During surgery for aortic arch aneurysm under deep hypothermic circulatory arrest which of the following anaesthetic agent administered prior to circulatory arrest that also provides cerebral protection ?

Ans. is 'b' i.e., Thiopentone sodiumDuring the surgery for the aortic arch, all the blood supply to the brain has to be stopped so that proper arch anastomosis can be performed. This carries great risk for the brain. So the surgery for an aortic arch aneurysm is performed now days using deep hypothermia and circulatory arrest method.It is based on the principle that brain can safely tolerate circulatory arrest for periods of up to 45minutes if the temperature is carefully lowered to 15-17degC wide surgery. So during surgery for aortic arch aneurysm temperature is lowered till the temperature of the body is lowered up to 15-17 degc and then surgery is performed.During this process, we need an anesthetic agent which lowers the metabolic demands of the brain, so that the brain can sustain longer periods of circulatory arrest.Thiopentone sodium is one such drug, which lowers the metabolic demands of brains and provides it added protection when its blood supply is reduced during surgery.