Emergency tourniquets are cuff-like devices designed to stop severe traumatic

bleeding Bleeding, hemorrhage, haemorrhage or blood loss, is blood escaping from the circulatory system from damaged blood vessels. Bleeding can occur internally, or externally either through a natural opening such as the mouth, nose, ear, urethra, vag ...

before or during transport to a care facility. They are wrapped around the limb,

proximal Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...

to the site of

trauma Trauma most often refers to: * Major trauma, in physical medicine, severe physical injury caused by an external source * Psychological trauma, a type of damage to the psyche that occurs as a result of a severely distressing event *Traumatic i ...

, and tightened until all

blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away ...

s underneath are occluded. The design and construction of emergency tourniquets allows quick application by

first aid First aid is the first and immediate assistance given to any person with either a minor or serious illness or injury, with care provided to preserve life, prevent the condition from worsening, or to promote recovery. It includes initial in ...

responders or the injured persons themselves. Correct use of tourniquet devices has been shown to save lives under austere conditions with comparatively low risk of injury. In field trials, prompt application of emergency tourniquets before the patient goes into

shock Shock may refer to: Common uses Collective noun *Shock, a historic commercial term for a group of 60, see English numerals#Special names * Stook, or shock of grain, stacked sheaves Healthcare * Shock (circulatory), circulatory medical emergen ...

are associated with higher survival rates than any other scenario where tourniquets were used later or not at all.

Tourniquet design

Existing guidelines call for the use of improvised "rope-and-stick" tourniquets as a last resort to stop severe bleeding. However, purpose-made tourniquet devices that are well designed can provide greatly increased safety and efficacy. Variability in performance has been shown to exist between various designs and application methods.

Mechanical advantage

Mechanisms that confer sufficient

mechanical advantage Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. The device trades off input forces against movement to obtain a desired amplification in the output force. The model for ...

are essential for applying adequate pressure to stop bleeding, particularly on the lower extremities. Pressures that occlude

venous Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated ...

but not

arterial An artery (plural arteries) () is a blood vessel in humans and most animals that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.). Most arteries carry oxygenated blood; the two exceptions are the pu ...

flow can exacerbate

hemorrhage Bleeding, hemorrhage, haemorrhage or blood loss, is blood escaping from the circulatory system from damaged blood vessels. Bleeding can occur internally, or externally either through a natural opening such as the mouth, nose, ear, urethra, v ...

and cause damage to healthy tissue.

Mechanical characteristics of emergency tourniquet devices

Results from laboratory and field testing suggest that windlass and pneumatic mechanisms are effective where other systems fail due to excessive pain, slipping, inadequate force, or mechanical failure.

Pressure gradients

Pressure underneath a tourniquet cuff is not evenly distributed, with the highest pressures localized around the cuff centerline and decreasing to zero near the cuff edges. A high rate of change of pressure across the cuff width, or a high cuff pressure

gradient In vector calculus, the gradient of a scalar-valued differentiable function of several variables is the vector field (or vector-valued function) \nabla f whose value at a point p is the "direction and rate of fastest increase". If the gr ...

, is a leading cause of nerve and muscle injury from tourniquet use. Tourniquets with wider straps or cuffs, especially those with pneumatic actuation in contrast to mechanical force, distribute pressure more evenly and produce lower pressure gradients. They are therefore more likely to stop bleeding and less likely to cause damage to underlying tissue, in addition to being significantly less painful than tourniquets with narrow straps and bands. Overpressure protection in certain emergency tourniquets also help to prevent excessive force from damaging the limb.

Risks

Possible risks of complications—

morbidity A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...

—related to emergency tourniquet use include Emergency care services implementing routine tourniquet use, especially in the civilian setting, should exercise caution and ensure that training is adequate for optimal results. However, given proper precautions, the occurrence of complications due to tourniquet use is quite rare. Designed tourniquet devices are routinely tightened over healthy limbs during training with no ill effects, and recent evidence from combat hospitals in Iraq suggests that morbidity rates are low when users adhere to standard best practices. Since no better alternatives exist for users to self-apply with only basic training, the benefit of tourniquet use far outweighs the risks. Safe tourniquet practice involves:

Current developments

Field experience

Latest field trials suggest that wider straps are more effective and less painful than tourniquets with thinner straps. The concept of limb occlusion pressure is also gaining prominence over the misconception that greater applied force results in greater effectiveness. In addition, studies of failed cases indicate that the correct devices should be coupled with training that facilitates realistic expectations and correct user actions. The Stop The Bleed educational initiative provides knowledge aimed at the greater public on when to use a tourniquet and the correct user actions.

Emerging needs

Despite the success of widespread tourniquet deployment to limit combat casualties, many preventable deaths from hemorrhage occur where conventional tourniquet use is inappropriate. The need exists for controlling junctional bleeding, especially in the

pelvic The pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pelvis, or pelvic skeleton). The p ...

area. In 2012, the Combat Ready Clamp (CRoC) was selected by the U.S. Army Institute of Surgical Research (USAISR) for that purpose. Another emerging need is more refined training regimes and doctrine based on scientific evidence, which can ensure that future tourniquet practice and policies are in line with the most current body of knowledge.

References

{{DEFAULTSORT:Emergency Tourniquet First aid Medical equipment