Module 3a: IV induction agents

Question 1

What is an induction agent?

Answer 1

Agent that produces LOC within one arm brain circulation time (30sec)

They induce anaesthesia but will wear off so needs to be maintained

Question 2

What are the 4 rapid acting induction agents?

Answer 2

Thiopentone
Etomidate
Propofol
Ketamine

Question 3

What are the 3 slower acting induction agents

Answer 3

Benzodiazepines
neuroleptic
opioids in large doses

Question 4

Name 5 advantages of IV induction?

Answer 4

Rapid onset
More pleasant and acceptable
Pollution free
Low incidence of side effects
Smooth induction with rapid transfer through Guedel stages

Question 5

What are 4 disadvantages of IV induction?

Answer 5

requires IV access

easy to overdose->side effects

No removal of drug via lungs-> requires redistribution, metabolism and excretion

Sudden loss of normal protective reflexes

Question 6

What is the mechanism of action of IV induction agents ?

Answer 6

inhibit GABA(A) receptors-> increased chloride conductance->hyperpolarization->neuronal inhibition

Question 7

What is the pharmacokinetics of IV anesthetics?

Answer 7

Onset depends on drug reaching effect site(BRAIN) by crossing BBB

Question 8

What is the arm brain circulation time determined by in pharmacokinetics?

Answer 8

Speed of injection
Lipid solubility
Protein binding
Blood flow to brain

Question 9

What determines recovery in pharmacokinetics?

Answer 9

redistribution from vessel rich to vessel poor organs

Metabolism + excretion

Question 10

What is redistribution?

Answer 10

Following IV induction, patient will wake up after few minutes due to REDISTRIBUTION.

It is when drug move from well perfused to less perfused tissues.

Rapid awakening is NOT due to metabolism/excretion

Question 11

Why should you not make important decisions or drive for 48-72 hrs after anaesthesia?

Answer 11

Low concentrations of drug remain in brain for while

Question 12

What characteristics does the ideal IV induction agent have?

Answer 12

Smooth and rapid onset
Inexpensive
Minimal side effect
No pain on injection
Rapid recovery

Question 13

How can you reduce pain on injection with propofol?

Answer 13

IV lignocaine 10-20mg when giving propofol

Question 14

True or false:
less IV induction must be given in elderly and more in children

Answer 14

true

Question 15

What colour is true and false IV induction agents?

Answer 15

yellow-true
orange-false