Unit 4 Pharmacology: IV Anesthetics Flashcards
What is the chemical name of propofol?
2,6-diisopropylphenol
What is the drug class of propofol?
Isopropylphenol
What is the formulation of propofol?
1% oil in water
- soybean oil 10%
- glycerol 2.25%
- egg lecithin (yolk) 1.2%
What is the pKa of propofol?
11
What preservatives are used in propofol?
Diprivan : disodium edetate (EDTA)
Generics: metabisulfate OR benzyl alcohol
What side effect can be caused by the preservative EDTA in propofol?
None, it is not an irritant to the bronchi
What side effect can occur from the preservative metabisulfate in propofol?
Can cause bronchospasm in patients with asthma
What side effect can occur from the additive benzyl alcohol in propofol?
In infants the benzyl alcohol can accumulate in the brain because they can break it down, but they can not conjugate it
What is the MOA of propofol?
Direct GABA-A agonist
- increases Cl- conductance
- leads to neuronal hyperpolarization
What is the adult induction dose of propofol?
1-2 mg/kg
What is the adult infusion rate of propofol?
25-200 mcg/kg/min
What is the induction dose that should be used for the elderly, debilitated or hypokalemic patient?
1-1.5 mg/kg
What is the onset of propofol?
30-60 seconds
What is the duration of propofol?
5-10 minutes
When does brain concentration of propofol peak?
~ 1 min
What causes reawakening with propofol use?
Redistribution out of the brain
Propofol context sensitivity?
Pretty insensitive
XX
Clearance of propofol is by?
Liver : P450
-clearance exceeds liver blood flow
Extrahepatic metabolism : lungs (mostly)
Propofol alpha 1/2 time? Beta 1/2 life?
Alpha 1/2 time : 2-8 minutes
Beta 1/2 life : 1-2 hours
Does propofol have an active metabolite?
No
What is the pKa of propofol?
11
Is propofol an acid or base?
Weak acid
Propofol protein binding?
98%
Is propofol more ionized or non-ionized (with normal physiologic pH)?
More non-ionized
How long in an open bottle of propofol okay to use? Propofol in a syringe?
12 hours
6 hours
Does propofol cross the placenta?
Yes
Cardiovascular effects of propofol:
Decreased BP due to decreased tone and vasodilation
Decreased SVR
Decreased venous tone -> decreased preload
Decreased myocardial contractility
Why does propofol decrease BP?
Decreased SNS and vasodilation
In what patients is the decrease in BP from propofol greater?
Geriatric patients
LV dysfunction
Why does CO decrease with propofol?
Decreases contractility (negative inotrope) Decreases venous tone which decreases preload
Why does propofol cause respiratory depression?
It shifts the CO2 response curve down and right (less sensitive to CO2)
Inhibits hypoxic ventilatory drive
Does propofol cause bronchodilation?
No/maybe
Per Nagelhout: 0/⬆️
CNS effects of propofol:
Decreased cerebral oxygen consumption (CMRO2)
Decreased cerebral blood flow
Decreased intracranial pressure
Decreased intraocular pressure
Anticonvulsant properties
Myoclonus may occur
Few cases of it inducing seizures, but this is very rare
How can propofol make cloudy urine?
Increased Uris acid excretion - does not suggest renal impairment or infection
Why does propofol decrease cerebral perfusion pressure?
Due to the decrease in MAP
Does propofol contain antioxidant properties?
Yes - free radical scavenging properties
What is believed to be the cause of propofol infusion syndrome (PRIS)?
Propofol contains an increased level of long-chain triglycerides, which impairs oxidative phosphorylation and fatty acid metabolism, this starves cells of oxygen (particularly cardiac and skeletal muscle)
Why can propofol cause green urine?
From phenol exrection
What rate/dose is a risk factor for PRIS?
> 4mg/kg/hr (67mcg/kg/min)
How many days on propofol infusion is a risk factor for PRIS?
> 48 hours
What are other risk factors are there for PRIS besides rate and consecutive days infused?
Sepsis - inadequate oxygen delivery Catecholamine infusions High dose steroids Significant cerebral injury Children (FDA warning decreased occurrence)
Signs and symptoms of PRIS?
Acute refractory bradycardia that can lead to asystole AND at least one of the following:
- metabolic acidosis (base deficit > 10 mmol/L)
- Rhabdomylosis
- Enlarged/fatty liver
- Renal failure
- HLD
- lipemia may be an early sign
What CK results is a high risk for PRIS?
> 5,000
What is the treatment for PRIS?
Stop propofol Maximize gas exchange Cardiac pacing PDE inhibitors Glucagon ECMO and/or renal replacement therapy
What dose of propofol has an antipruritic effect? Antiemetic?
Antipruretic: 10mg - itching caused by opioids and cholestasis
Antiemetic: 10-20 mg - can be used for PONV (infusion 10 mcg/kg/min)
What is the chemical name of Fospropofol?
Phosphono-O-methyl-2-6-diisopropylphenol
What is the class of Fospropofol?
Isopropylphenol
What is the formulation of fospropofol?
Aqueous solution
What benefits does the formulation of fospropofol have over propofol?
Prevents burning on injection
Doesn’t support microbial growth
What is the MOA of fospropofol?
It is a prodrug
It is metabolized by alkaline phosphatase into propofol
What is the induction dose of fospropofol?
6.5 mg/kg
What is the repeat dose for fospropofol? How often can it be re-dosed?
1.6 mg/kg
Not more than every 4 minutes
What is the onset of fospropofol?
5 - 13 minutes
What is the duration of fospropofol?
15 - 45 minutes
How is fospropofol cleared?
Since it is metabolized to propofol, the same as it.
Liver P450 enzymes plus extra hepatic metabolism (mostly lungs)
Does fospropofol have an active metabolite?
Fospropofol is a prodrug, and propofol is the active metabolite
The formaldehyde is metabolized to formate and excreted in the urine
What is a “nasty” side effect of fospropofol?
Genital and anal burning
What is the chemical name of ketamine?
2-(o-Chloropheyl)-2 (methylamino) cyclohexanone hydrochloride
What class is ketamine?
Arylcyclohexylamine - a phencyclidine derivative
What is the formulation of ketamine?
Aqueous solution
It is a racemic mixture
What is the pKa of ketamine?
7.5
What is the MOA of ketamine?
NMDA receptor antagonist - antagonizes glutamate
Secondary receptors: opioid, MAO, serotonin, ME, muscarinic, Na+ channels
What dissociative effect does ketamine have?
It dissociates the thalamus (sensory) from the limbic system (awareness)
IV doses for Ketamine: Induction Maintenance Infusion Analgesia
Induction: 1 -2 mg/kg
Maintenance: 1 - 3 mg/min
Infusion: 1 - 3 mcg/kg/min (opioid sparing)
Analgesia: 0.1 - 0.5 mg/kg
What is the IM dose for ketamine?
4 - 8 mg/kg
What is the PO dose for ketamine?
10 mg/kg
What is the onsets for ketamine?
IV
IM
PO
IV: 30 - 60 sec
IM: 2 - 4 minutes
PO: variable
What is the duration of ketamine?
10-20 minutes
How is ketamine cleared?
Liver P450
Does ketamine have an active metabolite?
Norketamine
It is 1/3 - 1/5 the potency of ketamine
How is ketamine excreted?
Renal excretion
What are the CV effects of ketamine?
Increases SNS tone Increases CO Increases HR Increases SVR Increases pulmonary vascular resistance - caution with severe RV failure
What can you do if you want to use ketamine without activating the SNS?
Use subhypnotic dose - <0.5 mg/kg
What happens if ketamine is given to a patient with depleted cathecholamine stores (like sepsis or sympathetomy)
Ketamine is actually a myocardial depressant, with an intact SNS one will see the expected CV effects of ketamine. Without an intact SNS the myocardial depressant effects will be unmasked.
What are the respiratory effects of ketamine?
Bronchodilation
Upper airway muscle tone and airway reflexes remain intact
Maintains respiratory drive (brief period of apnea can occur)
Does not significantly shift the CO2 response curve
Increased oral and pulmonary secretions - Glyco helps
What are the CNS effects of ketamine?
Increased CMRO2 Increased cerebral blood flow Increased intracranial pressure Increased intraocular pressure Increased EEG activity - caution if Hx of seizures Nystagmus - caution with ocular sx Emergence delirium
How does emergence delirium from ketamine present, and how does the risk last?
Nightmares and hallucinations
Risk persists for up to 24 hours
What can you give to help prevent emergence delirium from ketamine? What works best?
Benzodiazepine
Midazolam is better than diazepam