The general reason for not being able to get an intravenous needle is the inflammation of the endothelium of the blood vessel after repeated injections, which leads to occlusion or occlusion of the blood vessel, and sometimes poor filling of the blood vessel due to shock and other states, so that it cannot get an intravenous needle. In this case, you can try to have a choice of upstream thicker diameter and well-filled veins. If this is not possible, a thicker vein, such as the beginning of the saphenous vein, can be used for the IV injection. If the vein still cannot be located, a skin incision can be made at the beginning of the saphenous vein to find the saphenous vein, and the needle can be pushed into the beginning of the saphenous vein and injected under direct vision.