Commercial heparin 25,000 units/ 250 mL (100 units/mL) infusion bags are provided as total volume of 250 mL. When intermittent shortages of commercial heparin infusion bags occur, my organization batch compounds bags in the IV room. Preparing these bags as Total Volume” of 250 mL is less efficient for IV room staff (as 5 mL of 1/2 NaCl or D5W volume must be removed from the bags). Med Safety has been asked if it is ok to switch to additive volume (using 5,000 un/mL vials for a total volume of 255 mL instead of 250 mL (would result in 2% lower heparin concentration). As heparin is a high alert infusion, we are concerned about this if a level is not routinely assessed following change to bag with slightly different concentration.
Question: Do any of you prepare heparin as additive volume with 5,000 unit/mL vials? If so, do you have process in place to ensure that a PTT or anti-Xa level is assessed 6 hours after converting between commercial bag vs. IV room compounded bag?