There are usually the following factors after the IV vascular pain: 1, the concentration of drugs is too large or the input of highly osmotic drugs lead to the permeability of the blood vessel wall, enhance the endothelial cells of the capillary wall damage and trigger, belong to the normal physiological reaction. For example, the input of hypertonic saline, hypertonic glucose, 50% glucose water or the input of mannitol injection with relatively high osmotic pressure will lead to vascular pain after infusion. 2, if the input of anti-inflammatory drugs, such as the input of penicillin, cephalosporin, levofloxacin and other drugs have the effect of irritating the blood vessels, which will lead to pain in the vessel wall. At this time, the patient should be closely observed, such as a short period of vascular pain within 2 hours will usually be relieved, the problem is not big at this time. But if there is a long period of vascular pain, you need to apply hot compress method or apply the external application of magnesium sulfate method can be relieved.