Historically our unit cannulates grafts using 16g needles have any units used larger gauge needles and does this affect the life span of a graft?

Val, We typically use 15guage needles on mature grafts and fistulas. I have seen this done consistently since I fist began working in dialysis in 1976. I am unaware of any data that suggests smaller needles will increase the life of the graft. I do know that most importantly site rotation must be done to extend the life of the graft. Regardless of what size needles you use the graft will eventually fail because it is not living tissue. It is plastic and will run out of space at some point.
Good Luck

Selecting the appropriate needle gauge to deliver the prescribed blood flow is very important.

Larger gauge needles are required to achieve blood flows greater than 350 - 400 in todays environment of 35 to 40% HCTs.
Using a smaller gauge needle will not necessarily improve the life of the graft.

Patient and staff education, including cannulation skills, rotating sites,and administering a dedicated access monitoring program are key elements in maximizing the life of vascular accesses for hemodialysis.