How should a tourniquet be applied during blood collection?

Applying a tourniquet 3-4 inches above the puncture site is the correct method because this placement effectively helps to engorge the veins without causing unnecessary discomfort or risk to the patient. The purpose of the tourniquet is to restrict venous return while allowing arterial flow, making the vein more prominent for easier access. It needs to be not only in the correct position but also of appropriate tension—tight enough to impede blood flow in the veins but not so tight that it obstructs arterial flow or causes pain.

The guideline to limit the duration to no more than one minute is crucial. Keeping the tourniquet on for longer can lead to complications such as hemoconcentration, where the blood components shift, or even potential nerve damage due to prolonged pressure. Shortening the time minimizes discomfort and ensures more accurate lab results, as blood constituents can begin to change after prolonged stasis.

This technique emphasizes the importance of both the anatomical placement of the tourniquet and timing, which are vital to ensuring a successful blood collection procedure.