This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Intravenous Anesthetic Agents, Subject name: Anaesthesia
[{'content': 'All of the following are modes to decrease pain on injection caused by propofol cxcept \nSelect and explain. \nA. Mix lignocaine with propofol, B. Give fentanyl prior to propofo, C. Use vein on the dorsum of hand, D. Cooling of the drug', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Propofol is formulated as a lipid emulsion which causes pain during injection that can be decreased by using a large vein, avoiding veins in the dorsum of the hand, prior injection of lidocaine or by mixing lidocaine with propofol prior to injection (2 mL of 1% lidocaine in 18 mL propofol). prior injection of opioid Thicker vein decreases pain on injection caused by propofol.', 'role': 'assistant'}]