Some medications, as well as blood transfusions and lethal injections, can only be given intravenously. The simplest form of IV therapy is given through a hypodermic needle. This kind of needle is hollow and allows for the drip to be administered directly to the vein. The needle can be directly attached to a syringe or even to tubing that may be attached to a drip of whatever medication is needed. The needle is usually put into a peripheral vein, this is any vein not in the chest or abdomen. Any easily accessible vein can be used but most commonly veins in the hand or arm are used.
In infants it is common to use the veins in the scalp. Central IV lines flow through a catheter with its tip within a large vein, usually the superior vena cava, or inferior vena cava, or within the right atrium of the heart. This has several advantages over a peripheral IV. It can deliver fluids and medications that would be too irritating to peripheral veins because of their concentration or chemical composition. These include some chemotherapy drugs. Medications reach the heart immediately, and are quickly distributed to the rest of the body.
However central IV’s run a higher risk of giving you an infection, causing bleeding, and possibly even causing gangrene. A common reason to be hooked up to an IV is for dehydration therapy. Those unable or unwilling to drink or who have repetitive vomiting can receive fluid replacement IV. You are hooked up to a drip and your fluids and electrolytes are replaced through the IV in your hand or arm. There are two types of fluids that are used for intravenous drips; crystalloids and colloids. Crystalloids are aqueous solutions of mineral salts or other water-soluble molecules.
Colloids contain larger insoluble molecules, such as gelatin; blood itself is a colloid. The most commonly used crystalloid fluid is normal saline, a solution of sodium chloride at 0. 9% concentration, which is close to the concentration in the blood. Ringer’s lactate or Ringer’s acetate is another isotonic solution often used for large-volume fluid replacement. A solution of 5% dextrose in water, sometimes called D5W, is often used instead if the patient is at risk for having low blood sugar or high sodium. The choice of fluids may also depend on the chemical properties of the medications being given.