q

Why do anticholinesterases have side effects?

What are the potential side effects of their use?

A

They increase ACh at muscarinic receptors as well as nicotinic receptors (autonomic ganglia, parasympathetic terminals)

  • Bradycardia
  • Bronchoconstriction
  • Salivation
  • Defecation/urination
  • Moisis
15
Q

How are the side effects associated with Anticholinesterases combatted?

A

Add an anticholinergic such as atropine (edrophonium) or glycopyrrolate (neostigmine)