Indicate the local anesthetic, which is mainly used for regional nerve block anesthesia:

Correct Answer: B

Rationale: The correct answer is B: Tetracaine. Tetracaine is a long-acting local anesthetic commonly used for regional nerve block anesthesia due to its duration of action. It provides effective and prolonged pain relief in a specific area by blocking nerve conduction. Procaine (A) is a short-acting local anesthetic, making it less suitable for regional nerve block anesthesia. Bupivacaine (D) is a long-acting local anesthetic like tetracaine, but it is more commonly used for epidural or spinal anesthesia rather than regional nerve blocks. Therefore, tetracaine is the most appropriate choice for regional nerve block anesthesia among the options provided.

Correct Answer: C

Rationale: The correct answer is C (Pancuronium). Pancuronium is a non-depolarizing neuromuscular blocker that can cause tachycardia by blocking muscarinic receptors leading to the inhibition of the parasympathetic system. This results in the dominance of the sympathetic system, leading to tachycardia. Tubocurarine (A) and Atracurium (B) are also non-depolarizing neuromuscular blockers, but they do not directly cause tachycardia. Succinylcholine (D) is a depolarizing neuromuscular blocker that can cause bradycardia due to its effects on acetylcholine receptors at the neuromuscular junction.

Correct Answer: D

Rationale: The correct answer is D because ephedrine actually increases arterial pressure by stimulating alpha-adrenergic receptors, leading to vasoconstriction. A is incorrect as ephedrine works by directly stimulating adrenergic receptors, not by releasing stored catecholamines. B is correct as ephedrine is indeed a mild CNS stimulant. C is incorrect as tachyphylaxis, or a rapid decrease in response with repeated administration, is not commonly associated with ephedrine.

Correct Answer: B

Rationale: The correct answer is B: Metoprolol. Metoprolol is a cardioselective beta blocker, meaning it primarily targets beta-1 receptors in the heart and has minimal effect on beta-2 receptors in the lungs. This makes it preferable in patients with asthma as it reduces the risk of bronchoconstriction compared to non-selective beta blockers like Propranolol (choice A). Metoprolol also has a lower risk of masking hypoglycemic symptoms in diabetic patients compared to non-selective agents. Nadolol (choice C) and Timolol (choice D) are non-selective beta blockers and may worsen asthma and peripheral vascular diseases due to their effects on beta-2 receptors.

Correct Answer: C

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