The port is a semi-permanent IV in which blood can be drawn from each time blood tests are needed and they also use it for your chemo/immunology it avoids having to be stuck by needles constantly - also if you have "difficult veins" such as those which have a tendency to roll and seemingly always avid the needle resulting sometimes in several misses or manuring to get a needle inserted properly for either a blood draw or infusion; or if you have fragile veins or veins that tend to "blow" just after a needle or IV is set-up its your choice to have one or not - many choose to have one as it simplifies everything besides the constant being stuck constantly. the "if needed" was probably written in case you change your mind that there is a standing order for it to be done - or in case it becomes impossible to draw blood or insert an IV with out great difficulty the motto is "Due no harm" I at least commend him in that it seems to be a standing order that "if needed" you do not need to await getting the approval which could take only minutes or hours depending on how busy he is with other patients. It can also be used in other emergency situations etc by other health officials for blood draws, administering medications etc.