What is the role of a tourniquet during venipuncture?

The role of a tourniquet during venipuncture is primarily to dilate the veins, which makes them more visible and palpable for the healthcare provider. When a tourniquet is applied, it temporarily restricts the flow of blood from the extremity where the sample is being drawn, causing the veins to fill with blood. This engorgement of the veins increases their size and makes them easier to locate and puncture with a needle.

It's important to note that while applying a tourniquet can lead to an increase in venous visibility, it does not directly increase blood pressure. Moreover, a tourniquet is not designed to minimize pain for the patient, as its primary function is to facilitate the venipuncture process by ensuring that veins are more accessible. Lastly, while keeping the arm steady is beneficial during the procedure, this is not the primary purpose of a tourniquet; proper technique and body positioning typically account for stability during venipuncture.