When preparing for an intravenous (IV) insertion, a medical tourniquet is used to make veins more accessible for cannulation. The device works by applying constricting pressure to a limb, which is carefully calibrated to temporarily block the return of venous blood flow while maintaining arterial blood flow into the limb. This difference in pressure causes the veins below the application site to engorge, making them easier to locate and anchor. The immediate goal is to achieve this venous distension, which greatly increases the success rate of finding a suitable vessel for the IV catheter.
Function and Material Choice
The function of the tourniquet in venipuncture is to create venous stasis, a temporary pooling of blood that dilates the veins and makes them firmer. This engorgement not only improves visibility but also helps to stabilize the vessel, preventing it from “rolling” when the needle is inserted. Unlike the heavy-duty, windlass-style tourniquets used in emergency trauma, the devices used for IV access are designed for minimal, localized compression. The most common materials include elastic rubber bands, often made of non-latex elastomers to avoid allergic reactions, or adjustable Velcro cuffs. The design of these materials prioritizes a quick-release mechanism, which is necessary to allow for immediate removal once the vein is successfully accessed.
Proper Placement Before Application
Correct placement of the tourniquet occurs before securing the band. The tourniquet should be applied to the limb approximately 3 to 4 inches (or 7.5 to 10 centimeters) above the intended IV insertion site. Placing the tourniquet too close to the site can interfere with the insertion process, while placing it too far away may not provide adequate venous distension. Before securing the band, the skin should be assessed to avoid placing the tourniquet over areas of compromised integrity, such as open wounds, scars, or an existing arteriovenous fistula. After the tourniquet is applied, a distal pulse check is performed to confirm that arterial circulation remains unrestricted.
Step-by-Step Application Technique
Securing the elastic band tourniquet uses the quick-release loop, which allows for one-handed removal. The band is placed behind the limb at the chosen location, with the ends brought to the front. Cross the two ends, as if beginning to tie a shoelace. One end of the band is then tucked under the cross-section and pulled into a loop, creating secure tension. The loop end should face away from the intended insertion site, allowing the practitioner to pull it with minimal movement during the procedure’s final steps. The tension is correct when the veins are visibly distended but the patient still has a palpable radial pulse, confirming that only venous return is blocked.
Duration and Release Protocols
Safety guidelines limit the time a tourniquet can remain tightly applied to the limb. The maximum duration should be no longer than one to two minutes. Prolonged restriction of blood flow can lead to complications such as nerve damage, patient discomfort, and hemoconcentration, which can affect the accuracy of any blood samples collected. The timing of the tourniquet release is a procedural step during the IV insertion. The band must be released immediately after the practitioner observes a successful “flashback” of blood into the IV catheter and before the final advancement of the catheter or the initiation of fluid infusion. In the event the patient reports tingling, numbness, or pain, the tourniquet should be released immediately and the procedure paused.