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: Surgery
[{'content': 'Biphasic respiratory depression is usually seen after: \nSelect and explain. \nA. Neuroleptanaesthesia, B. Regional anaesthesia, C. Halothane anaesthesia, D. Isoflurane anaesthesia', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Neuroleptanaesthesia is produced by droperidol + fentanyl. Fentanyl after IV injection is sequestered by stomach in significant amounts, released into circulation after 3-6 hours and can produce second phase of respiratory depression i.e., biphasic respiratory depression.', 'role': 'assistant'}]