What is the main reason for using a tourniquet during venipuncture?

Using a tourniquet during venipuncture primarily serves to restrict blood flow, which leads to the engorgement of the veins. This engorgement makes the veins more visible and easier to palpate, thereby facilitating the venipuncture process. By applying the tourniquet above the site of the intended puncture, the pressure builds up in the veins, causing them to fill with blood and become distended. Once the venipuncture is performed and the needle is inserted into the vein, the tourniquet is typically released to restore normal blood flow.

The options related to patient comfort and needle stability do not directly address the primary purpose of a tourniquet, which is to aid in vein visibility and accessibility, thereby enhancing the effectiveness and success of the blood draw.