Tourniquet

A primitive tourniquet

A tourniquet is a constricting or compressing device, specifically a bandage, 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 tourniquet is usually applied when the patient is in a life-threatening state as a result of continuous bleeding.

A primitive tourniquet can be made from a stick and a rope (or leather belt). The rope is made into a loop that fits over the damaged limb and the stick is inserted through the loop. The loop is tightened by twisting the stick. This primitive device stems the flow of blood but side-effects such as tissue damage and nerve damage may occur. In modern medicine, pre-assembled devices have been developed.^[1] They avoid side-effects of the traditional rope-and-stick tourniquets and can be faster or easier to apply. Some modern tourniquets can be applied, in theory, with one hand.

History

Petit tourniquet engraving from 1798

A traditional tourniquet system: the tourniquet itself and a wooden stick.

Modern tourniquet system attached to a modern wide contour cuff

During Alexander the Great’s military campaigns in the fourth century BC, tourniquets were used to stanch the bleeding of wounded soldiers.^[2] Romans used them to control bleeding, especially during amputations. These tourniquets were narrow straps made of bronze, using only leather for comfort.^[3]

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 = to 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.^[4]

In the early 1980s microprocessor-controlled tourniquets were invented by James McEwen,^[5] a biomedical engineer in Vancouver, Canada.^[6] 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.^{[2] [7]}

In the 2000s, silicon ring tourniquet, or elastic ring tourniquet, which was developed by Dr. Noam Gavriely, a professor of medicine and former emergency physician.^[8][9] The tourniquet consists of an elastic ring made of silicone, stockinet, and pull straps made from ribbon that are used to roll the device onto the limb. The silicone ring tourniquet exsanguinates the blood from the limb while the device is being rolled on, and then occludes the limb once the desired occlusion location is reached.^[10] Unlike the historical mechanical tourniquets, the device reduces the risk of nerve paralysis.^[11][12] The surgical tourniquet version of the device is completely sterile, and provides improved surgical accessibility due to its narrow profile that results in a larger surgical field. It has been found to be a safe alternative method for most orthopedic limb procedures, but it does not completely replace the use of contemporary tourniquet devices.^[13][14] More recently the silicone ring tourniquet has been used in the fields of emergency medicine and vascular procedures.^[9][15]

After World War II, the US military reduced use of the tourniquet because the time between application and reaching medical attention was so long that the damage from stopped circulation was worse than that from blood loss. Since the beginning of the 21st century, US authorities have resuscitated its use in both military and non-military situations because treatment delays have been dramatically reduced. The Virginia State Police and police departments in Dallas, Philadelphia and other major cities provide tourniquets and other advanced bandages. In Afghanistan and Iraq, only 2 percent of soldiers with severe bleeding died compared with 7 percent in the Vietnam War, in part because of the combination of tourniquets and rapid access to doctors. In civilian use, emerging practices include transporting tourniquetted patients even before emergency responders arrive and including tourniquets with defibrillators for emergency use.

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

A surgical tourniquet with a limb protection sleeve in preparation for surgery

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

A makeshift tourniquet made of masking tape, applied after a man cut his finger off while working on a bike

Emergency tourniquets are used in emergency bleeding control to prevent severe blood loss from limb trauma. Traditionally, emergency tourniquets are generally used as a last resort, especially in civilian applications, due to the understanding that if all blood flow below the application of an emergency tourniquet is stopped, it would subsequently kill the tissue, leading to eventual loss of the limb below application.^[16][17][18] More recently, experience in treatment of patients in civilian attacks such as the Boston Marathon bombing, and combat in Iraq and Afghanistan has changed the view of some within the emergency medicine field.^[19]

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 39% of civilian trauma fatalities are due to uncontrolled hemorrhage from an extremity.^[20][21] It is possible to die of exsanguination from femoral arterial bleeding in as little as three minutes. Use of tourniquets is widespread in military applications, as they 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.^[22]

Current technology

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

Silicone Ring Auto-Transfusion Tourniquet

The silicone ring auto-transfusion tourniquet (SRT/ATT/EED), or Surgical Auto-Transfusion Tourniquet (HemaClear), is a simple to use, self-contained, mechanical tourniquet that consists of a silicone ring, stockinet, and pull straps that results in the limb being exsanguinated and occluded within seconds of application.^[23] The tourniquet can be used for limb procedures in the operating room, or in emergency medicine as a means to stabilize a patient until further treatment can be applied.^[24]

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.^[25]

Combat/Self-Applied Tourniquet

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.^[26]

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 the proper pressure to ensure complete blood occlusion in about 30 seconds.^[27] 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.^[28] 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.

Integrated tourniquet cuff testing

The Association of Operative Registered Nurses (AORN) recommends that the tourniquet cuff, tubing, connectors, gauges, and pressure source should be kept clean and in working order.^[29] Some modern tourniquet systems are capable of testing these items in 30 seconds.^[30]

See also

• Intravenous regional anesthesia
• Emergency bleeding control
• Tourniquet test
• Hair tourniquet

References

External links

Look up tourniquet in Wiktionary, the free dictionary.

Media related to Tourniquets at Wikimedia Commons