Returning blood. Nurse's hands inserting a needle into an arm vein to return blood. The process of puncturing a vein is named venepuncture. The upper arm of the patient has a tourniquet (upper right) tied around it to make the veins stand out and be more visible. The blood is being returned after the removal of excess white blood cells to treat chronic lymphoblastic leukaemia. The leukaemia disorders involve excessive production of white blood cells. The excess white blood cells will be removed by withdrawing blood from the other arm, then passing the blood through a machine and back into this arm.