Help! Can anyone tell me why you cannot pressure inject at the same rate in a 22g PIV for Chest CT as you would through a 20g? both are rated to inject at the rate needed for the test but everything I read states the 22g puts you at increased risk for rupture of the vein but I can find no rationale for that??
Think about any fluid flowing through a pipe. When the pipe is smaller in diameter, the fluid will flow slower. With the slower flow rate, there must be a higher force to increase that flow rate. One study has found that a 22 g will achieve about 95% of the flow rate of a 20 g. What is the purpose of that chest CT? If you are trying to do a chest CT Angiogram or you are trying to rule out pulmonary emboli most radiologist want a very high flow, often as high as 8 mL per second. That equates to 28,800 mL per hour, to put it in rates that nurses most common think about. Power injection is possible through a 22 g, but probably not the best option when a very high flow rate is required. I question the statement about increased risk for vein rupture due to the gauge size. Studies on extravasation with contrast agents have not related this event to gauge size. It is related to the jet of fluid coming out of the tip of all catheter sizes. It is also associated with the choice of venipuncture sites, the method of securing the catheter, and patient movement between insertion and injection. A new catheter has side holes that reduces the force of the jet coming from the tip because it allows the contrast to flow out of the side holes. Some hospitals have found that they can reduce the size of the catheter with the use of this new catheter, Diffusics from BD. So in place of a 22 g, you can use a 24 g. In place of a 20 g, you can use a 22 g. There is an in vitro study published on this but no clinical studies yet. Lynn
Lynn Hadaway, M.Ed., RN, BC, CRNI
Lynn Hadaway Associates, Inc.
126 Main Street, PO Box 10
Milner, GA 30257
Website http://www.hadawayassociates.com
Office Phone 770-358-7861
Lynn,
Thank you so much for the insight and the information in regard to the new catheter!!
Similar to nurses having the INS Standards, Radiology Techs and Radiologists have the ACR American College of Radiology guidelines. They have published a Manual on Contrast media that is currently in Version 8 This Manual states "Although a 22G IV can be used for injections of up to 5 mL/Sec, it is recommended that a 20G or larger be used whenever injection rate exceeds 3mL/Sec
It is not a matter of "cant" it is a matter of best practice and standard of care.
If there were to be an extravasation, and these guidelines were not followed, it may be considered a breach in the standard of care.
Chris Cavanaugh, RN, BSN, CRNI, VA-BC