Neumuscular Blocking Agents

Question 1

What do neuromuscular blocking agents do?

Answer 1

relax the muscles

Question 2

Which muscle relaxants are there?

Answer 2

• local anaesthetics
• benzodiazepines
• alpha2-adrenoreceptors agonists
• guaiphensein
• neurmuscular blocking drugs

Question 3

What are benzodiazepines and alpha2s usually used with?

Answer 3

ketamine as it counteracts the rigidity from ketamine

Question 4

Where does guaiphenesin act?

Answer 4

centrally acting in the internuncial neurones of the spinal cord, brainstem and subcorticol areas of the brian

Question 5

What is guaiphenesin not?

Answer 5

an analgesic or anaesthetic

Question 6

What are the clinical indications for using neuromuscular blockade?

Answer 6

• relaxes skeletal muscles for sugical access
• facilitate control of ventilation
• facilitate tracheal intubation in cats and pigs
• ophthalmic surgery - central eye
• assist reduction of dislocated joints and fractures
• reduces the amount of anaesthetic required?

Question 7

What is the neurmuscular junction?

Answer 7

motor neurone and muscle cell separated by synaptic cleft

Question 8

What is released from nerve ending of the neuromuscular junction?

Answer 8

acetylcholine

Question 9

What does acetylcholine do?

Answer 9

binds to post-synaptic nicotinic receptor with two subunits that must be bound for the release

Question 10

What does release of acetylcholine release result in?

Answer 10

muscle contraction

Question 11

What is acetylcholine rapidly hydrolysed by?

Answer 11

acetylcholinesterase within the synaptic cleft

Question 12

What do neuromuscular blocking drugs do?

Answer 12

• facilitates for endotracheal intubation and intermittent positive pressure ventilation must be available

Question 13

What are neuromuscular blocking drugs?

Answer 13

depolarising muscle relaxants

Question 14

What are the benefits of neurmuscular blocking agents?

Answer 14

-fast onset
- one dose only

Question 15

What can neuromuscular blocking agents do?

Answer 15

• phase II block after more than one dose
• aid intuation in cats and pigs
• may trigger malignant hyperthermia
• increase serum potassium levels
• burns

Question 16

What are non-depolarisng (competetive) muscle relaxant?

Answer 16

• complete with Ach for post-junctional binding sites
• no initial muscle fasiculation
• slow onset

Question 17

What are the benefits of non-depolarising muscle relaxants?

Answer 17

can be topped with with 1/3 the initial dose and can be antagonised

Question 18

What do non-depolarising muscle relaxants prevent Ach from causing?

Answer 18

binding so there is no initial muscle twitch

Question 19

What is atracurium?

Answer 19

• bis-isoquinolinium compound
• mixture of 10 isomers
• Hoffman elimination
• agent of choice for animals with renal/hepatic compromise

Question 20

What does atracurium do?

Answer 20

release histamine

Question 21

What is Hoffman elimination?

Answer 21

temperature reaction in plasma

Question 22

What type of neuromuscular blockade is vecuronium?

Answer 22

non-depolarising

Question 23

What is vercuronium?

Answer 23

• steroid compound
• no release of histamine
• 40-50% undergo hepatic biotransformation

Question 24

What are examples of non-depolarising neurmuscular blockades?

Answer 24

rocuronium, mivacurium, pancuronium

Question 25

How do you monitor a patient after administration of NMB?

Answer 25

• ventilation
• check tube not kinked/dislodged
• ensure breathing syste, does not become disconnected
• monitor movement of thoracic wall
• ETCO2 and SPo2

Question 26

What are the signs of inadequated depth of anaesthesia?

Answer 26

• increase in pulse rate
• increase in blood pressure
• salivation/lacrimation
• vasovagal response (bradycardia/hypotension/pallor)
• increase ET CO2
• slight muscle twitching
• pupillary dilation

Question 27

How do you monitor degree of muscle relaxation?

Answer 27

• peripheral nerve stimulators
• ulnar nerve
• peroneal nerve
• facial nerve
• train of four

Question 28

What is the train of 4?

Answer 28

4 electrical impulses applied to the nerve over a 2 second period

Question 29

What factors influence duration of neuromuscular blockade?

Answer 29

• volatile agent
• hypothermia
• hepatic/renal insufficency
• electrolyte and acid base abnormalities
• muscle diseaase e.g myesthenia gravis
• aminoglycoside antibiotics
• dose administered

Question 30

When would you antagonise non-depolarising NMBs?

Answer 30

once 1 or 2 twitches return

Question 31

What are some unwanted side effects of anatgonising non-depolarising NMBs?

Answer 31

bradycardia, salivation. bronchospasm, diarrhoea

Question 32

What do antagonists for non-depolarising NMBs do?

Answer 32

increases concentration of Ach

Question 33

What are cyclodextrins?

Answer 33

donut like structures