.45NS vs .9NS

Hi, maybe someone can give me some info.. a pt had an order for .45NS for an elevated BUN at 96. The prior shift took the order and hung .9NS instead. I caught it,and hung the right bag. Question is am I correct that .9NS would have increased the blood volume but not necessarily hydrate cells( no hx of CHF or hypernatremia). How would it affect the BUN? also, anyone have tips on preventing peripheral IV dislodgement besides avoiding areas of flexion. Thanks

[bobnurse]

it makes you go pee pee more, so hopefully decreasing the BUN by increasing filtration.