induction agents Flashcards
Is propofol an acid or a base and what is its PKA?
weak acid
11
what chemical is propofol derived from?
phenol derivative
what is the Vd for propofol?
4L/kg
how much protein binding does propofol have?
98%
what is the elimination half life of propofol?
5 hours
how does propofol work as an anti-emetic?
D2 antagonism
at what effector site target conc of propofol will patients be asleep?
2.5-3ug/ml
which has more incidence of allergy thiopentone or methohexital?
methohexital
which has more tissue damage on intra-arterial injection thiopentone or methohexital ?
thiopental
how do Thiopental and pentobarbital compare?
both derived from barituric acid
thiopentone is a sulphur analogue of pentobarbital
pentobarbital has a =0 instead of S
how does solubility of thiopental change in different pHs?
The solubility of barbiturates increases on transformation from the keto to enol form, called tautomerism
what is barbituric acid derived from?
Barbituric acid is a condensation product of urea and malonic acid.
what is the pka of thiopentone? at what pH is it kept in solution?
7.6 - weak acid
pH 10.5 - ionised so soluble
in what form is thiopentone soluble?
enol form
which has a faster clearance thiopental or methohexital?
methohexital
what is the dose of thiopentone and methohexital?
he dose of thiopental for induction is 3-7 mg/kg. Methohexital has an induction dose of 1-2 mg/kg.
what is the use of methohexital out of hospital?
ultra short acting
does methohexital cause pain on injection?
yes
which of the barbiturates cause osteomalacia?
phenobarbital
how does thiopentone affect intra occular pressure?
reduces it
which induction agents promote bronchospasm/ laryngospasm?
thiopentone
how do the induction agents - propofol, thio, ketamine and etomidate effect seizures?
propofol and thio - reduce
ketamine - no effect
etomiidate increases
which opioid med induces seizures?
pethidine (a.k.a meperidine)
what is the major flaw of etomidate?
Etomidate is known to cause dose dependant adrenal suppression via reversible inhibition of the 11-beta hydroxylase enzyme.
does etomidate have analgesics properties or cause thrombophlebitis?
no
what chemical is etomidate?
imidazole
how many isomers does etomidate have ?
2
at physiological pH is etomidate water or lipid soluble?
lipid
how does etomidate effect cerebral blood flow and metabolism
reduced ICP, CBF, CMRO2
which induction agents precipitate porphyria?
thio
ketamine
etomidate
what type of chemical is ketamine?
phencyclidine derivative
what is the size of ketamine?
Its molecular weight is 238, making it relatively small and easier to diffuse across membranes.
which receptor does ketamine bind?
NMDA
what is the protein binding of ketamine
around 30%
what is the elimination half life for ketamine?
2-3 hours
can ketamine be derived via TCI?
yes - domino model
how does ketamine effect CVS and resp systems?
CVS - tachycardia, increased BP
Resp - increased RR, maintains airway reflexes, bronchodilator
At what does is ketamine an analgesic?
0.15-0.25mg/kg
glycopyrolate can be given with ketamine at induction - why?
ketamine increases secretions
what is the IM induction dose of ketamine?
4-10mg/kg
which isomer of etomidate is more active?
R
which induction agent has lowest incidence of hypersensitivity?
etomidate
which form of etomidate reduces pain on injection?
Etomidate-lipuro
how does the Sulphur in thiopentone affect its speed of onset?
increases it
what is the therapeutic index for thiopentone?
low
how is thiopentone prepared?
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
