A tourniquet is a medical device used to apply pressure to a limb, controlling blood flow. In medical procedures, it is particularly recognized for its role in phlebotomy, which involves drawing blood from a vein.
Purpose in Phlebotomy
In phlebotomy, the function of a tourniquet is to make veins more visible and palpable to facilitate venipuncture. When applied, it temporarily restricts venous blood flow returning to the heart, while allowing arterial blood to continue flowing into the limb. This restriction causes blood to accumulate in the veins distal to the tourniquet, leading to their engorgement and increased prominence.
Engorged veins become larger and firmer, which aids in locating and accessing the target vein. Without this temporary pooling, many veins would remain flat or difficult to discern, making venipuncture more challenging. This creates optimal conditions for a single, accurate needle insertion, improving efficiency and patient comfort.
Proper Application and Removal
A tourniquet is applied around the arm, three to four inches above the venipuncture site. Its tension should be firm enough to impede venous flow without restricting arterial circulation or causing undue discomfort. Proper application allows blood to pool in the veins without cutting off the pulse.
Tourniquet removal is important for proper phlebotomy. It should be removed as soon as blood flow is established, or before the last tube is filled. Prolonged application beyond one minute can lead to changes in blood composition, affecting test results. Tourniquets come in various forms, including elastic bands, Velcro straps, or pneumatic cuffs, with many modern options being latex-free to prevent allergic reactions.
Patient Safety
Improper application or prolonged use can lead to patient safety concerns. Applying it too tightly can cause nerve compression, causing temporary numbness or tingling. Excessive pressure might also obstruct arterial flow. Keeping the tourniquet on for an extended period, typically longer than one minute, can result in hemoconcentration, where plasma fluid shifts out of the vein, increasing the concentration of blood components. This can falsely elevate certain laboratory test results, affecting diagnosis and treatment.
Patient comfort and clear communication throughout the procedure are important. Healthcare professionals should explain the tourniquet’s purpose and advise the patient what to expect. To prevent infection transmission, single-use tourniquets are often preferred, or reusable ones must be properly cleaned and disinfected between patients.