Which of the following anesthetic agent causes dissociative anesthesia:-

Ketamine produces dose-dependent CNS depression leading to a so-called dissociative anesthetic state characterized by profound analgesia and amnesia, even though patient is conscious and maintains protective reflexes. Ketamine produces dissociative anesthesia through antagonistic actions at thephencyclidinesite of theNMDARmediated glutamatergic input to the GABA-ergic system. Dissociative anesthesia is a state where the patient appears conscious (eg, eye opening, swallowing, muscle contracture) but unable to process or respond to sensory input. Ketamine functionally "dissociates" thethalamus(which relays sensory impulses from the reticular activating system to the cerebral coex) from thelimbic coex(which is involved with the awareness of sensation).