MAC Pharmacology & Physiology in Anesthesia 5

Question 1

What is the recommended initial bolus of 20% lipid emulsion for local anesthetic systemic toxicity in an adult over 70 kg?

Accepted Answer

1.5 mL/kg (about 100 mL)

Answer

ASRA guidance is a 100 mL bolus over 2-3 minutes for patients over 70 kg (1.5 mL/kg if under 70 kg), followed by an infusion.

Question 2

Which local anesthetic carries the greatest risk of refractory cardiotoxicity?

Accepted Answer

Bupivacaine

Answer

Bupivacaine binds cardiac sodium channels avidly and dissociates slowly ('fast-in, slow-out'), which causes hard-to-treat arrhythmias.

Question 3

Dantrolene treats malignant hyperthermia by acting on which target?

Accepted Answer

Ryanodine receptor (RyR1) on the sarcoplasmic reticulum

Answer

Dantrolene binds RyR1 and reduces uncontrolled calcium release from the sarcoplasmic reticulum.

Question 4

Which topical anesthetic is most associated with methemoglobinemia?

Accepted Answer

Benzocaine

Answer

Benzocaine sprays are a classic cause of methemoglobinemia, along with prilocaine; treatment is methylene blue.

Question 5

Which adverse effect is a recognized concern with ondansetron?

Accepted Answer

QT interval prolongation

Answer

Ondansetron, a 5-HT3 antagonist, can prolong the QT interval in a dose-dependent way.

MAC - Maintaining Anesthesia Certification Practice Test