Venepuncture is preferable to capillary blood sampling when a significant volume of blood is needed for testing, e.g. coagulation studies, or when sterility of sample is important, e.g. blood culture.
• In older child, as in adults, a 21–23G needle and syringe or vacuum tube should be used.
• In infants and small children use either a 23G butterfly needle and syringe or 21–23G butterfly needle without the normal tubing.
• An alcohol impregnated swab.
• Appropriate sample bottles or capillary tubes.
• Cotton wool or an occlusive plaster.
• Suitable sites include the antecubital fossa, dorsum of the hand, and dorsum of the foot. Sometimes, necessity demands that other sites such as the scalp are used, particularly in infants.
• Identify suitable vein and warm limb if necessary.
• Topical local anaesthetic cream can be applied under an occlusive dressing for 30–60min reduces pain and may be appropriate in young children.
• Apply a tourniquet proximal to the intended venepuncture site. In infants this is often best done using your own gloved fingers or asking an assistant to squeeze the limb. Also use your fingers to stretch the overlying skin to stabilize the vein. In young children an assistant may be required to keep the child’s limb steady.
• Clean overlying skin with an alcohol impregnated swab.
• Along the line of the vein and in a proximal direction, insert needle through overlying skin at 20–30° into the vein until blood flashes back into the needle.
• Stabilize needle/butterfly with your fingers and then aspirate into syringe or, if using a butterfly with no tubing, allow blood to drip into sample bottles. Repeated gentle release and retightening of tourniquet often increases blood flow.
• Once blood has been collected, release the tourniquet, remove needle and then apply gentle pressure to puncture site for a few minutes with cotton wool.
• Once bleeding has stopped, an occlusive plaster is optional, but is often appreciated!