Pharmacology IV anesthetics Flashcards
What is the pKa of Propofol?
11
What is the preservative in brand name Propofol?
Diprivan has the preservative disodium edetate
What is the preservative in generic Propofol?
sodium metabisulfite
1% solution in an emulsion of egg lecithin, soybean oil, and glycerol describes what drug?
Propofol
What is the MOA of propofol?
Direct GABA - A agonist which increases Cl conductance and leads to neuronal hyperpolarization
What is the induction dose for propofol?
What is the infusion range?
induction - 1.5-2.5 mg/kg IV
infusion - 25-200 mcg/kg/min
duration for propofol?
5-10 min.
How is Propofol cleared?
Liver (P450 enzymes) + extrahepatic metabolism
Where does extrahepatic clearance of propofol occur?
in the lungs mainly
True or false:
clearance of Propofol exceeds liver blood flow?
True
What does the chemical structure of Propofol look like?
6 sided
CH(CH3)2 side chains (2)
and an OH side chain
After an IV bolus of Propofol the brain concentration peaks at what time period?
after 1 min.
Awakening from Propofol is due to what?
redistribution out of the brain
Explain the cardio vascular effects of propofol in relation to: BP SVR venous tone myocardial contractility
decreased BP (due to decreased SNS tone and vasodilation)
decreased SVR
decreased venous tone (leads to decreased preload)
decreased myocardial contractility
Respiratory effects of Propofol?
Shifts the CO2 response curve down and to the right ( less sensitive to CO2).
Resp. depression and / or apnea inhibits hypoxic ventilatory drive.
What are the CNS effects of Propofol? CMRO2 CBF ICP IOP
decreased CMRO2
decreased CBF
decreased ICP
decreased IOP
Does Propofol have analgesic properties?
No
Does Propofol have anticonvulsant properties?
Yes
Can Propofol cause seizures?
There are a few reported cases of Propofol inducing seizures, but these are very rare exceptions.
It can cause myoclonus
If a Propofol infusion changes the urine color to green or cloudy, what does it mean?
green urine = phenol excretion
cloudy urine = increased uric acid excretion (does not suggest renal impairment or infection)
Explain Propofol infusion syndrome on the molecular level?
Propofol contains long chain triglycerides, and an increased LCT load impairs oxidative phosphorylation and fatty acid metabolism. This starves cells of oxygen, particularly in the cardiac and skeletal muscle.
What are they symptoms of Propofol infusion syndrome?
It presents with acute refractory bradycardia leading asystole and 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 ) early sign
Are people who are allergic to eggs allergic to Propofol? Explain…
Most people with egg allergy are allergic to the albumin in the egg whites. Egg lecithin is derived from the yolk.
There is NO good evidence to support cross - sensitivity in egg allergic patients.
Is it safe to give people with egg allergies Propofol?
It is PROBABLY safe to administer to patients with egg allergies
Can patients who have a Soy allergy be given Propofol?
Any soy proteins that are capable of producing an immune response are removed during the refining process, thus propofol is safe to use in patients with soy allergies.
Can patients who have a peanut allergy be given Propofol?
Propofol is safe to administer to people with a Peanut allergy
What are the risk factors for developing Propofol infusion syndrome?
Propofol dose > 4mg/kg/hr ( 67mcg/kg/min)
Propofol infusion duration > 48 hours
Sepsis (inadequate oxygen delivery)
Continues catecholamine infusions
high-dose steroids
Significant cerebral injury
What is the treatment for Propofol infusion syndrome?
D/C propofol, maximize gas exchange, cardiac pacing, PDE inhibitors, glucagon, ECMO, and or renal replacement therapy
What patient population did PIS used to be the most common in?
PIS used to be most common in children but the FDA released a warning about prolonged infusions in children (ICU use not anesthesia) and now PIS is most common in adult and elderly critically ill patients.
Which formulations of Propofol are completely safe for asthmatic patients, can precipitate bronchospasm in asthmatic patients, and/ or should be avoided in infants?
Diprivan which contains EDTA is completely safe for asthmatic patients.
Generic propofol which contains metabisulfite can precipitate bronchospasm in asthmatic patients.
Also, generic propofol has benzyl alcohol which should be avoided in infants.
Is Propofol antipruritic?
10 mg IV can reduce itching caused by spinal opioids and cholestasis
Is Propofol antiemetic?
10-20 mg IV can be used to treat PONV,.
An infusion of 10mcg/kg/min can also be used.
induction agent most commonly (highest percentage) associated with PONV?
Etomidate
In patients with a history of acute intermittent porphyria, what medications should be avoided?
Ketamine Etomidate Barbiturates Ketorolac Amiodarone CCB (many but not all) Birth control pills
Clearance of Etomidate is by what?
Hepatic P450 enzymes and plasma esterase’s
Which induction agent is a known inhibitor of adrenocortical, and specifically what does it inhibit?
Etomidate - known inhibitor of 11-beta-hydroxylase and 17-alpha hydroxylase
Which induction agent is known to supress the baroreceptor reflex? (part of the reason for it’s drop in BP)
Propofol
Explain the chemical structure of Thiobarbiturates and give examples of this drug?
Sulfur molecule in the 2nd position (increases lipid solubility and potency)
examples = Thiopental, Thiamylal
Explain the ring / chemistry of all barbiturates in general?
The ring is six sided (six pointed). Position 1 starts in the lower right corner of the ring and position two is directly in the middle right side of the ring and position 3,4,5,6, proceed counter clockwise
If you add a methyl group onto the nitrogen of a barbiturate ring what does it do, what drug does it become?
lowers the seizure threshold and increases potency
Methohexital
If you add a phenyl group at the five carbon of a barbiturate ring what does it do, what drug does it become?
increases the anticonvulsant effect
Phenobarbital
How would you create an oxybarbiturate?
examples of oxybarbiturates?
There is an oxygen molecule in the 2nd position
example = methohexital, pentobarbital
Thiopental, what is its solubility medium? What is it’s pH?
water soluble
pH= 9 (highly alkaline)
What happens when you mix thiopental with an acidic solution?
precipitate forms
Does Thiopental have any active metabolites?
not at low doses but at higher doses it will have the active metabolite pentobarbital
GABA A agonist - depresses the reticular activating system in the brainstem describes?
Thiopental
Cardiovascular effects of Thiopental?
Hypotension is primarily the result of venodilation and decreased preload, myocardial depression is a 2ndary cause.
non-immunogenic histamine release is short lived (may contribute some to hypotension)
baroreceptor reflex stays intact thus reflex tachycardia helps restore cardiac output.
Neuroprotection of Thiopental?
Focal ischemia: yes, helpful with CEA, temporal occlusion of cerebral arteries.
Global ischemia: No (cardiac arrest)
What is Acute Intermittent Porphyria?
It is a defect in heme synthases that promotes the accumulation of heme precursors.
Heme is a key component of hemoglobin, myoglobin, and the cytochrome P450 enzymes.
AIP is made worse by stimulating the ALA synthase, emotional stress, prolonged NPO status, and CYP450 induction.
Phenobarbital is excreted unchanged in the urine, how is this different from other barbiturates?
all other barbiturates are metabolized by the P450 hepatic enzymes
What is the gold standard drug for ECT?
Methohexital, it decreases the seizure threshold and produces a better quality seizure