PCA pump syringe changes

We have an ongoing disagreement between nursing and pharmacy regarding how often the syringes in PCA pumps need to be changed. One group says every 24 hours, another group says every 48 to 72 hours. The "24 hour" group sites potential organism growth in the syringe itself, the "48-72 hour" group sites potential infection due to opening the closed system more frequently. I'm not finding much online. Does anyone have specific policies/procedures or article references that address this question?

Our PCA pumps use bags, not syringes. They usually run out or are discontinued before this, but the rule is 96 hours, bag and tubing. IV fluids which have dextrose in them are changed q 24 hours. I've been told that fluids without dextrose are less prone to grow stuff, and the risk is higher for infection d/t frequent opening of the line. High dextrose fluids, such as TPN, require that the bag AND tubing be changed q 24 hours.

we have syringes, we dont change them until they are empty...we dont have any protocol on how often to change them...we change the IV tubing which includes that of the PCA every 72 hours however usually our PCAs are only being used for 24-48 hours at the most.

We have syringes with 30 mg. of morphine in them. If a patient is not using close to the whole 30 mg. in around 24 hours, I don't know why he or she would even need a PCA. It would seem to me that in a case like this, the patient would be far safer and better off with oral pain meds or even prn IVPs.