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

Correct Answer: D

Rationale: The correct answer is D: Tetracaine. Tetracaine is a local anesthetic that is least likely to cause methemoglobinemia in infants due to its minimal systemic absorption. Lidocaine, benzocaine, and bupivacaine have been associated with an increased risk of methemoglobinemia, especially in young infants. Lidocaine and bupivacaine are more systemically absorbed and can lead to higher levels of methemoglobin formation. Benzocaine is particularly risky in infants due to its association with methemoglobinemia. Tetracaine, on the other hand, has a lower systemic absorption rate and therefore poses a lower risk of causing methemoglobinemia in infants, making it the most appropriate choice for a 4-day-old boy with this condition.

Correct Answer: B

Rationale: The correct answer is B: Dantrolene. Dantrolene is a muscle relaxant that acts directly on the skeletal muscle to reduce muscle tone and counteract tubocurarine-induced hypotension in the 65-year-old woman undergoing hysterectomy. Botulinum toxin is used for muscle spasticity, not hypotension. Succinylcholine is a short-acting muscle relaxant, not used for hypotension. Tubocurarine is the drug causing the hypotension, not used to counteract it.

Correct Answer: A

Rationale: The correct answer is A: Tubocurarine. Tubocurarine is a non-depolarizing neuromuscular blocking agent that can cause histamine release, leading to bronchoconstriction, which is dangerous for a patient with chronic obstructive pulmonary disease (COPD) and a heavy smoker undergoing major surgery. Glycopyrrolate (B) is a muscarinic antagonist that can be used to reduce secretions during surgery. Clonidine (C) is an alpha-2 adrenergic agonist that can help with perioperative hypertension. Vecuronium (D) is a non-depolarizing neuromuscular blocking agent, like tubocurarine, but it does not cause histamine release, making it a safer option for this patient.

Correct Answer: B

Rationale: The correct answer is B: Baclofen. Baclofen is a muscle relaxant commonly used to treat spasticity in conditions such as multiple sclerosis or spinal cord injuries. This drug would be appropriate for a patient experiencing muscle spasticity. Phenobarbital (A) is a barbiturate used for seizures, not muscle relaxation. Tubocurarine (C) and Succinylcholine (D) are neuromuscular blocking agents used for muscle paralysis during surgery, not for muscle spasticity. Therefore, Baclofen is the most appropriate choice for this patient.

Correct Answer: B

Rationale: The correct answer is B: Valproic acid. This drug is commonly used to treat bipolar disorder, which is characterized by mood swings. Valproic acid helps stabilize mood and prevent manic episodes. Lamotrigine (A) is used for bipolar disorder but is less effective for acute mania. Clonazepam (C) is used for anxiety and seizures, not bipolar disorder. Gabapentin (D) is primarily used for nerve pain and seizures, not bipolar disorder. Therefore, based on the context of the question, Valproic acid is the most likely drug she was taking.