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Guest Editorial

The New AAOS Clinical Practice Guidelines on Venous Thromboembolic Prophylaxis: How To Adapt Them to Your Practice

Lieberman, Jay R. MD

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American Academy of Orthopaedic Surgeon: December 2011 - Volume 19 - Issue 12 - p 717-721
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The American Academy of Orthopaedic Surgeons (AAOS) recently published its clinical practice guideline “Preventing Venous Thromboembolic Disease in Patients Undergoing Elective Hip and Knee Arthroplasty.” This evidence-based guideline, which contains 10 recommendations, replaces the previous AAOS guideline, “Prevention of Symptomatic Pulmonary Embolism in Patients Undergoing Total Hip or Knee Arthroplasty,” published in 2007.1,2 The strength of the prior guideline was that it focused on symptomatic pulmonary embolism and the potential deleterious effects of bleeding that could influence the selection of a prophylaxis regimen. The weakness of that guideline was that it did not make separate recommendations for hip and knee arthroplasty patients, whose risk of deep vein thrombosis (DVT) is clearly different from that of other orthopaedic patients. The 2007 guideline also required the orthopaedic surgeon to risk-stratify patients for either venous thromboembolism (VTE) or bleeding, which is difficult to do because of the lack of evidence-based data and consensus in this area.

For the AAOS guidelines to be listed on the National Guideline Clearinghouse of the Agency for Healthcare Research and Quality (AHRQ), the guidelines must be updated every 5 years. Therefore, it was time for the development of a new VTE guideline.

This new clinical VTE practice guideline is based on a systematic review of published studies on preventing symptomatic VTE in patients undergoing elective knee and hip arthroplasty. A rigorous review of the literature was performed, and a relatively new statistical technique called network meta-analysis was used to analyze the various studies. Network meta-analysis allows the efficacy of different agents to be compared even when the published trials do not make these comparisons themselves. In addition, strict criteria were established to evaluate the quality of published studies and to try to avoid bias.

The 10 recommendations are accompanied by a rationale for each, and each is graded as strong, moderate, weak, inconclusive, or consensus. Unfortunately, there is only one strong recommendation (No. 1) and just three moderate recommendations (4, 5, and 9). The remaining recommendations are graded weak, consensus, or inconclusive (Table 1). In this commentary, I will try to put these recommendations into context so they can be used in clinical practice to provide effective and safe prophylaxis for total joint arthroplasty patients.

Table 1
Table 1:
Preventing Venous Thromboembolic Disease in Patients Undergoing Elective Hip and Knee Arthroplasty: Work Group Recommendationsa

Recommendations 1, 8, 9, and 10 are not controversial. No. 1 is a strong recommendation against the routine use of postoperative duplex ultrasound screening. Conclusive data in the literature suggest that such screening is not effective. Recommendation 8 supports early mobilization of patients; because there is a lack of data, a consensus rec- ommendation was made. A general belief exists that early mobilization is good for patients, and there is minimal risk associated with it. No. 9 is a moderate recommendation to use some form of neuraxial anesthesia for these patients. This recommendation is made because there is evidence to support a decrease in blood loss associated with neuraxial anesthesia, although there are insufficient data to conclude that neuraxial anesthesia is associated with a decreased occurrence of symptomatic VTE. No. 10 is an inconclusive recommendation regarding the potential use of inferior vena cava filters for patients with a contraindication to receive chemoprophylaxis. There was insufficient evidence to make a recommendation either to support or oppose this strategy.

No. 5 is the recommendation that likely will be of greatest interest to most orthopaedic surgeons. It is recommended that pharmacologic and/or mechanical prophylaxis be used for prevention of VTE following elective hip or knee arthroplasty. However, based on the available data, the guideline does not recommend the use of any specific prophylactic agent after routine total joint arthroplasty. In addition, there is insufficient evidence to make a recommendation regarding duration of prophylaxis. The rationale for the panel recommendation was that, using the network meta-analysis, it was not possible to determine a difference in efficacy between these prophylactic agents with respect to symptomatic events. Orthopaedic surgeons may be disappointed with the lack of recommendation of a specific prophylaxis regimen because we continue to search for an agent that will provide the optimal balance between safety and efficacy. Although numerous randomized trials are reported in the literature, most studies do not compare the efficacy of different agents based on symptomatic events. Most studies use venographically documented proximal and distal DVT as a surrogate outcome measure for symptomatic pulmonary embolism and DVT. The reason for this is that, during the past decade, most clinical trials have been sponsored by pharmaceutical companies, and the US FDA accepts the use of the venogram to determine the efficacy of a prophylactic agent. Controversy exists in the literature regarding the clinical relevance of asymptomatic clots, particularly those in the region of the calf.

The good news with respect to recommendation 5 is that it does not require orthopaedic surgeons to change their present prophylaxis regimen. The guidelines established by the Surgical Care Improvement Project (SCIP) are used as a quality measure in hospitals. These guidelines have been based on those of the American College of Chest Physicians.3 The SCIP guidelines recommend the use of low-molecularweight heparins, warfarin, and fondaparinux for prophylaxis after both total hip and knee arthroplasty. Mechanical compression devices alone are satisfactory after total knee arthroplasty, based on the results of small randomized trials in single centers.

Finally, if one chooses to use an alternative prophylaxis regimen because of concerns related to bleeding, doing so is acceptable as long as it is clearly stated in the chart. For example, mechanical compression and aspirin would meet the SCIP guideline for VTE prophylaxis after total hip arthroplasty as long as a note is written in the record. The new AAOS guideline is clearly compatible with the SCIP measures. The recent approval of rivaroxaban by the FDA for prophylaxis after total hip and knee arthroplasty will probably lead to the inclusion of this agent in the SCIP guidelines in the future.4,5 More studies are necessary to evaluate the efficacy of different agents in preventing symptomatic VTE after total joint arthroplasty.

Recommendations 2, 3, 4, and 7 have grades of recommendation of moderate, weak, consensus, or inconclusive. These recommendations require further clarification to be used effectively by orthopaedic surgeons. Recommendation 2 is a weak recommendation to encourage the practitioner to further assess the risk of previous VTE. This is not a controversial recommendation, but other than asking a patient whether he or she has had a previous VTE, it is not clear what the surgeon is supposed to do (Table 1). However, it is clearly reasonable to query the patient before surgery because patients with a history of VTE appear to be at higher risk of developing a thromboembolic event.

Recommendation 4 suggests that patients discontinue antiplatelet agents (eg, aspirin and clopidogrel) before undergoing a total hip or knee replacement. This moderate recommendation is made because data demonstrate that these agents are associated with bleeding, although no evidence-based data exist in the total joint arthroplasty literature regarding the optimal management of these patients. This is a reasonable recommendation for patients on low-dose aspirin without a history of cardiac disease.

However, the guideline does not address the situation in which patients are on aspirin and/or clopidogrel because of a history of cardiac disease. The obvious concern is that there must be a balance between the bleeding risk associated with antiplatelet agents and the potential thrombotic risk for patients if these agents are stopped before surgery. Patients who are treated with clopidogrel because they have cardiac stents are at increased risk for thrombosis. Some cardiologists have suggested that, in patients being treated with clopidogrel and aspirin, the aspirin be continued but the clopidogrel stopped approximately 7 days before the procedure. Again, these are not evidence-based recommendations. A reasonable approach would be for the orthopaedic surgeon to consult the patient's cardiologist and/or primary care physician to discover the overall thrombotic risk for that particular patient and to determine whether it is safe to perform surgery. If elective total joint arthroplasty is acceptable, then the surgeon requires guidance with respect to the continuation of one or both of these drugs during the perioperative period. This information would also help the surgeon educate the patient about the bleeding risk associated with the procedure.

For No. 6, the work group makes a consensus recommendation that patients who have had a previous VTE receive pharmacologic prophylaxis and a mechanical compression device. Again, this recommendation is made because there are no evidence-based data with respect to the type of prophylaxis that patients should receive when a history of VTE exists. This recommendation is consistent with current practice because most patients undergoing primary total joint arthroplasty receive both chemoprophylaxis and mechanical compression during the hospital stay.

However, the guideline does not address two critical issues in managing a patient with a prior history of symptomatic VTE. First, a major concern is whether bridge therapy is necessary during the immediate postoperative period and, second, whether it is reasonable to consider increasing the duration of prophylaxis. For example, if warfarin prophylaxis is being used, does the patient require a low-molecular-weight heparin until the international normalized ratio is 2.0? In addition, in these high-risk patients, the use of aspirin may not provide sufficient protection. However, there is insufficient evidence in the literature by which to make a definitive recommendation. It would have been helpful had the panel suggested that orthopaedic surgeons consider discussing the VTE risk with the patient's primary care physician or a hematologist and consider using prolonged prophylaxis. In these cases, the risk of VTE is probably of greater concern than is the bleeding risk.

In Nos. 3 and 7, the work group makes consensus recommendations that patients be assessed for known bleeding disorders (eg, hemophilia) and the presence of active liver disease (3) and that, if patients do have a bleeding disorder or liver disease, the patient receive mechanical compression for prophylaxis (7). No. 3, again, is a consensus recommendation because there are no evidencebased data available. It is not clear from either the recommendation or the rationale how patients should be assessed for a known bleeding disorder or liver disease. It is not clear whether the work group is suggesting that patients be queried for some type of history of active liver disease or bleeding disorder or if the group is advocating that a blood test be obtained. At the present time, there is insufficient information available to recommend that all patients have blood tests to screen for these types of disorders. Although an abnormal platelet count and an elevated international normalized ratio may suggest the presence of hematologic disorders and liver disease.

With respect to using mechanical compression in patients with known bleeding disorders or liver disease (recommendation 7), I think that, because there is no definitive evidence the prophylaxis regimen should be tailored for the individual patient. This is another instance in which it would be helpful for the orthopaedic surgeon to review the patient history with either the primary care physician, hematologist, or gastroenterologist. Although mechanical compression is clearly safe with respect to bleeding, it may not provide sufficient prophylaxis for patients undergoing total hip arthroplasty, particularly if mechanical compression is just used in the hospital. Some of the anticoagulant agents are actually metabolized in the kidney, and they may be safely administered in patients with liver disease. In addition, patients may have other risk factors that make it necessary for them to receive a more potent prophylaxis regimen.

Overall, the goal of this guideline is to enhance the care of patients with respect to VTE. The selection of a specific prophylaxis regimen requires that a balance be maintained between efficacy and safety. Although it is disappointing that the network meta-analysis did not allow the work group to make definitive recommendations with respect to the optimal type of prophylaxis or duration of prophylaxis, the AAOS guideline is compatible with the SCIP VTE measures. Surgeons should continue to follow the SCIP guidelines. Recommendations 2, 3, 4, and 7 all cover issues in which no definitive evidence exists to make strong recommendations, and these are also issues in which orthopaedic surgeons may not have expertise. In these instances, I think it is appropriate for orthopaedic surgeons to seek guidance from primary care physicians or specialists such as cardiologists, hematologists, or gastroenterologists to enhance the safety of patients undergoing primary total joint arthroplasty.

The new AAOS guideline correctly focuses on the importance of symptomatic events and bleeding on the selection of a prophylaxis regimen. A clear message from this guideline is that more studies are necessary to provide evidence regarding the prevention of symptomatic VTE and associated bleeding. The work panel was unable to make definitive recommendations with respect to type of prophylaxis because of insufficient evidence. Some may criticize the guideline for the broad scope of topics that it addressed, some of which were not truly related to prophylaxis and for which there was limited evidence. However, it is to be hoped that, by highlighting these issues, the guideline will stimulate investigators to pursue answers to these questions in the future.

References

1. AHRQ National Guidelines Clearinghouse: American Academy of Orthopaedic Surgeons Clinical Guideline on Prevention of Symptomatic Pulmonary Embolism in Patients Undergoing Total Hip or Knee Arthroplasty, May 19, 2007. Available at: http://www.guideline.gov/content.aspx?id=10850&search=prevention+of+symptomatic+pulmonary+embolism+in+patients+undergoing+total+hip+or+knee+arthroplasty. Accessed October 24, 2011.
2. Johanson NA, Lachiewicz PF, Lieberman JR, et al: Prevention of symptomatic pulmonary embolism in patients undergoing total hip or knee arthroplasty. J Am Acad Orthop Surg 2009;17(3):183-196.
3. Geerts WH, Bergqvist D, Pineo GF, et al; American College of Chest Physicians: Prevention of venous thromboembolism: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Chest 2008; 133(6 suppl):381S-453S.
4. Eriksson BI, Borris LC, Friedman RJ, et al; RECORD1 Study Group: Rivaroxaban versus enoxaparin for thromboprophylaxis after hip arthroplasty. N Engl J Med 2008; 358(26):2765-2775.
5. Turpie AG, Lassen MR, Davidson BL, et al; RECORD4 Investigators: Rivaroxaban versus enoxaparin for thromboprophylaxis after total knee arthroplasty (RECORD4): A randomised trial. Lancet 2009;373(9676):1673-1680.
© 2011 by American Academy of Orthopaedic Surgeons