Insert a Cannula

The technique of inserting a cannula is a straightforward one, which is often also known as venous cannulation or peripheral cannulation. While it is a basic medical procedure, it does take some technique and preparation to complete safely. Follow the basic steps of the procedure for success. However each professional may adapt the technique a bit to their own preferences.

Steps

Preparing to Insert a Cannula

1. Gather materials. Cannulation requires some basic preparation and precaution. You will need to protect yourself from contact with a patient's body fluids and you need to protect the patient from injury or infection. In order to do this you will need:
   • Sterile disposable gloves
   • Tourniquet
   • Sterile bandage or dressing
   • Gauze
   • Alcohol wipes
   • Medical tape
   • Sharps container
   • Sterile surface to set tools on
   • Additional supplies for your specific procedure
2. Choose the size of the cannula you will use. In general, the larger gauge needle you use, the higher the maximum flow rate of the fluid entering into the vein. Larger sized needles actually have a smaller number, so a 14 gauge is large, while a 22 gauge is small. Choose a size that can easily fulfill the purpose of the procedure but is not oversized.
   • The smallest needles are used in children. The largest are used for rapid blood transfusion.
3. Have a discussion with your patient. Get informed consent from the patient before you begin the procedure. This is usually done verbally. This builds up a rapport with the patient and allows for a less traumatic experience.
   • Also take a quick history, primarily to exclude any allergy or sensitivity that the patient may have. This is particularly true for latex allergy. Should an allergy to latex be confirmed, then the tourniquet, gloves, and the cannula must be latex-free.
4. Wash your hands and put on gloves. All medical professionals should follow thorough and proper hygiene practices before coming into contact with a patient. Thus, it is important to keep the risk of the patient getting infection to a minimum while inserting a cannula by washing your hands thoroughly and putting on gloves.
   • You also need to protect your own hands while using a needle. Gloves will help to minimize the risk of a needle prick or fluid contact.
5. Apply the tourniquet around the patient's arm. It should be placed on the arm, just above the cannulation site. Tighten it appropriately, so that the patient's veins are highlighted.
   • The tourniquet allows you to find a good vein for the cannulation. You can highlight a good vein even more by tapping on it. This makes the vein dilate.
6. Clean the skin. Using an alcohol wipe, clear away pathogens on the skin around the vein used for cannulation. This will help prevent the risk of infection.
   • If the area is really covered in hair, you may need to shave it. This will help you to identify the vein, get a clear aim at it, and it will help when cleaning the area.

Inserting the Needle

1. Insert the cannula needle at approximately 30 degrees. Hold the cannula in the front of its wings with your pointer and middle finger and in the back with your thumb. Advance it slowly into the skin until blood enters the base of the cannula, which is called a flashback and signals that you have entered a vein.
   • When inserting the needle, make sure its eye is facing upwards. This means that the point of the needle is down against the skin.
2. Advance the plastic piece of the cannula. The needle should now be held stationary while the plastic component of the cannula is advanced further into the vein. The goal is to get the plastic sheath into the vein, and keep it there, while the needle is removed.
   • Keep advancing the plastic component of the cannula until the plastic tube is fully inserted. The "hub" of the plastic component will hit the skin when it is all the way in.
3. Allow blood to flow into an attachment. Remove the tourniquet from the patient's arm. Remove the needle from the base of the cannula, leaving the plastic component in sight. Allow blood to flow into the base of the cannula, so there is less risk of air going into the vein if something is injected through the cannula, called an air embolism.
   • Then cap the cannula or attach test tubes or other supplies.

Finishing the Procedure

1. Secure the cannula with an appropriate dressing. If the cannula needs to stay in the vein, you will need to secure it. Using medical tape, or a specialized dressing that comes with the cannula, attach the cannula to the skin so that it is comfortable for the patient but stays in place in the vein. You may need to tape attachments to the skin as well, for example a tube leading to another attachment point.
   • If you are simply using the cannula to get several samples of blood, for example, extensive securing is not required. However, you do need to be sure that it stays in place long enough to get your sample, so you may want to tape it down a bit.
2. Inspect and clean the cannula. Flush the cannula with a flushing solution, usually normal saline. This is done by inserting a This will assure that the site is clean and will check for adequate positioning within the vein.
   • To flush the cannula you will need 5-10ml of saline in a syringe. This may come in a pre-filled syringe or you may need to fill it yourself. Flush the cannula by attaching the syringe of saline onto the cannula port, inject the saline into the port, detach the syringe, and then close the port.
   • If you are returning to put an injection into a cannula, flush the it with saline solution again. This will assure that the cannula is still in place.
3. Clean up after the procedure. Dispose of the needle in a sharps container to reduce the risk of a needle poke. Dispose of any other waste appropriately.
   • Document the procedure in the appropriate set of notes.
   • If removing the cannula, place a piece of gauze on the injection site and keep it in place with medical tape or a bandage. This will assure that the patient is not bleeding after the procedure.

Warnings

• Never perform this procedure unless you are trained. This article is intended for reference only and should not be used by untrained persons to perform this procedure.
• In the case of needle stick injury, contact appropriate occupational health professional for advice.
• This procedure uses sharp objects, so care should be taken while working with them.

Sources and Citations

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