When you’re about to have an operation, you’ll need to have an injection so that we can insert a tiny plastic tube in a blood vessel. These plastic tubes come in different colours and sizes, and you’ll be given the one that’s best for you. We have to make a tiny hole in your skin with a small needle in order to get this plastic tube into your blood vessel. Once we’ve got the needle in, we take it out and throw it away, and just leave the soft plastic tube in your blood vessel. We can then give you fluids and various medicines straight into your bloodstream through this plastic tube instead of having to give you another injection. There are various hospital words for this kind of tube – some people call it a line, a cannula, or a catheter.