The scope of sterilization of the indwelling needle 3-5cm is enough. Before playing the indwelling needle, you need to sterilize the skin twice with iodophor, the scope is 3-5cm, which can kill the bacteria, fungus and budding spores on the surface of the skin. After puncturing the indwelling needle in the blood vessel, the needle core should be removed, and then the indwelling needle continues to advance a section. When blood flows out after the puncture, it means the puncture is successful and the indwelling needle needs to be fixed, then a patch is put on the surface and the time of the injection is written. Later, the time of medication change is decided according to the use of the indwelling needle and the condition of the wound on the surface of the indwelling needle, usually on the third day. If there is redness and pain on the surface of the indwelling needle, the indwelling needle should be removed. If there is no redness, swelling or pain on the surface of the indwelling needle, the medication can be changed. Disinfect the area where the needle was inserted twice with iodophor to the extent of 5 cm, and it can be kept for about two more days.