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Learning About Your Central Venous Catheter: Flushing the Line and Changing the Cap

What is a central venous catheter?

A central venous catheter is a thin, flexible tube. It is also called a central line. Central lines are used when you need to receive medicine, fluids, nutrients, or blood products for several weeks or more. The fluids are put through the central line so that they move quickly into your bloodstream. The line can be used many times, so you are not stuck with a needle every time.

A central line is put through the skin into a vein, often in the neck, chest, arm, or groin and threaded through the vein until the tip of the catheter reaches a large vein near the heart. The point where the central line leaves the skin is called the exit site. Usually about 30 cm of the line stay outside of the body. Sometimes the line has two or three ends so that you can get more than one medicine at a time. These ends are called lumens. The end of each lumen is covered with a cap.

Sometimes the central line is completely under the skin.

You will feel a little pain when the doctor numbs the area. You will not feel any pain when the central line is put in. The exit site may be a little sore for a day or two. You can take over-the-counter pain medicine, such as Tylenol or Advil, for pain control.

Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor or nurse call line if you are having problems. It's also a good idea to know your test results and keep a list of the medicines you take.

General guidelines

  • Make sure you do not get the exit site wet. When you shower, cover the site with waterproof material, such as plastic wrap. Be sure you cover both the exit site and the central line cap(s).
  • Never touch the open end of the central line if the cap is off.
  • Never use scissors, knives, pins, or other sharp objects near the central line or other tubing.
  • If your central line has a clamp, keep it clamped when you are not using it.
  • Fasten or tape the central line to your body to prevent pulling or dangling.
  • Avoid clothing that rubs or pulls on your central line.
  • Avoid bending or crimping your central line.
  • Always wash your hands before you touch your central line.
  • Check the central line every day for signs of infection. These include pain, tenderness, swelling, drainage, pus, redness, or warmth at or near the exit site.

How to flush the central line

A central line must be flushed every day to keep it clear of blood and prevent clotting. If it ends in more than one line (lumen), flush them in the same order each time. Depending on the type of central line you have, you will flush it with either heparin or saline solution. Your doctor or nurse will probably give you supplies and instructions on how to flush it. A nurse may come to your home to help you at first.

You will usually lie down when you flush the line. This helps prevent air from getting into your vein.

Preparing the syringe or cannula

  1. Be sure you have all your supplies ready. These may include the heparin or saline solution, syringes, needleless injection cannulas, alcohol swabs, and a disposal box. What you need will vary with the type of central line you have. You may have syringes that are already filled with the solution (preloaded).
  2. Wash your hands with soap and water for 15 to 30 seconds. Dry them with paper towels.
  3. Wipe the stopper of the heparin or saline solution bottle with an alcohol swab for 15 to 30 seconds.
  4. Remove the cover from the syringe, and twist the needle or cannula on to it. (It may already be attached.)
  5. Remove the cover from the needle or cannula. Note: If you have a preloaded syringe, skip to the next section, "Flushing the central line."
  6. Pull back the plunger of the syringe, and draw air into the syringe equal to the amount of heparin or saline solution you are using.
  7. Push the needle or cannula through the rubber lid of the solution bottle.
  8. Push the plunger of the syringe to force air into the bottle.
  9. Turn the bottle and syringe upside down. Position the tip of the needle or cannula so that it is below the surface of fluid in the bottle. Pull back the plunger to fill the syringe with the amount of solution you need.
  10. Before you take the needle or cannula out of the bottle, check for air bubbles in liquid in the syringe. If there are bubbles, push the plunger back in and then pull back on it again.
  11. Remove the needle or cannula from the bottle.
  12. Fill other syringes if you need to flush more than one lumen.

Flushing the central line

  1. Use an alcohol swab to rub the cap of the lumen you want to flush. Rub for 15 to 30 seconds, and then let the cap dry.
  2. Hold the end of the central line so it does not touch anything.
  3. If you have a clamp on the lumen, open it.
  4. Slowly inject heparin, or quickly inject saline solution. If there is resistance, stop. Do not force it. Call your doctor or nurse call line.
  5. If your central line has a clamp, clamp the lumen as you are finishing the injection and then remove the syringe. If your central line has a positive pressure cap, remove the syringe and then clamp the catheter.
  6. Put the syringe in the disposal box.
  7. Repeat the above steps for each lumen you are flushing.
  8. Wash your hands again with soap.

How to change the cap

You need to change the cap on each lumen every 3 to 7 days, or anytime it is leaking, or follow the manufacturer's instructions.

  • Wash your hands with soap and water for 15 to 30 seconds. Dry them with paper towels.
  • If there is a clamp on the lumen, be sure it is closed.
  • Remove the new cap from the package. Loosen, but do not remove, the cover on the end of the new cap.
  • Hold the lumen with one hand. With your other hand:
    • Remove the old cap, and set it aside.
    • Remove the cover from the new cap.
    • Screw the new cap into place.
  • Repeat these steps for each lumen.

When should you call for help?

Call 911 anytime you think you may need emergency care. For example, call if:

  • You passed out (lost consciousness).
  • You have severe trouble breathing.
  • You have sudden chest pain and shortness of breath, or you cough up blood.
  • You have a fast or uneven pulse.

Call your doctor or nurse call line now or seek immediate medical care if:

  • You have signs of infection, such as:
    • Increased pain, swelling, warmth, or redness.
    • Red streaks leading from the exit site.
    • Pus or blood draining from the exit site.
    • A fever.
  • You have a fever over 38°C, or you have chills.
  • You have swelling in your face, chest, neck, or arm on the side where the central line is.
  • Your central line is leaking.
  • You feel resistance when you inject medicine or fluids into your line.
  • Your central line is out of place. This may happen after severe coughing or vomiting, or if you pull on the central line.

Watch closely for any changes in your health, and be sure to contact your doctor or nurse call line if:

  • You have any concerns about your central line.

Where can you learn more?

Go to

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Care instructions adapted under license by your healthcare professional. If you have questions about a medical condition or this instruction, always ask your healthcare professional. Healthwise, Incorporated disclaims any warranty or liability for your use of this information.