Extended out-of-hospital low-molecular-weight heparin prophylaxis against deep venous thrombosis in patients after elective hip arthroplasty: a systematic review

Perioperative care of the patient with hip fracture

Primary care physicians can intervene to reduce perioperative complications due to comorbid medical illness in patients hospitalized with hip fracture. We review the role of the primary care physician in the treatment and prevention of perioperative morbidity and mortality.

Incidence rates of dislocation, pulmonary embolism, and deep infection during the first six months after elective total hip replacement

BACKGROUND

The lengths of acute hospital stays following total hip replacement have diminished substantially in recent years. As a result, a greater proportion of complications occurs following discharge. Data on the incidence trends of major complications of total hip replacement would facilitate recognition and management of these adverse events.

METHODS

We used Medicare claims data on beneficiaries sixty-five years and older who had had elective, primary total hip replacement for a reason other than a fracture (58,521 patients) or had had revision total hip replacement (12,956 patients) between July 1, 1995, and June 30, 1996. We calculated incidence rates of dislocation, pulmonary embolism, and deep hip infection per 10,000 person-weeks for four time-periods following the admission for the surgery (during the index hospitalization, from discharge to four weeks postoperatively, from five to thirteen weeks postoperatively, and from fourteen to twenty-six weeks postoperatively). We then used life-table methods to estimate the cumulative incidence of each complication over the first six postoperative months.

RESULTS

Of the patients who had had a primary total hip replacement, 3.9% had a dislocation, 0.9% had a pulmonary embolism, and 0.2% had a deep infection in the first twenty-six postoperative weeks. In the revision total hip replacement cohort, the proportions with dislocation, pulmonary embolism, and deep infection were 14.4%, 0.8%, and 1.1%, respectively. The rates of these adverse outcomes were highest during the index hospitalization, diminished considerably in the period from discharge to four weeks postoperatively, and continued to drop in the periods from five to thirteen and fourteen to twenty-six weeks postoperatively.

CONCLUSIONS

The incidence rates of dislocation, pulmonary embolism, and deep infection are highest immediately after total hip replacement, but they continue to be elevated throughout the first three postoperative months. With the lengths of hospital stays continuing to diminish, an increasing proportion of complications will occur in outpatients. These findings provide a basis for developing strategies to prevent these complications in the postdischarge management of patients who have had elective total hip replacement.

LEVEL OF EVIDENCE

Prognostic study, Level II-1 (retrospective study). See p. 2 for complete description of levels of evidence.

New anticoagulants: current status and future potential

Arterial and venous thrombosis are a major cause of morbidity and mortality. Anticoagulants are a cornerstone of treatment in patients with these disorders. The two most frequently used anticoagulants, heparin and warfarin, have pharmacological and/or biophysical limitations that make them difficult to use in day-to-day clinical practice. Development of new anticoagulants, which were designed to overcome these limitations, has been facilitated by an increased understanding of the coagulation cascade, the advent of molecular modeling and structure-based drug design, and the realization that the treatment of thrombosis and its complications consumes billions of dollars in annual healthcare expenditures. New anticoagulants target various steps in the coagulation pathway. Coagulation is triggered by the factor VIIa/tissue factor complex and propagated by factors Xa and IXa, together with their activated cofactors, factor Va and VIIIa, respectively. Thrombin, the final effector in coagulation, then converts soluble fibrinogen into insoluble fibrin, the major matrix protein of the clot. New anticoagulation drugs that target each of these clotting enzymes have been developed. This review will focus on those drugs in more advanced stages of clinical evaluation. These include inhibitors of initiation of coagulation (tissue factor pathway inhibitor, nematode anticoagulant peptide and active-site blocked factor VIIa), inhibitors of propagation of coagulation (active-site blocked factor IXa, antibodies against factor IX/IXa, fondaparinux sodium, direct factor Xa inhibitors, protein C derivatives and soluble thrombomodulin), and thrombin inhibitors (hirudin, bivalirudin, argatroban and ximelagatran).

Measuring the outcomes and pharmacoeconomic consequences of venous thromboembolism prophylaxis in major orthopaedic surgery

Patients who have undergone orthopaedic surgery represent a high-risk group for venous thromboembolism (VTE). Despite the routine prophylactic use of antithrombotic agents, patients still experience thrombotic events that can result in mortality and acute morbidity and, in significant numbers of patients, may lead to long-term consequences such as the post-thrombotic syndrome. Increasingly, initial VTE events occur after hospital discharge since the length of stay in hospital after major orthopaedic surgery has decreased in many countries. There is a need for further improvement in the prevention of VTE. As well as undergoing extensive safety and efficacy studies for registration purposes, new prophylactic strategies need to be evaluated from a pharmacoeconomic perspective to help guide their introduction into routine clinical practice. Over the past 15 years a number of pharmacoeconomic evaluation studies of VTE prophylaxis have been carried out in orthopaedic patients, most of which evaluated short-term clinical endpoints. During the same period, improvements in our understanding of the natural history of VTE as well as the emergence of new treatments have led to changes in the management of patients with, or at risk of, VTE. The aim of this paper was to address how best to conduct pharmacoeconomic analyses of new antithrombotic agents in light of changes in practice patterns for orthopaedic patients and greater understanding of the disease process. We put forward recommendations for relevant outcome measures, timeframes, endpoints and epidemiologic data sources. We also suggest a structure for a pharmacoeconomic model. In this model, the outcomes and costs of VTE-related care during both the acute and chronic phases of the disease are incorporated. Symptomatic deep vein thrombosis and pulmonary embolism, recurrent VTE, post-thrombotic syndrome, major hemorrhage and all-cause death are included. We also recommend that the relevance of quality-adjusted survival is investigated, and that economic appraisals are presented in both cost-consequence and budget-impact approaches. These recommendations are based on extensive examination of recent advances in the management of VTE combined with a greater understanding of its natural history.

Thromboprophylaxis and Total Hip Replacement: A Cost-Efficacy Study Comparing Duplex Screening of Asymptomatic Venous Thrombosis versus Prolonged Prophylaxis with Low-Molecular-Weight Heparins

Background:

Despite use of the anti-thrombotic prophylaxis, clinical thrombo-embolic events and fatal pulmonary embolism are still observed after total hip replacement. To reduce these complications, two strategies have been adopted: to prolong the use of low-molecular-weight heparins (LMWH) to 35 days or to screen patients systematically before discharge, using duplex ultrasonography, following the short-course prophylactic treatment.

Objective:

To assess, based on published literature, the relative costs and benefits of these two strategies for prophylaxis following total hip arthroplasty.

Method:

The author identified relevant papers in this field from his own resources and from medical literature databases.

Synthesis:

Prolonging LMWH treatment to a total of 35 days represents a direct cost in France of approximately £340 per patient, or for 100000 total hip replacements per year, an annual budget of £34 000000. If this strategy attained maximum efficacy, it would avoid 150 fatal pulmonary embolisms. The direct cost would therefore be at least £227000 per life saved. A systematic single duplex ultrasound examination before discharge from hospital would cost £76 per patient, or for 100 000 arthroplasties a total annual budget in France of £7 600000. If this approach achieved maximum efficacy, preventing the 150 fatal pulmonary embolisms corresponding to 100000 total hip replacements, the minimum direct cost would be £50 300 per life saved.

Conclusion:

Duplex screening may be more effective and lest costly than prolongation of prophylactic treatment using LMWH. This deduction needs to be confirmed by complex cost-benefit studies using clinical end-points.

Current controversies in deep vein thrombosis prophylaxis after orthopaedic surgery

As a result of easy measurable perioperative bleeding and a high number of subclinical deep vein thromboses after surgery, total hip replacement has become a benchmark for antithrombotic drug development. Today, a nonscientific evidence-based transatlantic view on thromboprophylaxis in orthopaedic surgery exists. Efforts should be taken to bridge these divergent opinions. We need to standardize study designs that allow unbiased comparison and aggregation of data to get insight in rare complications like the cauda equina syndrome associated with spinal analgesic techniques and anticoagulation and to optimize thromboprophylaxis in homogeneous groups of patients. Dosage, timing of initiation in relation to surgery, and duration of prophylaxis seems a crucial and open question for all homogeneous groups of orthopaedic patients. A definition on surgical bleeding, which allows practical measurement procedures and quantification, is lacking. Clinical studies on vascular endpoints are warranted to achieve relevant basic data for health economic analyses, which also lack scientific standardized procedures. An intercontinental close cooperation is needed to solve these issues.

Risk factors for venous thromboembolism after total hip and knee replacement surgery

Elective total hip and total knee arthroplasty surgeries are associated with an extraordinarily high incidence of asymptomatic venous thromboembolism (VTE). Symptomatic deep vein thrombosis (DVT) or pulmonary embolism (PE) is diagnosed in only 2%-4% of these patients. A number of studies have defined the incidence and time course of symptomatic thromboembolism after these procedures. Knee arthroplasty is associated with a very high incidence of asymptomatic calf vein thrombosis, with almost all symptomatic VTE events diagnosed in the first 21 days after surgery. Hip arthroplasty, however, is associated with a higher incidence of asymptomatic proximal thrombi and a modestly higher incidence of symptomatic VTE events, many diagnosed up to 6 or 8 weeks after hospital discharge. Extended medical thromboprophylaxis has been shown to reduce the incidence of symptomatic and asymptomatic VTE among hip arthroplasty patients but not among knee arthroplasty patients. Risk factors for VTE after knee arthroplasty are not well defined. Important risk factors that have been shown to be associated with the development of VTE after hip surgery include (1) a history of prior VTE, (2) obesity (body mass index > 25), (3) delay in ambulation after surgery, and (4) female sex. Factors associated with lower risk include (1) Asian/Pacific Islander ethnicity, (2) use of pneumatic compression among non-obese patients after surgery, and (3) extended thromboprophylaxis after hospital discharge.

The post-thrombotic syndrome: current knowledge, controversies, and directions for future research

The post-thrombotic syndrome (PTS) is a long-term complication of deep venous thrombosis (DVT) that is characterized by chronic, persistent pain, swelling and other signs in the affected limb. PTS is common, burdensome and costly. It is likely to increase in prevalence, since despite widespread use of and improvements in the efficacy of thromboprophylaxis, the incidence of DVT has not decreased over time. About 20-50% of patients develop PTS within 1-2 years of symptomatic DVT, and severe PTS, which can include venous ulcers, occurs in 5-10% of cases. Although there is no gold standard for the diagnosis of PTS, the presence of typical clinical features in a patient with previous DVT provides strong supporting evidence. Objective evidence of venous valvular incompetence helps to confirm the diagnosis in symptomatic patients. Preventing ipsilateral recurrence of DVT, by ensuring an adequate duration and intensity of anticoagulation for the initial DVT and by prescribing situational thromboprophylaxis after discontinuation of oral anticoagulants, is likely to reduce the risk of developing PTS. There is no proven role for thrombolysis of the initial DVT to prevent PTS. Daily use of graduated compression stockings after DVT may reduce the risk of PTS, and may prevent worsening of established PTS. Pending the results of ongoing studies, stockings are recommended in patients with persistent symptoms or swelling after DVT. Future research should focus on standardizing criteria for PTS diagnosis, identification of DVT patients at high risk for PTS, and rigorously evaluating the effectiveness of stockings, thrombolysis, and venoactive drugs in preventing or treating PTS.