An intravenous needle (靜脈輸液針) is a type of needle that is inserted into a vein to administer medications and fluids as ordered by a doctor. These types of needles are usually a small, hollow tube called a cannula (插管) that is sheathed over a sharp needle called a trochar (套管針). The needle is used to pierce the skin and access the vein. Once inside the vein, the trochar is retracted, leaving the plastic cannula in place for medication administration.
The intravenous needle comes in various diameter sizes called gauges. The smaller the gauge number, the larger the diameter of the needle. A 16-gauge needle is larger than a 24-gauge needle. The type of intravenous (IV) therapy that is ordered can determine the size of IV catheter that is needed. For example, a blood transfusion requires an 18- or 20-gauge needle.
Insertion of an intravenous needle should be performed only by trained personnel. The needle is usually placed in a vein in the hand, arm, or bend of the elbow. Occasionally, if there are no visible veins in the arms, the IV needle will be placed in a vein in the foot or leg. Scalp IVs are sometimes used on infants.
After the needle is inserted into the vein, it can be connected to an IV line or a short piece of hollow tubing called a heplock. The IV line will be connected to a bag of fluids or medications. An intravenous pole with a programmable pump is used to administer the IV therapy.
There are complications that can occur when inserting an intravenous needle. If the needle nicks the side of the vein it can cause blood to leak out into the surrounding tissue. This is called "blowing" the vein. The vein will eventually heal but the individual may have a large bruise in that area.
Other complications may include infection at the insertion site. The U.S. Centers for Disease Control recommends changing the needle every 72 to 96 hours to reduce the rate of infection. If the IV cannula migrates outside the vein, the intravenous fluids can infuse into the surrounding tissues. This can cause swelling and pain. Some IV medications are extremely caustic and can actually cause the surrounding tissue to die.
Once the need for an intravenous needle has passed, it can easily be removed. The health care personnel will put on gloves and remove tape that is holding the IV needle in place. She will then carefully pull the plastic cannula out of the vein. Sometimes it is necessary to apply pressure to the insertion site to stop the bleeding. A small bandage will then be placed over the insertion site.