15 Deep Vein Thrombosis and Thromboembolism
Prevention and Treatment in Hip Fracture Patients
Patients with proximal femoral fractures often have preexisting medical conditions. The initial trauma, subsequent surgery, and subsequent relative immobility may provoke further medical problems. VTE is one of the most likely complications of this injury.
Many of these patients have other morbidities or conditions (infection, advanced age, immobility, poor cardiac reserve, chronic venous insufficiency) that may predispose them to thrombogenesis. The physical reserves of these patients are often reduced, rendering them more vulnerable to succumb to an embolism that would not necessarily be fatal in fitter patients. Autopsy studies suggest that fatal pulmonary embolism (PE) is a common cause of death in this group of patients.1 However, this group is also vulnerable to death from many other causes such as pneumonia, myocardial infarction, bed sores, and infection. PE may be only a contributing factor in their demise. It is therefore difficult to determine reliably the fatal PE rate after hip fracture without prophylaxis; perhaps it is approximately 1%.
The frequency of venographic deep vein thrombosis (DVT) after hip fracture without prophylaxis is unclear because so few studies have been conducted; a rate of approximately 50% is likely. The rates of symptomatic DVT and PE are similarly difficult to adduce because there are no unconfounded epidemiologic studies or clear data from the placebo arm of randomized controlled trials. A figure of approximately 5% is reasonable. The longer-term risk of chronic venous insufficiency is also unknown. Many patients with hip fracture are predisposed to this problem regardless of their fracture; many are in an age group who will not live long enough to develop this longer-term complication.
The thrombogenic process begins as soon as the patient falls. In fact, some patients are so immobile that they may have developed subclinical thrombosis even before their fall. Virchow’s triad is well represented.
The fractured bone releases thromboplastins into the circulation. This process induces hypercoagulability, which is compounded by the subsequent surgical procedure. The hypercoagulability may last for several weeks.2
Venous stasis occurs as soon as the patient falls and is unable to bear weight. There is often a substantial delay before the patient is found and is taken to a medical facility. The maneuvers required to reduce the hip fracture cause further venous stasis.3
Early mobilization of the patient is held to be an impor-tant way of reducing the risk of thrombosis by inducing venous return. However, patients with hip fracture often had very limited mobility before their injury. Postoperatively, mobility is often inhibited by pain, medical complications, or the mechanical adequacy of fixation.
Anesthesiologists prefer to use spinal or epidural anesthesia because it reduces mortality and enhances perioperative analgesia.5 Furthermore, neuraxial anesthesia also reduces the risk of VTE by approximately 50%, probably as a result of increased blood flow.6 Care must be taken when neuraxial anesthesia is used in conjunction with chemical prophylaxis, and appropriate guidelines must be followed.
Orthopaedic surgeons have to balance risk and benefit in the perioperative period. Therefore, they intuitively find mechanical methods appealing because these methods carry no bleeding risk. All mechanical methods have the disadvantages of expense and noncompliance. Furthermore, these methods are not practical for, nor is there evidence for, extended prophylaxis. Very few data are derived from hip fracture patients. However, one can reasonably extrapolate from other surgical studies.
Graduated compression stockings are commonly used, although evidence of their efficacy is sparse for orthopaedic surgery in general, and no data are available specifically for hip fracture surgery. A meta-analysis of other surgical studies suggested a modest benefit.6–9 To work, these stockings must be well fitted and properly woven, and they must remain in place. There is no clear benefit of above-knee over below-knee stockings.
Rhythmic compression enhances venous flow and also releases fibrinolytic factors from the venous endothelium. In general, intermittent pneumatic compression devices are effective, with an overall VTE risk reduction of approximately 26%.7
Chemical methods are generally easy to administer (tablet or injection) and can be used for an extended duration. They are fairly inexpensive relative to the overall cost of surgery. However, orthopaedic surgeons are properly concerned about the risk of bleeding inherent in the use of these agents.
Aspirin was not recommended for use after hip fracture by the three authoritative evidence-based guidelines groups.14–16 This drug is predominantly an antiplatelet agent rather than an antithrombotic agent. The Pulmonary Embolism Prevention (PEP) study17 compared 13,000 hip fracture patients with or without aspirin for prophylaxis. The investigators reported a risk reduction for symptomatic VTE of approximately 25%, but this was matched by an increase in bleeding problems. The death rate was unchanged in either group. The risk reduction achieved is far lower than that noted with low-molecular-weight heparin (LMWH) or fondaparinux. Furthermore, aspirin carries a risk of gastrointestinal complications and bleeding, particularly in elderly patients.18