Phlebotomy Technician Practice Exam (NCPT/CPT)

One might think that applying cold or tightening the tourniquet would increase blood flow at the venipuncture site, as both restrict blood flow. However, in reality, applying cold will cause vasoconstriction which will decrease blood flow, while tightening the tourniquet excessively can actually damage the vein and decrease blood flow. Thus, the best option is to apply heat, which will increase blood flow by causing vasodilation and promoting relaxation of the vein. Elevating the limb may also help, as it reduces the hydrostatic pressure in the veins and allows blood to flow more freely.