Barriers to the optimal use of anticoagulants after orthopaedic surgery

Anticoagulant therapy in orthopedic surgery - a review on anticoagulant agents, risk factors, monitoring, and current challenges

Orthopedic surgeries are associated with high-risk of thromboembolism which occurs in 40% to 60% of orthopedic patients in the absence of thromboprophylaxis. Conventionally heparin anticoagulants were used for thromboprophylaxis and currently direct oral anticoagulants (DOACs) are widely used due to their minimal complexity. Anticoagulant use carries bleeding risk and requires optimal laboratory monitoring through conventional thrombin-based assays, anti-Xa assay, anti-IIa assay and contemporary ecarin chromogenic assay (ECA) and rotational thromboelastometry. Monitoring requires multiple hospital visits and hence, the development of point-of-care assays is gaining momentum. Also, a thorough risk assessment model (RAM) is necessary for successful anticoagulant therapy since it enables personalized approach for better thromboprophylaxis outcomes. Despite welcoming changes, lack of guideline consensus, population-based thromboprophylaxis, deficiencies in risk stratification and non-adherence are still a concern. Stronger clinical and process support system with uniform guidelines approaches and patient-specific RAM can aid in the successful implementation of anticoagulant therapy.

The study of the thrombin generation mechanism and the effect of low molecular weight heparin as thromboprophylaxis in patients undergoing total knee and hip replacement

INTRODUCTION

The recommended duration of post-operative Low-Molecular-Weight-Heparins (LMWHs) thromboprophylaxis in Total-Hip-Replacement (THR) and Total-Knee-Replacement (TKR) surgery is controversial. Our aim is to study the thrombin generation (TG) modifications induced by surgery and to evaluate the effect of LMWH on TG during and after the recommended duration.

PATIENTS/METHODS

Thirty-one patients received 4000IU anti-Xa/day of enoxaparin, 8-hours post-operatively (15 THR for 30-days and 16 TKR for 15-days). TG assay sensitive to enoxaparin was performed, pre-operatively (D0), 7-hours post-surgery (D1), 8-days post-surgery (D8), and 2-days after thromboprophylaxis withdrawal (D32 and D17), evaluating: lag-time, endogenous thrombin potential (ETP), peak amount of generated thrombin (Peak), time-to-Peak (tt-Peak), and the Mean-Rate-Index [MRI=Peak/(tt-Peak-lag-time)].

RESULTS

TKR surgery decreased lag-time and tt-Peak and increased MRI on D1 vs D0 (p<0.05). In contrast, THR did not significantly modify TG. Enoxaparin effectively reduced thrombin generation in both groups. Thromboprophylaxis withdrawal resulted in rebound increase of TG in the TKR patients (ETP, Peak & MRI significantly increased on D17 vs D0; p<0.05, and vs. D1; p<0.05) but not in THR patients. Variability in the response to enoxaparin was observed among patients of the same group.

CONCLUSIONS

TKR surgery is more thrombogenic than THR surgery. In THR patients TG was efficiently inhibited by 30-day thromboprophylaxis, whereas, in TKR patients treated for 15-days TG was not effectively inhibited. Individual variability of the response to enoxaparin was observed in both groups revealing some form of biological resistance to enoxaparin. TG assay may represent the breakthrough step to efficient antithrombotic strategy in clinical settings with high thrombotic risk.

Improving prevention and treatment of venous thromboembolism: clinical trial results

BACKGROUND

Venous thromboembolism (VTE) incurs considerable socioeconomic costs, partly owing to the fact that the treatment and prevention of VTE via effective thromboprophylaxis remains suboptimal in the inpatient and outpatient settings of many healthcare systems. A number of organizations-including the National Quality Forum, The Joint Commission, and the Centers for Medicare and Medicaid Services-have established measures to assess and reduce the healthcare burden of VTE. These improvement strategies focus on increasing the use of thromboprophylaxis, implementing existing guidelines, and improving awareness.

FINDINGS

Based on clinical trial results, the oral anti-coagulants rivaroxaban, apixaban, and dabigatran etexilate have been approved in many countries for the prevention of VTE in patients after elective hip or knee replacement surgery. Recently, dabigatran etexilate and rivaroxaban have also been approved in the US for the prevention of stroke and systemic embolism in patients with non-valvular atrial fibrillation. In addition, rivaroxaban is currently the only newer anti-coagulant that has been approved in Europe for the treatment of deep vein thrombosis and for the long-term prevention of recurrent VTE. These oral anti-coagulants have several advantages over established anti-coagulants, including no need for routine coagulation monitoring and only minimal food and drug interactions. These characteristics, together with convenient oral administration, may improve adherence and quality of life for patients, which could result in reductions in the rate of VTE.

CONCLUSIONS

These three oral agents have several advantages over established anti-coagulants and could, therefore, address the unmet needs of patients, physicians, and healthcare systems, with the potential to reduce the burden of anti-coagulant management and the occurrence of VTE.

Medical problems in hip fracture patients

Increasing number of older patients are admitted to hospital with hip fractures. This review evaluates the common medical problems that arise as a consequence of having a hip fracture. Older patients with fractures commonly have co-morbidities that require evaluation prior to and after surgery. Joint acute orthopaedic-geriatric units have been established to provide comprehensive orthopaedic and medical care with some studies showing a reduction in postoperative complications and mortality. Recommendations surrounding the care of the older orthopaedic patient include early surgical fixation, the use of prophylactic antibiotics and thromboembolic prophylaxis, good perioperative pain control to improve ambulation, delirium detection and management to decrease the risk complications, such as institutionalisation, the avoidance of malnutrition, urinary tract management, osteoporosis management and the promotion of early mobilisation to improve functional recovery. Physicians are well placed to manage these patients with orthopaedic surgeons during the perioperative period. Sufficient evidence exists for most recommendations for fracture patients, but further research is needed in most areas.

Emerging antithrombotic agents for thromboprophylaxis, clinical potential and patient considerations

Patients undergoing major orthopedic surgery, total hip arthroplasty (THA) and total knee arthroplasty (TKA) are at high risk of venous thromboembolism, manifesting as deep vein thrombosis or pulmonary embolism. The recommended pharmacologic treatment options for thromboprophylaxis after major orthopedic surgery include the vitamin K antagonists (VKAs eg, warfarin), low molecular weight heparins (LMWHs; eg, enoxaparin) and the synthetic pentasaccharide fondaparinux. Most clinics use some kind of thromboprophylaxis routinely. However, due to the frequent need for coagulation monitoring (VKAs) and subcutaneous injections (LMWHs and fondaparinux) barriers exist to prescribing prophylaxis after discharge from hospital. Targeting specific components of the coagulation cascade has yielded several new antithrombotic agents for use as thromboprophylaxis after THA or TKA. Two of these, dabigatran etexilate and rivaroxaban, have already reached the markets in the European Union member states and Canada. Both are administered by the oral route, once-daily fixed dose and without the need to monitor the anticoagulant effect. Whether these new drugs facilitate guideline adherence, particularly in the outpatient settings and thereby improve the overall clinical outcomes remains to be shown.