Management of Venous Thromboembolism in Total Hip and Total Knee Replacement Surgery

William D. Fisher, M.D., FRCSC
Montreal, QC

Prophylaxis
Despite improvements in surgical technique, anesthesia and postoperative care, venous thromboembolism (VTE) remains a significant risk in hip and knee replacement surgery1. Symptomatic VTE is seen, even with prophylaxis, in at least 1 to 2% of patients and the risk extends into the months following hospital discharge2. A far greater number of asymptomatic events can be expected to occur - each with the potential of progression to later symptomatic events such as recurrent microemboli leading to later respiratory failure or venous insufficiency from damage to the valves of the deep venous system leading to the post-thrombotic syndrome. Certain risk factors such as age, obesity, cardio-vascular disease, a past history of VTE and inherited and acquired thrombophilias increase the incidence. However, the need for some form of routine prophylaxis remains paramount in all patients. Attempts to stratify the degree of risk are difficult and unreliable and a standard written hospital policy should be established including, where possible, electronic orders to ensure adequate management post discharge3.

For the last 22 years, the American College of Chest Physicians has produced regular guidelines for thromboprophylaxis. Although these are only recommendations, they are based on an analysis of the many well-constructed and well-controlled clinical studies1.

Two approaches, essentially, are available; mechanical and pharmacological methods. The former are attractive to the surgeon in that bleeding is not a problem but may be less effective, more difficult to institute and poorly tolerated by patients. They are moreover unsuitable for long-term use especially in the outpatient setting. They are ideal in two situations: 1) for short-term use in the patient at high risk of bleeding or 2) as an adjunct to chemoprophylaxis in the patient at high risk of VTE. Intermittent pneumatic compression devices are the preferred treatment in these

For the vast majority of patients, the choice is among the low-molecular-weight heparins (LMWH), warfarin and the pentasaccharide, fondaparinux. The last drug has, despite its good efficacy profile, the reputation for increased bleeding and thus infrequently used4,5. It may, however, have a place in the management of the high-risk patient. Warfarin is attractive as an oral agent with a slow onset to avoid the risk of bleeding in the immediate postoperative period. It is, however, difficult to maintain the ideal INR (international normalized ratio) of between two and three early in the postoperative period and maintain it after discharge. Surprisingly, despite being an oral drug, it has been shown to have a poorer compliance post discharge6.

The LMWHs are attractive in their lack of a need for monitoring and good track record. Although they are all derived from the same complex polysaccharide, heparin, they differ in their composition, half-life, mode of action (with varying factor Xa and IIa activities) and administration protocols. As such they are not interchangeable. Their preoperative use is difficult, with same day admission a standard practice, and is probably unnecessary. Furthermore, preopereative use is associated with increased bleeding7. To allow time for adequate homeostasis, their administration should be at least six hours post wound closure. The two most commonly used LMWHs in Canada are enoxaparin and dalteparin.

The attraction of the former, using the so-called North American protocol, is that the start time is 12 to 24 hours postoperatively or essentially, the following morning, removing some of the anxiety with associated bleeding although the higher dose (30mg bid) may increase that risk8. There are, however, no good comparisons of the individual agents. The twice-daily use does raise problems if epidural analgesia is used for postoperative pain control; necessitating the withholding of one dose prior to removal of the catheter.

With a now standard shorter hospital stay, inpatient use only is no longer a viable option and out-patient use is also clearly required. The use of pre-discharge ultrasound screening has been shown not to be useful9. Therapy is recommended for at least ten days1. Continuing treatment for up to 28 to 35 days for total hip replacement has been shown to be more effective10 and, depending on the jurisdiction, to be cost-effective in avoiding readmission for pulmonary emboli (PE), treatment of these incidents, and further DVTs. An equal prolongation for total knee replacement should be considered especially if associated with increased risk factors1.

The introduction of the new oral agents dabigatran (Pradax) and rivaroxaban (Xarelto) is particularly exciting as they do not require monitoring or injection. The former has been shown to be non-inferior and the latter superior to enoxaparin 40mg daily. Their successful introduction may only await confirmation of their safety in general clinical use when compared to the LMWHs.

Diagnosis of VTE
In the view of the low incidence of symptomatic VTE, detection of the individual case relies on a high index of suspicion. Swelling of the legs is not uncommon following hip or knee surgery, particularly on the operative side, and there may also be tenderness in the calf, although a false Homan's sign is rarely seen. A low-grade pyrexia is not infrequently an associated feature of the silent deep venous thrombosis (DVT) as well as tenderness in the popliteal fossa and along the deep femoral vein in the thigh. Chest pain should alert one to the possibility of a pulmonary embolus (PE) without evidence of a clinical DVT. The use of Doppler ultrasound as a general screening test is unreliable in the postoperative patient because an incomplete venous occlusion in these patients is difficult to detect11. It is, however, more successful in the symptomatic patient, particularly in the proximal limb. While contrast venography remains the gold standard, it is rarely if ever used except in the research environment. While a positive venogram in the symptomatic patient requires active treatment, management of all the small below knee thrombi in the asymptomatic patient is more controversial. These may best be managed by following the filling defect with sequential ultrasound studies.

The diagnosis of PE is first made on clinical signs and symptoms with a high index of suspicion especially in the presence of a proximal DVT12. Early diagnosis is important as 10% of cases will be fatal in the first hour and a missed diagnosis will lead to recurrent episodes of VTE which can also be fatal. Respiratory symptoms with or without hemoptysis and associated with a tachycardia and hypotension at times are the principal findings. The use of the D-dimer test (a measure of lysed fibrin fragments), while raised in DVT and PE, is perhaps most useful in excluding PE when the value is normal. Ventilation-perfusion scans are useful confirmation with "high probability" defects but intermediate scans require a positive leg ultrasound for diagnosis. Spiral CT scanning is often more available but not always strongly predictive. Pulmonary angiography, while being the gold standard, has serious side effects, is difficult to perform, and is expensive and unsuitable for many patients with poor renal function or in shock.

References

  1. Geerts W.H., Bergqvist D., Pineo G.F., et al. Prevention of venous thromboembolism. American College of Chest Physicians evidence-based clinical practice guidelines (8th Edition). Chest 2008; 133: 381S-453S.
  2. White R.H., Romano P.S., Zhou H., et al. Incidence and time course of thromboembolic outcomes following total hip or knee arthroplasty. Arch Intern Med 1998; 158:1525-1531
  3. Rahme E., Dasgupta K., Burman M., et al. Post discharge thromboprophylaxis and mortality risk after hip- or knee-replacement surgery. CMAJ 2008; 178: 1545-1554.
  4. Turpie A.G., Bauer K.A., Eriksson B.I., et al. Fondaparinux vs enoxaparin for the prevention of venous thromboembolism in major orthopedic surgery: a meta-analysis of 4 randomized double-blind studies. Arch Intern Med 2002; 162:1833- 1840
  5. Turpie A., Bauer K., Eriksson B., et al. Efficacy and safety of fondaparinux in major orthopedic surgery according to the timing of its first administration. Thromb Haemost 2003; 90:364-366
  6. Warwick D., Freidman R.J., Agnelli G. et al. Insufficient duration of venous thromboembolism prophylaxis after total hip or knee replacement when compared with the time course of thromboembolic events. J Bone Joint Surg [Br] 2007; 89-B: 799-807.
  7. Hull R.D., Pineo G.F., Francis C., et al. Low-molecular-weight heparin prophylaxis using dalteparin in close proximity to surgery vs warfarin in hip arthroplasty patients: a double-blind, randomized comparison. Arch Intern Med 2000; 160:2199-2207.
  8. Colwell C.W., Spiro T.E., Trowbridge A.A., et al. Use of enoxaparin, a low-molecular-weight heparin, and unfractionated heparin for the prevention of deep venous thrombosis after elective hip replacement: a clinical trial comparing efficacy and safety. J Bone Joint Surg Am 1994; 76A: 3-14.
  9. Robinson K.S., Anderson D.R., Gross M., et al. Ultrasonographic screening before hospital discharge for deep venous thrombosis after arthroplasty: the Post-Arthroplasty Screening Study: a randomized, controlled trial. Ann Intern Med 1997; 127:439-445.
  10. Hull R.D., Pineo G.F., Stein P.D., et al. Extended out-of-hospital low-molecular-weight heparin prophylaxis against deep venous thrombosis in patients after elective hip arthroplasty a systematic review. Ann Intern Med 2001; 135:858-869.
  11. Schellong S.M., Beyer J, Kakkar A.K., Halbritter K., Eriksson B.I., Turpie A.G.G., Misselwitz F., Kälebo P. Ultrasound screening for asymptomatic deep vein thrombosis after major orthopaedic surgery: the VENUS study. J Thromb Haemost 2007; 5: 1431-7.
  12. Kearon C. Diagnosis of pulmonary embolism: CMAJ 2003; 168: 183-94

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