Another student recently posted a question about what happens when air bubbles get into an IV line and are allowed to infuse into the patient. You might be surprised to find the answers! Here is the thread for you to link into and read on this. Actually, a few air bubbles won't hurt the patient, but it's not a good idea to get into the habit of allowing yourself to let it happen. It's just sloppy practice. I gave a description of how to remove air bubbles from IV tubing in the reply I made to this thread.
Having been an IV therapist for many years I can tell you that I've never heard of a patient having a complication of a PE or infarction resulting from a problem with a peripheral IV. Usually, when fibrin clots forms around, or at, the site of a peripheral IV, it just occludes that particular vein. The peripheral veins are just that--peripheral. These peripheral veins are only on the surface of the skin, small lumen'd and not major vessels. This is not a major problem unless an infection occurs that becomes a full-blown phlebitis that becomes a cellulitis. I've never seen that happen either because it is usually watched and addressed by the physician before it ever gets that far.
Now, they need to watch for problems in the central lines a lot more closely. But, even in the central lines, if someone is stupid enough to try to push a blood clot out of a central line in order to clear the line and make it patent the chances of a PE happening are not that great because the lumens of these catheters are not that large. Since the tip of the central line is already sitting in the entrance to the right atrium of the heart, that blood clot is going to break up from the turbulence in the chambers of the heart as is goes through that organ. A PE COULD occur, but most likely what is going to happen is that the catheter is going to rupture from the foolish nurse trying to push the clot out of it. That is going to require a physician to go in and retrieve the broken catheter before it travels to and occludes the pulmonary artery, if it is even able to get that far in the heart's circulation. And if the catheter is still intact and hasn't broken off, it will just need to be removed via it's insertion site.