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A tourniquet is a constricting or compressing device used to control venous and arterial circulation to an extremity for a period of time. Pressure is applied circumferentially upon the skin and underlying tissues of a limb; this pressure is transferred to the walls of vessels, causing them to become temporarily occluded. It is generally used as a tool for a medical professional in applications such as cannulation or to stem the flow of traumatic bleeding, especially by military medics.
The earliest known usage of a tourniquet dates back to 199 BCE-500 CE. It was used by the Romans to control bleeding, especially during amputations. These tourniquets were narrow straps made of bronze, using only leather for comfort.
In 1718, French surgeon Jean Louis Petit developed a screw device for occluding blood flow in surgical sites. Before this invention, the “tourniquet” was a simple garrot, tightened by twisting a rod (thus its name tourniquet, from "tourner" = turn).
Joseph Lister is credited for being the first to use a tourniquet device to create a bloodless surgical field in 1864. He also recommended exsanguinations prior to tourniquet application by limb elevation. In 1873, Friedrich von Esmarch developed a rubber bandage that would both control bleeding and exsanguinate. This device is known as Esmarch's bandage for surgical haemostasis or Eschmarch's Tourniquet. At the time this device was superior to Petit’s device as there were no screws to loosen or cloth to tear. In 1881, Richard von Volkmann showed that limb paralysis can occur from the use of the Esmarch tourniquet.
In 1904, Harvey Cushing created a pneumatic tourniquet. This type of tourniquet compressed the underlying blood vessels using a compressed gas source to inflate a cylindrical bladder. This was superior to the Esmarch tourniquet in two ways: (1) the tourniquet could be applied and removed quickly; and (2) this method of limb occlusion decreased the incidence of nerve paralysis.
August Bier used two tourniquets for administering segmental anesthesia in 1908. In this procedure circulation is isolated in a limb and the limb is then infused intravenously. In 1963 Hamilton E. Holmes reintroduced Bier’s method as a single tourniquet technique. Today, the two-tourniquet technique is used frequently and is called intravenous regional anesthesia (IVRA). It is also commonly referred to as Bier block, or Bier’s method.
In the early 1980s microprocessor-controlled tourniquets were invented by James McEwen, a biomedical engineer in Vancouver, Canada. The first US patent for an electronic tourniquet system was awarded to Dr. McEwen in 1984 and to date he has been awarded many more US and foreign patents for tourniquet improvements. The use of automatic tourniquet systems has significantly improved tourniquet safety. Modern automatic tourniquets are self-calibrating and self-contained. These new tourniquet devices also provide a variety of safety features that are not possible in older mechanical tourniquets.
There are two types of tourniquets: surgical tourniquets and emergency tourniquets. Surgical tourniquets are frequently used in orthopedic surgery while emergency tourniquets are limited to emergency situations to control blood loss.
Surgical tourniquets prevent blood flow to a limb and enable surgeons to work in a bloodless operative field. This allows surgical procedures to be performed with improved precision, safety and speed. Tourniquets are widely used in orthopedic and plastic surgery, as well as in intravenous regional anesthesia (Bier block anesthesia) where they serve the additional function of preventing local anesthetic in the limb from entering general circulations.
Complications of tourniquet application 1. Tourniquet pain - Characterized by hyperemia, hyperthermia and pain following reperfusion 2. Post-tourniquet syndrome - Manifesting as pain, numbness, paresis, stiffness and pallor 3. Skin changes - Blistering, ischemic necrosis 4. Compartment syndrome 5. Cerebral hypoxia
Emergency tourniquets are used in emergency bleeding control to prevent severe blood loss from limb trauma. Emergency tourniquets are generally used as a last resort, especially in civilian applications, for all blood flow below the application of an emergency tourniquet is stopped, and can subsequently kill the tissue, leading to eventual loss of the limb below application.
Uncontrolled hemorrhage is the most preventable cause of deaths on both the battlefield and the streets of the United States. Studies show up to 50% of combat fatalities and 80% of civilian trauma fatalities are due to uncontrolled hemorrhage from an extremity.   It is possible to bleed out from a femoral arterial bleed in as little as three minutes.
However, use of tourniquets is widespread in military applications, and have the potential to save lives during major limb trauma. Analysis has shown that in cases of major limb trauma, there is no apparent link between tourniquet application and morbidity of the limb.
In recent years there have been significant advancements in tourniquets. These advancements have vastly improved tourniquet safety.
Limb occlusion pressure (LOP) is the minimum tourniquet pressure required to occlude blood flow to a specific patient's limb at a specific time and accounts for a patient’s limb and vessel characteristics, and the type and fit of the cuff. LOP can be determined by gradually increasing tourniquet pressure until distal arterial pulses cease, as indicated by a device sensing blood flow, such as a Doppler stethoscope. Studies have shown that cuff pressure based on LOP measured immediately prior to surgery is generally lower than commonly used cuff pressures and is sufficient to maintain a satisfactory surgical field.
The Combat Application Tourniquet (C-A-T) was developed by Composite Resources, Inc. and is used by the U.S. and Coalition military to provide soldiers a small, effective tourniquet in field combat situations, and is also in use by NHS ambulance services, and some UK fire and rescue services. The unit utilizes a windlass with a locking mechanism and can be self-applied. The (C-A-T) has been adopted by military and emergency personnel around the world.
Automatic tourniquet systems are capable of providing safety features that are not possible in older mechanical tourniquets. These systems can monitor the cuff inflation time as well as regulate the cuff pressure to a known pressure throughout the surgical procedure. Some microprocessor controlled tourniquets are capable of calculating the proper pressure to ensure complete blood occlusion in about 30 seconds. This assists the operating room staff in deciding what the tourniquet pressure should be set at on a per-patient basis.
Studies have shown that tourniquet cuff pressure can be substantially reduced by using wide, contoured cuffs. A wider and contoured cuff has more contact with the limb's surface area and disperses the cuff's force. This concept is emerging from the surgical field into the emergency field with wider emergency tourniquets.
The Association of periOperative Registered Nurses (AORN) recommends that the tourniquet cuff, tubing, connectors, gauges, and pressure source should be kept clean and in working order. Some modern tourniquet systems are capable of testing these items in 30 seconds.
Media related to Tourniquets at Wikimedia Commons