A tourniquet is a tightly tied band applied around a body part (an arm or a leg) in an attempt to stop severe bleeding or uncontrolled hemorrhage.
Most first aid instruction no longer teaches the use of the tourniquet because it is extremely dangerous to limb and life. An incorrectly applied tourniquet can unnecessarily cripple and even kill. The best advice to stop bleeding is to apply pressure to the wound.
Tourniquets are not used to treat snakebite; a constrictive band intended to slow the spread of poison through the lymphatic system in a snakebite victim should be fairly loose compared to a tourniquet.
Even in cases of amputation, most bleeding can be controlled through direct pressure, elevation (above the heart) and the use of pressure points. The rare exception is when a limb is shattered by massive trauma or a major blood vessel is torn along its length. Even in these cases, the use of a hemostat to clamp the vessel above the tear is strongly preferred.
To properly apply a tourniquet, a piece of rubber tubing is wrapped around the limb and tied tightly. A stick is wound underneath the tubing and twisted until the tubing is tightened so that the bleeding is stopped. Do not tighten the tubing more tightly than is required to stop the bleeding. Tie the stick in its present position with additional tubing or bandages.
In an emergency, items that can be used for a tourniquet include a belt, rope, string, wire, twine, or even a piece of clothing. These improvised tourniquets have saved many lives, especially on the battlefield.
If a tourniquet is used, immediately mark the letter "T" on the casualty's forehead with a marker, pen, blood or dirt. If possible write the date and 24-hour time the tourniquet was applied. (Example: "8/7 2215") When transferring the patient to another person's care, be certain that receiving medical personnel know that a tourniquet has been applied.
Never loosen a tourniquet in the field. Toxins are likely to have built up in the dead tissue below the tourniquet, and loosening the tourniquet may cause immediate shock and kill the patient. When a tourniquet is used, the injured limb must generally be amputated just below the level the tourniquet is applied. This is "losing a limb to save a life" and is a decision that should be made by a paramedic or preferably a doctor if at all possible.
In wilderness first aid, it is imperative that any person with a tourniquet be evacuated to advanced medical care as soon as reasonably possible; MEDEVAC is indicated if transport will be delayed more than twenty-four hours.
In triage, a person with a tourniquet should be considered "I" for immediate in the START protocol and at least "Yellow" or higher in other protocols.