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': "In all of the following, sympathectomy is effective except one - \nSelect and explain. \nA. Intermittent claudication, B. Hyperhydrosis, C. Raynaud's disease, D. Causalgia", 'role': 'user'}, {'content': "Answer: A \nExplanation: Sympathectomy is of no value in intermittent claudication as sympathectomy does not influence muscle blood flow. Blood flow in the skin but not in the muscle is controlled by sympathetic nervous system. If the arterial supply is inadequate, ischemic changes in the skin may be relieved by sympathetic blockage but the impaired blood flow to muscles is unlikely to improve.\nPossible indications\xa0for svmpathectomy.\n\nIschemic disorders mainly of the limbs.\nBuerger's ds.\nRaynand's ds.\nArterial injury or embolism\nAcrocyanosis\nErythrocyanosis\nFrost bite\nHyperhydrosis\nCausalgia\nVisceral pain\nFor healing of an amputation stump\nAtherosclerotic ischemia of limb", 'role': 'assistant'}]