Now it is time to learn the facts so you can base your practice on evidence. It is true that a larger syringe size (ie. 10 mL) will generate less pressure on injection than a smaller syringe (ie, 3 mL or 5 mL). That was the basis for the outdated “rule” about only using a 10 mL syringe. But the issue is actually catheter damage and syringe size is only one factor, and I would hasten to add, not the most important factor!
Catheter damage depends on 2 things happening.
- First is resistance to manual flushing. Resistance can be caused by intraluminal thrombus or drug precipitate formation, or by any number of mechanical causes such as a kinked catheter or pinch-off syndrome for subclavian insertion sites.
- Second is force applied to the syringe plunger rod. This varies due to the size and strength of the nurse’s hand and we really have no way to measure the amount of force we apply when pushing a syringe plunger rod. When resistance is encountered, there is a natural tendency to apply more force to overcome that resistance. VERY bad idea as this will lead to an increase in intraluminal pressure and can easily result in a linear split on the catheter wall. This can occur with any syringe size, even a 10 mL size. So a 10 mL syringe is not the “safe harbor” that we have been led to believe.
Two important documents now address this issue. The 2016 Infusion Therapy Standards of Practice states that the functionality of all VADs should first be assessed with a saline-filled 10 mL syringe. Patency is confirmed when there is NO resistance, a blood return that is the color and consistency of whole blood, and the absence of any signs or symptoms of VAD complications. Pay attention to any complaints the patient may have. Strange sensations in the chest, neck, shoulder or extremity are not normal and require further investigation. If the VAD is patent, proceed with giving the medication in a syringe that is appropriate for the dose of medication being given. Yes, that means using a 3 mL syringe. The Infusion Therapy Standards can be purchased here.
The second document is from the Institute for Safe Medication Practices, Safe Practice Guidelines for Adults IV Push Medications.
This document contains lots of great information about avoiding unnecessary drug dilution. It strongly states to NOT use a prefilled flush syringe to dilute medications, providing the reasons for this. There is also similar guidance on assessing VAD patency with a 10 mL diameter-sized syringe and to use a syringe appropriately sized for the medication, pointing out the risk associated with a syringe-to-syringe transfer of the drug. This document is a free download.
Many new documents are now available to guide your clinical practice, including those we discussed in this week’s blog message above. You may have many questions about these or other new guidelines documents. Lynn Hadaway has been an author on many of these documents and can help you to understand their content. We are setting aside time each month for discussing your questions. Register for our monthly video conference session on Thursday, April 14 at 12 noon ET. Submit your questions before the scheduled day. Join the conference with Lynn Hadaway to get more information, explanation, and clarification on your questions.