Preventing Hospital-Associated Venous Thromboembolism

Chapter 3. Outline the Evidence and Identify Best Practices

This chapter outlines the evidence and best practices applied for many common conditions encountered in hospitals. This information is likely most useful to the team’s physician lead and/or the facility’s clinical leadership.

Know What the Literature Says About the Risk of Venous Thromboembolisms and Measures for Prevention

Before initiating an intervention, it is important to determine the venous thromboembolism (VTE) prophylaxis protocol that the facility will follow. The VTE steering team will want to review the evidence base to identify best practices for preventing hospital-associated VTE (HA-VTE), and then refine the evidence to emphasize the most crucial points in protocols, education, and clinical decision support tools that are applicable for your institution. The majority of the guidance given by professional societies is consistent, but there are areas of difference and controversy to identify and manage.

Table 3.1 depicts pertinent guidelines on VTE prevention, presented in reverse chronological order beginning with the latest recommendations.1-13

Table 3.1: Major Guidelines Addressing VTE Prophylaxis

Guideline Acronym and Date Description
American Society of Clinical Oncology guideline update: Venous Thromboembolism Prophylaxis and Treatment in Patients with Cancer.9 ASCO
Update from 2007 guideline. More explicit guidance than 2007 on patients that do not warrant prophylaxis as well as those that do.
Antithrombotic Therapy and Prevention of Thrombosis, 9th ed.: American College of Chest Physicians (ACCP) Evidence-Based Clinical Practice Guidelines.1 AT9
Guidelines for VTE prevention presented as four separate articles by the patient's reason for hospitalization, including:

  • Nonsurgical.2
  • Nonorthopedic surgical.3
  • Orthopedic.4
  • Pregnancy.5

More information on AT9

Venous Thromboembolism Prophylaxis in Hospitalized Patients: A Clinical Practice Guideline From the American College of Physicians (ACP).7 ACP1
Guideline focused on nonsurgical patients.7 Medical and stroke. Published with separate supporting literature review.8
American College of Obstetricians and Gynecologists Practice Bulletin No.123. Thromboembolism in Pregnancy.12 ACOG
Update expands and updates VTE prevention in pregnancy and cesarean deliveries.
Preventing Venous Thromboembolic Disease in Patients Undergoing Elective Hip and Knee Arthroplasty. Evidence-Based Guideline and Evidence Report From the American Academy of Orthopaedic Surgeons. Second Edition.10 AAOS2
Second edition and AT9 now aligned on most issues. Many areas with limited guidance.
Reducing the Risk of Venous Thromboembolism (Deep Vein Thrombosis and Pulmonary Embolism) in Patients Admitted to Hospital. NICE clinical guideline 92.13 NICE
National Institute for Health and Clinical Excellence, Great Britain, offers more aggressive stance than AT9, with a host of implementation tools.14
Antithrombotic Therapy and Prevention of Thrombosis, 8th ed: American College of Chest Physicians (ACCP) Evidence-Based Clinical Practice Guidelines. AT8
Guidelines for VTE prevention presented as one article.6
American College of Obstetricians and Gynecologists Practice Bulletin No.84. Prevention of Deep Vein Thrombosis and Pulmonary Embolism.11 ACOG
Covers obstetrics and gynecology surgery issues.

Many of the recommendations described below, including the ACCP Antithrombotic Therapy and Prevention of Thrombosis, 9th edition (AT9), are those of the organizations referenced at the beginning of the chapter. More detailed information about the guidelines reviewed in Table 3.1 can be found at the National Guideline ClearinghouseTM.15 In a systematic approach, inpatients are screened on admission for VTE risk based on institutional policies, protocols, education plans, and clinical decision support systems. Bleeding risk and patient preferences are also considered in the decisionmaking process.

Patients With Medical Conditions (Nonsurgical)

Acutely ill hospitalized patients at risk for thrombosis are likely candidates for anticoagulant prophylaxis in the form of low-molecular-weight heparin (LMWH), low-dose unfractionated heparin (UFH) (5,000 units subcutaneous BID or TID), or fondaparinux 2.5 mg/day. Mechanical prophylaxis is usually not offered as a first choice for prophylaxis in medical patients in the absence of bleeding risk factors, but is more likely to be used in patients with both bleeding and clot risk. Intermittent pneumatic compression devices (IPCDs) are favored for patients in this situation over graduated compression stockings (GCS) by some guidelines (e.g., ACP1), extrapolating from clinical trials in immobilized stroke patients that found that thigh-high GCS increased the risk of skin breakdown without reducing VTE.7,8

Patients who are at low risk for thrombosis very likely do not need either mechanical or pharmaco-prophylaxis.2,7 There is no consensus on defining this low-risk medical group, but it may be a substantial proportion of medical inpatients in non-intensive care settings. Examples of low-risk medical inpatients include chronically immobilized patients without acute illness, short-stay observation patients, patients awaiting disposition who were never or are no longer acutely ill, and fully ambulatory patients not at risk for VTE or without multiple VTE risk factors.

The ACCP VTE prevention guidelines were published in 2012 as four distinct articles2-5 as part of the larger ACCP Antithrombotic Therapy and Prevention of Thrombosis, 9th edition, commonly referred to as AT9.1 This review reflects the broad scope and general prominence of AT9 but should not be construed as an endorsement of this guideline over others.

The AT9 guidelines reflected a different approach to analyzing prior studies than did the 2008 ACCP guidelines6 (AT8) in terms of philosophy, methodology, and exclusion of asymptomatic VTE outcomes, resulting in new or altered recommendations. The approach by AT9 carefully grades the levels of evidence based on the strength of the recommendations and the quality of the evidence and places a focus on patient-centered outcomes.16

However, the approach taken by AT9 may pose unique challenges for clinicians attempting to translate the new recommendations into practice. Guidance from AT8 and other guidelines has generally been summarized in a manner and format that is more actionable. This tradeoff is reflected in this chapter. Most of the guidance on major topics, however, is consistent across guidelines.

Patients Undergoing Surgical Procedures (Nonorthopedic)

The risk of VTE in patients having nonorthopedic surgery depends on both patient-specific and procedure-specific factors.3

Very low to low-risk procedures include most same-day surgical procedures and surgeries that do not involve longer open procedures on body cavities. Examples of these low-risk procedures include laparoscopic procedures of less than 30 minutes in duration, appendectomy, transurethral prostatectomy, inguinal hernia repair, mastectomy, and spinal surgery for nonmalignant disease. No VTE prophylaxis is typically recommended for patients undergoing these procedures unless the patient is hospitalized for more than a day and/or has other VTE risk factors.

Patients undergoing uncomplicated, scheduled cardiac procedures have only a slightly higher risk of VTE providing they can be mobilized within a day. Patients undergoing posterior approach spinal surgery for nonmalignant disease can be provided with mechanical prophylaxis, preferably with IPCD, as a sole option. Regular reassessments of VTE risk are generally done to ensure a transition to a more aggressive prophylaxis regimen if needed (i.e., the patient experiences delays in mobility or complications occur).

Procedures associated with a very high risk of VTE include abdominal or pelvic surgery for cancer, multiple major trauma, craniotomy/spinal surgery for malignant disease, and spinal surgery with an anterior approach. Patients undergoing thoracic surgeries, including pneumonectomy, extended pulmonary resection, esophagectomy, and extrapleural pneumonectomy of mesothelioma, are also at very high risk.3 A combination of mechanical prophylaxis (preferably with IPCD) and anticoagulant prophylaxis is suggested for these high-risk patients.

For procedures with particularly high (~2%) risk of perioperative bleeding, in which local bleeding can have more severe consequences, IPCD alone can be used initially, until the risk of bleeding has subsided, at which time pharmacologic prophylaxis can be added. Examples include craniotomy, traumatic brain injury, spinal cord injury repair, major trauma, plastic surgery with a free flap, and pneumonectomy or extended pulmonary resection.

Patients undergoing most other surgical procedures requiring hospitalization fall into the moderate-risk category, including those having general surgical procedures, gastrointestinal surgery not related to malignancy, open urological procedures, gynecologic surgery, vascular surgery, and reconstructive surgery. In AT8 and other guidelines, anticoagulant prophylaxis is preferred over mechanical prophylaxis.6,13 In AT9, pharmacologic prophylaxis with UFH or LMWH or mechanical prophylaxis are deemed acceptable choices, even though AT9 notes that better evidence exists for pharmacologic prophylaxis.

Patients Undergoing Orthopedic Surgery

A patient's risk for VTE after major orthopedic surgery is among the highest of all risks for VTE. Dual prophylaxis with an antithrombotic agent and an IPCD during the hospital stay is commonly recommended for patients undergoing major orthopedic surgical procedures.

Duration of Prophylaxis

Major orthopedic surgery patients are likely to require prophylaxis for a minimum of 10 to 14 days. Extending prophylaxis further up to 35 days results in additional reductions in DVT with a comparable safety profile and is also recommended.4

Choice of Antithrombotic Agent in Major Orthopedic Surgery

For total hip arthroplasty and total knee arthroplasty, LMWH is favored by AT9.4 For hip fracture surgery, the anticoagulant choices are the same.

If LMWH is used for thromboprophylaxis, avoiding dosing in a 12-hour window preoperatively and postoperatively is recommended to reduce bleeding risk. Comorbidities or complicating factors may delay hip fracture repair, and starting LMWH between admission and surgery is desirable, providing this 12-hour window is maintained.

Aspirin in Major Orthopedic Surgery Patients

AT94 allows for the use of aspirin (acetylsalicylic acid, or ASA) in major orthopedic procedures, citing the 2000 Pulmonary Embolism Prevention trial.17 This trial was designed to investigate the effect of ASA on vascular death (pulmonary embolism, myocardial infarction, cerebrovascular accident). A positive impact on reducing VTE was only apparent in a post hoc analysis. The study findings were discounted in AT8 but accepted in AT9. Thus, in AT9, ASA is listed as an option for major orthopedic surgery patients even while AT9 labels LMWH as the preferred choice for this indication and stipulates that LMWH likely has greater efficacy. Although ASA use remains controversial (even among the AT9 panel), relatively low rates of VTE have been reported using ASA with progressive orthopedic techniques, early mobilization regimens, and concomitant use of IPCD.

Intermittent Pneumatic Compression Devices in Major Orthopedic Surgery Patients

IPCD devices are generally recommended as part of a dual prophylaxis regimen, but for patients at risk of bleeding or those who place a high value on avoiding bleeding complications, IPCD is recommended over no prophylaxis. Only portable, battery-powered IPCDs capable of recording and reporting wear time on a daily basis are recommended for inpatient and extended duration outpatient use, ideally used for 18 hours or more.4

Prophylaxis for Knee Arthroscopy and Isolated Lower Leg Injuries Distal to the Knee

Absent a prior history of VTE or multiple strong VTE risk factors, AT9 recommends no prophylaxis rather than pharmacologic prophylaxis for patients undergoing knee arthroscopy. The same recommendation applies to patients with isolated lower leg injuries distal to the knee that require leg immobilization.

Implementation Challenges

The multitude of "acceptable" choices for major orthopedic surgery and the requirement for extended duration prophylaxis can pose problems for standardization and reliable delivery of appropriate prophylaxis. Insurance issues and limited availability of some options may exist. As always, patient preference may play a role in prophylaxis choice, particularly for those patients who require prophylaxis extended beyond the hospital stay.

Oncology Inpatients

The 2013 American Society of Clinical Oncology (ASCO) guidelines for prophylaxis and treatment of VTE in patients with cancer provide indepth guidance for this important population.9 VTE is a leading cause of mortality in patients with malignancy. VTE risk is especially high for inpatients and those receiving active therapy, and the frequency of VTE appears to be increasing among cancer patients. VTE risk is highest in the first 3 to 6 months after diagnosis and is higher with advanced stage and histologic aggressiveness.

Chemotherapy, anti-angiogenesis therapy, hormonal therapy, radiation therapy, transfusion, and indwelling venous access are all risk factors, in addition to surgery and the cancer itself. Age, obesity, and comorbidities such as infection and pulmonary disease are additive risk factors, just as they are in patients without malignancy, and there is also an association of VTE with functional status. Biomarkers, such as an elevated platelet count or leukocyte count or hemoglobin <10 g/dL, are also cited as VTE risk factors.

ASCO recommends that hospitalized inpatients with acute medical illness or reduced mobility receive pharmacologic VTE prophylaxis, in the absence of any contraindications. In view of underlying high risk, even patients who have an active malignancy without additional risk factors may be considered for prophylaxis; however, the ASCO guidelines stipulate that data are inadequate to support routine thromboprophylaxis in patients admitted for minor procedures or short chemotherapy infusion. More research is also needed regarding appropriate options for stem cell/bone marrow transplantation.

Either UFH or LMWH are recommended for patients with malignancy undergoing major surgical intervention, unless contraindications are present, with prophylaxis commenced preoperatively. Combination prophylaxis is ideal for those at especially high risk. Mechanical prophylaxis as a sole agent in the absence of bleeding risk is not suggested. Extended duration prophylaxis for at least 7 to 10 days and up to 4 weeks postoperatively is considered for patients undergoing major abdominal or pelvic surgery for cancer who have high-risk features. Education and engagement of the patient regarding VTE risk factors, signs, and symptoms is strongly encouraged.

Prophylaxis for outpatients is generally beyond the scope of this implementation guide but is mentioned here for cancer patients in the context of making decisions about prophylaxis for patients leaving the hospital. While routine thromboprophylaxis is not recommended in cancer outpatients, patients with multiple myeloma receiving thalidomide or lenalidomide-based regimens with chemotherapy or dexamethasone are candidates for thromboprophylaxis with either LMWH or ASA for lower risk patients, or with LMWH for higher risk patients. Other highly selected patients with solid tumors receiving chemotherapy may be considered for thromboprophylaxis on a case-by-case basis.

While there are some subtle differences, the AT9 guidelines are largely consistent with ASCO guidelines. Institutions with large oncology services may want to consider separate "carve out" order sets and protocols tailored to that population.

Putting It All Together—Next Steps

VTE prophylaxis can be a complex issue when one considers all the variations in prophylaxis to accommodate the risk for clots or bleeding, as well as patient preferences in diverse inpatient populations. In addition, multiple agents available for prophylaxis, and the nuances of dosing, timing, and duration of anticoagulants in different situations, further complicate the issues.

While this chapter condenses information from multiple guidelines and other sources to some degree, the VTE prevention team will want to simplify this conglomeration of best practices further in order to provide good clinical decision support at the point of care, build protocol-driven educational resources, and construct measurement tools. The following suggestions may help compartmentalize these tasks and make it easier.

Provide Guidance Tailored to Services at Your Hospital

Much of this chapter reviews recommendations for different types of patients. The prevention team may consider breaking down this information into more digestible formats tailored for different services (e.g., medical, surgical). This will simplify directions in order sets on options for prophylaxis and when to start/stop them and help to create succinct targeted educational tools.

Reduce the Options to Preferred Options

The improvement team may be able to simplify the information presented in this chapter by selecting a few preferred options for prophylaxis in situations, such as major orthopedic surgery, in which several options are available.

Divide Up the Work

There is a lot of information to absorb and integrate into policies, protocols, education programs, and clinical decision support. Dividing up the information and tasking different stakeholders makes this more manageable. For example, physicians on the team might focus on summarizing and reinforcing best practices for prescribing appropriate prophylaxis, while nursing staff could focus on best practices regarding adherence to mechanical prophylaxis, improving patient mobility, and helping to reassess the patient at various intervals. By the same token, pharmacists could take ownership of helping to narrow down pharmacologic choices, assisting with neuraxial blockade protocols, and integrating guidance about dosing and timing of prophylaxis into order sets, medication administration records, and care pathways.


Improvement teams may wish to consider focusing on the information that applies to 80 percent of the inpatient population at first—instead of the exceptions to the rule. This chapter and the references can be accessed when questions arise regarding the less common scenarios. Many practical tips for summarizing the most important best practices into a protocol, reinforcing protocol guidance with multiple layered interventions, and strategies to monitor performance are offered in subsequent chapters.

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Page last reviewed February 2016
Page originally created February 2016
Internet Citation: Chapter 3. Outline the Evidence and Identify Best Practices. Content last reviewed February 2016. Agency for Healthcare Research and Quality, Rockville, MD.