Tourniquet use in upper limb surgery

Abstract

Tourniquets are compressive devices that occlude venous and arterial blood flow to limbs and are commonly used in upper limb surgery. With the potential risk of complications, there is some debate as to whether tourniquets should continue to be routinely used. In this review, we first look at the different designs, principles, and practical considerations associated with the use of tourniquets in the upper limb. The modern pneumatic tourniquet has many design features that enhance its safety profile. Current literature suggests that the risk of tourniquet-related complications can be significantly reduced by selecting cuff inflation pressures based on the limb occlusion pressure, and by a better understanding of the actual level of pressure within the soft tissue, and the effects of cuff width and contour. The evidence behind tourniquet time, placement, and limb exsanguination is also discussed as well as special considerations in patients with diabetes mellitus, hypertension, vascular calcification, sickle cell disease and obesity. We also provide an evidence-based review of the variety of local and systemic complications that may arise from the use of upper limb tourniquets including pain, leakage, and nerve, muscle, and skin injuries. The evidence in the literature suggests that upper limb tourniquets are beneficial in promoting optimum surgical conditions and modern tourniquet use is associated with a low rate of adverse events. With the improvement in knowledge and technology, the incidence of adverse events should continue to decrease. We recommend the use of tourniquets in upper limb surgery where no contraindications exist.

Tourniquets are compressive devices that occlude venous and arterial blood flow to limbs and their use has been described in antiquity. The term tourniquet derives from the French verb “tourner” that means to turn, and was coined by the French Surgeon Jean Louis Petit (1,674–1,750) who described a belt like device that was used to reduce blood loss in limb amputations. The belt was pulled tight around a limb with a screw sited over the main artery, and the screw subsequently turned to compress the artery [35].

Tourniquets are commonly used in surgery to create a bloodless field, to engorge vessels for venepuncture, and in rare instances to control bleeding in life or limb threatening situations. They are also used in Bier's block as an adjunct to regional anesthesia whereby a tourniquet is applied to the limb and local anesthetic administered intravenously at a site distal to the tourniquet to anesthetize the entire distal limb.

The use of tourniquets reduces the incidence of technical difficulties during surgery but there is no conclusive evidence that it influences pain perception or lessens duration of surgery [74]. This lack of conclusive evidence coupled with well-publicized few adverse events have led to some debate as to whether tourniquets should continue to be routinely used in upper limb surgery.

Modern Pneumatic Tourniquets

The modern pneumatic tourniquet was invented by James A McEwan in the early 1980's and consists of an inflatable cuff, a compressed gas source, and a microprocessor-controlled pressure regulator that maintains cuff pressure within 1% of the set pressure [42]. The cuff pressure and inflation time are displayed on a monitor that can be easily read by clinical staff. The design protects against over-pressurization or sudden de-pressurization, and an audiovisual alarm is usually incorporated and triggered by cuff leaks, excessively high or low cuff pressures, or a prolonged tourniquet time.

A number of additional design features enhance its safety profile such as the dual-line cuff that facilitates the detections of kinks or occlusions in the line, and a back-up battery that ensures normal function in the event of a power-supply failure. The modern tourniquet system allows the judicious administration of lower tourniquet pressures than was hitherto advocated and used [5, 19] achieving a better safety profile while still maintaining a blood-less field.

Manufacturing guidelines advise on how to achieve good tourniquet care [42], and these should be supplemented by local hospital policy. Gauges and valves should be checked regularly to avoid malfunction that can lead to dangerously high inflation cuff pressures. Frequent calibration checks and intraoperative monitoring of tourniquet function can ensure that actual cuff pressures are accurate to the specified set pressure.

Manufacturing guidelines and local hospital policy should be followed for decontamination. At our hospital, the cuff, tubing and tourniquet unit are checked for soiling and are cleaned between cases with a neutral hospital detergent diluted in warm tap water to prevent cross infection. The open end of the tubing however should not be immersed in water as it could alter the pressure distribution of the cuff. The equipment is then dried with a clean disposable cloth following decontamination.

Limb Occlusion Pressure

The concept of Limb Occlusion Pressure (LOP) is important in safe and effective tourniquet use. It is the pressure at which arterial blood flow is occluded past a specific tourniquet cuff at a specific time in a specific limb. It considers the anatomical and physiological characteristics of a patient's limb and the physical properties of the tourniquet in question. Current literature suggests that the risk of tourniquet related complications can be significantly reduced by measuring the LOP and selecting cuff inflation pressures accordingly [24, 41, 60, 86].

Conventionally LOPs are determined manually by inflating the tourniquet and recording the pressure at which the distal arterial pulsation ceases, usually verified by a doppler stethoscope. A margin of error of 50–100 mmHg is added in consideration of changing conditions during surgery. These values are based on the results in the literature where bloodless fields have been consistently achieved [14, 60]. The manual process however is both time consuming and labor intensive and despite its proven safety benefit, has not been readily accepted in clinical practice. Another option is to use systolic blood pressure plus a standard margin of error to obtain a safe cuff inflation pressure [10, 85]. However the results of this estimation are suboptimal because of the variable relationship between LOP and systolic blood pressure [41, 71].

More recently, advanced tourniquet systems have been developed that are able to measure the LOP automatically. These systems are based on the photoplephysmographic priniciple that uses a light transducer to deduce blood flow and calculate the cuff inflation pressure at which distal circulation is occluded [43]. The accuracy of this device is comparable to the standard doppler technique and has been shown to significantly reduce the tourniquet pressure used in a clinical setting [86].

Current guidelines from the Association of peri-Operative Registered Nurses [9] recommends that for adults, a safety margin of 40 mmHg be added for LOP less than 130 mmHg, 60 mmHg be added for LOP 131–190 mmHg, and 80 mmHg be added for LOP greater than 190 mmHg. In children a standard safety margin of 50 mmHg is recommended for all LOPs.

Tourniquet Design

Studies have shown that the actual level of pressure applied in the pneumatic cuff varies widely in comparison to the pressure within the encircled soft tissue [23, 66, 71]. Peak pressure occurs in the subcutaneous tissue just proximal to the mid-position along the tourniquet width, and decrease from this point towards the center and towards the cuff edge. There is a direct relationship between cuff inflation pressure, peak pressure in subcutaneous tissue and the pressure gradient in underlying soft tissue. The probability of tourniquet-related complications increases as the peak pressure and pressure gradient increase [44, 53, 71], thus it is desirable to achieve vascular occlusion with the lowest possible cuff inflation pressure.

Crenshaw et al. (1988) measured tissue pressure in cadaveric limbs at four depths following the application of a pneumatic cuff [10]. They found that wide cuffs had a more gradual pressure profile at all tissue depths, with relatively smaller changes between the peak pressures at the mid-position of the tourniquet width and lowest pressures at the periphery of the tourniquet width. They also found that wide cuffs required lower inflation pressures to stop the flow of arterial blood distal to the tourniquet. Graham et al. (1993) showed an inverse relationship between LOP and the ratio of the cuff width to the limb circumference [22]. They showed that the occlusion pressure reached sub-systolic levels when the cuff width to limb circumference ratio exceeded 0.5.

Contoured cuffs have been proven to occlude blood flow at lower pressures than standard straight cuffs and, when used with LOP, can significantly reduce the necessary cuff pressures to maintain a bloodless surgical field in both the adult and paediatric population [22, 60]. This has led to the development of variable-contour cuffs that are suitable to a wide range of limb sizes and shapes. Thus a wide and contoured tourniquet is favored to achieve the lowest possible limb occlusion pressure.

Non-pneumatic Tourniquet

Non-pneumatic tourniquet devices typically produce applied pressures and pressure gradients that are significantly higher than the LOP, and at levels associated with significantly higher rates of morbidity. Previously these non-pneumatic tourniquets were used in hospitals but the transition has been made to pneumatic tourniquets for safety reasons. Non-pneumatic tourniquets still serve a purpose in the military due to their ability to stop arterial bleeds, their ease of use and their proven life and limb salvage potential [38].

Practical Considerations

1. There is no completely safe duration of tourniquet use, and it is important to minimize tourniquet time to minimize the chances of any potential complications. Historical studies did not show any post-operative complications where tourniquet time exceeded 2 h [6, 18], and in clinical practice 2 to 3 h was considered a safe upper limit for tourniquet use. Excessive tourniquet time however increases the rate of tourniquet-related ischemic complications and more recently human studies have shown that significant ischemia and muscle dysfunction occurs after 2 h [57]. The issue of temporarily tourniquet deflation during prolonged surgery to allow tissue reperfusion is not supported by evidence in the literature [74]. Tourniquet inflation should occur at least 5 min after any intravenous antibiotic administration to allow adequate tissue perfusion of antimicrobial agents [3].

2. Tourniquets are conventionally placed on the upper arm in upper limb surgery, but there has been an increasing trend of using forearm tourniquets supported by literature evidence of their efficacy and safety [80]. In Bier block, forearm tourniquets have the advantage of requiring a lower dose of local anesthetic [73]. Hutchinson and McClinton (1993) have shown that, for minor surgical procedures under local anesthetic lasting less than 30 min, patients reported less pain and tolerated tourniquets placed on the forearm better than those on the upper arm [29]. Odinsson and Finsen (2006) concurred with these findings but found that surgeons experienced greater difficulty with more distally placed tourniquets [55].

3. Mechanical limb exsanguination can be performed prior to applying the tourniquet and commencing surgery to facilitate the creation of a blood-less field. The Esmarch bandage is a rubber bandage devised by the German surgeon, Johann von Esmarch that is tied around the limb for exsanguination or as a tourniquet. Its efficacy in exsanguination is well described but its use as a tourniquet is controversial as it achieves greater pressure and has been associated with higher rates of complication. Alternatively a Rhys-Davies exsanguinator can be used [64]. This consists of an inflated elastic cylinder that is rolled over a limb to produce exsanguination. It is highly effective and has a very good safety profile. Simple elevation can achieve a good result where mechanical limb exanguination is contraindicated e.g. in sickle-cell. Warren et al. (1992) recommend upper limb elevation for 5 min at 90° before tourniquet application [83].

4. Tourniquet use in the presence of arterial calcification such as in people suffering with diabetes mellitus should be carried out judiciously. Theoretical risks are failure to achieve a blood-less field leading to inadequate visualization during surgery, systemic toxicity from anesthetic agents as a result of a failed regional intravenous block, and an increased risk of tourniquet-related complications due to the higher cuff inflation pressures that may be needed to achieve arterial occlusion. Jeyaseelan et al. (2007) report on the case of a patient with Mönckeberg’s calcinosis in whom a limb tourniquet failed due to calcification of the femoral artery wall [31]. Excessive bleeding at the surgical site was observed due to failure to achieve arterial occlusion but a very effective venous occlusion.

   As discussed above, LOP is the directly measured minimum pressure required to stop the flow of blood for a specific situation, and is generally lower than a predetermined generic pressure, e.g., 250 mmHg. In situations where the arterial calcification hinders adequate arterial occlusion, the use of LOP is likely to avoid the use of higher predetermined generic pressures.

   There have been reports of crises precipitated by the use of tourniquets in surgery in sickle cell disease and, conversely, successful procedures carried out with minimal adverse events. Clinical decisions regarding tourniquet use should be made on the basis of risk versus benefit to the patient, and supplemented with careful exsanguination technique and good general principles of sickle cell patient management [1, 75, 84].

   Obese patients often present a problem in tourniquet application due to their excessive subcutaneous tissue. A wide and appropriately sized tourniquet should be selected and contoured tourniquets have been found to be extremely useful. Its efficacy is improved by having an assistant draw the skin and subcutaneous tissue distally before fastening the tourniquet [37].

Complications

There are a variety of local and systemic complications that may arise from the use of upper limb tourniquets in the surgical or anesthetic settings. Localized physiological changes can result from the direct effect of cuff compression or tissue hypoperfusion due to vascular occlusion. Systemic complications appear related to tourniquet inflation and deflation [33].

Studies suggest that tourniquet associated complications remain fairly rare. Reports in Australia in the 1970's showed adverse events related to tourniquet use in one in 5,000 and one in 13,000 procedures on the upper and lower limb respectively [46]. More recent studies in Norway showed 26 complications in approximately 63,484 surgical procedures using tourniquets [55].

Most clinical and animal based research suggests that tourniquet-related complications increase with time [16, 32, 40] and this has led to the widespread practice of limiting tourniquet use to less than 2 h [3, 82].

1. Pain may be experienced with tourniquet use on the upper limb and tolerance depends upon a number of variables such as patient pain threshold, duration of use, cuff pressure and cuff diameter [13].

   When tourniquets are inflated, patients experience a vague, dull pain in the limb and there is an associated increase in blood pressure [20, 76]. A prospective study showed overall good tolerance of tourniquets up to 20 min and suggested an idiosyncratic relationship between pain perception and tourniquet use [56]. Prolonged tourniquet inflation results in an increase in heart rate and blood pressure, and the anesthetist often increases the depth of anesthesia to counteract this [36]. The duration of pain tolerance improves in sedated patients [11, 36]. Hagenouw et al. (1986) demonstrated that higher cuff pressures with narrower tourniquet diameters can cause less pain than wider cuffs with lower pressures [11], whereas Estebe (2000) showed that a wide-cuff pneumatic tourniquets improve arterial occlusion and are less painful than narrow cuffs when pressure is limited to arterial pulse loss [17, 25].

   There is a complicated multifactorial aetiology for tourniquet pain. Tourniquet pain is thought to be nerve fiber related with pain transmitted along slow-conducting unmyelinated C-fibers. It is suspected that fast conducting myelinated A-δ-fibers, that under normal circumstances inhibit this C-fiber related pain transmission, are blocked by mechanical compression through ischemia [32, 36]. Another explanation of tourniquet pain is that during compression there is an increase in spontaneous firing activity and expansion of the receptive fields of noci-responsive dorsal horn neurones around the area of tourniquet application [12]. Limb reperfusion pain has also been described after tourniquet deflation when blood flow is restored and toxic metabolites removed [11, 36, 63].

2. Leaks are important because of the risks local anesthetic agents pose during Bier block anesthesia if they reach the systemic circulation, and the effect ooze may have on the surgical field. Leakage in upper limb tourniquets is affected by a variety of factors. Blood pressure, cuff pressure and width, and cannula location in the arm have all been described as having a bearing on movement of anesthetic agents into systemic circulation and oozing of blood through arterial leakage into the surgical field.

   Studies using radiolabeled isotopes have tried to quantify leakage in upper limb surgery of substances reaching systemic circulation. Hoffmann et al. (1995) revealed a mean leak of 15 ± 5% of radiolabeled compound from distal to an upper arm tourniquet to the systemic system [27]. Coleman et al. (1999) described leakage of 10 ± 20% of radiolabeled compound from distal to an upper arm tourniquet to the systemic system, and of 6 ± 12% for a forearm tourniquet [8]. Arterial leakage has proved more difficult to measure accurately.

   Interosseous, especially biosseous, routes have been implicated as a source of leakage since such vessels are not readily compressed by tourniquets, but such evidence is yet to be clinically quantified and substantiated [8, 65]. There is an increased risk of leakage in hypertensive patients. As there is an inverse relationship between the LOP and the ratio of tourniquet cuff width to limb circumference [22], any increase in limb circumference increases the pressure required to prevent a leak. Limb congestion thus may increase the risk of local anesthetic agent leaking past the tourniquet into the systemic circulation.

3. There have been numerous publications on tourniquet-related nerve damage. The incidence varies in the literature but nerve complications appear uncommon ranging from 1 in 750 [18] to 1 in 11,000 [46] in upper limb surgery. The radial nerve is most prone to injury [32, 46].

   A number of factors have been implicated in tourniquet related nerve damage including longer durations of tourniquet application [28] and higher tourniquet pressure gradients [45, 47]. Studies performed prior to the use of lower pressures in tourniquets demonstrated a higher incidence of neuromuscular dysfunction [51]. Tourniquet related nerve complications exist on a spectrum from minor transient loss of function to permanent irreversible damage. The typical duration of reversible denervation ranges from 2 to 6 months [47, 55, 66] with irreversible damage being rare [66].

   The pathophysiology of nerve damage relates to direct compressive forces under the tourniquet and at its edges. Compression causes stretching of myelin sheaths, displacement of nodes of Ranvier from their normal position, microvascular damage, edema and ischemia related tissue nutrition depletion [32, 67, 68]. There is associated partial to complete rupture of the paranodal myelin promoting axonal degeneration. Nerve constituent displacement occurs in the direction of non-compressed tissue and is greatest at the tourniquet edge, i.e., the area of highest pressure gradient [21, 53, 54].

4. As with tourniquet related nerve damage, muscle tissue injury beneath and distal to tourniquet sites have been shown in clinical and animal studies to be directly correlated to application times and pressures [32, 61]. Inflammatory changes, focal and regional necrosis and hyaline degeneration take place following microvascular compression and superoxide free radical endothelial damage. The extent depends on muscle location in relation to the tourniquet and duration of ischemia [49, 62].

   There are cellular, metabolic and microvascular changes that take place as a result of anaerobic metabolism during tourniquet application. The reduced tissue perfusion during tourniquet application leads to a depletion of the intracellular nutrients creatine phosphate, glycogen and adenosine triphosphate, while lactate and carbon dioxide levels increase and intracellular pH decreases. Tissue nutrition appears depleted after 2 to 3 h of ischemia [26, 32, 69].

   After deflation further cellular injury can ensue due to microvascular congestion. This is related to “Post-tourniquet syndrome” where the patient may experience weakness, stiffness and numbness of the affected limb, which tends to recover on average 3 weeks postoperatively. Recovery time is proportional to ischemic duration. After 3 h of cuff inflation the recovery time may be significantly increased [32, 49, 61, 69, 70]. Rhabdomyolysis due to prolonged tourniquet application is well-documented [58, 72, 81].

5. This is a rare complication related to pressure necrosis or friction burns due to tourniquet movement [7]. Chemical burns can be caused when solutions used for operative preparation pass under the tourniquets and remain there under pressure during surgery [15].

6. Deflation and reperfusion allow nutritional replenishment of the affected limb and metabolite removal. This stage of the operation requires close patient monitoring [48, 67]. Myonephropathic metabolic syndrome has been described when toxic metabolites enter systemic circulation. Clinically it is characterized by metabolic acidosis, hyperkalemia, myoglobulinaemia, myoglobinuria, and renal failure [48, 59]. Post-tourniquet bleeding may occur after deflation, related to increased activation of protein-C and antithrombin-III thrombolytic pathways [62].

Discussion

The use of epinephrine, and other vasoconstrictive drugs, provides an alternative to the use of tourniquets. The effectiveness of local anesthetics is improved by the addition of a epinephrine, and provides an increased duration of action and decreased local bleeding. The addition of epinephrine to the local anesthetic has been shown to cause sufficient vasoconstriction to maintain a dry field and allow carpal tunnel decompression procedures without the need of a tourniquet [79]. In arthroscopy procedures, 10 ml of 1:10,000 epinephrine may be mixed in 3 L irrigation fluid to control hemostasis [39]. Tourniquets may however still need to be applied in a standby manner, in more extensive or higher risk procedures, and where there is a history of coagulopathy. Epinephrine use has limitations due to potential cardiac and local toxic effects.

Adverse effects due to tourniquet use are well-documented but remain reassuringly uncommon. With the improvement in knowledge and technology, the incidence of adverse events should continue to decrease. Many methods have been described and continue to be developed that aim to reduce adverse events. These include the use of lower inflation pressures [47, 60], entire limb cooling to extend ischemic time [34], alternately inflated two tourniquet cuffs to avoid prolonged compression under the cuff [50] and anesthetic techniques to improve cuff use and tolerance [2, 4, 30, 77, 78]. There nevertheless remains an absence of convincing scientific evidence to support any of these techniques. Noordin et al. stated that accurate monitoring and minimization of tourniquet time was the most important factor in preventing adverse events [52].

The risks and benefits associated with the use of an arterial tourniquet should be assessed by the clinician performing the procedure, and the patient should be appropriately informed and consented. Accurate procedural and patient assessment prior to surgery will help optimize upper limb tourniquet use and individualize the technique. The clinician using the tourniquet should give clear instructions regarding the appropriate choice of cuff and gauge pressure, decide when to inflate and deflate the tourniquet, and ensure good communication.

The evidence in the literature suggests that upper limb tourniquets are beneficial in promoting optimum surgical conditions and modern tourniquet use is associated with a low rate of adverse events. We recommend the use of tourniquets in upper limb surgery where no contraindications exist.

Summary for Safe Tourniquet Use

• The use of well-maintained wide modern contoured pneumatic tourniquets reduces the pressures applied to the underlying tissues and improves their safety profile.

• The measurements of LOP can potentially reduce the tourniquet pressures used.

• There is no completely safe duration of tourniquet use, and it is important to minimize tourniquet time to minimize the chances of any potential complications.

• Higher tourniquet pressures and durations are associated with higher risk of pain, and skin, muscle and nerve-related complications.