What is the role of a tourniquet in venipuncture?

The role of a tourniquet in venipuncture primarily involves making veins more visible and palpable. By applying the tourniquet, venous blood flow is partially occluded, causing the veins to fill with blood, which enlarges and distinguishes them against the surrounding tissue. This is especially helpful in individuals with smaller or difficult-to-locate veins, as it allows for easier identification and access during the puncture process.

In this context, the partial occlusion does not prevent blood from clotting; rather, it is a temporary measure to visualize the veins for successful needle insertion. Additionally, while the tourniquet can contribute to the process by making veins easier to see, it is not designed to ensure sterility at the puncture site or to guarantee a sufficient blood draw, which depend on other factors such as proper technique and the use of sterile equipment.