A tourniquet is a device used to control severe, life-threatening bleeding on an arm or leg, which is a major cause of preventable death in trauma situations. When direct pressure fails to stop profuse hemorrhage, a tourniquet provides a temporary measure to restrict blood flow until professional medical care can be administered. The windlass style represents the modern standard for effective field use, offering a reliable mechanism for achieving and maintaining the necessary high pressure.
Defining the Windlass Mechanism
The term “windlass” refers to the mechanical principle used to apply extreme circumferential force to the limb. This mechanism is based on a rigid rod or handle that is twisted, acting like a winch to dramatically increase the tension of the band wrapped around the extremity. This action compresses the underlying tissues and blood vessels, achieving arterial occlusion, which completely stops the flow of blood through the major arteries supplying the limb.
The physics of the windlass provide a mechanical advantage impossible to achieve with improvised materials like belts or ropes. This controlled twisting action generates the sustained pressure required to collapse the deeper, thicker-walled arteries. Without this mechanism, a tourniquet is likely to only occlude the veins, which can paradoxically increase blood loss in the limb.
Essential Components of the Device
Commercial windlass tourniquets are composed of several specialized parts working together to control bleeding. The primary component is the strap or band, which is a wide, durable piece of material that encircles the limb. The width of this strap is important, as it helps distribute the pressure evenly and minimizes the risk of localized nerve or tissue damage.
The windlass rod is a rigid, often plastic or aluminum, structure that serves as the device’s main tightening mechanism. Once the bleeding has stopped, the rod must be secured, which is accomplished by the securing mechanism or clip, often called a C-Clip. This clip locks the rod in place, preventing it from unwinding and maintaining the pressure until the casualty reaches definitive medical care.
Step-by-Step Application Guide
Applying a windlass tourniquet begins with placing it high on the injured extremity, ideally two to three inches above the wound, and never directly over a joint. The device should be applied directly to the skin, but if clothing removal would cause a delay, it can be placed over clothing, ensuring the strap is flat. Next, the strap should be pulled as tightly as possible to remove all slack before engaging the windlass rod. The rod is then twisted until the bleeding completely stops, as achieving limb occlusion is the only measure of correct application. Finally, the windlass safety strap is often routed over the clip and adhered to secure the entire mechanism.
Indications for Use and Critical Safety Considerations
The windlass tourniquet is reserved strictly for life-threatening, massive bleeding on a limb that cannot be stopped by direct pressure alone. The decision to use it should be made rapidly when faced with severe external hemorrhage, such as from an amputation or a deep wound. It should always be placed high and tight on the limb, as close to the torso as possible if the exact source of the bleeding is difficult to find.
A major safety consideration is that once the tourniquet has been applied and bleeding has stopped, it must never be loosened or removed by the initial rescuer. Loosening the device can cause a sudden drop in blood pressure and should only be done by a medical professional in a controlled environment. It is also imperative to document the exact time of application, as this information is vital for medical personnel to manage the patient’s care.