The needle is injected into the vein, not into the artery. Because of the high pressure in the arteries, it is generally difficult to administer fluids if the needle is injected into the arteries, and intra-arterial puncture is generally used to monitor the patient’s blood pressure during surgery or in the intensive care unit after surgery. In general, the needle is given in a vein, either a superficial vein on the surface of the arm, a cephalic vein or a noble vein, or a puncture in an internal jugular vein or subclavian vein. The advantage of the needle in the vein is that the pressure in the vein is low, and the vein is superficial, so it is easy to give the needle, and after the needle is removed at the end of the drip, it can be pressed by hand for a short time to stop the bleeding.