You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is Once phaeochromocytoma is diagnosed, preoperatively following is given and explain in detail?
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