What is the main benefit of using a tourniquet during blood collection?

The primary benefit of using a tourniquet during blood collection is that it helps to engorge the veins. When a tourniquet is applied, it restricts blood flow in the area below the point of application. This causes the blood to accumulate in the veins, making them more prominent and easier to locate and puncture with a needle. The engorged veins facilitate successful venipuncture, reducing the likelihood of complications such as multiple needle sticks or difficulty in drawing blood.

While aspects like speed, bleeding prevention, and sterility are important in the overall blood collection process, the immediate and direct effect of a tourniquet is to enhance venous filling, thus making it easier for healthcare providers to identify and access a suitable vein for blood draw.