Peripheral arterial blood sampling
Used for determination of blood gases, acid–base status, or when large volumes of blood are required and venous access is difficult.
• As for venepuncture.
·Heparinized arterial blood syringe, if blood gas analysis intended.
• In descending order of appropriateness, the suitable sites are: radial artery, posterior tibial artery (in newborns), dorsalis pedis artery (newborns) and ulna artery (only if Allen’s test confirms patent adjacent radial artery). If the femoral artery is to be used in the older child, cannulation is preferable before sampling. Brachial artery should rarely, if ever, be used because of its ‘end arterial’ distribution.
• Identify artery by pulse or ‘cold’ light.
• Partially extend limb, (e.g. extend wrist for radial artery sampling), and with a finger slightly stretch skin over artery to stabilize its position.
• Clean overlying skin using an alcohol impregnated swab.
• Insert needle through overlying skin at 15–30° angle into artery until blood flashes back; if after inserting needle there is still no flash back withdraw slowly as often blood will then appear.
• Collect blood by aspirating into the syringe.
• Remove needle and apply pressure with cotton wool or gauze swab to puncture wound for at least 5min and bleeding has stopped.