According to the CDC Guidelines for the Prevention of Intravascular Catheter-Related Infections:
Peripheral venous/midline catheters: Replace intravenous tubing, including add-on devices, no more frequently than at 72-hour intervals unless clinically indicated. Replace tubing used to administer blood, blood products, or lipid emulsions within 24 hours of initiating the infusion. Complete infusion of lipidcontaining parenteral nutrition fluids (e.g., 3-in-1 solutions) within 24 hours of hanging the fluid. Complete infusion of lipid emulsions alone within 12 hours of hanging the fluid. Complete infusions of blood products within 4 hours of hanging the product.
Central Venous Catheters/PICCs: Replace intravenous tubing and add on devices no more frequently than at 72-hour intervals. Replace tubing used to administer blood products or lipid emulsions within 24 hours of initiating the infusion. Complete infusions of lipid containing fluids within 24 hours of hanging the fluid.
http://www.cdc.gov/mmwr/PDF/rr/rr5110.pdf