Induction Drugs-(Propofol) (Ex 2) Flashcards
For Propofol, what are the doses for:
1. Induction
2. Maintenance
3. Conscious sedation
- Induction = 1.5 - 2.5 mg/kg IV
- Maintenance = 100 - 300 μg/kg/min
- Conscious sedation = 25 - 100 μg/kg/min
What is the concentration of a 1% solution?
- 10mg/mL
What are the inactive ingredients in propofol? Why is one particularly important?
- 1.2% Lecithin (from egg yolks) can cause anaphylaxis with egg allergies.
- 2.25% glycerol
- 10% soybean oil
What are the disadvantages of propofol’s inactive ingredient composition?
- ↑ bacterial growth
- ↑ plasma triglycerides with prolonged infusions
- Pain on injection
Differentiate Ampofol and Aquavan.
- Ampofol - low-lipid, no preservative that burns on injection more often.
- Aquavan - prodrug with less injection pain but causes dysesthesias. Slower onset, larger Vd, and high potency.
What is the mechanism of action of propofol?
- GABA-A receptor modulator that increases Cl⁻ conductance.
How does propofol cause immobility through spinal cord-depression?
- Trick question. Immobility from propofol is not from drug-induced spinal cord depression.
What are the clearance characteristics of propofol?
The clearance of propofol from plasma exceeds hepatic blood flow.
What metabolizes propofol?
- Hepatic CYP450 enzymes and excreted by kidneys.
What is the E ½ time of propofol?
- 30 - 90 minutes
What is the context-sensitive half-time of propofol? Is this a relatively low or high context half-time?
- 40 minutes (for an 8 hour infusion)
- Low CS ½ time.
What are the following characteristics of propofol:
1. Elimination ½ time.
2. Volume of distribution
3. Clearance (mL/kg/min)
- E ½ time = 30 - 90 minutes
- Vd = 3.5 - 4.5
- Clearance = 30 - 60 mL/kg/min
Differentiate blood pressure and heart rate changes that occur with propofol vs thiopental.
- Propofol: ↓BP & ↓HR
- Thiopental: ↓BP & ↑HR
Does propofol cross the placenta? What are the consequences of this?
- Yes but is rapidly cleared from neonatal circulation.
Do cirrhosis and renal dysfunction have significant effects on propofol metabolism?
No significant impact
What drug is the induction drug of choice?
Propofol
What is the induction dose of propofol in adults? Children?
- Adults: 1.5-2.5 mg/kg IV
- Pediatrics: higher doses due to larger central volume and clearance rate.
What is the induction dose of propofol in the elderly?
25 - 50% lower than regular adult
What plasma propofol levels would correlate with unconsciousness?
What about awakening?
- Unconscious: 2 - 6 μg/mL
- Awake: 1 - 1.5 μg/mL
What is the conscious sedation dose of propofol?
- 25 - 100 μg/kg/min
What are the anesthetic characteristics of propofol in the context of conscious sedation?
- Minimal analgesia but has anti-convulsive and amnestic properties.
- Prompt recovery w/ low residual sedation
- ↓ risk of PONV
- Midazolam or opioids as adjuncts.
What are the anti-emetic properties of propofol?
Why is this thought to occur?
- Very anti-emetic (more effective than ondansetron)
- Direct depressant of vomiting center
What is the sub-hypnotic dosing for propofol?
- 10 - 15 mg IV, followed by 10 mcg/kg/min
What is the anti-pruritic dosing of propofol?
- 10 mg IV
What is the anti-convulsant dosing of propofol?
1mg/kg IV
What are “other” category benefits of propofol?
- Bronchodilation
- Anti-emetic
- Anti-pruritic
- Anti-convulsant
- Low dose analgesia
- Antioxidant
- Does not trigger MH
What are propofol’s effects on CMRO₂, CBF, and ICP?
- ↓ CMRO₂, CBF, and ICP
Large doses of propofol may ______ cerebral perfusion pressure.
decrease
Though propofol will not produce seizures, it will produce _______.
myoclonus (originates from the muscle)
Between thiopental, propofol, and isoflurane, which is the least EEG suppressive?
- Propofol
Which would decrease blood pressure more, thiopental or propofol?
Propofol
What is the mechanism for propofol-induced hypotension?
What conditions will exaggerate this effect?
- SNS inhibition causing ↓SVR and ↓ intracellular Ca⁺⁺.
- Hypovolemia, elderly, and LV compromise
How is propofol-induced hypotension from induction usually counteracted?
- Intubation (from laryngeal stimulation).
Why is bradycardia seen with propofol?
What would occur with propofol overdose?
- ↓SNS response & baroreceptor reflex
depression. - Profound bradycardia & eventual asystole.
What are the pulmonary effects of propofol?
How does this change with opioids?
- Dose-dependent depression of ventilation.
- Synergistic resp depression with opioids
What severe condition(s) can occur with prolonged propofol infusions?
- Hepatocellular injury or Propofol Infusion Syndrome.
What is Propofol Infusion Syndrome?
- Metabolic acidosis thought to occur from poisoning of electron transport chain and impaired oxidation of fatty acids.
What relatively benign condition(s) can occur from prolonged propofol infusions?
Why does this happen?
Green and cloudy urine from phenols and uric acid crystals.
Neither alters renal function.
What sort of infusion dosing can result in propofol infusion syndrome?
- > 75 μg/kg/min for longer than 24 hours
What is the worst side effect in children who have propofol infusion syndrome?
- Severe, refractory, fatal bradycardia
What are the symptoms of propofol infusion syndrome?
How is propofol infusion syndrome diagnosed?
- Urine changes, lactic acidosis, brady-dysrhythmias, and rhabdomyolysis.
- ABG & serum lactate concentrations.
What are the “other” organ system effects of propofol?(5)
- Injection pain (lido before)
- ↓ IOP
- Plt aggregation inhibition
- Allergic reactions (lecithin)
- Prolonged myoclonus
