I.V. Cannula Sizes and Colors

I.V. cannula is a very small, flexible tube placed in the vein to allow administration of medication, fluids or nutrients directly into the bloodstream. The catheter is introduced into the vein by a needle, which is subsequently removed while the small plastic cannula remains in place. The catheter is then fixed by taping it to the patient's skin or using as adhesive dressing.

I.V. cannula sizes and colors

The smaller the gauge, the larger the diameter of the cannula and faster the flow of fluid. Different cannula sizes are indicated by different colors, making them easier to differentiate, especially in emergency situation in which size might be critical.

Choosing the correct cannula size is important so that treatments can be carried out properly. Larger cannula sizes are necessary for rapid transfusion of blood, intravenous fluids and medications. Smaller cannula sizes result greater pressure in the vein. This can cause hemolysis during the aspiration of a blood sample if the cannula is too small. Furthermore, if a patient requires the rapid infusion of medication, a cannula is too small will not allow the fluid to flow quickly enough and, the combined with increase pressure, could result in the blowing out the vein. Phlebitis (inflammation of the vein) can occurs when the size of the cannula is too big for the selected vein causing unnecessary friction on the internal lining of the vein leading to inflammation.