This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anaesthesia
[{'content': 'Which of the following anesthetic agent lacks analgesic effect: March 2013 \nSelect and explain. \nA. N20, B. Thiopentone, C. Ketamine, D. Fentanyl', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B i.e. Thiopentone Thiopentone Ultra sho acting barbiturate (because of rapid redistribution), Lacks analgesic effect, First sign on intra-aerial injection: - White hands I/V injection presents as: - Pain, - Hypotension etc. C/I in: Porphyria (may precipitate porphyria)', 'role': 'assistant'}]