This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous General Anesthesia, Subject name: Anaesthesia
Which of the following produces dissociated anesthesia 
Select and explain. 
A. Ketamine, B. Propofol, C. Thiopentone, D. Enflurane
A: Ketamine
Answer: A: Ketamine 
Explanation: Ans. is 'a' i.e. Ketamine Mechanism of action of ketamineKetamine dissociatesThalamus from limbic cortexThalamus relays sensory inputs from R.A.S. (reticular activating system) to limbic cortex. Clinically this produces dissociative anaesthesia. In this state the patient appears conscious (e.g. eye opening, swallowing, muscle contracture); but is unable to process or respond to sensory input.