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* Jeffery L. Pierson, MD, is from the Indiana University School of Medicine, Indianapolis, IN.
Correspondence to: Morton Tavel, MD, FCCP, 8333 Naab Road, Suite 200, Indianapolis, IN 46260; e-mail: mtavel6986{at}aol.com
%Abbreviation: INR = international normalized ratio
Case Presentation
A 74 -year-old woman was scheduled for an elective total hip replacement for degenerative joint disease. She had always enjoyed good health. At the age of 45, she underwent an elective hysterectomy with salpingo-oopharectomy, without complication or excessive bleeding. Since that time, she has been using oral estrogen replacement therapy, which has been well tolerated. There was no prior history of vascular disease, venous varicosities, or thromboembolism.
Evaluation of the patient’s blood at the time of admission to the hospital disclosed a normal hemogram, with normal platelets and normal blood chemistry values, including fasting blood sugar and urea nitrogen. Lipid profile, chest roentgenogram, and ECG were also normal.
Questions for Consultant
Comments by Consultant
Jeffery L. Pierson, MD
Decision making regarding thromboembolic prophylaxis after total
joint replacement (total hip and/or total knee replacement) depends on
a classic analysis of risk and benefit.
The primary benefit of thromboembolic prophylaxis after total joint replacement is prevention of pulmonary embolism and its potentially fatal outcome. A possible secondary benefit is the prevention of so-called postphlebitic limb syndrome.
In general, the risk of fatal pulmonary embolism after total joint replacement today is approximately 0.10 to 0.15%,1 and this would apply to the case described herein. This extraordinarily low incidence (roughly one in one thousand) is much lower than generally perceived in the medical community—a perception probably gained from historical data reported during the infancy of total joint replacement. This dramatic reduction in risk is likely multifactorial in etiology. Important changes have included significant decreases in operating time, early and aggressive mobilization, and possibly, routine use of thromboembolic prophylaxis. It is clear, however, that the major benefit of thromboembolic prophylaxis is prevention of a rare event. This is an important observation and becomes particularly relevant when performing risk/benefit analysis.
The literature is replete with information regarding deep venous thrombosis after total joint replacement. In contrast to fatal pulmonary embolism, deep venous thrombosis is a relatively common occurrence, even with early mobilization and pharmacologic prophylaxis. Deep venous thrombosis can be expected to occur in 10 to 25% of cases, a likelihood applicable to the case described above. These events are nearly always asymptomatic and, as noted above, rarely result in serious consequences. Therefore, many have questioned the validity of using the incidence of deep venous thrombosis as an appropriate surrogate marker for the risk of pulmonary embolism and as the primary outcome to evaluate different methods of thromboembolic prophylaxis after total joint replacement. Stated differently, the primary goal of prophylaxis after total joint replacement is the prevention of fatal pulmonary embolism. It is not clear that the incidence of asymptomatic deep venous thrombosis is an appropriate surrogate marker. In fact, it may be possible to reduce the incidence of asymptomatic deep venous thrombosis with more aggressive methods of anticoagulation; however, this may be possible only by assuming higher risks of bleeding. So-called postphlebitic limb syndrome is characterized by venous stasis, swelling, and in some cases, skin discoloration and even ulcerations. Although one might expect that a reduction in the incidence of asymptomatic deep venous thrombosis after joint replacement would decrease the incidence of postphlebitic limb syndrome, there are no studies that actually demonstrate that thromboembolic prophylaxis prevents such an outcome.
Bleeding risks are related to the type of prophylaxis chosen and the intensity of the treatment. Obviously, the lowest risks of bleeding are associated with nonpharmacologic prophylaxis such as sequential compression devices. Higher risks are associated with pharmacologic prophylaxis. Bleeding associated with pharmacologic agents may be systemic (ie, GI or cerebrovascular) or local (ie, into the operative site itself).
It is important to distinguish between prophylactic and therapeutic anticoagulation. This distinction is primarily characterized by the intent and intensity of anticoagulation. Prophylactic dosing is used to prevent venous thrombosis and is less intense (eg, enoxaparin, 30 mg subcutaneously every 12 h). Therapeutic dosing is used to treat venous thrombosis and is more intense (eg, enoxaparin, 1 mg/kg subcutaneously every 12 h).
The highest risks of bleeding are associated with therapeutic dosing (in contrast to prophylactic dosing) of unfractionated heparin.2 3 Therapeutic dosing of unfractionated heparin within the first 7 days after hip or knee replacement is associated with a 30% risk of a major bleed into the operated joint. These major bleeds often compromise the outcome of the arthroplasty by increasing the risks of wound disruptions, skin-flap necrosis, and infection. Low molecular weight heparins, given at prophylactic dosing levels, have low risks of significant wound bleeding. However, many studies have shown a slightly higher risk of bleeding when compared to adjusted-dose warfarin.
In the United States, the vast majority of orthopedic surgeons would employ routine pharmacologic prophylaxis for this patient, which would include adjusted-dose warfarin (with target international normalized ratio [INR] of 2 to 2.4) or low molecular weight heparin. In my practice, I would use 4 weeks of adjusted-dose warfarin. Specifically, prophylaxis begins on the day of surgery with 7.5 to 10 mg warfarin (dosing dependent on size and age of patient). Daily warfarin is then given based on monitoring of prothrombintime/INR during hospitalization. After hospital discharge, weekly monitoring of INR is performed with adjustments made, as needed, in warfarin dosing. Therapy is continued for 4 weeks from the date of surgery, with a target INR of 2.0 to 2.4. Adjuvant prophylactic measures would include early mobilization (day of surgery or first postoperative day) and compression stockings. This protocol represents an appropriate balance between the benefit of thromboprophylaxis (prevention of pulmonary embolism) and the risks (local and systemic bleeding) and is supported by the literature.4 5
Virtually all patients develop some degree of lower extremity swelling after total hip and total knee arthroplasty. The clinical diagnosis of deep venous thrombosis is extraordinarily inaccurate. Time-honored clinical tests, such as calf tenderness and Homans sign, are notoriously inaccurate and should not be used to make decisions regarding a change in thromboprophylaxis after joint replacement. As noted, deep venous thrombosis is relatively common, yet fatal pulmonary emboli are extremely uncommon. The risk of bleeding associated with therapeutic anticoagulation within the first week after total joint arthroplasty is very high. In the patient with lower extremity edema after total joint replacement, it is rarely indicated to perform additional diagnostic testing of the venous system when using the thromboprophylaxis regimen outlined. For example, venous ultrasonography is an accurate diagnostic test for lower extremity deep venous thrombosis. However, its use in this clinical scenario would not change the treatment plan and, thus, it provides insignificant clinical data.
If, however, the patient develops clinical symptoms that are suggestive
of a pulmonary embolism within the first week of surgery, further
diagnostic testing with pulmonary angiography, ventilation/perfusion
(
/
) scan, or spiral CT is appropriate. If the angiogram
results are positive, or the / scan or spiral CT is
categorized as "high probability," the risks of therapeutic
anticoagulation within the first postoperative week must be assumed. At
that point, it is appropriate to begin therapeutic anticoagulation,
recognizing that the risks of bleeding are significant. Such intensive
anticoagulation (particularly with unfractionated heparin) should
rarely be used in the absence of clinical features of pulmonary
embolism as supported by a high probability / scan or by
pulmonary arteriography. Alternatively, consideration for placement of
a vena cava filter with less intensive anticoagulation is an option.
Fortunately, this is a very rare situation. Due to the bleeding risks
within the first postoperative week, therapeutic anticoagulation
generally should not be based on empiric clinical observations alone.
In summary, thromboprophylaxis after total joint replacement represents a classic risk/benefit analysis. Inasmuch as fatal pulmonary embolism is rare in this context, it is important to minimize the morbidity of prophylaxis. In this regard, therapeutic anticoagulation within the first week after joint replacement is associated with significant bleeding risks that often compromise the outcome of the arthroplasty and should be avoided, except in the rare situations previously outlined.
Received for publication February 7, 2001. Accepted for publication February 12, 2001.
References
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