Which of these effects is NOT associated with nitrous oxide?

Long-lasting sedation is not associated with nitrous oxide, making it the correct answer in this context. Nitrous oxide is primarily used for its rapid onset and offset effects, allowing patients to recover quickly after its use. It produces sedation that is transient and does not persist once the administration of the gas is stopped. This characteristic makes it an ideal choice for procedures requiring short-term anxiety relief or pain management, as the effects wear off relatively quickly.

In contrast, nitrous oxide does promote anxiety reduction and provides analgesic (pain-relieving) effects, which are crucial for its role in various medical and dental procedures.