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tourniquet

tourniquet

[tur-ni-kit, toor-]
tourniquet, compression device used to cut off the flow of blood to a part of the body, most often an arm or leg. It may be a special surgical instrument, a rubber tube, a strip of cloth, or any flexible material that can be tightened to exert pressure. Compression should not be maintained for more than 20 min at a time because of the danger of congestion and gangrene. In cases of a bleeding emergency, a tourniquet is used to stop the flow of blood if other means, e.g., the application of a pressure bandage to the wound, are not effective. In arterial hemorrhage (bright red blood spurting out in jets) the tourniquet is applied above the wound, i.e., between the wound and the heart. In hemorrhage from a vein (an even flow of dark red blood) the tourniquet is applied below the wound, i.e., away from the heart.

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.

History

In 1718 French surgeon Jean Louis Petit developed a screw device for occluding blood flow in surgical sites. He named this device after the French verb “tourner” (to turn), “tourniquet” as it is commonly known today. This would not have been possible without the prior work of William Harvey, an English surgeon who traced the human circulation in 1628.

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 Esmarch'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 intra-venous 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.

Types

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

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 circulation.

Emergency tourniquets

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.

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.

Current technology

In recent years there have been significant advancements in tourniquets. These advancements have vastly improved tourniquet safety.

Limb occlusion pressure

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.

Automatic systems

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 LOP 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.

Contoured and wide cuffs

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.

See also

References

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