Which of the following items best explains the short action of diazepam in inducing unconsciousness for a laparoscopic hernia repair?

Correct Answer: C

Rationale: The correct answer is C: Redistribution of the drug from the central nervous system to other tissues. Diazepam exerts its effects by initially acting on the central nervous system to induce unconsciousness. However, its short action is mainly due to its redistribution from the central nervous system to other tissues, leading to a decrease in its concentration at the site of action. This redistribution process results in a rapid termination of its sedative effects. Choice A is incorrect because rapid metabolism within the central nervous system does not explain the short action of diazepam. Choice B is incorrect as rapid excretion by the kidneys is not the primary reason for the short duration of action. Choice D is also incorrect because biotransformation into inactive metabolites does not directly contribute to the rapid induction of unconsciousness.

Correct Answer: C

Rationale: The correct answer is C: Fentanyl and ketamine. Fentanyl is a potent opioid analgesic, while ketamine is a dissociative anesthetic. This combination is commonly used for procedures requiring analgesia and sedation. Fentanyl provides pain relief, and ketamine induces a dissociative state for anesthesia. Thiopental and midazolam (choice D) are both sedatives, not commonly used together. Fentanyl and thiopental (choice A) are both sedatives, but lacking in analgesic effects. Fentanyl and midazolam (choice B) offer sedation and anxiolysis, but lack the dissociative anesthesia provided by ketamine.

Correct Answer: A

Rationale: The correct answer is A: Halothane. Halothane is contraindicated in patients with a history of malignant hyperthermia, a rare but life-threatening condition triggered by certain anesthetics. Using halothane in such patients can lead to a dangerous reaction. Fentanyl (B), Lorazepam (C), and Thiopental (D) do not have the same risk of triggering malignant hyperthermia and are commonly used in anesthesia protocols. Therefore, Halothane is the only drug in the options that would be contraindicated in this scenario.

Correct Answer: C

Rationale: The correct answer is C: Lidocaine. Lidocaine is an amide-type local anesthetic that does not contain PABA, making it suitable for a patient with a history of anaphylactic reaction to PABA. Procaine (A) is an ester-type local anesthetic that metabolizes into PABA. Tetracaine (B) is also an ester-type local anesthetic that may cross-react with PABA. Benzocaine (D) is a para-aminobenzoic acid derivative and should be avoided in patients with a history of anaphylaxis to PABA.

Correct Answer: C

Rationale: The correct answer is C: Vecuronium. This drug was most likely administered to achieve muscle relaxation in the 74-year-old man with impaired hepatic and renal function undergoing abdominal surgery because it is primarily eliminated through the liver and does not require renal excretion. This makes it a safer choice in patients with impaired hepatic and renal function. Succinylcholine (A) can cause hyperkalemia in renal failure patients. Tubocurarine (B) is eliminated through the kidneys, which can be problematic in renal impairment. Mivacurium (D) is metabolized by plasma cholinesterase, which can be affected in liver dysfunction.