1. Incomplete catheter blockage may occur when the concentration of heparin sodium is too low to seal the catheter.

　　2. The dose of heparin saline sealing solution is too small to flush out all the drugs in the local blood vessels.

　　3. The catheter is blocked without normal saline flushing after the infusion of high concentration of drugs. When the catheter is blocked, the syringe should not be used to push the catheter, but should be withdrawn to avoid pushing the clotted thrombus into the blood vessel.

　　4, blood disease, sealing fluid too much can cause spontaneous bleeding