How to Use a Butterfly Needle Step-by-Step

needle image by Marek Kosmal from <a href=''></a>

Butterfly needles are fitted with a soft plastic wing on each side of a short cannula, or needle, joined to a short length of narrow plastic tubing and a syringe port. They can be used to take blood, or to give anesthetics and short-term infusions.

They are not suitable for blood transfusions, as they are liable to block around the needle tip. The wings are used to form a handle when inserting the cannula, and are flattened and secured with tape. Use an aseptic technique to protect the patient from bacteria, or other contaminants entering the venous system.

Explain the procedure to your patient and reassure her. Select a needle size appropriate to the age and size of your patient, following the manufacturer's guidelines. Open the syringe and the butterfly needle packets and drop the contents -- without touching them -- into a sterile bowl. Add your patient skin-cleaning method, such as an ethyl alcohol swab, or other method, as used in your place of work.

Apply a band tourniquet to the patient's upper arm. Ask her to clench and unclench her hand a few times, to bring up the veins.

Wash your hands thoroughly with soap and water, or an antiseptic hand scrub solution, and dry them with a disposable towel. Alternatively, use a hand-sanitising gel. Put on surgical gloves, or latex-free gloves, if you are allergic to latex.

Pull back the plunger of your syringe a couple of times, to break any air block, particularly for 20ml syringes. Push it back-in fully.

Clean the skin of the injection site thoroughly, using the method approved by your place of work. Pick up the butterfly needle, fold up the wings, and hold them between your thumb and forefinger. Remove the cannula cover.

Tap up a vein by holding your thumb against your middle finger and flicking the skin over a vein, in the back of the hand, or in the antecubital fossa, or crook of the arm. Alternatively, gently palpate a likely vein with your thumb or finger, to test its fullness and elasticity.

Insert the cannula through the skin, into the vein at a 10- to 20-degree angle. Blood should seep into the cannula tubing, if you are in the right place. If this is the case, attach the syringe to the tubing and remove the tourniquet. Withdraw the syringe plunger very slightly, to recheck that the needle is stable. If blood initially seeps into the cannula, but you cannot withdraw any blood, you might have perforated the back wall of the vein. Pull the needle back very slightly and withdraw the plunger again, very gently, and feel your way into the vein.

Lay the syringe against the patient's arm or hand, and tape the butterfly in place. Use a length of thin tape, pass it under the cannula, close to the skin. Wrap each end over the top, in opposite directions. Flatten the wings, and place another piece of tape across -- to hold them flat to the skin.

Immobilise the hand or arm with a small splint board, if the patient's normal movements are likely to dislodge the needle. For example, because peripheral veins tend to collapse when patients are in shock, you might need to cannulate over the joint of the wrist, which is an unstable site.

Proceed with administering the medication, or withdrawing blood, if the butterfly needle is attached to an intravenous infusion.

Remove the butterfly needle by peeling away the tape holding it to the skin. Keep a finger on the wings, to prevent the needle being withdrawn prematurely. Place a sterile cotton wool pad or dressing on the injection site.

Press firmly, to prevent blood leakage when you withdraw the needle; which you should do in a direction horizontal to the skin. Use the pressure dressing advocated by your place of work, to keep the vein closed, and ask the patient not to remove it for 24 hours.

Check the patency of the butterfly needle regularly, if the patient has an intravenous infusion. Monitor the injection site for signs of cold or swelling, which would indicate leakage into the surrounding tissues. If blood seeps up, into the narrow tubing attached to the needle, check that the infusion is running. If not, you might have to remove the tape, move the needle slightly within the vein, retape, and then flush the needle with 5 mls of injectable water -- before reverting to the prescribed drip rate. If none of these measures work, you might need to remove the needle and repeat the cannulation, using a new needle.