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
Biphasic respiratory depression is usually seen after: 
Select and explain. 
A. Neuroleptanaesthesia, B. Regional anaesthesia, C. Halothane anaesthesia, D. Isoflurane anaesthesia
A: Neuroleptanaesthesia
Answer: A: Neuroleptanaesthesia 
Explanation: 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.