NMB

Question 1

How is succinylcholine metabolised?

Answer 1

By plasma pseudocholinesterases
- If giving Sux, check PNS prior to giving non-depolarising muscle relaxant to assess for Sux apnoea.

Question 2

What is the presentation and intubating dose of succinylcholine?

Answer 2

Presentation: 2ml glass vial of colourless solution, 50mg/ml
Intubating dose: 1-2 mg/kg

Question 3

What is the presentation and intubating dose of vecuronium?

Answer 3

Presentation: Glass vial with a powder mixed with its accompanying vial of sterile water. Standard concentration of 2mg/l
Intubating dose: 0.1 mg/kg

Question 4

What is the presentation and intubating dose of atracurium?

Answer 4

Presentation: Clear colourless solution in 2.5 ml and 5 ml ampoules containing 10 mg/ml
Intubating dose: 0.5 mg/Kg

Question 5

What are the patient and clinical contraindications to using succinylcholine?

Answer 5

Patient:
- Malignant hyperpyrexia
- Anaphylaxis to succinylcholine
- Succinylcholine apnoea

Clinical:
- Widespread denervation injury e.g. burns and spinal cord injury -> extrajunctional receptors lose K+ pushing blood conc up.
- presence of an open or penetrating eye injury. Contraction of extra ocular muscles can lead to significant rise in intraocular pressure.

Question 6

What are the two groups of non depolarising muscle relaxants?

Answer 6

• Aminosteroids e.g. Vecuronium and Rocuronium
• Benzylisoquinoliniums e.g. Atracurium

Question 7

How is Vecuronium metabolised?

Answer 7

Hepatic
excreted in bile and urine
Effect may be prolonged in hepatic and renal dysfunction or induced liver enzymes.

Question 8

How is Atracurium metabolised?

Answer 8

1. Hoffman degradation. Spontaneousley broken down to laudanosine and an acrylate. This is temperature dependant.
2. Ester hydrolysis by non specific plasma esterases (distinct from plasma esterases).

Question 9

what is the mechanism of neostigmine, its dose and presentation?

Answer 9

• Neostigmine is a cholinesterase inhibitor
• Clear and colourless solution in a glass vial 2.5mg/ml
• Dose 2.5mg (0.05 mg/kg)

Question 10

What is the mechanism of action of Glycopyrrolate, its presentation and dose?

Answer 10

-Glycopyrronium is a muscarinic antagonist (anticholinergic) with the highest affinity for M1 receptors,
- Clear colourless solution 200 mcg/ml
- 500 mcg with 2.5 mg neostigmine, or 200 mcg boluses.

Question 11

Describe TOF

Answer 11

-Train of four
- 4 supramaximal stimuli each with a duration of 0.1 msec delivered at 2Hz.
- Supramaximal stimulus: A current that ensures all fibres in the targeted peripheral nerve are depolarised. This allows an indexed response.
- Typically >60 mA
- TOF count: number of twiches
- TOF ratio: The ratio of the fourth twich height to the first twitch height.

Question 12

When is the earliest point you can reverse a non depolarising NMB with regard to the TOF and neostigmine.

Answer 12

TOF count of 3 twitches minimum