Prevention of venous thromboembolism in the orthopedic surgery patient

Knee replacement surgery

The same three anticoagulant options that received Grade 1A recommendations for patients undergoing total hip replacement—LMWH, fondaparinux, and adjusted-dose warfarin—are also given Grade 1A recommendations as routine thromboprophylaxis in patients undergoing elective knee replacement (see Table 1 for dosing). In addition, optimal use of intermittent pneumatic compression devices is recommended as an alternative option to anticoagulant prophylaxis in these patients (Grade 1B, indicating a “strong recommendation” based on RCTs with important limitations). Use of UFH as the sole agent for prophylaxis is recommended against.⁶

For both hip and knee replacement surgery, the Seventh ACCP Conference does not endorse superiority of any one of its three recommended prophylaxis options—LMWH, fondaparinux, and adjusted-dose warfarin—over the other two. However, at least four large randomized trials have directly compared LMWH and adjusted-dose warfarin in the setting of arthroplasty—two in total hip replacement surgery^19,20 and two in total knee replacement surgery.^21,22 Each of these four studies found LMWH to be significantly more effective than warfarin in preventing VTE. In three of the four trials, there was no significant difference between the therapies in rates of major bleeding.^19,21,22 In the remaining trial, which was conducted in hip replacement surgery patients and compared postoperative warfarin with dalteparin initiated either immediately before or early after surgery, patients who received preoperative dalteparin initiation (but not those who received postoperative dalteparin initiation) had an increased rate of major bleeding compared with warfarin recipients (P = .01).²⁰

Hip fracture surgery

The supportive evidence for anticoagulant prophylaxis in hip fracture surgery is less robust than that in hip and knee replacement surgery. As a result, only fondaparinux has a Grade 1A recommendation as routine prophylaxis in patients undergoing hip fracture surgery. Options with less definitive recommendations are LMWH (Grade 1C+), low-dose UFH (Grade 1B), and adjusted-dose warfarin (Grade 2B, indicating a “weak recommendation” based on RCTs with important limitations) (see Table 1 for dosing of all agents).⁶

These differing recommendations are supported by the double-blind Pentasaccharide in Hip Fracture Surgery Study (PENTHIFRA) of 1,711 consecutive patients undergoing surgery for hip fracture repair.²³ Patients were randomized to at least 5 days of fondaparinux 2.5 mg once daily, initiated postoperatively, or enoxaparin 40 mg once daily, initiated preoperatively. The incidence of DVT or PE by postoperative day 11 was 8.3% in the fondaparinux arm versus 19.1% in the enoxaparin arm, a statistically significant difference (P < .001) in favor of fondaparinux. There were no differences between the groups in rates of death or clinically relevant bleeding.

As noted above, the newly added recommendation in the Seventh ACCP Conference for extended prophylaxis, for up to 28 to 35 days after surgery, applies to patients undergoing hip fracture surgery as well as those undergoing hip replacement surgery. In the setting of hip fracture repair, extended prophylaxis is a Grade 1A recommendation with the use of fondaparinux and a Grade 1C+ recommendation with the use of either LMWH or adjusted-dose warfarin.⁶

Lower extremity fractures and trauma

Although lower extremity fractures are very common, the risk of DVT has been poorly studied in this setting. For patients with isolated lower extremity fractures, the Seventh ACCP Conference recommends that clinicians not use thromboprophylaxis routinely (Grade 2A, indicating an “intermediate-strength recommendation” based on RCTs without important limitations).⁶

Trauma patients, in contrast, are well recognized as being at very high risk for DVT and PE. The Seventh ACCP Conference gives a Grade 1A recommendation to thromboprophylaxis for all trauma patients who have at least one risk factor for VTE. LMWH is recommended (Grade 1A) as the agent of choice for this purpose, provided there are no contraindications to its use, and should be administered as soon as safely possible. Mechanical modalities are reserved for trauma patients with active bleeding or high risk for hemorrhage (Grade 1B). The guidelines recommend against use of inferior vena cava (IVC) filters as primary thromboprophylaxis in trauma patients (Grade 1C, indicating an “intermediate-strength recommendation” based on observational studies).⁶

Use of ultrasonography

Duplex ultrasonographic screening is recommended in orthopedic trauma patients who are at high risk for VTE and have received suboptimal or no prophylaxis (Grade 1C). In contrast, the Seventh ACCP Conference recommends against routine use of duplex ultrasonography to screen for VTE at hospital discharge in asymptomatic patients following major orthopedic surgery (Grade 1A).⁶

Knee arthroscopy

Arthroscopic knee procedures are increasing in frequency and raise the specter of a potential role for thromboprophylaxis. However, the clinical diagnosis of DVT is unreliable, and even diagnosis by ultrasonography is unreliable following knee arthroscopy, as interpreting scans of veins below the knee is challenging in this setting.²⁴

The Seventh ACCP Conference recommends that clinicians not use routine thromboprophylaxis, other than early mobilization, for patients who undergo knee arthroscopy (Grade 2B). However, for arthroscopy patients who have inherent risk factors for VTE or who undergo a prolonged or complicated arthroscopy procedure, thromboprophylaxis with LMWH is suggested (Grade 2B).⁶

RECOMMENDED APPROACH TO VTE PROPHYLAXIS IN ORTHOPEDIC SURGERY

Drawing on the ACCP guidelines and the evidence reviewed above, we have outlined our evidence-based recommendations for pharmacologic VTE prophylaxis in patients undergoing orthopedic surgery, as presented in Table 1. All patients undergoing major orthopedic surgical procedures (ie, procedures other than arthroscopy) should routinely receive anticoagulant prophylaxis unless they have contraindications to anticoagulation. Recommended agents and their duration of use vary according to the type of surgery, as detailed in Table 1.

Extended-duration prophylaxis is recommended for patients undergoing total hip replacement and hip fracture surgery. Aspirin is not recommended as the sole agent for prophylaxis in any orthopedic surgery setting.

Importance of a postoperative prophylaxis protocol

In addition to these broad pharmacologic recommendations, it is important that a postoperative VTE prophylaxis protocol be in place at all hospitals.

At the Ochsner Medical Center in New Orleans, where one of us (S.B.D.) practices, postoperative orders include antithrombotic therapy for surgical patients, starting with placement of thigh-high antiembolism stockings on both legs on the day of surgery for patients undergoing hip replacement and on postoperative day 1 in those undergoing knee replacement. Plantar pneumatic compression devices are applied to both legs in the recovery room and kept on except when the patient is walking. The hospitalist team dictates further anticoagulation orders. If extended prophylaxis is prescribed, the discharge planner sets up drug delivery and reimbursement, provides a LMWH discharge kit, and teaches the patient to self-inject. If there is concern about increasing swelling at the surgical site while anticoagulant therapy continues, the protocol calls for prompt notification of the responsible physician. To minimize the risk that spinal or epidural hematomas will develop, all agents that increase bleeding propensity should be recognized and ordered accordingly.