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Before you use any VAD for any infusion of any fluid/medication, you must obtain a blood return that is the color and consistency of whole blood. That is the standard of practice. When you use tPA to instill into the lumen and allow it to dwell for 30-120 minutes, you could easily get a blood return. That procedure is designed to reach what is inside the lumen and the overspill of what you instill will reach the fibrin and thrombus that is located directly that the catheter tip. This is enough to get a blood return, maybe. But the outside catheter walls are covered with the same fibrin/thrombus formation so it regrows. The next time you go to use it - days, weeks later - there is no blood return again. So the tPA instillation is not a permanent remedy for the problem. Are you obtaining the contrast study before or immediately after the tPA instillation? If after, you will not see the layer of fibrin on the outside catheter wall. If before, and you are injecting contrast under flurosocopy you could see the retrograde flow of the contrast between the fibrin and the catheter wall. This layer may extend the entire catheter length and cause fluid to escape into the tissue at the puncture site or it could only cover part of the catheter length and the contrast is seen flowing downstream at the point where the fibrin sheath end. There could also be a fibrin tail or flap on the catheter tip that acts like a valve. When you inject or flush, the flap opens. When you aspriate, you pull this flap over the lumen. At the bedside you have no way to know what is happening. There could also be a change in tip location where it is in a totally different vein from where it was originally placed. Or no blood return could also mean the tip has eroded through the vein wall completely. Again, you simply have no way to know this without a contrast study. So the answer to your question is no blood return means a nonfunctioning catheter. You can't use it. So you must figure out what is happening with it. What is done is radiology depends on what you ask for and what you tell them about the problem. Maybe you need to be more collaborative with radiology to figure out exactly what is the problem and how it can be fixed. The fibrin sheath may need a low dose infusion of tPA, stripping the fibrin from the catheter wall with a snare inserted from the femoral vein or some other method to correctly position a malpositioned catheter. But don't use it unless you have a blood return. Lynn