A phlebotomy tourniquet is a flexible constricting device used during venipuncture procedures, commonly known as blood drawing. Its purpose is to temporarily restrict the flow of venous blood back toward the heart, causing the veins in the extremity to swell or “engorge.” This restriction makes the veins more prominent and easier for the technician to locate and access with a needle.
Preparation and Placement Guidelines
Before applying the tourniquet, the patient’s arm should be positioned straight and fully supported. The venipuncture site is often the antecubital fossa, the area inside the elbow, which contains accessible veins. The technician should visually inspect and palpate this area to select the best vein for the procedure.
The tourniquet is placed proximal to the intended site, meaning between the site and the patient’s torso. Guidelines suggest positioning the tourniquet three to four inches above the chosen vein to allow sufficient space. Proper placement ensures the vein below the constriction fills adequately without interfering with the procedure.
The constricting band must be applied over clothing or bare skin and never over an open wound or compromised skin integrity. Confirm that the patient does not feel extreme pain or numbness after placement. The material must lie flat against the arm to prevent pinching or twisting.
Step-by-Step Application Technique
To secure the tourniquet, the ends are first brought together and crossed over the top of the arm, creating an “X” shape. The technician uses one hand to maintain tension while manipulating the ends to form a quick-release mechanism, which is a half-knot or tuck. This technique is designed for rapid, single-handed removal after the venipuncture is complete.
For the quick-release tuck, one end of the tourniquet is folded back on itself and tucked underneath the other end where the ends cross. The goal is to create a loop or tab that, when pulled, releases the tension immediately. The resulting ends should point in different directions: one toward the patient’s hand and the other toward the shoulder.
The tension of the tourniquet is a precise balance: tight enough to impede venous blood flow but not restrict arterial flow. The radial pulse at the wrist should remain easily palpable, confirming that arterial circulation is not compromised. If the tourniquet is too tight, it can cause pain or nerve compression; if too loose, the veins will not engorge adequately.
Timing, Removal, and Patient Safety
Timing and Hemoconcentration
The duration of tourniquet application is a safety and quality control measure in phlebotomy. The device should remain on the arm for the shortest time possible, ideally no longer than 60 seconds. Prolonged application can lead to hemoconcentration, which causes an increase in the concentration of blood components.
Hemoconcentration can falsely elevate laboratory test results, potentially compromising the accuracy of the patient’s diagnosis. If the vein selection process takes longer than one minute, the tourniquet must be released for at least two minutes to allow the blood to re-equilibrate before reapplying.
Removal and Safety
The removal procedure must be executed swiftly and safely, using the quick-release loop created during the application. The tourniquet should be released and removed immediately after blood flow is established and generally before the final collection tube is filled. Releasing the tourniquet before withdrawing the needle is standard practice to prevent a hematoma, a localized pool of blood under the skin.
If the patient reports tingling, numbness, or extreme pain, the tourniquet must be released immediately as these symptoms may indicate nerve compression or excessive pressure. Responding quickly to signs of discomfort is a fundamental aspect of patient safety during the blood collection process.