If a vein isn't easily accessible, a temporary plastic tube can be implanted under the skin in the chest or in an
  arm or leg. These catheters, or central lines, as they are called, extend into larger veins. They provide an access
  point either for injections or for the slow drip (continuous infusions) of therapy over hours or even days. All
  kinds of fluids can enter the vein through the catheter—chemotherapy drugs, nutritional formulas, antibiotics,
  blood or platelet transfusions, antinausea drugs or morphine or other pain-killing narcotics .
      The catheters avoid any discomfort from vein "sticking" and also any worry about having shots of irritating
  drugs that might leak out into the tissues. They can't be pulled out with an average pull or jerk, so they are
  quite safe. And they are simple to care for. They just need occasional cleaning and changing of the injection cap
  and periodic injections of heparin, a drug that prevents blood clotting in the catheter.
• Implanted infusion ports  Another type of catheter is completely under the skin. It is called a port, and
  it's filled by placing a special needle through the skin into the chamber. The chamber contains a rubber or
  Silastic cover that can be punctured thousands of times with a special needle to deliver therapy, antibiotics or
  nutrients directly into a large vein.
      The advantage of the implanted system is that since it is completely under the skin, no dressings or cleaning
  are needed and care is much simpler. Heparin injections won't be needed so often either. The disadvantage is
  that there is a slight risk of the drug leaking out. Also, a port can occasionally get out of position and become
  more difficult to enter.
• Ambulatory pumps  Small portable pumps that deliver chemotherapy while you go about your normal
  activities are called ambulatory pumps. ("Ambulatory" just means you can walk around.)