induction agents Flashcards

1
Q

Is propofol an acid or a base and what is its PKA?

A

weak acid
11

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2
Q

what chemical is propofol derived from?

A

phenol derivative

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3
Q

what is the Vd for propofol?

A

4L/kg

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4
Q

how much protein binding does propofol have?

A

98%

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5
Q

what is the elimination half life of propofol?

A

5 hours

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6
Q

how does propofol work as an anti-emetic?

A

D2 antagonism

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7
Q

at what effector site target conc of propofol will patients be asleep?

A

2.5-3ug/ml

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8
Q

which has more incidence of allergy thiopentone or methohexital?

A

methohexital

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9
Q

which has more tissue damage on intra-arterial injection thiopentone or methohexital ?

A

thiopental

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10
Q

how do Thiopental and pentobarbital compare?

A

both derived from barituric acid
thiopentone is a sulphur analogue of pentobarbital
pentobarbital has a =0 instead of S

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11
Q

how does solubility of thiopental change in different pHs?

A

The solubility of barbiturates increases on transformation from the keto to enol form, called tautomerism

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12
Q

what is barbituric acid derived from?

A

Barbituric acid is a condensation product of urea and malonic acid.

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13
Q

what is the pka of thiopentone? at what pH is it kept in solution?

A

7.6 - weak acid
pH 10.5 - ionised so soluble

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14
Q

in what form is thiopentone soluble?

A

enol form

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15
Q

which has a faster clearance thiopental or methohexital?

A

methohexital

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16
Q

what is the dose of thiopentone and methohexital?

A

he dose of thiopental for induction is 3-7 mg/kg. Methohexital has an induction dose of 1-2 mg/kg.

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17
Q

what is the use of methohexital out of hospital?

A

ultra short acting

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18
Q

does methohexital cause pain on injection?

A

yes

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19
Q

which of the barbiturates cause osteomalacia?

A

phenobarbital

20
Q

how does thiopentone affect intra occular pressure?

A

reduces it

21
Q

which induction agents promote bronchospasm/ laryngospasm?

A

thiopentone

22
Q

how do the induction agents - propofol, thio, ketamine and etomidate effect seizures?

A

propofol and thio - reduce
ketamine - no effect
etomiidate increases

23
Q

which opioid med induces seizures?

A

pethidine (a.k.a meperidine)

24
Q

what is the major flaw of etomidate?

A

Etomidate is known to cause dose dependant adrenal suppression via reversible inhibition of the 11-beta hydroxylase enzyme.

25
Q

does etomidate have analgesics properties or cause thrombophlebitis?

A

no

26
Q

what chemical is etomidate?

A

imidazole

27
Q

how many isomers does etomidate have ?

A

2

28
Q

at physiological pH is etomidate water or lipid soluble?

A

lipid

29
Q

how does etomidate effect cerebral blood flow and metabolism

A

reduced ICP, CBF, CMRO2

30
Q

which induction agents precipitate porphyria?

A

thio
ketamine
etomidate

31
Q

what type of chemical is ketamine?

A

phencyclidine derivative

32
Q

what is the size of ketamine?

A

Its molecular weight is 238, making it relatively small and easier to diffuse across membranes.

33
Q

which receptor does ketamine bind?

A

NMDA

34
Q

what is the protein binding of ketamine

A

around 30%

35
Q

what is the elimination half life for ketamine?

A

2-3 hours

36
Q

can ketamine be derived via TCI?

A

yes - domino model

37
Q

how does ketamine effect CVS and resp systems?

A

CVS - tachycardia, increased BP
Resp - increased RR, maintains airway reflexes, bronchodilator

38
Q

At what does is ketamine an analgesic?

A

0.15-0.25mg/kg

39
Q

glycopyrolate can be given with ketamine at induction - why?

A

ketamine increases secretions

40
Q

what is the IM induction dose of ketamine?

A

4-10mg/kg

41
Q

which isomer of etomidate is more active?

A

R

42
Q

which induction agent has lowest incidence of hypersensitivity?

A

etomidate

43
Q

which form of etomidate reduces pain on injection?

A

Etomidate-lipuro

44
Q

how does the Sulphur in thiopentone affect its speed of onset?

A

increases it

45
Q

what is the therapeutic index for thiopentone?

A

low

46
Q

how is thiopentone prepared?

A

500 mg thiopental is mixed with 20ml water
This produces a 2.5% solution
The powder contains 6% anhydrous sodium carbonate
The pH of this solution is approximately 10.5
The ampoule contains nitrogen gas

47
Q
A