Using the 1/3 catheter to vein ratio, we have found difficulty meeting patient needs when the vein doesn't "measure up".
I recently had a discussion with an interventional radiologis regarding the ratio that we use. He states he has not heard of this and would like to see evidence based literature that supports. From his stand point, if we are worried about thrombosis - plug the whole vessel so thrombosis can't occur.........I was left speechless.
I have the 2011 Chest article by Dr. Nifong that demonstrates the impact of flow r/t catheter size but this study does not state the catheter should only take up 1/3 the vessel size.
Can anyone help me with this request?
Yes, that comment would make most of us on this forum speechless!
Glad to hear you are considering the size of the vessel when placing the PICC. As you stated, Tom Nifong's Chest 2011 does not make recommendations as to "which size catheter in which size vein" as it only looks at how flow changes with the various combinations of steel wires (catheters) in tubes (veins). It should also be recognized that PICC's in vessels are not identical to wires in tubes. However, it's the best we have for the moment for looking at the potential venous stasis that occurs with PICC placement One should also consider the various studies recently published looking at large sized PICC's having a higher rates of thrombosis.
The 1/3 catheter vessel ratio (CVR) simply means that a 4F catheter in a 4mm vessel will decrease the flow by approximately 2/3 leaving only 1/3 of the original flow remaining. That's a pretty significant reduction in flow. Just think what happens when one uses a larger catheter. How much is too much? That's what your doc wants to know. I suspect it is not simply venous stasis that creates the thrombotic issues--it is a combination of the underlying hypercoagulability of the patient--the condition of the vasculature--the insertion process--etc....and as you know how these factors are inter-related. (Virchow's Triad)
I also understand your problem in finding vessels that can accommodate the specific sized catheter the patient requires. Of course, going higher in the arm is a possibility--basilic generally gets larger further up the arm. But each clinician must make a personal decision as to "how much is too much?" What are your outcomes if you tread cautiously, always requiring a 1/3 CVR? Same question if you always "push the envelope" and put large catheters in small veins? Are your outcomes similar for 24 year old athletes as for 88 year old cancer patients?
Lastly, until we have the evidence based literature, maybe applying a little common sense would be a prudent starting point...and I doubt if the doc's notion of completely occluding the vessel fits the bill! Thanks for an interesting topic, Daylily!
Cheryl Kelley RN BSN, VA-BC