Inhalation and analgesic agents

Question 1

What is the dose of nitrous oxide?

What inhalation agent can be used in organ retrieval and why?

Answer 1

• 104%

- isoflurane: has least effect on blood flow (1.15%)

Question 2

what inhalation agent is used in children?

what is its dose?

Answer 2

• sevoflurane: sweet smelling

- 2%

Question 3

which inhalation agent should be used for longer operations and why?

what is its dose?

Answer 3

• desflurane: low lipid solubility with rapid onset and offset
• 6%

Question 4

How would you work out concentration of vapour needed?

Answer 4

• Minimum Alveolar Concentraton that prevents reaction to a standard surgical stimulus (incision) in 50% of patients

Question 5

What factors increase MAC? (3)

What factors decrease MAC? (5)

Answer 5

• hyperthermia, hyperthyroidism, alcoholism

- increasing age, hypothermia, hypoxia, CNS depressants, alpha 2 agonists.

Question 6

Name 3 short acting analgesic agents?

Answer 6

• remifentanil
• fentanyl
• alfentanil

Question 7

what is the main advantange of remifentanil? (2)

name the side effects? (4)

Answer 7

• duration of action very quick (5-10 mins)
• used for longer op’s as IV infusion gives tighter control
• muscle rigidity
• respiratory depression
• hypotension
• bradycardia

Question 8

what is advantages of fentanyl? (2)

what are the disadvantages including side effects? (2)

Answer 8

• high lipid solubility
• cardiostable
• longer duration of action (30-60 mins)
• circulatory and ventilatory depression

Question 9

How quick acting is alfentanil?

what is the dose?

Answer 9

• short acting, (10 mins)

- 250- 750 mcg

Question 10

what analgesics are given for post- op analgesia?

Answer 10

• morphine (given 20 mins before op)

- oxycodone

Question 11

Name a depolarising neuromuscular blocker?

what is its dose?

how does it work?

Answer 11

• suxamethonium
• 1- 1.5mg/ kg
• causes muscle contraction, the muscle then fatigues and relaxes

Question 12

what are the negatives of suxamethonium? (4)

Answer 12

• muscle fatigue post-op
• hyperkalaemia
• malignant hyperthermia
• rise in IOP, ICP and gastric pressure

Question 13

How do non- depolarising neuromuscular blockers work?

Answer 13

• block nicotinic receptors via competitive binding, so muscle relaxes

Question 14

Name an important short acting, medium acting and long acting non depolarising agent?

Answer 14

• atracurium (15 mins)
• rocuronium (40 mins)
• pancuronium (60 mins)

Question 15

How are these non depolarising agents reversed? (2)

Answer 15

• glycopyrolate (reduces side effects of neostigmine)

- neostigmine (blocks AChE, so causes build up of Ach in junction)