We recently identified a potential issue with our extended infusion zosyn administration when we found that one of our parter hospitals was routinely following up each dose with a 50ml NS minibag. When experimenting I found that our infusion pumps will stop running once the aid in the tubing reaches our pumps, as they are designed to do. Unfortunately, this means that in many cases 15-18 ml of fluid may remain in our primary infusion sets. When reviewed with nursing staff we found that there is significant variation in practice. Some staff will flush the line to clear any left over meds, some will simply take down and toss. Either way the patient is not getting the full dose at the extended 4 hour infusion period. It they only receive 2/3 of the dose over ~2.8 hrs and then the remainder is pushed, they are not receiving the full benefit of extended infusion. Our sister site is profiling a 50 ml bag along with each zosyn bag to prompt staff to hang it at the same 12.5 ml/hr rate to assure the completion of the extended infusion. I am wondering if anybody has information that shows this to be insignificant, or has a protocol in place to assure full dose delivery.