Beta Blockers USMLE Step 1 Practice Question
A 27-year-old man with a hand abscess presents for incision and drainage. Vital signs show BP 128/82 mmHg, HR 92 bpm, RR 16/min, Temp 38.9°C, SpO2 98% on room air. Despite lidocaine injection, he reports severe pain. Local culture grows Staphylococcus aureus with abscess pH of 5.8. He denies prior antibiotic use. Which mechanism best explains the reduced anesthetic effectiveness in this acidic, inflamed tissue environment?
Answer choices
- AThe anesthetic requires alkaline urine for activation
- BMore drug remains ionized and cannot cross the nerve membraneCorrect answer
- CInflammation causes increased protein binding and reduced potency
- DThe acidic environment irreversibly blocks sodium channels
- EThe drug is degraded too quickly by plasma esterases
- FIncreased vascularity at the infection site accelerates systemic absorption
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