I am trying to give saline IVs to a patient with delicate veins that are difficult to begin with -- but I insert either a butterfly needle or a catheter, get flashback, advance the needle, and the IV starts just fine -- but then stops after only a small amount of the saline goes in (first the drip slows, and then it stops). A couple of times it was obvious the needle blew out of the vein, but the other times, the drip just stopped with no explanation (and the tubing, bag, etc., were all fine upon removal). I don't know what I'm doing wrong. Can anyone tell me possible scenarios where this would happen, and fixes? I'm trying to learn -- thanks.