MCQ's: Intravenous Agents and Sedatives Flashcards
Propofol: Produces vasodilatation by nitric oxide production? T/F
True.
Propofol causes hypotension (reduction in systemic vascular resistance and cardiac output) without tachycardia. Bradycardia is common, especially with opiate co-administration.
Propofol has has a hydroxyl group situated on which carbon?
The hydroxyl group is situated on the 1st carbon.
Phase 1 metabolism into a quinol derivative involves hydroxylation of the 4th carbon.
T/F: Propofol - Undergoes both phase 1 and phase 2 metabolism
True - Glucuronidation is the predominant metabolic pathway, hydroxylation by cytochrome P450 to a quinol derivative prior to conjugation is also an important pathway. The relative importance of each pathway varies amongst patients.
Propofol:
Select true or false for each of the following statements.
A. Is used at a dose of around 4 mg/kg for IV paediatric induction.
B. Causes a reduction in cardiac output solely by reducing heart rate.
C. Clearance is by hepatic metabolism alone.
D. Acts as an anti-emetic by competitive antagonism of central serotonin receptors situated in the chemoreceptor trigger zone.
E. Is a cause of hypertrigylcerideaemia
A. True. Approx double the typical adult dose.
B. False. Propofol also reduces myocardial contractility and sympathetic tone.
C. False. Extra-hepatic metabolism is significant, suggested by the fact that clearance is higher than hepatic bolod flow. Sites for extra-hepatic metabolism include the kidneys (responsible for about a third of extra-hepatic metabolism) and lungs (to 2, 6 - diisopropyl - 1, 4 - quinol).
D. False. The anti-emetic effect of propofol is probably mediated through dopamine receptor antagonism.
E. True. This may be a part of the metabolic syndrome seen in children after prologed infusion. Propofol infusions have been linked to organ fatty infiltration with severe bradycardias, metabolic acidosis and increased mortality.
% midazolam protein bound?
98%
Midazolam % unionised at physiological pH.
With a pKa of 6.5
89% of molecules are unionized at physiological pH.
Midazolam is a tautomeric molecule consisting of benzene and diazepine rings. In a pH > 4 the diazepine ring closes producing a lipid soluble unionized molecule.
What drug co-administration can prolong midazolam action and why?
Alfentanil because they are both metabolised by CYP3A3/4
Midazolam - active or inactive metabolites?
The phase 1 metabolite 1-alpha-hydroxy-midazolam is active.
This may then be conjugated (glucuronidation) prior to excretion.
Ketamine - what type of activity predominant on EEG?
THETA and DELTA
activity is pre-dominant during ketamine induced dissociative anaesthesia.
Etomidate: prepared with what substance?
35% propylene glycol
IV induction dose etomidate?
0.2 - 0.3 mg/kg
% of patients that experience pain with injection of etomidate?
25%
Etomidate effect on EEG reading?
Produces excitatory movements with epileptiform activity on EEG.
Etomidate is the most likely IV induction agent to cause myoclonic movements and epileptiform activity on EEG - in around 20% of cases.
Etomidate:
effect on adrenal medulla?
other hormone synthesis.
Does not effect adrenal medulla.
Etomidate has been shown to inhibit 11-beta and 17-alpha hydroxylase function and impair aldosterone and cortisol synthesis for up to 24 hours after administration. Steroidogenesis occur in the adrenal cortex.
thiopentone: enzyme inhibitor or inducer?
Inducer
