This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology and breast, Subject name: Surgery
[{'content': 'Once phaeochromocytoma is diagnosed, preoperatively following is given \nSelect and explain. \nA. Alpha adrenergic agonist, B. Alpha adrenergic blocker, C. Beta adrenergic blocker, D. Beta adrenergic blocker', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Once a phaeochromocytoma has been diagnosed, an a- adrenoreceptor blocker (phenoxybenzamine) is used to block the effects of catecholamine excess and its consequences during surgery. A dose of 20 mg of phenoxybenzamine initially should be increased daily by 10 mg until a daily dose of 100-160 mg is achieved and the patient repos symptomatic postural hypotension. Additional b-blockade is required if tachycardia or arrhythmias develop; this should not be introduced until the patient is a-blocked. The infusion of large volumes of fluid or administration of noradrenaline can be necessary to correct postoperative hypotension in the presence of unopposed a-blockade.Ref: Bailey and Love 27e pg: 846', 'role': 'assistant'}]