Fentanyl can produce significant respiratory depression by:

Correct Answer: D

Rationale: The correct answer is D because fentanyl can produce significant respiratory depression by inhibiting brain stem respiratory mechanisms (choice A) and by causing truncal rigidity (choice C). Inhibiting brain stem respiratory mechanisms affects the control of breathing, leading to decreased respiratory rate and depth. Truncal rigidity can impair chest wall movement, further reducing respiratory function. Choice B, suppression of the cough reflex leading to airway obstruction, is incorrect as it does not directly relate to respiratory depression caused by fentanyl.

Correct Answer: D

Rationale: The correct answer is D: Phenelzine. Phenelzine is an irreversible MAO inhibitor that irreversibly binds to and inhibits monoamine oxidase enzymes. This irreversible binding leads to a long-lasting inhibition of MAO activity. Moclobemide (A) is a reversible MAO inhibitor, while Selegiline (B) is a selective irreversible MAO-B inhibitor. Tranylcypramine (C) is a reversible MAO inhibitor. Therefore, Phenelzine is the only irreversible MAO inhibitor among the options provided.

Correct Answer: D

Rationale: The correct answer is D: Gastric ulceration. Caffeine is not typically associated with causing gastric ulcers. Caffeine is actually used as a treatment for migraines due to its ability to constrict blood vessels. It is also used to relieve drowsiness (somnolence) by stimulating the central nervous system. Additionally, caffeine can help improve cardiovascular function and respiratory efficiency, so choices A, B, and C are all potential therapeutic uses of caffeine.

Correct Answer: A

Rationale: The correct answer is A: TRUE. Opioid withdrawal symptoms typically start 8-10 hours after the last dose due to the short half-life of opioids. This timing aligns with the onset of symptoms such as anxiety, sweating, and muscle aches. The other choices are incorrect. Choice B is false because the onset of opioid withdrawal symptoms does not occur immediately after the last dose. Choice C, All, is incorrect as it implies that all choices are correct, which is not the case. Choice D, Null, is also incorrect as it does not provide any relevant information regarding the onset of opioid withdrawal symptoms.

Correct Answer: D

Rationale: The correct answer is D because ketamine anesthesia is associated with cardiovascular stimulation due to its sympathomimetic effects. It also increases cerebral blood flow, oxygen consumption, and intracranial pressure. Additionally, disorientation, sensory and perceptual illusions, and vivid dreams can occur post-anesthesia due to its psychotomimetic properties. Choices A, B, and C individually do not fully encompass the range of effects associated with ketamine anesthesia, making D the correct choice.