Procedural Sedation Practice Exam

Emergence phenomena are dissociative experiences—vivid dreams, disorientation, and sometimes hallucinations—that can occur as anesthesia wears off. Ketamine, a dissociative anesthetic that strongly blocks NMDA receptors, creates a unique brain state during recovery. As ketamine’s effects fade, the brain may re-enter consciousness in a fragmented, dreamlike way, leading to these unsettling experiences. That’s why emergence phenomena are most notably associated with ketamine.

Propofol, in contrast, typically produces a smooth, predictable emergence with minimal perceptual disturbances. Fentanyl, while it can cause sedation and respiratory effects, does not usually produce the dissociative, dreamlike awakenings characteristic of emergence phenomena. Dexmedetomidine can actually lessen emergence delirium and is sometimes used to mitigate ketamine’s effects.