1.Definition: unintentional perioperative leakage of intravenous fluid into the extravasation. 2.Pathophysiology: vasoconstriction, ischemic necrosis; direct drug toxicity; osmotic pressure change; drug pressure-related injury; co-infection, etc. 3, clinical manifestations: patients complained of pain and tightness around the site of intravenous infusion, signs include tissue edema, skin burning, redness, skin temperature changes, etc. 4.Complications: skin tissue necrosis, ulceration, osteo-fascial compartment syndrome. 5.Treatment: stop infusion, elevate the affected limb, apply heat, use antagonistic drugs, local nerve block, incision of NS flushing and general surgery consultation if necessary. 6.Prevention: avoid infusion catheter or infusion needle at the joint, touch the venous puncture site before pushing the drug, observe whether there is skin elevation at the tip of the needle when pushing the drug, pay attention not to rely on the speed of infusion to judge whether the liquid will not leak outside the blood vessel, and do blood return test for central venous catheter before pushing the drug.