Which of the following reasons best explains why general anesthesia induced by a standard dose of thiopental lasts 5 to 15 minutes?

Correct Answer: C

Rationale: The correct answer is C. Thiopental's short duration of action is primarily due to its rapid redistribution from the brain to peripheral tissues, leading to a quick recovery. Slow distribution into the CNS, fast elimination, and poor diffusion into central neurons would not explain the short duration of action observed with thiopental.

Correct Answer: C

Rationale: Lidocaine would be the most appropriate choice for a pregnant woman with a history of anaphylactic reaction to para-aminobenzoic acid (PABA). Lidocaine is an amide local anesthetic that does not contain PABA and is less likely to trigger an allergic reaction in individuals sensitive to this compound. It is important to choose a local anesthetic that is safe for the patient and avoids any potential allergic responses.

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.