A tourniquet is used by the phlebotomist to assess and determine the location of a suitable vein for venipuncture. Single-use, latex-free tourniquets are preferred but reusable tourniquets are acceptable. However, if the reusable tourniquet becomes contaminated with blood or body fluid, it must be discarded immediately to avoid the spread of harmful contaminants to other patients. Follow the guidelines established by your facility for cleaning reusable tourniquets.
Proper application of a tourniquet will partially impede venous blood flow back toward the heart and cause the blood to temporarily pool in the vein so the vein is more prominent and the blood is more easily obtained. The tourniquet is applied three to four inches above the needle insertion point and should remain in place no longer than one minute to prevent hemoconcentration.
If the tourniquet is used during preliminary vein selection, it is best to release the tourniquet after assessing the vein and while you are assembling your supplies. Reapply the tourniquet just before starting the venipuncture; it should then be released soon after the needle has been inserted into the vein and the blood flows into the first tube. If collecting multiple tubes, the tourniquet may remain in place until blood enters the last tube.