Which of the following local anesthetics would be most appropriate for a 4-day-old boy with methemoglobinemia?

Correct Answer: A

Rationale: Lidocaine is the most appropriate choice for a 4-day-old boy with methemoglobinemia as it is less likely to cause further methemoglobinemia compared to other local anesthetics. This is important to prevent exacerbating the baby's condition. Lidocaine is considered safe for use in pediatric patients and is commonly used in this population for minor procedures.

Correct Answer: C

Rationale: In a patient with impaired hepatic and renal function, Vecuronium is the most appropriate choice for muscle relaxation as it is primarily eliminated through hepatic metabolism and does not require renal excretion. Succinylcholine is contraindicated in patients with impaired renal function due to the risk of hyperkalemia. Tubocurarine, Mivacurium, and Cisatracurium may have prolonged effects in patients with impaired liver function, making Vecuronium the safest choice in this scenario.

Correct Answer: B

Rationale: Botulinum toxin primarily acts at somatic nerve terminals by blocking the release of acetylcholine, leading to muscle paralysis. In the context of strabismus treatment, the toxin targets the nerve terminals supplying the extrinsic ocular muscles, specifically affecting neuromuscular transmission at the neuromuscular junction. This action results in localized muscle weakness and temporary paralysis, aiding in the correction of strabismus.

Correct Answer: A

Rationale: Tubocurarine is a non-depolarizing muscle relaxant that is metabolized by plasma cholinesterase. In a patient with a deficiency of plasma cholinesterase, tubocurarine would not be metabolized properly, leading to prolonged effects and potential toxicity. Therefore, it would be contraindicated in this patient.

Correct Answer: B

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.