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Wade R, Sideris E, Paton F, et al. Graduated compression stockings for the prevention of deep-vein thrombosis in postoperative surgical patients: a systematic review and economic model with a value of information analysis. Southampton (UK): NIHR Journals Library; 2015 Nov. (Health Technology Assessment, No. 19.98.)

Cover of Graduated compression stockings for the prevention of deep-vein thrombosis in postoperative surgical patients: a systematic review and economic model with a value of information analysis

Graduated compression stockings for the prevention of deep-vein thrombosis in postoperative surgical patients: a systematic review and economic model with a value of information analysis.

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Chapter 1Background

Aetiology and prevention of deep-vein thrombosis

Venous thrombosis is a condition in which a blood clot forms in a vein, resulting in blockage of the affected vein. It most commonly occurs in the deep veins of the lower limbs, and this is known as deep-vein thrombosis (DVT). DVT can be asymptomatic (detected by screening) or symptomatic, usually presenting as leg pain and/or swelling as a result of occlusion of the vein. If the blood clot breaks off and travels through the venous system, an embolism is created; if the clot lodges in the lung, a pulmonary embolism (PE) arises. DVT and PE are collectively known as venous thromboembolism (VTE).

Deep-vein thrombosis can occur in hospitalised patients owing to changes in the blood vessel wall, changes in blood flow and changes in the properties of the blood, caused by factors such as immobilisation, decreased fluid intake and excessive body fluid loss. In addition, trauma and surgery can also cause activation of the coagulation system, leading to a higher risk of DVT.1 It has been estimated that between 45% and 51% of patients undergoing orthopaedic surgery develop DVT if they are not provided with adequate thromboprophylaxis, as shown in Table 1.2 However, these estimates are from out-dated studies in which patients were not receiving DVT prophylaxis. Estimates of baseline risk of DVT for patients on pharmacological prophylaxis have been presented below (see Chapter 4), along with the methods used to derive these more up-to-date, clinically relevant estimates.

TABLE 1

TABLE 1

Incidence of DVT by specialties: risk level by patient group

Data from a UK prospective cohort study (Million Women Study3) showed that women undergoing an inpatient surgical procedure were 70 times more likely than those who had not undergone surgery to be admitted with VTE in the 6 weeks post surgery, while those undergoing a day-case procedure were 10 times more likely to be admitted.3 Risks remained increased 7–12 weeks post surgery, and the pattern of risk was similar for PE and DVT. Risk varied considerably by surgery type. It is estimated that up to 25,000 people in England may die each year from potentially preventable VTE developed while in hospital.2

Surgical patients and patients with trauma are at an increased risk of VTE if they meet one of the following criteria:4

  • surgical procedure with a total anaesthetic and surgical time of more than 90 minutes, or 60 minutes if the surgery involves the pelvis or lower limb
  • acute surgical admission with inflammatory or intra-abdominal condition
  • expected significant reduction in mobility
  • one or more of the following risk factors:
    • active cancer or cancer treatment
    • aged over 60 years
    • critical care admission
    • dehydration
    • known thrombophilias
    • obesity
    • personal or first-degree family history of VTE
    • use of oestrogen-containing oral contraceptives or hormone replacement therapy
    • varicose veins with phlebitis
    • one or more significant medical comorbidities (e.g. heart disease; metabolic, endocrine or respiratory pathologies; acute infectious diseases; inflammatory conditions).

In recent years, there have been changes in the factors that impact on the risk of postsurgery DVT. Surgical practice has changed so that the duration of general anaesthetic is shorter, or surgery is performed under local anaesthetic. The duration of a patient’s stay in hospital is much shorter, with many procedures now performed as day cases. Patients are mobilised more quickly, and patients discharged home are supported by community-based physiotherapists. In addition, new oral anticoagulants (NOACs) [e.g. dabigatran (Pradaxa®, Boehringer Ingelheim), rivaroxaban (Xarelto®, Bayer Healthcare), apixaban (Eliquis®, Bristol-Myers Squibb and Pfizer)] can be used for longer periods, offering extended protection to patients.4 In March 2010, the Department of Health produced a Risk Assessment for Venous Thromboembolism tool for use in hospitalised patients.5 It is also a National Institute for Health and Care Excellence (NICE) quality standard that all patients on admission to hospital receive an assessment of individual risk of VTE and bleeding using clinical risk assessment criteria described in the national tool.6

Despite these efforts to prevent postsurgery DVT, other factors, such as the increasing numbers of older patients undergoing surgery and the increasing proportion of obese and morbidly obese patients, adds upwards pressure on the population risk of postsurgery DVT.

Consequences of deep-vein thrombosis

Deep-vein thrombosis on its own does not frequently result in death, but left untreated it can result in PE.7 The number of hospitalised patients dying each year from PE following DVT in the UK has been estimated to be 25,000.4 PE is the immediate cause of death in 10% of all patients who die in hospital.8 Those who do survive DVT or PE are at increased risk of recurrence, particularly within the first 2 years.9

Untreated patients may also be at risk of post-thrombotic syndrome (PTS) which can occur immediately or within 10–20 years of the initial episode.4 Signs and symptoms of PTS include pain, swelling, oedema and ulcers.10 These conditions can also have a significant impact on an individual’s quality of life.9

Other long-term complications of VTE include pulmonary hypertension (PHT), abnormally elevated blood pressure within the pulmonary artery and stroke.4 These long-term consequences have implications on extended prophylaxis and the costs arising from treatment, which will be discussed further below (see Chapter 4).

Thromboprophylaxis

There is evidence that routine prophylaxis reduces morbidity, mortality and health-service costs in hospitalised patients at risk of DVT and VTE.11 Prophylaxis can be pharmacological [fondaparinux sodium, low-molecular-weight heparin (LMWH) or unfractionated heparin] and/or mechanical. Mechanical methods of prophylaxis include graduated compression stockings (GCSs), intermittent pneumatic compression devices (IPCDs) and pneumatic foot pumps (FPs). GCSs have been shown to reduce the incidence of postoperative DVT in surgical patients to approximately 11%, whereas low-dose heparin (LDH) administered via subcutaneous injection reduces the rate of DVT to around 9%; used together, the rate of DVT is reduced further.12

Graduated compression stockings/antiembolism stockings

There are two different types of compression hosiery: antiembolism stockings and GCSs. Both products offer graduated compression and the two terms are often used interchangeably, although antiembolism stockings are designed for the prevention of VTE in immobile patients, whereas GCSs are designed for the management and treatment of conditions such as venous leg ulcers and lymphoedema in the ambulant patient. For consistency with the Health Technology Assessment (HTA) scope, we will use the more commonly used term GCS.

Graduated compression stockings exert graded pressure at a decreasing gradient from the ankle to the thigh, which increases blood flow velocity and promotes venous return. In addition, preventing passive venous distension is thought to prevent subendothelial tears and the activation of clotting factors.4

The Sigel profile, which equates to a graduated compression pressure profile of 18 mmHg at the ankle, 14 mmHg at the mid-calf, 8 mmHg at the knee (popliteal break), 10 mmHg at the lower thigh and 8 mmHg at the upper thigh was found to increase deep venous flow velocity by 75%.13 The current British and European Standards for antiembolism stockings [BS7672 (1); ENV 12719 (70)] do not replicate the Sigel profile and the British Standard requires pressure to be measured at only three points rather than the five specified by Sigel.4

Graduated compression stockings are available as knee-length or thigh-length stockings. Patients report that both knee-length and thigh-length stockings are difficult to use, but knee-length stockings wrinkle less than thigh-length, and fewer patients report discomfort when using them.14 Patient adherence is reported to be higher with knee-length stockings, and thigh-length stockings are more likely to be worn incorrectly.15,16 Incorrectly worn stockings can be unsafe: thigh-length stockings that are fitted incorrectly or roll down can create a tourniquet effect. In addition, for some patient subgroups, one length of stocking may be more appropriate than the other; for example, it is widely believed that knee-length stockings are more likely to induce wound complications in patients undergoing knee replacement surgery. There are also some patients for whom GCSs are contraindicated, such as those who have peripheral arterial disease.

Existing guidelines and systematic reviews

A rapid appraisal of the review and guideline literature was undertaken to inform the protocol and give an indication of the size of the literature. We searched key resources for published systematic reviews and guidelines on GCSs, including The Cochrane Library, PROSPERO, Clinical Trials.gov, National Guidelines Clearinghouse, National Institute for Health Research HTA website, Turning Research into Practice, Clinical Evidence, NHS Evidence, NICE website and the NICE Clinical Knowledge Summaries Database. The search identified the NICE and Scottish Intercollegiate Gudielines Network (SIGN) guidelines for the prevention of VTE,4,11 and two relevant Cochrane reviews,1,17 described below. Guidelines were also identified for several other countries, including the USA and Australia.

National Institute for Health and Care Excellence guidelines

In January 2010, NICE published Clinical Guideline (CG) 92 on reducing the risk of VTE (DVT and PE) in patients admitted to hospital (updating previous CG46).4 The key recommendations relating to thromboprophylaxis in surgical patients are detailed below.

If using mechanical VTE prophylaxis, base the choice of mechanical VTE prophylaxis on individual patient factors including clinical condition, surgical procedure and patient preference. Choose any one of thigh- or knee-length GCSs, foot impulse devices or IPCDs (thigh or knee length).

Further recommendations are made, for example regarding correct sizing and fitting of stockings. The guideline states that patients should be encouraged to wear their stockings day and night until they no longer have significantly reduced mobility.

Pharmacological VTE prophylaxis is also recommended for surgical patients at a low risk of major bleeding, taking into account individual patient factors and according to clinical judgement. Pharmacological VTE prophylaxis should also be continued until the patient no longer has significantly reduced mobility (generally 5–7 days), although for patients with hip fracture or undergoing elective hip replacement surgery, pharmacological VTE prophylaxis should be continued for 28–35 days (according to the summary of product characteristics for the individual agent being used) and, for patients undergoing knee replacement surgery, pharmacological prophylaxis should be continued for 10–14 days.

The NICE guideline states that the length of stockings is a controversial issue and there is no clear randomised evidence that one length of stocking is more effective than another. Clinical judgement, patient preference, concordance and surgical site are all important issues when deciding on stocking length.

Contraindications to GCS use are suspected or proven peripheral arterial disease; peripheral arterial bypass grafting; peripheral neuropathy or other causes of sensory impairment; any local conditions in which stockings may cause damage, such as gangrene or dermatitis; known allergy to material of manufacture; cardiac failure; severe leg oedema or pulmonary oedema from congestive heart failure; unusual leg size or shape; or major limb deformity preventing correct fit.

In February 2012, NICE published an evidence update to CG92.18 New evidence was found (a Cochrane review by Sachdeva et al.17) that supported the use of GCSs in surgical patients with or without other methods of thromboprophylaxis, which is in line with current recommendations in CG92. The evidence update stated that the review was not able to answer the question of the efficacy of thigh-length versus knee-length GCSs.

A decision-analytic model was also developed in CG92 to determine the most cost-effective thromboprophylaxis strategy for different hospital population subgroups [hip fracture surgery, total hip replacement (THR), total knee replacement (TKR), general surgery (GS) and general medical admissions]. VTEs and major bleeding events were modelled for the acute period [determined by the randomised controlled trial (RCT) follow-up, typically only 10–14 days) but quality-adjusted life-years (QALYs) and health-service costs arising from these events were modelled over the patient’s lifetime, including treatment of PTS and PHT. Results differed across the different population subgroups, although GCSs either alone or combined with pharmacological prophylaxis was consistently found to be the most clinically effective and cost-effective approach for the prevention of VTE. The different results were largely driven by population differences in terms of the baseline risks of major bleeding and PE. The cost of GCSs was assumed to be £6.36 per pair (2009 prices) but the length was not specified. In addition, no attempt was made to formally model the relative cost-effectiveness of different GCSs lengths.

Scottish Intercollegiate Guidelines Network guidelines

The SIGN published guideline 122 on the prevention and management of VTE in December 2010 (updating previous guidelines 62 and 36).11 The key recommendations relating to thromboprophylaxis in surgical patients are detailed below.

Patients undergoing abdominal surgery who are at risk as a result of the procedure or personal risk factors should receive thromboprophylaxis with mechanical methods unless contraindicated and either subcutaneous LMWH, unfractionated heparin or fondaparinux.

Patients undergoing THR or TKR surgery should receive pharmacological prophylaxis (with LMWH, fondaparinux, rivaroxaban or dabigatran) combined with mechanical prophylaxis unless contraindicated. Extended prophylaxis should be given.

The SIGN guideline states that studies comparing above-knee with below-knee stockings have been too small to determine whether or not they are equally effective, although a meta-analysis suggested no major difference in efficacy in surgical patients.19 The guideline recommends that above-knee or below-knee GCSs may be used for prophylaxis of DVT in surgical patients, provided that there are no contraindications and that attention is paid to correct fitting and application. Contraindications are massive leg oedema; pulmonary oedema (e.g. heart failure); severe peripheral arterial disease; severe peripheral neuropathy; major leg deformity; and dermatitis.

Cochrane review: knee-length versus thigh-length graduated compression stockings

A Cochrane review undertaken by Sajid et al.1 included three small RCTs12,20,21 that compared the effectiveness of thigh-length versus knee-length GCSs in hospitalised postoperative surgical patients. There was no statistically significant difference in clinical effectiveness between the two stocking lengths in terms of reducing the incidence of DVT; however, there was significant heterogeneity among the trials and considerable methodological limitations. The authors concluded that there was insufficient high-quality evidence to determine whether or not thigh-length or knee-length stockings differ in their effectiveness in terms of reducing the incidence of DVT in hospitalised patients. They recommended that a large multicentre RCT be conducted to address this issue.

Cochrane review: elastic compression stockings for prevention of deep-vein thrombosis

A Cochrane review undertaken by Sachdeva et al.17 included 18 RCTs that compared the effectiveness of GCSs, with or without another method of DVT prophylaxis, versus no stockings in hospitalised patients. Eight RCTs compared GCSs alone with no stockings; the incidence of DVT was statistically significantly lower in the stocking group than in the no stockings group.2229 Ten RCTs compared GCSs plus another prophylactic method versus the prophylactic method alone; the incidence of DVT was statistically significantly lower in the stocking plus other prophylactic method group than in the other prophylactic alone group.3039 The authors concluded that GCSs are effective at diminishing the risk of DVT in hospitalised patients. However, where stated, all of the included RCTs used thigh-length stockings. The authors of this review also recommended a RCT comparing thigh-length with knee-length GCSs.

The two previous Cochrane reviews did not answer our specific research question. The review by Sajid et al.1 included only three RCTs and did not seek indirect evidence. The review by Sachdeva et al.17 did not restrict the inclusion criteria to surgical patients or compare the clinical effectiveness of thigh- versus knee-length stockings; the length of stocking used in some of the included studies was unclear.

Research aims and objectives

The aim of the research was to establish the expected value of undertaking additional research comparing the relative effectiveness of thigh-length versus knee-length GCSs, in addition to standard pharmacological prevention, for prevention of DVT in surgical patients. There were two key objectives:

  • to undertake an evidence synthesis by systematic review to estimate clinical effectiveness and inform key clinical parameters for a decision model
  • to develop a decision model to estimate cost-effectiveness and to undertake a value of information (VOI) analysis.
Copyright © Queen’s Printer and Controller of HMSO 2015. This work was produced by Wade et al. under the terms of a commissioning contract issued by the Secretary of State for Health. This issue may be freely reproduced for the purposes of private research and study and extracts (or indeed, the full report) may be included in professional journals provided that suitable acknowledgement is made and the reproduction is not associated with any form of advertising. Applications for commercial reproduction should be addressed to: NIHR Journals Library, National Institute for Health Research, Evaluation, Trials and Studies Coordinating Centre, Alpha House, University of Southampton Science Park, Southampton SO16 7NS, UK.

Included under terms of UK Non-commercial Government License.

Bookshelf ID: NBK327582

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