Tourniquet Overview

Historical Perspective Definition of Tourniquets Types of Tourniquets Components of Pneumatic Tourniquets Cuff Location Single vs. Dual - Bladder Design Cuff Shape Cuff Length Cuff Width Disposable vs. Reusable Cuffs Specialty Applications Limb Protection Beneath Cuffs Tourniquet Instruments

PREFACE

To the layperson, a tourniquet is a cloth - and - stick device used to stop bleeding in an emergency. Yes, that is a tourniquet. But modern surgical tourniquets are also much more. Today, surgical tourniquets are specifically designed to enable surgeons to perform delicate dissections in a bloodless operative field. They use compressed gas to apply a carefully controlled amount of pressure to an extremity. Some computerized tourniquet systems perform self - checks of calibration, display elapsed inflation time, and sound alarms if problems arise. And problems can arise: equipment can malfunction and patients can be injured. The perioperative nurse shares the responsibility for protecting patients from hazards related to tourniquet use. Surgery is a frightening experience for many patients; ideally, they can be spared the additional anguish of nerve injury, compartment syndrome, prolonged swelling, toxic reactions, and other tourniquet - related complications.

Historical Perspective

Compression dressings to control bleeding are described in papers attributed to ancient Greeks from the renowned medical school at Cos. As far back as Roman times, military surgeons used compressing devices to control bleeding during amputations

In 1628, William Harvey, an English surgeon, paved the way for future technological developments by tracing the human circulation. In 1718, Louis Petit, a French surgeon, developed the screw device shown in Figure 1. From the French verb "tourner" (to turn), he named the device "tourniquet." Joseph Lister (1827 - 1912) is credited with being the first to use a tourniquet to create a bloodless surgical field in 1864. For exsanguination, he recommended elevation of a limb for 4 minutes before applying the tourniquet. In 1873, Johann von Esmarch devised a rubber bandage for exsanguination and tourniquet use. The device was superior to Petit's screw device, because Petit's cloth bandages tore and the screw could untwist. In 1881, Volkmann demonstrated that limb paralysis could result from use of the Esmarch tourniquet.

Figure 1. Louis Petit's tourniquet, 1718.

An inflatable (pneumatic) tourniquet was developed by Harvey Cushing in 1904. To constrict the blood vessels, compressed gas was introduced into a cylindrical bladder. This device had two advantages over the Esmarch tourniquet: (1) rapid application and removal; and (2) decreased incidence of nerve paralysis.

The use of two tourniquets for administering segmental anesthesia was introduced by August Bier in 1908. In this two - tourniquet procedure, circulation is isolated in a portion of the extremity and anesthesia is infused intravenously. The procedure did not become popular at that time; however, in 1963, Holmes reintroduced it using the single - tourniquet technique and improved anesthesia. Today, the two - tourniquet technique is used frequently. This so - called intra - venous regional anesthesia (IVRA) is commonly referred to as a Bier Block, or Bier's method.

In the early 1980's, modern electronic tourniquet systems (also called computerized tourniquets or microprocessor - controlled tourniquets) were invented by James McEwen, PhD, a biomedical engineer in Vancouver, Canada. The first US patent for such a modern 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 introduction and use of automatic tourniquet systems based on Dr. McEwen's inventions has significantly improved safety and convenience over previous mechanical pressure regulator systems. Most of these new tourniquet systems are self - calibrating and self - contained (not requiring an external high pressure gas source) and provide a variety of safety features not possible in older mechanical tourniquets.

Definition of Tourniquets

A tourniquet can be defined as 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. In surgical settings, a tourniquet is used following exsanguination to produce a relatively bloodless operative field.

Types of Tourniquets

Two distinct types of tourniquets are found in the surgical setting:

• Noninflatable (nonpneumatic) tourniquets constructed of rubber or elasticized cloth.
• Pneumatic tourniquets, which have cuffs that are inflated by compressed gas.

The surgical use of noninflatable tourniquets is very limited. Historically, the use of a surgical glove as a wrist tourniquet for hand surgery has been reported, as has the use of a Penrose drain for digit surgery. However, in surgery today, noninflatable tourniquets have largely been supplanted by the safer and more convenient use of modern electronic tourniquet systems connected to inflatable cuffs. For phlebotomy or intravenous infusion, simple rubber tubing may be utilized. Elastic bandages are used to control bleeding following procedures such as vein stripping. Plain cloth bandages and dowel tourniquets are used primarily in nonsurgical settings. For prehospital care of a patient with trauma to an extremity, a nonpneumatic tourniquet may be employed as a last resort to control hemorrhage.

A pneumatic tourniquet uses a gas - inflated cuff to constrict blood flow. A regulating device on the tourniquet apparatus can be preset to control the amount of cuff pressure exerted on the limb.

Components of Pneumatic Tourniquets

Modern pneumatic tourniquets have five basic components: An Inflatable Cuff. A Compressed Gas Source. A Pressure Display. A Pressure Regulator. Connection Tubing. Inflatable Cuff Pressure is exerted on the circumference of an extremity by means of compressed gas, which is introduced into a bladder within the tourniquet cuff. All bladders have one or two port connectors for the attachment of connecting tubing. Typically, pneumatic cuffs are fastened by contact closures and may be secured with a ribbon tie to prevent cuff movement during the procedure.

Figure 2. Modern tourniquet cuffs: Reusable single bladder standard rectangular cuff (top left), reusable contour lower leg cuff (center), sterile disposable single bladder cuff (lower right), and reusable pediatric cuff (bottom center).

Many different types of cuffs are available, and the appropriate choice is determined primarily by proper fit and surgical procedures. The choice of a tourniquet cuff should be individualized, taking into consideration the size and shape of the patient's limb and the specific demands of the operative procedure. When selecting a cuff, consider the following criteria:

• Cuff Location.
• Single - vs. Dual - Bladder Design.
• Cuff Shape.
• Cuff Length.
• Cuff Width.
• Disposable vs. Reusable Cuffs.
• Specialty Applications.
• Limb Protection.

Cuff Location Different cuffs are designed to be placed on different extremities. For most lower extremity procedures, select a thigh cuff. For foot procedures where it is desirable to place the cuff above the ankle on the lower third of the calf select a lower leg cuff. Most upper extremity procedures call for a standard cuff applied to the upper arm, although hand surgeons may utilize a small tourniquet inflated around the wrist, or even two relatively narrow pneumatic cuffs on the forearm. Single vs. Dual - Bladder Design The surgical procedure will also influence the surgeon's choice of a single - bladder cuff or a dual - bladder cuff (one with two narrow bladders within a single cuff, see Figure 3). For general anesthesia cases, such as total knee arthroplasty, a single - bladder cuff is usually used. For intravenous regional anesthesia (or IVRA, also known as Bier block anesthesia), a dual - bladder cuff is usually applied. Inflation and deflation of each bladder of a dual - bladder cuff is controlled separately; this permits greater safety and patient comfort, particularly for longer procedures. Cuff Shape Standard rectangular (or cylindrical) tourniquet cuffs are designed to fit optimally on cylindrically shaped limbs. However, human limbs may be conical in shape (particularly in extremely muscular or obese individuals) which can result in poor fit, sliding of the cuff distally on the limb during the procedure, and inability to achieve a bloodless field at normal pressures if standard rectangular cuffs are used. Contour cuffs have an arced design that gives them a smaller diameter distally than proximally when wrapped (see Figure 4). Some contour cuffs also have pivoting fastening straps that allow the proximal and distal diameters to be adjusted to suit the limb. Contour cuffs enhance comfort in patients with conically shaped limbs and reduce the risk of mechanical shearing. It has been reported that contour tourniquets occlude blood flow at lower inflation pressure than standard rectangular cuffs of equal width, which may be attributable to better cuff fit and more efficient transmission of pressure to deep tissues. Cuff Length Perioperative nurses often assume responsibility for selecting an appropriate cuff size. A cuff that is too long or too short can cause problems. Selecting a cuff that is too long (resulting in excessive overlap as shown in Figure 5 may be difficult to apply snugly and may be less stable (causing the cuff to move distally or "walk" on the patient's limb). Both problems may prevent occlusion of arterial bloodflow at normal cuff pressures, lead to loss of occlusion during the procedure, and lead to skin injury. Selecting a cuff that is too short (resulting in too little overlap of the inflatable bladder portion of the cuff as shown in Figure 6) produces uneven distribution of pressure and can lead to loosening of the cuff or an inability to sustain occlusion. On some cuffs the inflatable bladder portion extends the full length of the cuff, while on other types of cuff there is a 1 - 2 inch long non - inflating portion at one end through which the strap is sewn. Some manufacturers color code their cuffs to assist the user in selecting the most appropriate cuff for the patient. Note that these color codes may differ between the various cuff manufacturers. To determine the appropriate cuff length, measure the circumference of the limb near the middle of the location chosen for the cuff and refer to the cuff manufacturer's instructions for the appropriate cuff size. In general, the shortest cuff giving at least the manufacturer's specified minimum overlap should be used. Some cuffs have an additional hook - type fastener patch on the inside surface near the strap end for additional safety and to assist with application of the cuff to the limb. If this patch does not fully engage the loop fastener on the outside of the cuff, overlap is insufficient and a longer cuff must be selected (see Figure 7). Maximum overlap varies depending on cuff manufacturer, cuff type, and limb size but is typically between ¼ and ½ of the overall cuff length.

Figure 3. Dual bladder IVRA cuff (left) and single bladder cuff (right), both dual port.   Figure 4. Standard cylindrical cuff (left) wide contoured lower leg cuff (right)   Figure 5. Excessive cuff overlap condition.   Figure 6. Non - overlapping condition (gap between cuff ends).

Figure 7. Dual Fastening Feature

Some cuffs are supplied in a single size for each limb location (e.g. adult arm, thigh, or lower leg) and are designed with a range sufficient to fit 95% of the patient population. With these cuffs ensure that the limb circumference falls within the range specified in the manufacturer's cuff instructions and that the fasteners engage properly as outlined above. Pediatric patients or adults with unusually small limbs require extra care in tourniquet practice and normally require specially designed cuffs and lower inflation pressures.

Table 1. Single bladder Tourniquet Cuffs

Individual manufacturers may offer different sizes than those listed in Table 1. The 8 - inch (20 - cm) cuff is intended for thin or small limbs. Generally, it is used with lower inflation pressures than the other cuff sizes.

Table 2. Dual Bladder Tourniquet Cuffs

Cuff Width

Select as wide a cuff as possible. It has been shown that a cuff with a wider bladder occludes blood flow at a lower pressure level than does a cuff with a narrow bladder. This may be related to more efficient pressure transmission to the deeper tissues with a wider cuff. The lower pressure may reduce the risk of pressure related injury to the patient. Extra care must be taken with unusually small adult patients and pediatric patients to ensure that the correct cuff width is used and the cuff edges do not lie close to the joints of the limb to reduce the risk of nerve injury.

Disposable vs. Reusable Cuffs

Sterile, disposable cuffs are available for situations that require placement of a sterile tourniquet near the operative site, or for use in contaminated surgical cases. The design and materials of disposable cuffs are suitable for a single sterilization cycle and single use only and must not be resterilized or re - used. If a disposable cuff is selected, it must be discarded at the end of the procedure. Reusable cuffs are not designed to be sterilized and must be used with sufficient sterile draping to isolate the cuff from the sterile field.

Specialty Applications

Patients with unusually small or large limbs may require specialized tourniquet cuffs. Some specially designed pediatric cuffs have optimized width appropriate for short limb segments and thinner, more supple construction suitable for wrapping around small diameter limbs. Fitting the cuff and maintaining occlusion of arterial bloodflow may be difficult with obese patients and particular care must be taken. Standard cuffs may not be large enough in some cases, and custom cuffs may be required.

Limb Protection Beneath Cuffs

For some cuffs, a matching limb protection sleeve is available to help protect the soft tissues under the cuff. These sleeves are sized to give optimal protection to limbs within the recommended size range of the matching cuff and can help reduce wrinkling, pinching and shearing of the soft tissues. A sleeve that is not specifically matched to the cuff being used may not protect the underlying soft tissues and may impair the performance of the cuff. Some tourniquet cuff manufacturers color code their matching limb protection sleeves to help ensure that the correct sleeve is used with the selected cuff. As this color coding is specific to each manufacturer, tourniquet cuffs and sleeves from different manufacturers should never be mixed. Figure 8 shows a comparison of molds taken under a typical tourniquet cuff with no underlying limb protection, with only cast padding used as limb protection, and with a limb protection sleeve specifically matched to the tourniquet cuff being used.

(a)	(b)	(c)
Figure 8. Comparison of molds taken under a typical cuff with: a) no limb protection sleeves b) cast padding c) a limb protection sleeve matched to the cuff being used.

Tourniquet Instruments

Compressed Gas Source The tourniquet cuff bladder requires a source of compressed gas to supply a carefully controlled amount of tourniquet pressure. The gas used may be nitrogen, ambient air, or some other gas. Some tourniquet systems utilize high - pressure gas, while other systems use low - pressure gas. Never use nitrous oxide or oxygen to inflate the tourniquet cuff, because of the increased risk of fire. Some modern electronic tourniquet systems (also called microprocessor - controlled or computerized tourniquet systems) utilize an internal electrical pump to compress the ambient air; these systems do not require an external pressure source. Others are designed to use external pressure sources, such as portable canisters, portable tanks, or built - in hospital systems. Pressure Display The pressure display is a device that visually indicates the amount of pressure in the tourniquet cuff bladder. All pneumatic tourniquets have a pressure display; in older non - electronic systems it is normally a dial (aneroid) gauge. In most modern electronic systems, pressure is shown on a microprocessor - controlled digital display.

Figure 9. Dual port tourniquet instrument with two channels for two separate cuffs or bladders

Pressure Regulator

The pressure regulator adjusts and controls the gas pressure in the cuff bladder. Non - computerized tourniquet systems utilize valves that respond mechanically to changes in pressure. For example, if pressure in the cuff bladder falls, a valve opens to allow more gas to enter the regulator from the gas source; if pressure exceeds a certain level, the pressure forces a release valve to open and expel gas into the environment. Sometimes, the pressure levels at which these two valves turn on and off are quite different and cuff pressure may fluctuate within a certain range above and below the selected pressure. Due to the sensitive mechanical components of these systems, it is very important to follow the manufacturer's instructions regarding testing and calibration and to perform these checks before each surgical procedure as recommended.

In most modern electronic tourniquet systems, the internal electrical pump, pressure display, and pressure regulator are combined in a single instrument in which a microprocessor continuously monitors and compensates for changing levels of pressure in the cuff bladder. Regulation does not rely on mechanical (pressure) forces to turn valves off and on. Instead, the microprocessor can detect extremely small changes in the cuff pressure and regulate the inflow of gas to control the pressure. Some modern electronic tourniquet systems use a sophisticated "dual port" system which gives the most accurate control of cuff pressure and the fastest response to pressure changes. In a dual port system, each bladder has two ports and a double cuff - to - instrument hose. One port is for monitoring the pressure ("sensing port"); the other port is for inflating and deflating the cuff and for automatically supplying and releasing small amounts of gas during use to control cuff pressure ("supply port"). In some more basic systems a single port performs both functions for each cuff.

The tourniquet instrument may provide one or two channels, allowing one or two cuffs to be used simultaneously. Figure 9 shows a dual port two channel tourniquet instrument. A dual cuff control valve is sometimes added to a single channel system to allow use of two separate cuffs or bladders, typically for IVRA (Bier block) procedures.

Modern electronic tourniquet systems include many safety features to help improve patient safety when working with a pneumatic tourniquet. While some tourniquet systems may provide much in the way of sophisticated safety monitoring and interlocks, perioperative personnel should be aware of potentially hazardous conditions and monitor the tourniquet system during the time the cuff is applied to the patient. Potential hazards include the following:

• Kinked or occluded tubing connecting the cuff to the instrument may prevent the instrument from displaying the correct cuff pressure, or controlling the cuff pressure correctly. Some modern electronic tourniquet instruments include sophisticated monitoring techniques to warn users of tubing occlusions.
• Inadvertent deflation of both cuffs during a Bier Block (IVRA) procedure due to operator error may allow a bolus of anesthetic to enter the circulatory system suddenly and prematurely. Some modern electronic tourniquet instruments include special safety interlocks specifically to help prevent such inadvertent deflation of both cuffs.
• Leaking cuffs or leaking tubing connections may prevent the tourniquet instrument from maintaining the set pressure in the cuff. Alarms are provided in some modern tourniquet instruments to warn of leaking cuffs or low cuff pressures.
• If the power switch of an some types of electronic tourniquet instruments is inadvertently switched to an 'off' or 'standby' position while the cuff is still pressurized (due to operator error), then the pressure will be maintained in the cuff to maintain patient safety but the pressure display, timer and alarms of the tourniquet instruments may no longer function and so the operator may no longer be aware of the cuff pressure or tourniquet time. Some of the most modern tourniquet instruments include safety interlocks to prevent the power from being switched to 'off' or 'standby' positions while a pressurized cuff is connected.

The use of adaptors or accessories not approved by the instrument manufacturer may interfere with the ability of some types of modern electronic tourniquet instruments to detect alarm conditions and potentially hazardous conditions. Read the instruction manual for the specific tourniquet instrument(s) in your facility and be sure you understand the alarms and safety features of your specific tourniquet instruments.

Connecting Tubing Most pneumatic tourniquet systems use a hose assembly between the tourniquet instrument and the cuff utilizing newer Positive Locking Connectors or older Luer - lock connectors (see Figure 10). Some pneumatic tourniquets require an additional hose assembly between the external compressed gas source and the regulator. Note that additional care must be taken with the older twist - type Luer - lock connectors because they may accidentally disconnect if the hoses are twisted during movement of the hoses, cuff, patient, or instrument during use. Newer Positive Locking Connectors are less likely to disconnect accidentally. Additional Features Manufacturers of some pneumatic tourniquets have a calibration kit available for checking the tourniquet regulator and pressure display. Some modern electronic tourniquet systems perform a self - calibration each time the power is switched on. Additional features of modern electronic systems, often built into the regulating equipment, are alarm systems to detect unusual increases or decreases in pressure, to indicate elapsed inflation time and alert staff when a pre - selected maximum tourniquet time has been exceeded, and to warn of a possible kinked or blocked hose, disconnected hose, or leak in the system.

Figure 10. Positive Locking connectors (top and middle), and older style Luer Lock connectors (bottom)

To help prevent accidental release of anesthetic in dual cuff Bier Block (IVRA) procedures, some systems include a warning function requiring the user to confirm deflation of the last of the two cuffs before that cuff is actually deflated. Batteries are included in some electrically operated tourniquets, enabling a patient to be transported with the cuff(s) inflated, if necessary, and so that the tourniquet will continue to function in the event of an electrical failure. Such systems usually include an indicator or warning if battery power becomes low and recharging is required. The most advanced of the computerized tourniquet systems also incorporate safety functions to warn the user and prevent the electrical power to the system from being accidentally switched to 'off' or 'standby' positions if the user makes an error and attempts to do so while a tourniquet cuff is still inflated.