Not an expert in the technical stuff by any means but you asked so I will try to answer perhaps Sqad could offer more
Not sure about irritated but I could suggest a few of things could concievably give odd results
Blood cell damage by the bypass machine could give a raised bilirubin as the liver deals with the breakdown products, micro clots could block smaller vessels in the liver, and cause a tiny amount of damage, as could a prolonged drop in blood pressure... all the above could cause a slight abnormality in results I would think....someone like Lazygun would be a better bet as my nursy physiology only goes so far.