New versus established drugs in venous thromboprophylaxis: efficacy and safety considerations related to timing of administration

Comparison of Enoxaparin and Rivaroxaban in Balance of Anti-Fibrinolysis and Anticoagulation Following Primary Total Knee Replacement: A Pilot Study

Background

This study aimed to assess whether the efficacy of tranexamic acid (TXA) would be altered when rivaroxaban or enoxaparin was used for thromboprophylaxis in primary total knee replacement (TKR). It was hypothesized that the hemostatic effect of TXA would be better with the use of enoxaparin.

Material/Methods

A randomized clinical trial was conducted on 194 patients undergoing primary TKR for osteoarthritis. An intravenous dose of 15 mg/kg (TXA) and 1 g topical TXA were used. Patients randomly received enoxaparin or rivaroxaban prophylaxis when the drainage was less than 30 ml/h 6–8 h postoperatively. The primary endpoint was hidden blood loss (HBL). Indexes of total blood loss drainage, hemoglobin drop, transfusion, range of motion (ROM), HSS score, VAS pain score, knee swelling, length of hospital stay (LOHS), incidence of venous thromboembolism, major/minor bleeding, and wound complications were also compared between the groups.

Results

More than 80% of patients initiated anticoagulation within 6 h postoperatively. No statistically significance difference was detected in terms of HBL (679.0±205.6 vs. 770.5±206.1, p=.062) or other bleeding index, ROM, or LOHS. The motion VAS pain score and knee swelling (16.7% vs. 6.1%, p=.021) were significantly lower, and HSS score at discharge was higher in the enoxaparin group. The rivaroxaban group had less asymptomatic deep venous (4.1% vs. 0%, p=.121) and muscular venous thrombosis (2.1% vs. 9.2%, p=.033); more ecchymosis (13.5% vs. 10.2%, p=.472), and wound complications (13.5% vs. 6.1%, p=.082). No episodes of transfusion, pulmonary embolism, or major bleeding occurred in either group.

Conclusions

More attention should be paid to the increased risk of wound complications and knee swelling associated with rivaroxaban, although the hidden blood loss was similar in both groups.

Preoperative Versus Postoperative Initiation of Warfarin Therapy in Patients Undergoing Total Hip and Knee Arthroplasty

The optimal strategy for postoperative deep venous thrombosis prophylaxis remains controversial in hip and knee arthroplasty. Warfarin causes transient hypercoagulability; however, the optimal timing of treatment remains unclear. We evaluated the effects of preoperative versus postoperative warfarin therapy with a primary endpoint of perioperative change in hemoglobin. Warfarin was dosed according to a standard nomogram. No difference in perioperative hemoglobin change was observed. The preoperative group demonstrated higher INRs. Initiation of warfarin preoperatively was not associated with any difference in perioperative hemoglobin change. Larger studies are needed to determine whether the risk of adverse events is increased with either strategy.

Using new oral anticoagulants in patients undergoing major orthopedic surgery

Four new oral anticoagulants (NOAC), apixaban, rivaroxaban, edoxaban, and dabigatran, are now available in the USA; however, only apixaban and rivaroxaban are FDA approved for the prevention of venous thromboembolism following orthopedic surgery. Apixaban, rivaroxaban, and edoxaban's anticoagulant activity can be measured using a chromogenic anti-factor Xa assay but there is no widely available means of measuring dabigatran blood levels. None of the NOAC has an antidote. Dabigatran is 80% renally excreted, and patients with atrial fibrillation taking dabigatran for stroke prevention should stop the drug 4-5 days prior to major orthopedic surgery. Apixaban, rivaroxaban, and edoxaban should be held for 48 h preoperatively in this setting.

Chinese orthopedic surgeons' practice regarding postoperative thromboembolic prophylaxis after major orthopedic surgery

OBJECTIVE

To assess Chinese surgeon practice of thromboprophylaxis following major orthopedic surgery.

METHODS

A questionnaire survey was conducted amongst Chinese orthopedic surgeons. A total of 293 surgeons were surveyed concerning five key aspects of thromboembolic prophylaxis after major orthopedic surgery at the proseminar of Chinese guidelines for prevention of venous thromboembolism (VTE) after major orthopedic surgery in January of 2009.

RESULTS

Totally, 208 surgeons (71.0%) responded, successfully completing the questionnaire. Of them, 57.6% respondents selected combined basic, mechanical, and pharmacologic methods for thromboprophylaxis; 51.0% respondents prefer starting prophylaxis 12-24 hours after surgery; 60.3% surgeons would use chemoprophylaxis for 7-10 days; 47.6% respondents prefer VTE prevention based on patients' special conditions and needs upon discharge."Safety" was the most repeated and emphasized factor during VTE prophylaxis.

CONCLUSIONS

Multimodal thromboprophylaxis is frequently used after major orthopedic surgery. Half surgeons prefer to start chemoprophylaxis 12-24 hours after surgery. Thromboprophylaxis regimen varies for discharged patients.

The ''critical thrombosis period'' in major orthopedic surgery: when to start and when to stop prophylaxis

Patients undergoing major orthopedic surgery are at high venous thromboembolism (VTE) risk, with morbid and potentially fatal consequences. Anticoagulant VTE prophylaxis reduces rates of postoperative deep vein thrombosis by up to 60% to 70% in these patients. Therefore, pharmacological prophylaxis with low-molecular-weight heparins (LMWHs), vitamin K antagonists, or fondaparinux is recommended by current guidelines. However, there remains an ongoing debate regarding when to initiate and the optimal duration for prophylaxis. Here, we discuss the mechanisms underlying thrombus formation in patients undergoing major orthopedic surgery, and we review the current literature on the benefit-to-risk ratio associated with preoperative and postoperative initiation of thromboprophylaxis and also the benefit-to-risk ratio in cases of neuraxial anesthesia. We also discuss the duration of postoperative VTE risk following major orthopedic surgery and assess the ''critical thrombosis period'' when prophylaxis should be provided. Current literature reflects the need to balance the improved efficacy of initiating prophylaxis close to the surgery with increased risk of perioperative bleeding. Evidence from pathology, epidemiology, and clinical studies suggests the risk period for VTE begins at surgery and extends well beyond hospitalization-a crucial issue when considering how long to give prophylaxis-and, in the case of total hip arthroplasty, for at least 3 months after surgery. Literature supports the greater use of ''just-in-time'' thromboprophylaxis initiation and after-discharge continuation of optimal prophylaxis in orthopedic surgery patients. Providing optimal thromboprophylaxis throughout the critical thrombosis period where a patient is at VTE risk will ensure the best reductions in VTE-related morbidity and mortality.

Prevention of postoperative venous thromboembolism in Japanese patients undergoing total hip or knee arthroplasty: two randomized, double-blind, placebo-controlled studies with three dosage regimens of enoxaparin

BACKGROUND

Enoxaparin is a low-molecular-weight heparin indicated in Europe and North America for the prevention of venous thromboembolism (VTE) in patients undergoing major orthopedic surgery. Registration trials of enoxaparin have been conducted primarily in Caucasian populations, and the efficacy and safety of enoxaparin in Japanese patients have not been demonstrated. We evaluated three dosage regimens of postoperative enoxaparin in Japanese patients undergoing elective total hip or knee arthroplasty.

METHODS

Two multicenter, randomized, double-blind studies enrolled 436 and 396 Japanese adults undergoing total hip or knee arthroplasty, respectively. The dosage regimens of enoxaparin were 20 mg once daily (qd), 40 mg qd, 20 mg twice daily (bid), or placebo for 14 consecutive days. The primary efficacy endpoint was the incidence of VTE in the modified intention-to-treat (mITT) population up to 15 days after surgery. VTE was defined as a composite of deep vein thrombosis (determined by venography) and symptomatic pulmonary embolism (confirmed by appropriate objective methods). Patients were also followed up at 90 days for VTE events. The primary safety outcome was the incidence of any bleeding during treatment and the follow-up period.

RESULTS

In the mITT populations, the incidence of VTE was 41.9% and 60.8% in the placebo groups after hip or knee arthroplasty, respectively, 25.9% and 44.9% in the enoxaparin 20 mg qd groups, 33.8% and 35.1% in the enoxaparin 40 mg qd groups, and 20.0% and 29.8% in the enoxaparin 20 mg bid groups. Only enoxaparin 20 mg bid significantly lowered the risk of VTE relative to placebo (by 52.2% and 51.0% after hip and knee arthroplasty, respectively). At the 90-day follow-up, no further cases of VTE were reported. In both the hip and knee studies, the four treatment groups did not differ significantly regarding the incidence of patients with any bleeding.

CONCLUSIONS

Our findings support the use of enoxaparin (20 mg bid daily, commencing 24-36 h postoperatively) in Japanese patients undergoing total hip or knee arthroplasty.

Current awareness: Pharmacoepidemiology and drug safety

In order to keep subscribers up‐to‐date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of pharmacoepidemiology and drug safety. Each bibliography is divided into 20 sections: 1 Reviews; 2 General; 3 Anti‐infective Agents; 4 Cardiovascular System Agents; 5 CNS Depressive Agents; 6 Non‐steroidal Anti‐inflammatory Agents; 7 CNS Agents; 8 Anti‐neoplastic Agents; 9 Haematological Agents; 10 Neuroregulator‐Blocking Agents; 11 Dermatological Agents; 12 Immunosuppressive Agents; 13 Autonomic Agents; 14 Respiratory System Agents; 15 Neuromuscular Agents; 16 Reproductive System Agents; 17 Gastrointestinal System Agents; 18 Anti‐inflammatory Agents ‐ Steroidal; 19 Teratogens/fetal exposure; 20 Others. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted.