A 3-year-old boy was brought to the emergency department. Which of the following ion channels does activation of GABA receptors in the brain and spinal cord most likely open?

Correct Answer: B

Rationale: The correct answer is B: Cl. When GABA receptors are activated, they allow Cl- ions to flow into the neuron, leading to hyperpolarization and inhibition of neuronal firing. This process is crucial for maintaining the balance of excitation and inhibition in the brain and spinal cord. Choices A, C, and D are incorrect as activation of GABA receptors does not directly involve K+, Ca2+, or Mg++ ion channels.

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: Eszopiclone. Eszopiclone is a non-benzodiazepine hypnotic commonly used to treat insomnia. It is suitable for the 49-year-old woman experiencing difficulty sleeping as it helps initiate and maintain sleep without causing dependence or tolerance issues. Flunitrazepam (A) is a benzodiazepine with high potential for abuse and dependence. Buspirone (B) is an anxiolytic drug, not specifically indicated for insomnia. Fluoxetine (D) is an antidepressant, which may not directly address the sleep issue. Therefore, Eszopiclone is the most appropriate choice for treating the woman's sleep problem.

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.