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Current Concepts Review   |    
Surgical Tourniquets in Orthopaedics
Shahryar Noordin, MBBS, FCPS1; James A. McEwen, PhD, PEng2; Colonel John F. KraghJr., MD3; Andrew Eisen, MD, FRCPC4; Bassam A. Masri, MD, FRCSC2
1 Section of Orthopaedics, Department of Surgery, Aga Khan University, Stadium Road, P.O. Box 3500, Karachi 74800, Pakistan. E-mail address: shahryar.noordin@aku.edu
2 Division of Lower Limb Reconstruction and Oncology, Department of Orthopaedics (J.A.McE., and B.A.M.), and Department of Electrical and Computer Engineering (J.A.McE.), University of British Columbia, 3114, 910 West 10th Avenue, Vancouver, V5Z 4E3 BC, Canada
3 United States Army Institute of Surgical Research, Regenerative Medicine, 3400 Rawley East Chambers Avenue, Building 3611, Room L82-16, Fort Sam Houston, TX 78234-6315
4 Department of Neurology, University of British Columbia, 2862 Highbury Street, Vancouver, V6R 3T6 BC, Canada
View Disclosures and Other Information
Disclosure: The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity.
Disclaimer: The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or reflecting the views of the Department of Defense or United States Government.
Investigation performed at the Department of Orthopaedics, University of British Columbia, Vancouver, British Columbia, Canada

The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2009 Dec 01;91(12):2958-2967. doi: 10.2106/JBJS.I.00634
The erratum to this article has been published | view the erratum
5 Recommendations (Recommend) | 3 Comments | Saved by 3 Users Save Case

Abstract

Higher levels of tourniquet pressure and higher pressure gradients beneath tourniquet cuffs are associated with a higher risk of nerve-related injury.

Measurement of limb occlusion pressure can help to minimize tourniquet pressure levels and pressure gradients for individual patients and individual surgical procedures.

Selective use of pneumatic, wider, and contoured tourniquet cuffs reduces tourniquet pressure levels and the applied pressure gradients.

Figures in this Article

    Topics

    tourniquets ; limb
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    References

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    Shahryar Noordin, MBBS, FCPS
    Posted on February 19, 2010
    Dr. Noordin and colleagues respond to Mr. Smith and Ms. Hing
    Aga Khan University, Karachi, Pakistan

    We appreciate the interest expressed by Smith and Hing in our recently published current concepts review article on tourniquets (1). “Tourniquet–related nerve injuries” was presented as a separate section because of the tremendous amount of basic and applied research that has been done in this area that has important implications for optimal tourniquet cuff design and inflation pressures, as we have discussed. The remaining complications associated with tourniquet use that Smith and Hing mention have been discussed and referenced in the sections of “duration of tourniquet use” and “tourniquet deflation”. This segregation was done to avoid redundancy and to use valuable journal space to provide the readers with the broader perspective on the use of tourniquets as it has evolved with our understanding of underlying bioengineering principles.

    The issue of microbial colonization on operating room tourniquet cuffs has been plain: objects can become fomites if used without routine safeguards. However, after each surgical procedure, standard operating procedures are in place internationally that address disinfecting reusable tourniquet cuffs. The Association of Operating Room Nurses also includes a protocol for disinfecting reusable pneumatic tourniquet cuffs after every surgery (2). Furthermore, reusable tourniquet cuffs are routinely draped out of the field, or alternatively sterile disposable tourniquet cuffs are used, and none of the randomized control trials have shown a higher infection rate.

    Based on our current concepts review as well as the conclusions reached by the meta-analyses by Smith and Hing, we think the better question to ask would be how to optimize the use of tourniquets to get the best results for our patients rather than asking whether tourniquets are still required. To do otherwise would amount to throwing out the baby with the bathwater.

    The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or reflecting the views of the Department of the Army or United States Government.

    References

    1. Noordin S, McEwen JA, Kragh JF Jr, Eisen A, Masri BA. Surgical tourniquets in orthopaedics. J Bone Joint Surg Am. 2009;91:2958-67.

    2. AORN, recommended practices for use of the pneumatic tourniquet. In: Perioperative standards and recommended practices. 2009 ed. Denver, CO: AORN Inc; 2009. p 373-85.

    Toby O. Smith
    Posted on February 02, 2010
    The Clinical Outcomes of Surgical Tourniquets in Orthopaedics?
    Norfolk and Norwich University Hospital & University of East Anglia, Norwich, United Kingdom

    To the Editor:

    We would like to congratulate Dr. Noordin and this team for their recent review of the use of surgical tourniquets in orthopaedics (1). However, while the authors clearly described the evolution of tourniquet scientific knowledge and its associated risk of nerve injury, they neglected to highlight a number of other important complications which have been previously cited within the literature as a consequence of its use. Such complications have included distal joint effusion and wound inflammation (2), reduced knee range of motion (3), cardiovascular fluctuation (4-6) and pain (7,8) in both upper and lower extremity tourniquet use. However, more recently, Ahmed et al. (9), assessed the potential of microbial colonization on tourniquets used in orthopaedic theaters. They reported that all samples taken from the twenty-two tourniquets assessed were contaminated, with colony counts varying from 9 to greater than 385. Coagulase-negative Staphylococcus spp. were the most commonly grown organisms from the tourniquet (9). However, these authors also reported some tourniquets had growths of other important pathogens including methicillin-resistant Staphyloccus aureus (MRSA), Pseudomonas spp. , and S. aureus (9). Accordingly, pneumatic tourniquets may be a source of infection, which may have devastating consequences to the success of routine orthopaedic procedures. These complications should therefore be acknowledged as important potential consequences, in addition to nerve palsy, which should be considered by orthopaedic surgeons when using surgical tourniquets.

    While informative, this review did not ask the most clinically important question: are surgical tourniquets really necessary in current orthopaedic practice? Having identified that tourniquets have been attributed to a variety of post-operative complications, we undertook a series of meta-analyses in order to answer this question based on the current evidence base (10-13). We found that the use of a surgical tourniquet did not significantly increase the risks of post-operative nerve injury, wound infection, joint range of motion or recovery (p>0.05), there was similarly no statistically significant difference between the use of a tourniquet and not using a tourniquet with respect to peri-operative or post-operative blood loss, requirements for blood transfusion, operative time or length of hospital stay (p>0.05) in total knee arthroplasty (TKA) and arthroscopic knee surgery (10,11). There was however, evidence to indicate that, for TKA and anterior cruciate ligament reconstruction, the addition of a tourniquet significantly reduced operative visual disturbance, compared to not using a tourniquet (p <_0.05 _1011.="_1011." similarly="similarly" the="the" use="use" of="of" a="a" tourniquet="tourniquet" in="in" upper="upper" extremity="extremity" surgery="surgery" was="was" shown="shown" to="to" significantly="significantly" reduce="reduce" operative="operative" field="field" disturbance="disturbance" compared="compared" not="not" using="using" p0.01="p0.01" _12.="_12." however="however" when="when" foot="foot" and="and" ankle="ankle" procedures="procedures" were="were" analyzed="analyzed" patients="patients" who="who" underwent="underwent" without="without" presented="presented" with="with" statistically="statistically" significant="significant" shorter="shorter" hospital="hospital" length="length" stay="stay" reduced="reduced" post-operative="post-operative" pain="pain" swelling="swelling" from="from" fifth="fifth" day="day" tourniquet-assisted="tourniquet-assisted" p0.05="p0.05" _13.="_13." evidence="evidence" base="base" on="on" which="which" these="these" findings="findings" made="made" demonstrate="demonstrate" substantial="substantial" methodological="methodological" limitations="limitations" leading="leading" us="us" question="question" whether="whether" there="there" is="is" sufficient="sufficient" support="support" or="or" refute="refute" tourniquets="tourniquets" orthopaedic="orthopaedic" _10-13.="_10-13." p="p" /> Whilst Noordin and colleagues (1) rightfully acknowledged that the safety of tourniquets would appear to have improved over the past 20 years, it should still be stated that, based on the best available literature, there remains confusion as to whether tourniquets are still required given advances in surgical technique, and the option of adrenaline infiltration in current practice.

    Conflict of Interest: The authors have previously published a series of systematic reviews and meta-analysis assessing the clinical outcomes of tourniquet use in orthopaedics (10-13).

    The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the authors, or a member of their immediate families, are affiliated or associated.

    References

    1. Noordin S, McEwen JA, Kragh JF Jr, Eisen A, Masri BA. Surgical tourniquets in orthopaedics. J Bone Joint Surg Am. 2009;91:2958-67.

    2. Johnson DS, Stewart H, Hirst P, Harper NJ. Is tourniquet use necessary for knee arthroscopy? Arthroscopy. 2000;16:648–51.

    3. Wakankar HM, Nicholl JE, Koka R, D'Arcy JC. The tourniquet in total knee arthroplasty. A prospective, randomised study. J Bone Joint Surg Br. 1999;81:30–3.

    4. Abdel-Salam A, Eyres KS. Effects of tourniquet during total knee arthroplasty. A prospective randomised study. J Bone Joint Surg Br. 1995;77:250-3.

    5. Padala PR, Rouholamin E, Mehta RL. The role of drains and tourniquets in primary total knee replacement: a comparative study of TKR performed with drains and tourniquet versus no drains and adrenaline and saline infiltration. J Knee Surg. 2004;17:24-7.

    6. McGrath BJ, Hsia J, Epstein B. Massive pulmonary embolism following tourniquet deflation. Anaesthesiology. 1991;74:618-20.

    7. Braithwaite BD, Robinson GJ, Burge PD. Haemostasis during carpal tunnel release under local anaesthesia: a controlled comparison of a tourniquet and adrenaline infiltration. J Hand Surg Br. 1993;18:184-6.

    8. Omeroĝlu H, Uçaner A, Tabak AY, Güney O, Biçimoğlu A, Günel U. The effect of using a tourniquet on the intensity of postoperative pain in forearm fractures. A randomized study in 32 surgically treated patients. Int Orthop. 1998;22:369-73.

    9. Ahmed S, Ahmed R, Case R, Spencer RF. A study of microbial colonisation of orthopaedic tourniquets. Ann R Coll Surg Engl. 2009;91:131-4.

    10. Smith TO, Hing CB. A meta-analysis of tourniquet assisted arthroscopic knee surgery. Knee. 2009;16:317-21.

    11. Smith TO, Hing CB. Is a tourniquet beneficial in total knee replacement surgery? A meta-analysis and systematic review. Knee. 2009 Jul 17. [Epub ahead of print]

    12. Smith TO, Hing CB. Should tourniquets be used in upper limb surgery? A systematic review and meta-analysis. Acta Orthop Belg. 2009;75:289-96.

    13. Smith TO, Hing CB. The efficacy of the tourniquet in foot and ankle surgery? A systematic review and meta-analysis. Foot Ankle Surg. In press.

    Shahryar Noordin, MBBS, FCPS
    Posted on December 29, 2009
    Dr. Noordin and colleagues respond to Mr. Purushothaman
    Aga Khan University, Karachi, Pakistan

    The concept of limb occlusion pressure (LOP) is critical to understanding how to safely minimize the tourniquet pressure level and pressure gradients applied by a cuff to the underlying extremity and hence mitigate iatrogenic neurological injuries (1). Limb occlusion pressure is affected by a number of variables, of which systolic blood pressure is only one. Other variables that affect LOP include limb circumference and shape at the tourniquet cuff site, local tissue characteristics underlying the cuff, aspects of cuff design (e.g. cuff width and shape) and cuff application technique (e.g. degree of snugness) (2). Therefore, simply measuring systolic blood pressure is an oversimplification, resulting in tourniquet pressure levels that may be hazardously high or hazardously low. This is readily demonstrated by measuring the LOP of a subject having a particular systolic blood pressure, using cuffs of differing widths and designs, at limb locations having differing circumferences and shapes, and applied with various degrees of snugness or looseness; the measured LOPs will vary substantially for the same systolic blood pressure.

    When LOP is measured, an additional pressure margin based on recommendations in the published surgical literature may be added to the automatically measured LOP to provide a “Recommended Tourniquet Pressure” (RTP), as a guideline to help the surgical staff select the lowest tourniquet pressure that will safely stop arterial blood flow for the duration of a surgical procedure (3). The difference in pressure between the measured LOP and the tourniquet pressure selected for surgery, which may be the RTP, can be defined as the cuff pressure safety margin. Ideally the cuff pressure safety margin is selected to be greater than the magnitude of any increase in LOP normally expected during surgery due to changes caused by drugs used for anesthesia, the patient’s physiologic response to surgery, and other variables.

    The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or reflecting the views of the Department of the Army or United States Government. COL Kragh is an employee of the U.S. government. This work was prepared as part of his official duties and, as such, there is no copyright to be transferred.

    References

    1. Reilly CW, McEwen JA, Leveille L, Perdios A, Mulpuri K. Minimizing tourniquet pressure in pediatric anterior cruciate ligament reconstructive surgery: a blinded, prospective randomized controlled trial. J Pediatr Orthop. 2009;29:275-80.

    2. Younger AS, McEwen JA, Inkpen K. Wide contoured thigh cuffs and automated limb occlusion measurement allow lower tourniquet pressures. Clin Orthop Relat Res. 2004;428:286-93.

    3. McEwen JA. What is tourniquet “limb occlusion pressure” (LOP)? http://www.tourniquets.org/lop.php. Accessed 2009 Dec 29.

    Shahryar Noordin, MBBS, FCPS
    Posted on December 24, 2009
    Dr. Noordin and colleagues respond to Dr. Gavriely
    Aga Khan University, Karachi, Pakistan

    The authors thank Dr. Gavriely for raising important questions which will serve to stimulate further thinking about current concepts relating to tourniquets in orthopaedics. His question about conflict of interest has been addressed directly with the editor, and an erratum has been published.

    We trust that this will not detract from consideration of some important questions raised by Dr. Gavriely’s letter, which include the following:

    1. What are the basic mechanisms of tourniquet-related injuries, as reported in the literature?

    2. What is the relationship between tourniquet-related injuries and the levels and gradients of pressures applied to limbs by tourniquet cuffs?

    3. Do narrower tourniquet cuffs, whether pneumatic or non-pneumatic, necessarily require higher pressures and higher pressure gradients to stop arterial blood flow?

    4. What ranges of pressures may be produced by narrow, non-pneumatic tourniquet devices which are applied manually and in which applied pressures cannot be accurately monitored or regulated after application?

    5. What is the reported incidence of tourniquet-related injuries, and what factors may affect their recognition and reporting?

    In our manuscript, we attempted to analyze the pertinent literature relating to each of these questions, among others.

    The literature on the mechanism of tourniquet injuries is clear and consistent and well established by many investigators over many years. There is a relationship between higher tourniquet pressures, higher pressure gradients and a higher probability of injury.

    Dr. Gavriely’s main assertion is that narrow elastic tourniquet rings are superior to wider cuffs (1-6). It appears to us that Dr. Gavriely has misunderstood or misinterpreted aspects of earlier peer-reviewed papers by Ochoa et al. (4), Hodgson (5) and Crenshaw et al. (6). Ochoa’s important findings about the mechanism of tourniquet-related injuries are accurately described in our manuscript (7) (see Figure 3 and page 2959) and do not support Dr. Gavriely’s assertion. Hodgson (5) in 1993 described an interesting biomechanical model and hypothesized, based on that model, that wider tourniquet cuff designs having a gradual roll-off of pressure near the edges would be optimal in avoiding tourniquet-induced neuropathy; cuffs having such designs subsequently became available. Also, Dr. Gavriely may have misunderstood the significance of the results of Crenshaw et al. (6): “The cuff pressure required to eliminate blood flow decreased as cuff width increased” and “Thus, wide cuffs transmit a greater percentage of the applied tourniquet pressure to deeper tissues than conventional cuffs; accordingly, lower cuff pressures are required, which may minimize soft-tissue damage during extremity surgery.” Dr. Gavriely may not have appreciated that if a lower tourniquet pressure can eliminate blood flow past a specific cuff, then the pressure gradients produced by that cuff will be correspondingly lower. Figure 4 of the manuscript summarizes the relationship between tourniquet cuff width and limb occlusion pressure reported in the literature over many years. Nevertheless we recognize there are circumstances, particularly certain military applications, when narrow, non-pneumatic tourniquets are appropriate and life-saving.

    We find it necessary to correct Dr. Gavriely in his assertion regarding the data presented in Fig. 5 in our manuscript (7): these data were not hypothetical, but based on measurements. Dr. Gavriely suggested that different sizes of an elastic ring tourniquet could be matched to a limb location according to a look-up table able to produce a desired applied pressure. We were not able to find data or evidence of pressure measurements supporting the recommendations of a lookup table and the resultant pressures produced. Further, that suggestion raises safety concerns arising from an inadvertent mismatch between ring/limb size by a user if actual tourniquet pressure is not measured. In the manuscript, we pointed out that the use of non-pneumatic tourniquet devices of current designs precludes accurate pressure measurement, pressure monitoring and pressure control during use. A direct understanding of some of the relevant safety concerns can be gained by a reader by self-application of any of the tourniquet devices in Figure 5, by operating each as recommended to eliminate blood flow, and by comparing the relative levels of pain experienced. The variation in focal pressure concentration and pain perception is substantial.

    We would remind Dr. Gravriely of aspects of our brief historical review: narrow rubber bandages were used as tourniquets at the end of the nineteenth century, but their use in surgical, non-military applications was quickly supplanted after Cushing introduced the pneumatic tourniquet in 1904, thereby reducing tourniquet-related injuries by permitting tourniquet pressure to be measured, monitored and controlled. The safety and effectiveness of wider pneumatic devices is also supported by the military literature which is analogous to the surgical literature.

    In summary, we thank Dr. Gavriely for his thought provoking comments discussing important current concepts relating to tourniquets in orthopaedics.

    The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or reflecting the views of the Department of the Army or United States Government. COL Kragh is an employee of the U.S. government. This work was prepared as part of his official duties and, as such, there is no copyright to be transferred.

    References

    1. Mittal P, Shenoy S, Sandhu JS. Effect of different cuff widths on the motor nerve conduction of the median nerve: an experimental study. J Orthop Surg Res. 2008;3:1.

    2. Drosos GI, Stavropoulos NI, Kamezis I, Kazakos K, Verettas D. Silicone ring versus pneumatic cuff tourniquet: a preliminary comparative quantitative study in healthy individuals. Read at the EFORT conference; 2005 Jun; Lisbon, Portugal.

    3. Mohan A, Solan M, Magnussen P. Pain tolerance with a novel tourniquet in hand surgery – a comparative study. Read at the EFORT conference; 2008 Jun, Nice, France

    4. Ochoa J, Fowler TJ, Gilliatt RW. Anatomical changes in peripheral nerves compressed by a pneumatic tourniquet. J Anat. 1972;113(Pt 3):433-55.

    5. Hodgson AJ. Avoiding tourniquet-induced neuropathy through cuff design. Biomed Instrum Technol 1993;27:401-7.

    6. Crenshaw AG, Hargens AR, Gershuni DH, Rydevik B. Wide tourniquet cuffs more effective at lower inflation pressures. Acta Orthop Scand. 1988;59:447-51.

    7. Noordin S, McEwen JA, Kragh JF Jr, Eisen A, Masri BA. Surgical tourniquets in orthopaedics. J Bone Joint Surg Am. 2009;91:2958-67.

    Balaji Purushothaman
    Posted on December 20, 2009
    Limb Occlusion Pressure
    Wansbeck General Hospital, Northumberland, United Kingdom

    To the Editor:

    I would like to congratulate Dr. Noordin and colleagues on the well-written Current Concepts Review on surgical tourniquets in orthopaedics (1). I would like to clarify two things.

    1. It is interesting to note that the current guideline for setting tourniquet pressure is based on limb occlusion pressure (LOP). The description of measuring the LOP by McEwen et al. (2) does not seem to be different from the measurement of the systolic blood pressure other than the site of measurement. The systolic pressure is always measured at the brachial artery while the LOP is measured in the specific limb. So, is LOP the same as the systolic pressure of the limb?

    2. The blood pressure in the dorsalis pedis artery has been shown to be slightly higher (up to 20mm Hg) than the brachial artery in adults (3). However, the authors found no correlation of the LOP to the systolic blood pressure. Could this be explained?

    The author did not receive any outside funding or grants in support of his research for or preparation of this work. Neither he nor a member of his immediate family received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the author, or a member of his immediate family, is affiliated or associated.

    References

    1. Noordin S, McEwan JA, Kragh JF Jr, Eisen A, Masri BA. Surgical tourniquets in orthopaedics. J Bone Joint Surg Am. 2009;91:2958-67.

    2. McEwan JA. What is tourniquet "limb occlusion pressure" (LOP)? http://www.tourniquets.org/lop.php. Accessed 2009 Dec 20.

    3. Hamilton WF, Woodbury RA, Harper HT Jr. Physiologic relationships between intrathoracic, intraspinal, and arterial pressures. JAMA. 1936;107:853-6.

    Noam Gavriely, MD, DSc
    Posted on December 14, 2009
    Response to Surgical Tourniquets in Orthopaedics
    OHK Medical Devices, Inc.

    To the Editor:

    In a recent article, "Surgical Tourniquets in Orthopaedics" by Shahryar Noordin, James A. McEwen, Colonel John F. Kragh et al. (1), the authors expressed highly critical opinions on the use of "a non-pneumatic elastic ring designed to combine exsanguination and tourniquet functions". The only commercial device that is currently available on the market that fits this description is the S-MART/HemaClear® (www.hemaclear.com; www.ohkmed.com) manufactured by OHK Medical Devices Ltd. The authors confidently predict that "uncritical acceptance and use of such non-pneumatic devices for extended periods of time increases the incidence of tourniquet-related injuries to surgical patients and unnecessarily exposes users in surgical and civilian settings to potential legal liability." Clearly, if these presumed facts are substantiated, it is imperative that the use of the HemaClear® is discontinued immediately and indefinitely. However, the excellent safety track record of the S-MART/HemaClear®, as outlined below, is far from supporting the allegations by Noordin et al. As the developers, manufacturers and distributors of HemaClear® we find it necessary to set the record clear on the scientific as well as the procedural levels.

    Before getting into the physics and physiology of the subject matter, it is important to clarify the status of the authors and the motives that they may have had in publishing this supposedly objective scientific manuscript. It is unfortunate that the ethics rules of full disclosure have not been followed by at least one of the Authors. Their Disclosure Statement says: "The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity." This statement is in fact false and misleading: The intensive commercial conflicts of interest of Dr. McEwen, the Founder, Inventor and Officer of several commercial entities in the field of pneumatic tourniquet (e.g. www.tourniquet.org) were withheld from the Journal and its Readers. Clearly, since the S-MART/HemaClear® has been gaining rapid popularity among leading orthopedic surgeons in the US and elsewhere, there potentially exists a commercial and financial interest in displacing such competition from the market.

    It is within this context that we now wish to address some of the scientific aspects of this paper.

    Safety Track Records of wide pneumatic tourniquets vs. the narrow elastic exsanguination-arterial blocker ring

    In a recent paper referenced by the authors (#15) Odinsson et al.(2) describe the rate of complications using tourniquets in orthopedic surgery in Norway. The authors found 15 cases of neurological deficit in more than 60,000 cases (incidence of ~24/100,000) the majority of which were in the lower extremity. This incidence was not better than that reported 25 years earlier in Australia (#16) [Middleton et al (3)] and in fact was somewhat worse, despite the use of modern tourniquets (using wide tourniquets with controlled pressure and monitoring) and use (i.e. adjusting the pressure at ~100 mmHg above systolic BP) by the majority of the Norwegian surgeons. It is interesting to note that none of the neurological complications occurred among the 14% of the survey responders who routinely use an Esmarch bandage to control blood flow. Clearly, the one parameter that changed from Australia, 1974 to Norway, 1999 is the cuff width that may have gotten bigger and may have been a contributing factor to the worsening of the data.

    These numbers, while not high in and by themselves, are substantially higher than the data on possible nerve involvement available to OHK on the use of its S-MART/ HemaClear® in more than 150,000 cases Worldwide (n=3, incidence of 2/100,000, all when used beyond the recommended 120 minutes time limit). This is despite the fact that the S-MART/HemaClear® elastic ring is much narrower than the wide pneumatic tourniquet promoted by Dr. McEwen and his Companies over the last 25 years (references related to the Noordin et al. paper (4)). This obviously superior safety track record is supported by a number of independent scientific studies that clearly provide the physical and physiological explanation to the observed difference in incidence. Examples include:

    1. In a recent independent study of nerve conduction during application of narrow and wide pneumatic cuffs in volunteers, Mittal et al. (5), found significantly lesser subclinical, yet physiologically documentable, nerve conduction speed deficits with the narrow cuff than with the wide one.

    2. In two independent studies by Drosos et al. (6) and by Mohan et al. (7) the tolerance of volunteers to placement of pneumatic tourniquet and S-MART/HemaClear® showed longer endurance with the S-MART/HemaClear® with statistical significance in one of the studies (Mohan et al).

    3. A study of the effects of wide tourniquet on neuronal damage in experimental animals published in 1972 by Ochoa et al. (8) revealed the nature of tourniquet-induced nerve injury. They clearly showed that it is axial displacement (elongation) of compressed nerves beneath a pressurized wide tourniquet that causes the transmission disruption due to telescoping ("intussusceptions", "invagination") of the nerve into itself at the nodes of Ranvier near the edges of the tourniquet (Figure 1). The contribution of the cuff width to the damage was clearly stated by Ochoa in the Discussion of his paper as shown in Figure 2.


    Figure 1. Diagram copied from Ochoa et al. (8) showing the axially displaced elongated nerve due to the compression by the wide cuff used in their study. The telescoping damage was found at the proximal and distal edges of the cuff. (Reproduced, with permission, from: Ochoa J, Fowler TJ, Gilliatt RW. Anatomical changes in peripheral nerves compressed by a pneumatic tourniquet. J Anat. 1972;113:433-55.)


    Figure 2. Citation from Ochoa's discussion, where the direct contribution of the cuff width is emphasized. (Reproduced, with permission, from: Ochoa J, Fowler TJ, Gilliatt RW. Anatomical changes in peripheral nerves compressed by a pneumatic tourniquet. J Anat. 1972;113:433-55.)

    4. In yet another independent study published in 1993, in Biomedical Instrumentation and Technology by Dr. Anthony Hodgson (9) he concluded: "Use of wider a cuff in and of itself will not reduce axial strain, so if the hypothesis is correct, wider cuff would not be intrinsically safer than a regular cuff, a result that is contrary to current opinions."

    Thus, there is a strong and well documented body of evidence that is independent from any commercial interests to show that narrow tourniquets is actually better than wide pneumatic tourniquet cuffs. In fact, the evidence in support of using a wide cuff, outside of Dr McEwen's own publications, is scant or non-existent.

    What is happening inside the limb when a tourniquet is applied? – Pressure It is rather regrettable that the authors failed to comprehend the fundamental aspects of the mechanics of tissue compression beneath surgical tourniquets (pneumatic or elastic ring). The first key parameter in preventing damage to the tissues inside the limb (e.g. nerves and blood vessels) is the pressure inside the limb, rather than at the skin surface as described by the authors in their Figure 5. In fact, in order to stop the arterial blood flow into a limb, all that is needed is to compress the artery over a few millimeters of its length by a pressure applied just outside of the artery and is a few millimeters of Mercury higher than the highest fluctuation of systolic blood pressure, e.g. 150 mmHg if the patient's mean systolic BP is 130 mm Hg.

    When using a wide tourniquet the pressures outside the artery and the nerve are the same as at the skin surface (i.e. ~100 mmHg higher than the systolic BP). This has to do with the fact that the pressure field (distribution) beneath a wide cuff is uniform, except towards the margins of the cuff. When applying the narrow cuff or the HemaClear® elastic ring the skin surface pressure dissipates when transmitted through the soft tissues (skin, fat layer, muscle) to the level of the artery and the nerve (i.e. radial pressure gradient), so that even if the skin-surface pressure is high, the pressure at the nerve level is quite low. Actually, in the vast majority of cases the skin pressure with the HemaClear™ is around 250 mm Hg when HC40 is used on the arm and 300-350 mm Hg when the HC60 and HC-XL are applied to the thigh (see HemaClear Pressure Look-up Table, www.hemaclear .com) and not as illustrated in Noordin's Figure 5.

    Pressure Gradients

    The second most important parameter with respect to nerve damage is the axial pressure gradients at the edges of the tourniquet. There is an across the board agreement that the higher this axial gradient at the level of the nerve, the higher the risk for sheer stress and telescoping injury to the axons as documented by Ochoa (8) and others. However, the notion that narrower cuffs and rings exert higher axial gradients than wide cuff (as eluded to in the hypothetical graph shown in Figure 5 of Noordin's paper) is simply not true. In fact, the experimental data to date show exactly the opposite. The figure below from the landmark 1988 study by Hargens et al. (10) clearly demonstrates it. The graphs (Figures 3a, 3b, 3c and 3d) show the intra-limb axial pressures at 4 radial locations with narrow (left, 3a and 3c) and wide (right, 3b and 3d) tourniquet cuffs inflated to 400 mmHg. It is readily seen that the gradients with the narrow cuff (red lines in 3c) are much less steep than with the wide cuff (blue lines in 3d). Similar experimental data as well as computational models confirm this observation. This graph also shows that the actual pressure internally is lower with the narrow cuff.


    Figure 3. Original data from Crenshaw, Hargens et al. (10) showing the pressures measured inside the cadaver limb beneath narrow (left, 3a and 3c) and wide (right, 3b and 3d) pneumatic tourniquet. Panels 3a and 3b are copies of the original figures. Panels 3c and 3d show only the corresponding "Near Bone" (innermost) pressure profiles with superimposed lines to indicate the steeper axial pressure gradient with the wide cuff. Arrows indicate that the peak pressure inside the limb is lower with the narrow cuff. The data in this classic paper clearly show that the shear strain and pressure stress at the inner part of the limb are higher with the wide cuff. (Reproduced, with modification, from: Crenshaw AG, Hargens AR, Gershuni DH, Rydevik B. Wide tourniquet cuffs more effective at lower inflation pressures. Acta Orthop Scand. 1988;59:447-51. Reproduced with permission.)

    Thus, with pressures at the nerve level that are lower with the narrow cuff and with gradients that are much less steep, it is not surprising that the incidence of nerve injury is higher with the wide cuff.

    Does the higher pressure at the skin level with narrow cuffs / elastic ring a cause for concern?

    The pressure exerted on the skin by the S-MART/HemaClear® depends only on the limb circumference and the distance of the placed ring from the toes/fingers. This pressure is factory calibrated and cannot be exceeded. With pneumatic tourniquets, while the pressure used in the majority of patients is not more than 300-350 mmHg, it does happen that if bleeding starts into the surgical field due to a sudden surge in arterial blood pressure, the surgeon will instruct to increase the pressure on the controller. Pneumatic tourniquet controllers can be dialed up to 475 mmHg cuffs; with a 700 mmHg reservoir (e.g. Zimmer Model ATS 2000 (11)). It is, however, more important to note the overall skin safety record of wide pneumatic tourniquets vs. S-MART/HemaClear™. The recent study by Robert Din and Tony Geddes (12) on skin complications following use of wide pneumatic tourniquet indicates an incidence of 6% even when adequate padding is used. This is far beyond the very few cases known to us from among the over 150,000 cases done with the HemaClear®. This is attributed to the round contour of the ring-skin interface and the many layers of stockinet left around the elastic ring. The pictures below (Figures 4a and 4b) show examples of skin conditions with a wide pneumatic tourniquet (left) and the S-MART/HemaClear®(right).


    Fig. 4a

    Fig. 4b
    Figure 4. Skin condition following use of wide pneumatic tourniquet (a) and HemaClear® (b). Note the blisters at skin folds and hemorrhagic abrasions caused by the pneumatic tourniquet. The transient skin erythema at the HemaClear ring position faded over the subsequent 45 minutes.

    Summary

    The data described above clearly documents the superior safety track record of the elastic exsanguination tourniquet (S-MART/HemaClear®) over the wide tourniquet promoted by Dr. McEwen and materially refute his unsubstantiated allegations. The smaller pressure inside the limb at the nerve level and the less steep internal axial pressure gradients are the underlying mechanisms of this improved patient outcome. The fact that the patient's skin tolerates the S-MART/HemaClear® better than the wide tourniquet cuff has to do with specific design details. These features are accompanied by other advantages such as the overall lower volume of tissue that is under compression conditions, the time needed for preparation and application, the fact that the S-MART/HemaClear® exsanguination is superior with an excellent surgical field and larger room for wider exposure due to the smaller footprint of the occlude, its being useful both on the upper part of the limbs (arm, thigh) as well as on the tapered parts of the limb (calf, forearm) and its sterility all contribute to the popularity this product is gaining.

    In support of his research for or preparation of this work, the author received, in any one year, outside funding or grants in excess of $10,000 from OHK Medical Devices Ltd. In addition, the author or a member of his immediate family received, in any one year, payments or other benefits in excess of $10,000 or a commitment or agreement to provide such benefits from a commercial entity (OHK Medical Devices Ltd). No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the author, or a member of his immediate family, is affiliated or associated.

    References

    1. Noordin S, McEwen JA, Kragh JF Jr, Eisen A, Masri BA. Surgical tourniquets in orthopaedics. J Bone Joint Surg Am. 2009;91:2958-67.

    2. Odinsson A, Finsen V. Tourniquet use and its complication in Norway. J Bone Joint Surg Br. 2006:88;1090-2.

    3. Middleton RW, Varian JP. Tourniquet paralysis. Aust N Z J Surg. 1974;44:124-8.

    4. References related to Noordin et al. paper:

    a. McEwen J, Casey V. Measurement of hazardous pressure levels and gradients produced on human limbs by non-pneumatic tourniquets. In: Proceedings of the 32nd Conference of the Canadian Medical and Biological Engineering Society 2009. Calgary, Canada; 2009 May 20-22. p 1-4. (ref #6 in original paper)

    b. McEwen JA. Complications of and improvements in pneumatic tourniquets used in surgery. Med Instrum. 1981;15:253-7. (ref #7 in original paper)

    c. McGraw RW, McEwen JA. The tourniquet. In: McFarlane RM, editor. Unsatisfactory results in hand surgery. New York: Churchill Livingstone; 1987. p 5-13. (ref #10 in original paper)

    d. Graham B, Breault MJ, McEwen JA, McGraw RW. Perineural pressures under the pneumatic tourniquet in the upper extremity. J Hand Surg Br. 1992;17:262-6. (ref #22 in original paper)

    e. Graham B, Breault MJ, McEwen JA, McGraw RW. Occlusion of arterial flow in the extremities at subsystolic pressures through the use of wide tourniquet cuffs. Clin Orthop Relat Res. 1993;286:257-61. (ref #23 in original paper)

    f. McEwen JA, Inkpen K, Younger A. Thigh tourniquet safety. Surg Technol. 2002;24:8-18. (ref #25 in original paper)

    g. McEwen JA, Kelly DL, Jardanowski T, Inkpen K. Tourniquet safety in lower leg applications. Orthop Nurs. 2002;21:55-62. (ref #27 in original paper)

    h. Reilly CW, McEwen JA, Leveille L, Perdios A, Mulpuri K. Minimizing tourniquet pressure in pediatric anterior cruciate ligament reconstructive surgery: a blinded, prospective randomized controlled trial. J Pediatr Orthop. 2009;29:275-80. (ref #29 in original paper)

    i. Tredwell SJ, Wilmink M, Inkpen K, McEwen JA. Pediatric tourniquets: analysis of cuff and limb interface, current practice, and guidelines for use. J Pediatr Orthop. 2001;21:671-6. (ref #41 in original paper)

    j. McEwen JA, Inkpen K. Tourniquet safety: preventing skin injuries. Surg Technol. 2002;24:6-15. (ref #42 in original paper)

    k. McEwen JA, McGraw RW. An adaptive tourniquet for improved safety in surgery. IEEE Trans Biomed Eng. 1982;29:122-8. (ref #53 in original paper)

    5. Mittal P, Shenoy S, Sandhu JS. Effect of different cuff widths on the motor nerve conduction of the median nerve: an experimental study. J Orthop Surg. 2008;3:1.

    6. Drosos GI, Stavropoulos NI, Kamezis I, Kazakos K, Verettas D. Silicone ring versus pneumatic cuff tourniquet: a preliminary comparative quantitative study in healthy individuals. Read at the EFORT conference; 2005 Jun; Lisbon, Portugal.

    7. Mohan A, Solan M, Magnussen P. Pain tolerance with a novel tourniquet in hand surgery — a comparative study. Read at the EFORT conference; 2008 Jun; Nice, France.

    8. Ochoa J, Fowler TJ, Gilliat RW. Anatomical changes in peripheral nerves compressed by a pneumatic tourniquet. J Anat. 1972;113(Pt 3):433-55.

    9. Hodgson AJ. Avoiding tourniquet-induced neuropathy through cuff design. Biomed Instrum Technol. 1993;27:401-7.

    10. Crenshaw AG, Hargens AR, Gershuni DH, Rydevik B. Wide tourniquet cuffs more effective at lower inflation pressures. Acta Orthop Scand. 1988;59:447-51.

    11. Zimmer ATS 2000 spec at: http://www.somatechnology.com/pdffiles/Zimmer%20ATS%202000.pdf.

    12. Din R, Geddes T. Skin protection beneath the tourniquet. A prospective randomized trial. ANZ J Surg. 2004;74:721-2.

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