Intravenous anesthetics Flashcards
What is the mechanism of action of propofol?
GABA-A agonist
What is the onset of action of propofol?
30-60 seconds
What is the duration of action of propofol?
5-10 minutes
What is the clearance of propofol?
liver+ extra hepatic metabolism
What is the active metabolite of propofol?
None
What is the induction dose of propofol?
1.5-2.5 mg/kg IV
What is the maintenance dose of propofol?
25-200 mcg/kg/min
What are the respiratory effects of propofol?
decreased respiratory drive
What are the CV effects of propofol?
decreased BP, SVR, preload, and contractility
What are the CNS effects of propofol?
decreased ICP & IOP, no analgesia, +/- seizure activity
decreased CBF, decreased CMRO2
What is the pKa of propofol?
11
GABA-A receptor stimulation leads to
hyperpolarization of the neurons by increasing Cl- conductance; more Cl- inside the cell makes the cell more negative; this reduces resting membrane potential leading to prevention of action potential
With propofol, there is a rapid redistribution
from the blood to the vessel rich group
redistribution from the VRG to the muscle and fat follows
The brain concentration of propofol peaks at
~1 minute
How does propofol affect the CO2 response curve?
shifts CO2 response curve down and to the right (less sensitive to CO2)–> respiratory depression and/or apnea
Can myoclonus occur with propofol?
yes
Does propofol provide analgesia?
no
How can propofol infusions change the color of urine?
green urine= phenol excretion
cloudy urine= increased uric acid excretion
Propofol has _______ properties.
antioxidant properties- free radical scavenging properties
What organs are primarily responsible for propofol metabolism?
liver (CYP 450)
lungs
Name 2 preservatives that may be added to the propofol vial.
disodium edetate (diprivan)
sodium metabisulfate (generic formula)
Propofol infusion syndrome is categorized by the presence of:
a. hypokalemia
b. bradycardia
c. respiratory failure
d. metabolic acidosis
b. bradycardia
d. metabolic acidosis
Propofol infusion syndrome presents with
acute refractory bradycardia–> asystole + at least one of the following:
metabolic acidosis (base deficit > 10 mmol/L)
rhabdomyolysis
enlarged or fatty liver
renal failure
hyperlipidemia
lipemia (cloudy plasma or blood)
Propofol may be safely administered to patients allergic to
soy, peanuts, and probably egg
Most people with egg allergies are allergic to the__________. Egg lecithin found in propofol is derived from
albumin in egg whites; derived from the yolk
Risk factors for propofol infusion syndrome include
children receiving high doses (4 mg/kg/hr) over long periods of time (>48 hours)
sepsis (inadequate oxygen delivery)
continuous catecholamine infusions
high-dose steroids
significant cerebral injury
Treatments for propofol infusion syndrome include
discontinuing propofol and initiating cardiac pacing, PDE inhibitors, and ECMO
maximize gas exchange
glucagon
renal replacement therapy
Propofol increases the risk of ______ contamination.
bacterial and fungal
What measures should be taken to reduce the risk of bacterial contamination with propofol?
propofol syringes must be discarded within 6 hours
infusions (and the tubing) must be discarded within 12 hours
_______ to generic propofol preparations can cause complications.
Additives
Describe two additives to generic propofol that can lead to complications.
metabisulfite–> bronchospasm in asthmatics
benzyl alcohol–> should be avoided in infants
Propofol also has the following properties:
antipruritic and antiemetic
Pain on injection with propofol is reduced by
lidocaine, opioids and administration through larger and more proximal veins
How does propofol cause propofol infusion syndrome?
propofol contains long-chain triglycerides (LCT) and an increased LCT load impairs oxidative phosphorylation and fatty acid metabolism. this starves cells of oxygen particularly in cardiac and skeletal muscle
Fospropofol is:
a. prepared as a lipid emulsion
b. metabolized by alkaline phosphatase
c. a prodrug
d. associated with pain at the injection site
b. metabolized by alkaline phosphatase
c. a prodrug
What is the mechanism of action of fospropofol?
GABA-A agonist
What is the onset of action of fospropofol?
5-13 minutes (much longer than propofol)
What is the duration of action of fospropofol?
15-45 minutes
What is the clearance of fospropofol?
liver+ extrahepatic metabolism
What is the active metabolite of fospropofol?
propofol (fospropofol is a prodrug)
What is the induction of fospropofol?
6.5 mg/kg IV
What is the repeat dose of fospropofol?
max 1.6 mg/kg every 4 minutes
What are the respiratory effects of fospropofol?
similar to propofol
What are the CV effects of fospropofol?
similar to propofol
What are the CNS effects of fospropofol?
similar to propofol
What are other side effects of fospropofol?
genital and anal burning
Advantages of fospropofol over propofol include
prevents burning
doesn’t support microbial growth in the same way as lipid emulsion (no preservative)
