CGRN Pharmacology and Sedation 2 — Questions and Answers
Question 1: What is the mechanism of action of propofol used for endoscopic sedation?
- Opioid receptor agonist
- GABA-A receptor potentiation (Correct answer)
- NMDA receptor antagonist
- Serotonin receptor modulation
Correct answer: GABA-A receptor potentiation
Propofol potentiates GABA-A receptor activity, producing rapid-onset sedation with very short duration.
Propofol enhances GABA-A receptor function at a distinct site from benzodiazepines. Rapid onset (30-45 sec), ultra-short duration (5-10 min), no analgesic properties. Lipid emulsion formulation — caution with egg/soy allergy. No specific reversal agent.
Question 2: A patient receiving fentanyl and midazolam becomes unresponsive. Which medication should be given first?
- Flumazenil 0.2 mg IV
- Naloxone 0.4 mg IV
- Naloxone 0.04-0.1 mg IV titrated (Correct answer)
- Epinephrine 1 mg IV
Correct answer: Naloxone 0.04-0.1 mg IV titrated
Start with low-dose naloxone (0.04-0.1 mg) titrated to reverse respiratory depression while minimizing pain reversal.
In combined sedation, respiratory depression is usually opioid-mediated. Low-dose naloxone titration avoids complete reversal which could cause severe pain and hemodynamic instability. If respiratory depression persists, add flumazenil 0.2 mg.
Question 3: Which PPI has the strongest CYP2C19 inhibition and highest drug interaction potential?
- Pantoprazole
- Omeprazole (Correct answer)
- Esomeprazole
- Rabeprazole
Correct answer: Omeprazole
Omeprazole has the strongest CYP2C19 inhibitory effect, particularly affecting clopidogrel.
Omeprazole inhibits CYP2C19, reducing clopidogrel's antiplatelet effect. The FDA warns against concurrent use. Pantoprazole has the least CYP2C19 inhibition and is preferred with clopidogrel.
Question 4: What is the primary advantage of CO2 insufflation over room air during endoscopy?
- Better visualization
- CO2 is absorbed 150 times faster than nitrogen, reducing post-procedure bloating (Correct answer)
- CO2 is less expensive
- CO2 eliminates the need for sedation
Correct answer: CO2 is absorbed 150 times faster than nitrogen, reducing post-procedure bloating
CO2 is absorbed 150 times faster than nitrogen, dramatically reducing post-procedure distention and pain.
CO2 absorption is 150x faster than nitrogen. Multiple RCTs confirm superior patient comfort. The absorbed CO2 is eliminated via pulmonary ventilation. Caution in severe COPD. Visualization quality is equivalent to room air.
Question 5: What antibiotic prophylaxis is recommended before endoscopy in a patient with a prosthetic heart valve?
- Amoxicillin 2g IV
- Ampicillin-sulbactam IV
- No antibiotic prophylaxis is recommended (Correct answer)
- Vancomycin 1g IV
Correct answer: No antibiotic prophylaxis is recommended
Current guidelines do NOT recommend routine antibiotic prophylaxis for GI endoscopy solely for cardiac conditions.
AHA and ASGE guidelines concluded that routine prophylaxis is not recommended even for prosthetic valves. Antibiotics ARE recommended for specific situations: cholangitis, incompletely drained biliary obstruction, EUS-FNA of cystic lesions, and PEG placement.
Question 6: What is the onset time and peak effect of IV midazolam for endoscopic sedation?
- Onset 30 seconds, peak 1 minute
- Onset 1-2 minutes, peak 3-5 minutes (Correct answer)
- Onset 5 minutes, peak 15 minutes
- Onset 10 minutes, peak 30 minutes
Correct answer: Onset 1-2 minutes, peak 3-5 minutes
IV midazolam has onset of 1-2 minutes with peak at 3-5 minutes.
Wait at least 2-3 minutes between doses to assess peak effect. Rapid stacking without waiting for peak is the most common cause of oversedation. Initial dose 0.5-2 mg; elderly patients need dose reduction. Synergistic with opioids — reduce combined doses by 30-50%.
CGRN Pharmacology and Sedation 2
What is the mechanism of action of propofol used for endoscopic sedation?