Subcutaneous Cannula
What is a subcutaneous cannula and why is it used?
People who are seriously ill and nearing the end of their life may find it difficult to take medications by mouth – either because they are experiencing nausea or vomiting or because they are becoming too weak to swallow. In the UK, when this happens, it is usual practice for a cannula to be put in – this is a small plastic tube placed under the skin designed to carry medication into a person’s body. The cannula is sometimes called a ‘Saf-T-Intima’ by nurses.
One end, inserted by a registered nurse, sits just under the person’s skin. The other end divides into two parts and is shaped like a Y. One part of the Y-arm can be connected to a syringe driver or pump; the other can be used for subcutaneous injections (See figure 1).
Fig. 1 Saf-T-Intima cannula It is often best to give as-needed medication through a separate subcutaneous cannula rather than to use the other arm of the cannula connected to a syringe driver or pump. The nurse will usually insert this second cannula in a different part of the body.
The healthcare team will check the cannula(s) most days and change it on a regular basis.
What is a subcutaneous injection and why is it used?
Subcutaneous means ‘just under the skin’. So, a subcutaneous injection means giving an injection just under the skin. There is a good blood supply under the skin and this carries the drug into the rest of the body. Subcutaneous injections are normally less painful than an injection into the muscle and are easier to give than an intravenous (in the vein) or intramuscular (in the muscle) injection. When a cannula is in place, subcutaneous medication can be given without the use of needles.
The subcutaneous method is a safe and effective way of giving medications, especially when a person is experiencing swallowing problems or has nausea and/or vomiting.
Where is a subcutaneous cannula inserted?
The cannula can be inserted into the person’s abdomen (tummy) or chest, upper thigh or upper arm. If the person is confused or muddled and is likely to remove the cannula, it can be placed in the upper back.
The nurse will secure the cannula to the person’s body (see figure 2) using clear film, so that you can see the insertion site. This allows you and the healthcare team to check the site regularly.
Fig. 2 Saf-T-Intima cannula inserted in the top of the arm How do I care for the cannula?
Caring for a cannula is quite easy. You will need to check the insertion site every time you give a no-needle injection using the cannula. If you notice that the cannula site is red, swollen, leaking or smelly, contact your healthcare team as it is likely the cannula will be need to be changed (see figure 3).
Fig 3. Redness at the cannula site How will I know if the cannula is not working? What should I do if this happens?
It is normal for a small lump to appear at the insertion site immediately after the injection has been given. This is the medication sitting in the tissue just under the skin. The small lump will disappear as the medication is absorbed into the bloodstream. If it does not, contact your healthcare team.
If it is hard to inject medications or if the medications leak out onto the skin when you inject, then contact your healthcare team as this means the cannula is no longer working. Leave the cannula in place for them to remove. In the meantime, if there is a second cannula, this can be used until the other cannula is changed.