Q: I read your post about priming volume vs. residual volume and I have a question. We give infusions of IV meds in a physician’s office. Is it better to prime the tubing with saline or prime the tubing with drug after it is added to the IV bag?

A:  First of all, thank you for reading my blog post and for your question. In case other readers missed that particular post, you can find it here –  read post.

In the previous post, we defined priming volume as the amount of fluid required to fill the entire length of the IV administration set eliminating the air in line.  At the beginning of an infusion, all IV sets are primed to avoid delivering air through the line. After the IV bag is spiked with the IV administration set, the IV solution/fluid flows through the tubing to remove the air.

The answer to your question will depend on the drug and how the drug is mixed by the pharmacy. Usually, the mixed IV medication bag is sent to the patient care area as is, no tubing attached. Then the nurses will prime the IV administration set when it’s ready to be given. In this case, the solution used for priming is the drug. Some pharmacy will prime the tubing with saline before they add the medication to the IV bag and sends the IV medication bag/tubing to the patient care area with the tubing pre-primed with saline. This is usually the case when the drug ordered is a cytotoxic or hazardous drug.

The priming volume of IV administration sets vary by manufacturer and affected by the length of the tubing and any add-on devices (e.g. filter). The priming volume information is on the packaging label of the IV administration set. In some cases, the priming volume can be a much as 25mL. It is important to note what solution is used to prime the tubing to ensure proper drug administration. Let’s take a closer look.

If an IV medication requires rate titration during administration, an IV set primed with saline means that the patient will not receive the actual drug until the priming volume is infused. For example,.if the priming volume of that tubing is 25mL and rate starts at 10mL for 15 mins, then 20mL for 15 mins, then 40mL  for 15 mins – so far, the patient has received 17.5 mL of saline only, not the drug.

Using the same rate schedule, if an IV set is primed with the drug in the IV bag, then right from the start of the infusion at 10mL for 15 mins, the patient is receiving the drug.

Hope this helps. Thanks again for your question.