Induction agents

Question 1

What type of drug is ketamine

Answer 1

phencyclidine derivative

Question 2

How is ketamine presented

Answer 2

colourless solution
Racemic mix or as pure S enantiomer

Question 3

How does ketamine work?

Answer 3

NOn competitive antagonist at NMDA receptor
Weak agonist at MOP, KOP, DOP
Inhibits reuptake of serotonin. dopamine, NA

Question 4

Effects of ketamine on systems

Answer 4

CVS:
- increase HR
-INcrease CO
-INcrease BP
-Increase O2 consumption

Resp
Bronchodilation
INcrease RR
No depression of laryngeal reflexes

CNS
Dissociative anaesthesia
Traditionally thought to increase ICP but probs just as much as opiods
amnesia
Muscle tone
Emergeence

Question 5

Chemical properties of ketamine

Answer 5

chiral compound- S ketamine available on own
(twice as potent, 3-4x affinity for NMDA)
Water soluble, forms an acidic solution

Question 6

Ketamine A/D

Answer 6

Well absorbed, poor oral bioavail (20%)
Protein binding of 20-50%
Vd of 3L
t1/2 of 2.5 hours

Question 7

Ketamine M/D

Answer 7

Metabolised in liver to norketamine (30% potency)
Conjugated to inactive metabolites
Excreted in urine

Question 8

What type of drug is etomidate

Answer 8

Imidazole

Question 9

How is etomidate presented

Answer 9

clear, colourless solution

Question 10

MOA etomidate

Answer 10

Increases duration of GABA cl channels in CNS
Only the D isomer causes hypnosis

Question 11

Effects of etomidate on different systems

Answer 11

Most stable induction agent, very slight drop in SVR but Myocardial O2 consumption/BP are not effected

Resp- depression
No inhibition of hypoxic pulmonary vasoconstriction
CNS
HYpnosis, tremor and drop in tone
Decreased ICP,CPP.IOP
Epileptiform activity in a quarted

Question 12

How does etomidate affect steroid synthesis ?

Answer 12

Inhibiting by inhibition of 11b and 17a hydroxylase- 24hours for just one dose. associated with deaths when used on ICU for sedation

Question 13

pKa etomidate

Answer 13

4.1

Question 14

Etomidate A/D

Answer 14

75% protein bound
Rapid distribution
Vd 3L/kg

Question 15

Etomidate M/E

Answer 15

Rapidly metabolised by hepatic and plasma esterases
May inhibit plasma choninestrase
Excreted 90% in the urine, 10% in the bile

Question 16

What is the name of propofol

Answer 16

2,6, diisopropylphenol

Question 17

What else is in propofol

Answer 17

soy bean oil. egg phosphatide

Question 18

MOA propofol

Answer 18

may be GABA potentiation, may be cannabinoid

Question 19

Propofol effects on systems

Answer 19

CVS
Less BP/SV
Less CO
Vasodilation
Bradycardia

Resp
Depression,
Increased RR, dec. TV
bronchodilation

CNS
HYpnotic, smooth and rapid
decreases CPP + ICP

Gut- antiemetic, antagonist at D2

Question 20

Propofol side effects

Answer 20

Pain on injection
Fat overload in kids
Green urine
INcreased energy for shocks

Question 21

Chemical properties of propofol

Answer 21

Not water soluble, weak acid.
pKa is 11

Question 22

Propofol A/D

Answer 22

98% protein bound
Vd 4L/kg
Rapid distribution
COntext sensitive but half time is about 1 to 5 hours

Question 23

Propofol M/E

Answer 23

Hepatic metabolism to make glucuronide
Renally excreted
Dysfunction has little effect
Clearance >hepatic blood flow suggesting extrahepatic metabolism
No active metabolites

Question 24

What type of drug is thiopentone

Answer 24

Barbituate

Question 25

How is thiopentone presented

Answer 25

Yellow powder with sodium carbonate added (prevents accumulation of undissociated acid when dissolved)
= stored under N2 (prevents acidification of powder by CO2 in air

Question 26

MOA of thiopentone

Answer 26

Increases duration of opening of gaba cl channels
Hyperpolarisation + neuronal inhibition

Question 27

Thiopentone effects by system

Answer 27

CVS-
Reduced CO, SV, SVR
Can increase HR

REsp-
Depression, laryngo/bronchospasm

CNS-
Anaesthesia, decr. blood flow, decr. CSF pressure

REnal- reduces UO

Question 28

Thiopentone S/E

Answer 28

Severe anaphylaxis
Precipitates porphyria
Intraarterial injection -> spasm and necrosis .

Question 29

pKA of thiopentone

Answer 29

7.6

Question 30

Thiopentoine A/D

Answer 30

80% protein bound. of remaining, 12% is unionised and available
Vd 2L/kg
Rapid emergence due to redistribution
Critically ill patients are acidotic, so less thiopentone is needed
NSAIDS reduce protein binding and increase free portion of the drug

Question 31

Thiopentone M/E

Answer 31

Hepatix oxidation by p450 to inactive metabolites (bar pentobarbitone which is active)
Induces p450 after a single dose
zero order kinetics