Association of Anti-Factor Xa-Guided Dosing of Enoxaparin With Venous Thromboembolism After Trauma

Venous Thromboembolism Prophylaxis in Obstetric Patients

Venous thromboembolism (VTE), including both pulmonary embolism (PE) and deep vein thrombosis (DVT), is the leading cause of maternal death in developed countries. Pregnancy is associated with an increased risk of VTE due to physiologic changes during the obstetric period that promote a hypercoagulable state. Appropriate use of prophylactic anticoagulants can decrease the event rate of thrombus formation in at-risk patients. In the United States, there is not a validated risk-assessment tool for VTE in obstetric patients or a clear consensus on initiation and optimal dosing strategy for the prophylactic use of anticoagulants. This article reviews the mechanism of coagulation disturbance that leads to an increased risk of VTE in obstetric patients, as well as the available literature surrounding pharmacologic prophylaxis.

Clinical outcomes associated with anti-Xa-monitored enoxaparin for venous thromboembolism prophylaxis

STUDY OBJECTIVE

The objective of the study was to assess clinical outcomes (composite of any venous thromboembolism [VTE], any bleeding, and mortality) associated with anti-Xa monitoring in the 30 days following enoxaparin initiation for VTE prophylaxis.

DESIGN

Retrospective cohort study.

SETTING

Hospital within an academic healthcare system.

PATIENTS

Propensity score-matched hospitalized adults receiving enoxaparin for VTE prophylaxis.

INTERVENTION

Low-molecular-weight heparin anti-Xa monitoring.

MEASUREMENTS AND MAIN RESULTS

During the 13-month study period, a total of 6611 patients received enoxaparin for VTE prophylaxis, 301 in the anti-Xa monitored group and 6310 in the unmonitored group (4.6% received monitoring). The mean age was 52.9 years and 52% of patients were male. The mean body mass index was 31 kg/m2 and the mean creatinine clearance was 109 mL/min. Twenty percent of patients had active cancer. The most common indication for enoxaparin prophylaxis was hospitalization for medical illness (52%) followed by nonorthopedic surgery (37%). The adjusted odds ratio for the primary outcome comparing monitored to unmonitored patients was 1.26 (95% confidence interval, 0.75-2.11). None of the between-group differences in the individual components of the composite outcome were statistically significant.

CONCLUSIONS

Thirty-day clinical outcomes in patients receiving enoxaparin for VTE prophylaxis were not improved by anti-Xa monitoring. Our results support current evidence-based guideline recommendations against anti-Xa monitoring for patients receiving enoxaparin for VTE prophylaxis.

Monitoring anti-Xa Levels to Optimize Low-Molecular-Weight-Heparin Thromboprophylaxis in High-Risk Hospitalized Patients: A Stratified Meta-Analysis

It is uncertain whether monitoring or targeting anti-Xa levels is necessary when using low-molecular-weight-heparin (LMWH) to prevent venous thromboembolism (VTE). This stratified meta-analysis assessed whether monitoring trough or peak anti-Xa levels with LMWH dosing would reduce risk of VTE. Twelve non-randomized studies involving 3604 hospitalized patients met the inclusion criteria and were subject to meta-analysis. Eight studies assessed the association between VTE and peak anti-Xa levels (between .2 and .5 IU/ml) and four studies assessed the benefits of targeting the trough anti-Xa levels (>.1 IU/ml). Achieving an adequate peak or trough anti-Xa level was associated with a reduced risk of VTE (random-effects model odds ratio [OR] .52, 95% confidence interval [CI] .34-.77; P = .001, I2 = 30% and P-value for heterogeneity = .171) compared with using a fixed standard dose of LMWH. Targeting the trough level (OR .40, 95%CI 0.22-.75, P = .004) appeared to be more effective than targeting the peak level (OR .62, 95%CI 0.37-1.03, P = .066), although a formal interaction analysis did not confirm they were statistically different (ratio of ORs = 1.52, 95%CI 0.68-3.40; z score = 1.03, P = .306). Targeting a higher anti-Xa level did not appear to increase the risk of bleeding or transfusion (OR 1.20, 95%CI 0.46-3.17, P = .707).

Evaluating residual anti-Xa levels following discontinuation of treatment-dose enoxaparin in patients presenting for elective surgery: a prospective observational trial

INTRODUCTION

Prior studies have demonstrated that patients presenting for elective surgery may have higher-than-expected residual anti-Xa level activity at or beyond 24 hours following their last treatment dose of enoxaparin. Given that 24 hours of abstinence is currently recommended by both European and American societies before the performance of neuraxial or deep anesthetic/analgesic procedures, determining the actual timeframe at which residual anti-Xa level activity reliably falls below 0.2 IU/mL, the lower limit of the target range for thromboprophylaxis, is critical.

METHODS

This was a prospective observational trial. Consenting patients on treatment-dose enoxaparin were randomized to either a 24-hour group (last dose at 07:00 the day prior to surgery) or a 36-hour group (last dose at 19:00 2 days prior to surgery). On arrival for surgery, blood samples were obtained to assess residual anti-Xa level activity and renal function. The primary outcome was residual anti-Xa level activity following the last treatment dose of enoxaparin. Incorporating all patients, linear regression modeling was performed to predict the timepoint at which the level of anti-Xa activity reliably fell below 0.2 IU/mL.

RESULTS

103 patients were analyzed. Time from the last dose at which residual anti-Xa activity fell below 0.2 IU/mL, based on the upper bound of the 95% CI, was 31.5 hours. No correlation overall between age, renal function, or sex was found.

CONCLUSION

Residual levels of anti-Xa activity do not reliably fall below 0.2 IU/mL 24 hours following discontinuation of treatment-dose enoxaparin. Therefore, current time-based guidelines are not conservative enough. Routine anti-Xa testing should be strongly considered, or current time-based guidelines should be reassessed.

TRIAL REGISTRATION NUMBER

NCT03296033.

Addition of aspirin to venous thromboembolism chemoprophylaxis safely decreases venous thromboembolism rates in trauma patients

Background

Trauma patients exhibit a multifactorial hypercoagulable state and have increased risk of venous thromboembolism (VTE). Despite early and aggressive chemoprophylaxis (CP) with various heparin compounds ("standard" CP; sCP), VTE rates remain high. In high-quality studies, aspirin has been shown to decrease VTE in postoperative elective surgical and orthopedic trauma patients. We hypothesized that inhibiting platelet function with aspirin as an adjunct to sCP would reduce the risk of VTE in trauma patients.

Methods

We performed a retrospective observational study of prospectively collected data from all adult patients admitted to an American College of Surgeons Level I Trauma center from January 2012 to June 2015 to evaluate the addition of aspirin (sCP+A) to sCP regimens for VTE mitigation. Cox proportional hazard models were used to assess the potential benefit of adjunctive aspirin for symptomatic VTE incidence.

Results

10,532 patients, median age 44 (IQR 28 to 62), 68% male, 89% blunt mechanism of injury, with a median Injury Severity Score (ISS) of 12 (IQR 9 to 19), were included in the study. 8646 (82%) of patients received only sCP, whereas 1886 (18%) patients received sCP+A. The sCP+A cohort displayed a higher median ISS compared with sCP (13 vs 11; p<0.01). The overall median time of sCP initiation was hospital day 1 (IQR 0.8 to 2) and the median day for aspirin initiation was hospital day 3 (IQR 1 to 6) for the sCP+A cohort. 353 patients (3.4%) developed symptomatic VTE. Aspirin administration was independently associated with a decreased relative hazard of VTE (HR 0.57; 95% CI 0.36 to 0.88; p=0.01). There were no increased bleeding or wound complications associated with sCP+A (point estimate 1.23, 95% CI 0.68 to 2.2, p=0.50).

Conclusion

In this large trauma cohort, adjunctive aspirin was independently associated with a significant reduction in VTE and may represent a potential strategy to safely mitigate VTE risk in trauma patients. Further prospective studies evaluating the addition of aspirin to heparinoid-based VTE chemoprophylaxis regimens should be sought.

Level of evidence

Level III/therapeutic.

Venous thromboembolic disease in admitted blunt trauma patients: what matters?

BACKGROUND

Venous thromboembolic events (VTE) are a significant cause of morbidity and mortality following traumatic injury. We examined demographic characteristics, chemoprophylaxis, and outcomes of VTE patients with blunt trauma requiring hospitalization.

METHODS

A retrospective review of adult blunt trauma hospitalizations with and without VTE between 2012 and 2019 was conducted. Deaths in the emergency department were excluded. Univariate and multivariable analyses, including machine learning classification algorithms for VTE, were performed.

RESULTS

Of 10,926 admitted adult blunt trauma patients, 177 had VTE events. VTE events occurred at a median of 6 [IQR 3-11] days, with 7.3% occurring within 1 day of admission. VTE patients were more often male, and more often underwent surgery. They had higher injury severity as well as longer intensive care unit and hospital lengths of stay. While VTE occurred throughout the spectrum of injury severity, 27.7% had low injury severity (ISS < = 9). In multivariable analyses, both heparin and enoxaparin had reduced adjusted odds ratios for VTE.

CONCLUSION

Approximately 7.3% of VTE events occurred within one day of admission. A substantial proportion of VTE events occurred in patients with low injury severity (ISS < = 9). Subcutaneous unfractionated heparin and enoxaparin chemoprophylaxis were both inversely associated with VTE. These findings underscore the need for vigilance for VTE identification in blunt trauma patients throughout their hospitalization and VTE prevention efforts.

Is There a Role for Anti-factor Xa Activity Assay in Venous Thromboembolism Prophylaxis Management Among Orthopaedic Trauma Patients? Systematic Review and Meta-analysis

OBJECTIVES

To determine the effect of anti-factor Xa assay dosing of low-molecular-weight heparin (LMWH) on rates of venous thromboembolism (VTE), deep vein thrombosis (DVT), pulmonary embolism (PE), bleeding, and mortality among orthopaedic trauma patients.

DATA SOURCES

PubMed/MEDLINE, Embase, Ovid, Cochrane Central Register of Controlled Trials (CENTRAL), clinicaltrials.gov , and Scopus were systematically searched from inception of the database to 2021.

STUDY SELECTION

Prospective, retrospective, and randomized controlled trial studies were included if they compared rates of VTE, DVT, PE, bleeding, and/or mortality between orthopaedic trauma patients receiving anti-factor Xa-based LMWH dosing and those receiving standard dosing.

DATA EXTRACTION

Two independent reviewers screened titles and abstracts for eligibility. Study characteristics including study design, inclusion criteria, and intervention were extracted.

DATA SYNTHESIS

Meta-analysis was performed using pooled proportion of events (effect size) with 95% confidence intervals. A random-effects model was used. Heterogeneity was quantified by Higgins I 2 . Heterogeneity and variability between subgroups indicated differences in the pooled estimate represented by a P -value.

RESULTS

Six hundred eighty-five studies were identified, and 10 studies including 2870 patients were included. In total, 30.3% and 69.7% received an adjusted and nonadjusted dose of LMWH, respectively. The rate of VTE and DVT were significantly lower in the anti-factor Xa-adjusted cohort, whereas there was no statistically significant difference in rates of PE, bleeding, or mortality between the cohorts.

CONCLUSIONS

This systematic review and meta-analysis demonstrates that anti-factor Xa activity assay dosing of LMWH among orthopaedic trauma patients leads to a reduction in overall DVT rates, although not PE rates, without an increased risk of bleeding events.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Evaluation of a novel blood volume-based enoxaparin dosing guideline for venous thromboembolism prophylaxis in trauma patients

PURPOSE

Fixed-dose and body mass index (BMI)-based enoxaparin regimens provide inadequate venous thromboembolism (VTE) prophylaxis for many trauma patients. The purpose of this study was to evaluate the effectiveness of a novel blood volume (BV)-based enoxaparin guideline vs a historical BMI-based guideline for VTE prophylaxis in trauma patients.

METHODS

This was a retrospective pre/post study completed at a large academic level 1 trauma center. All adult trauma patients admitted from October through December 2019 and August through October 2020 who received prophylactic enoxaparin per guideline were included. The BV dosing was as follows: patients with a BV of 3 to 4.9 L received enoxaparin 30 mg every 12 hours, those with a BV of 5 to 6.9 L received 40 mg every 12 hours, and those with a BV of ≥7 L received 60 mg every 12 hours. The primary outcome was the percentage of patients who attained a target anti-factor Xa (anti-Xa) postdosing level at the first steady-state assessment (0.2 to 0.5 IU/mL).

RESULTS

A total of 241 patients (99 for the BMI group and 142 for the BV group) were included. The study groups had a median age of 38 vs 42 years, a mean BMI of 27.4 vs 27.7 kg/m2, and a mean BV of 5.1 vs 5.1 L, respectively. A total of 63 patients (62.6%) in the BMI group attained target anti-Xa levels compared to 115 patients (81%) in the BV group (P = 0.008). In multivariate regression, the BV-based guideline was the only variable associated with attainment of target anti-Xa levels (adjusted odds ratio, 2.02; P = 0.01). Clinically relevant bleeding and VTE rates were similar between the groups.

CONCLUSION

Dosing prophylactic enoxaparin using a BV-based dosing guideline significantly increased attainment of target anti-Xa levels.

Rate of prophylactic anti-Xa achievement and impact on venous thromboembolism following oncologic hepato-pancreatico-biliary surgery: A prospective cohort study

BACKGROUND

Hepato-pancreatico-biliary (HPB) patients experience competing risk of venous thromboembolism (VTE) and bleeding. We sought to evaluate the effect of anti-Xa levels on VTE and bleeding, and to characterize factors associated with subprophylaxis.

METHODS

This prospective cohort study evaluated adult HPB surgical patients; cohorts were described by anti-Xa levels as subprophylactic (<0.2 IU/mL), prophylactic (0.2-0.5 IU/mL), and supraprophylactic (>0.5 IU/mL). Primary outcome evaluated bleeding and VTE complications. Secondary outcomes evaluated factors associated with subprophylaxis.

RESULTS

We included 157 patients: 68 (43.6%) attained prophylactic anti-Xa and 89 (56.7%) were subprophylactic. Subprophylactic patients experienced more VTE compared to prophylactic patients (6.9% vs 0%; p = 0.028) without differences in bleeding complications (14.6% vs 5.9%; p = 0.081). Factors associated with subprophylactic anti-Xa included female sex (OR 2.90, p = 0.008), and Caprini score (OR 1.30, p = 0.035). Enoxaparin was protective against subprophylaxis compared to tinzaparin (OR 0.43, p = 0.029).

CONCLUSIONS

Many HPB patients have subprophylactic anti-Xa levels, placing them at risk of VTE. Enoxaparin may be preferential, however, studies evaluating optimized prophylaxis are needed.

Efficacy and Safety of Anti-Xa-Guided Versus Fixed Dosing of Low Molecular Weight Heparin for Prevention of Venous Thromboembolism in Trauma Patients: A Systematic Review and Meta-Analysis

PURPOSE

Trauma patients are at high risk of venous thromboembolism (VTE). We summarize the comparative efficacy and safety of anti-Xa-guided versus fixed dosing for low molecular weight heparin (LMWH) for the prevention of VTE in adult trauma patients.

METHODS

We searched Medline and Embase from inception through June 1, 2022. We included randomized controlled trials or observational studies comparing anti-Xa-guided versus fixed dosing of LMWH for thromboprophylaxis in adult trauma patients. We incorporated primary data from 2 large observational cohorts. We pooled effect estimates using a random-effects model. We assessed risk of bias using the ROBINS-I tool for observational studies and assessed certainty of findings using GRADE methodology.

RESULTS

We included 15 observational studies involving 10,348 patients. No randomized controlled trials were identified. determined that, compared to fixed LMWH dosing, anti-Xa-guided dosing may reduce deep vein thrombosis [adjusted odds ratio (aOR); 0.52, 95% CI: 0.40-0.69], pulmonary embolism (aOR: 0.48, 95% CI: 0.30-0.78) or any VTE (aOR: 0.54, 95% CI: 0.42-0.69), though all estimates are based on low certainty evidence. There was an uncertain effect on mortality (aOR: 1.06, 95% CI: 0.85-1.32) and bleeding events (aOR: 0.84, 95% CI: 0.50-1.39), limited by serious imprecision. We used several sensitivity and subgroup analyses to confirm the validity of our assumptions.

CONCLUSION

Anti-Xa-guided dosing may be more effective than fixed dosing for prevention of deep vein thrombosis, pulmonary embolism, and VTE for adult trauma patients. These promising findings justify the need for a high-quality randomized study with the potential to deliver practice changing results.

Approaches for optimizing venous thromboembolism prevention in injured patients: Findings from the consensus conference to implement optimal venous thromboembolism prophylaxis in trauma

ABSTRACT

Venous thromboembolism (VTE) is a major issue in trauma patients. Without prophylaxis, the rate of deep venous thrombosis approaches 60% and even with chemoprophylaxis may be nearly 30%. Advances in VTE reduction are imperative to reduce the burden of this issue in the trauma population. Novel approaches in VTE prevention may include new medications, dosing regimens, and extending prophylaxis to the postdischarge phase of care. Standard dosing regimens of low-molecular-weight heparin are insufficient in trauma, shifting our focus toward alternative dosing strategies to improve prophylaxis. Mixed data suggest that anti-Xa-guided dosage, weight-based dosing, and thromboelastography are among these potential strategies. The concern for VTE in trauma does not end upon discharge, however. The risk for VTE in this population extends well beyond hospitalization. Variable extended thromboprophylaxis regimens using aspirin, low-molecular-weight heparin, and direct oral anticoagulants have been suggested to mitigate this prolonged VTE risk, but the ideal approach for outpatient VTE prevention is still unclear. As part of the 2022 Consensus Conference to Implement Optimal Venous Thromboembolism Prophylaxis in Trauma, a multidisciplinary array of participants, including physicians from multiple specialties, pharmacists, nurses, advanced practice providers, and patients met to attack these issues. This paper aims to review the current literature on novel approaches for optimizing VTE prevention in injured patients and identify research gaps that should be investigated to improve VTE rates in trauma.

Proceedings from the 2022 Consensus Conference to Implement Optimal Venous Thromboembolism Prophylaxis in Trauma

ABSTRACT

On May 4 and 5, 2022, a meeting of multidisciplinary stakeholders in the prevention and treatment of venous thromboembolism (VTE) after trauma was convened by the Coalition for National Trauma Research, funded by the National Heart, Lung, and Blood Institute of the National Institutes of Health, and hosted by the American College of Surgeons in Chicago, Illinois. This consensus conference gathered more than 40 in-person and 80 virtual attendees, including trauma surgeons, other physicians, thrombosis experts, nurses, pharmacists, researchers, and patient advocates. The objectives of the meeting were twofold: (1) to review and summarize the present state of the scientific evidence regarding VTE prevention strategies in injured patients and (2) to develop consensus on future priorities in VTE prevention implementation and research gaps.To achieve these objectives, the first part of the conference consisted of talks from physician leaders, researchers, clinical champions, and patient advocates to summarize the current state of knowledge of VTE pathogenesis and prevention in patients with major injury. Video recordings of all talks and accompanying slides are freely available on the conference website ( https://www.nattrauma.org/research/research-policies-templates-guidelines/vte-conference/ ). Following this curriculum, the second part of the conference consisted of a series of small-group breakout sessions on topics potentially requiring future study. Through this process, research priorities were identified, and plans of action to develop and undertake future studies were defined.The 2022 Consensus Conference to Implement Optimal VTE Prophylaxis in Trauma answered the National Trauma Research Action Plan call to define a course for future research into preventing thromboembolism after trauma. A multidisciplinary group of clinical champions, physicians, scientists, and patients delineated clear objectives for future investigation to address important, persistent key knowledge gaps. The series of papers from the conference outlines the consensus based on the current literature and a roadmap for research to answer these unanswered questions.

Adjusted versus fixed doses of LMWHs in trauma patients: A systematic review and meta-analysis

PURPOSE

Venous thromboembolism (VTE) causes significant morbidity and mortality in patients with traumatic injuries, despite thromboprophylaxis. To decrease both thrombotic and bleeding risks, some authors suggest adjusting the thromboprophylactic doses of low-molecular-weight heparins (LMWH), in particular according to body weight at treatment initiation or to changes in anti-factor Xa level during treatment. Our objective was to estimate in trauma patients the efficacy and safety of such adjustments, compared with the conventional strategy of fixed-dose LMWH thromboprophylaxis.

SOURCE

A systematic review and a meta-analysis were conducted to identify and assess randomised control trials and observational studies with prospective enrolment that included trauma patients and compared adjustment of LMWH thromboprophylaxis versus no adjustment. The primary and secondary endpoints were VTE and bleeding, respectively. The Odds Ratio (OR) and 95% Confidence Interval (95% CI) were calculated using the Mantel-Haenszel method.

PRINCIPAL FINDINGS

Nine studies were included in the meta-analysis. No significant reduction in the risk of VTE was observed with adjusted doses of LMWH compared with fixed doses when considering only randomised control trials (OR 1.02 [95% CI, 0.09 to 11.6]) or all trials (OR 0.70 [95% CI, 0.34 to 1.42]). Similarly, there was no significant difference in bleeding risk (OR 1.36, 95% CI 0.59 to 3.10).

CONCLUSION

This meta-analysis shows that, to date, there is no evidence to justify adjusting LMWH doses, in agreement with the recommendations of the American College of Chest Physicians.

Design and Retrospective Application of a Spine Trauma DVT Prophylaxis Protocol on Level 1 Trauma Center Patient Database

STUDY DESIGN

Systematic literature review.

OBJECTIVES

The impact of thromboembolic disease on the morbidity and mortality of patients with acute spinal cord injury is well documented, with rates as high as 67%-100% among untreated patients. The efficacy of mechanical prophylaxis as a stand-alone measure has been questioned, so we sought to determine a safe perioperative window for chemical anticoagulation use after spine surgery. Many surgeons have concerns anticoagulants may cause post-operative hematoma.

METHODS

A systematic literature review was performed, ultimately yielding 13 articles. Based on the existing literature and input from our multidisciplinary institutional trauma committee, a Spine Trauma DVT Prophylaxis Protocol was developed.

RESULTS

Effort was placed to identify cases within our institution in which patients suffered vertebral column fractures and/or spinal cord injuries. Of these 466 vertebral column fractures and/or spinal cord injuries, 4 patients were identified and diagnosed with DVTs while admitted.

CONCLUSIONS

Of these patients, there is a clear dilemma with regard to safety of chemoprophylaxis use versus risk of developing a DVT. Though none of the patients developed a PE, utilizing the protocol would have led to earlier IVC filter placement or initiation of a VTE surveillance protocol in 2 of the patients. Initiation of enoxaparin before surgery in one patient (despite delay of surgical timing) may have avoided his subsequent LUE DVT. Though not appropriate for all clinical scenarios, we are confident that our treatment algorithm will prove beneficial for patient care in avoiding DVTs and helping trauma surgeons with evidence-based clinical decision making.

Association of Changes in Antithrombin Activity Over Time With Responsiveness to Enoxaparin Prophylaxis and Risk of Trauma-Related Venous Thromboembolism

Importance

Venous thromboembolism (VTE) affects 2% to 20% of recovering trauma patients, despite aggressive prophylaxis with enoxaparin. Antithrombin is a primary circulating anticoagulant and crucial component of enoxaparin thromboprophylaxis. Approximately 20% of trauma patients present with antithrombin deficiency (antithrombin activity <80%).

Objective

To examine time-dependent changes in antithrombin activity, responsiveness to enoxaparin, as measured by anti-factor Xa (anti-FXa) levels, and incidence of VTE after severe trauma and to assess the association of ex vivo antithrombin supplementation with patients' sensitivity to enoxaparin prophylaxis.

Design, Setting, and Participants

This single-center, prospective cohort study was performed at a level 1 trauma center between January 7, 2019, and February 28, 2020. Adult trauma patients admitted to the trauma service at high risk for VTE, based on injury pattern and severity, were screened and enrolled. Patients who were older than 70 years, were pregnant, had a known immunologic or coagulation disorder, or were receiving prehospital anticoagulants were excluded.

Exposures

Blood samples were collected on emergency department arrival and daily for the first 8 days of hospitalization.

Main Outcomes and Measures

Patients' antithrombin activity and anti-FXa levels were measured by a coagulation analyzer, and thrombin generation was measured by calibrated automated thrombography. Responsiveness to enoxaparin was assessed by measuring anti-FXa levels 4 to 6 hours after the first daily enoxaparin dose and compared between patients who developed VTE and who did not. In addition, the associations of ex vivo supplementation of antithrombin with plasma anti-FXa levels were assessed.

Results

Among 150 patients enrolled (median [IQR] age, 35 [27-53] years; 37 [24.7%] female and 113 [75.3%] male; 5 [3.3%] Asian, 32 [21.3%] Black, and 113 [75.3%] White; and 51 [34.0%] of Hispanic ethnicity), 28 (18.7%) developed VTE. Patients with VTE had significantly lower antithrombin activity on admission compared with patients without VTE (median [IQR], 91% [79%-104%] vs 100% [88%-112%]; P = .04), as well as lower antithrombin activity on hospital days 5 (median (IQR), 90% [83%-99%] vs 114% [99%-130%]; P = .011), 6 (median [IQR], 97% [81%-109%] vs 123% [104%-134%]; P = .003), 7 (median [IQR], 82% [74%-89%] vs 123% [110%-140%]; P < .001), and 8 (median [IQR], 99% [85%-100%] vs 123% [109%-146%]; P = .011). Anti-FXa levels were significantly lower in patients with VTE vs those without VTE at hospital day 4 (median [IQR], 0.10 [0.05-0.14] IU/mL vs 0.18 [0.13-0.23] IU/mL; P = .006), day 6 (median [IQR], 0.12 [0.08-0.14] IU/mL vs 0.22 [0.13-0.28] IU/mL; P = .02), and day 7 (median [IQR], 0.11 [0.08-0.12] IU/mL vs 0.21 [0.13, 0.28] IU/mL; P = .002). Multivariable analyses found that for every 10% decrease in antithrombin activity during the first 3 days, the risk of VTE increased 1.5-fold.

Conclusions and Relevance

The results of this cohort study suggest that after severe trauma, antithrombin deficiency is common and contributes to enoxaparin resistance and VTE. Interventional studies are necessary to determine the efficacy of antithrombin supplementation in the reduction of VTE incidence.

Trauma-induced pulmonary thromboembolism: What's update?

Trauma-induced pulmonary thromboembolism is the second leading cause of death in severe trauma patients. Primary fibrinolytic hyperactivity combined with hemorrhage and consequential hypercoagulability in severe trauma patients create a huge challenge for clinicians. It is crucial to ensure a safe anticoagulant therapy for trauma patients, but a series of clinical issues need to be answered first, for example, what are the risk factors for traumatic venous thromboembolism? How to assess and determine the status of coagulation dysfunction of patients? When is the optimal timing to initiate pharmacologic prophylaxis for venous thromboembolism? What types of prophylactic agents should be used? How to manage the anticoagulation-related hemorrhage and to determine the optimal timing of restarting chemoprophylaxis? The present review attempts to answer the above questions.

Relationship Between Anti-Xa Level Achieved with Prophylactic Low-Molecular Weight Heparin and Venous Thromboembolism in Trauma Patients: A Systematic Review and Meta-Analysis

BACKGROUND

Trauma patients have simultaneously high venous thromboembolism (VTE) and bleeding risk. Optimal chemoprophylaxis regimens remain unclear. This study aims to answer three questions for trauma patients. Is there any association between anti-Xa and VTE? Does dose adjustment improve prophylactic anti-Xa rates? Does dose adjustment improve anti-Xa adequacy and VTE compared to standard dosing?

METHODS

Systematic search of MEDLINE, Embase, Scopus, and Web of Science occurred in May 2021.Two author review included trauma studies that: evaluated low molecular weight heparin chemoprophylaxis, reported anti-Xa level, and evaluated ≥1 outcome. Data was dually extracted and estimated effects were calculated using RevMan 5.4 applying the Mantel-Haenszel method. Analysis #1 compared patients with peak anti-Xa ≥ 0.2 IU/ml or trough ≥0.1 IU/ml to those with lower anti-Xa using VTE as the primary outcome. Analysis #2 reported the effect of dose adjustment on anti-Xa. Analysis #3 compared standard dosing to dose adjustment with the primary outcome being anti-Xa adequacy; secondary outcomes were VTE, pulmonary embolism, and bleeding complications.

RESULTS

3401 studies were evaluated with 24 being included (19 retrospective studies, 5 prospective studies). In analysis #1, achieving adequate anti-Xa was associated with reduced odds of VTE (4.0% to 3.1%, OR 0.52, p = 0.03). Analysis #2 demonstrated that 768 (75.3%) patients achieved prophylactic anti-Xa with adjustment protocols.Analysis three suggested that dose adjusted chemoprophylaxis achieves prophylactic anti-Xa more frequently (OR 4.05, p = 0.007) but without VTE (OR 0.72, p = 0.15) or PE (OR 0.48, p = 0.10) differences. In subgroup analysis, anti-Xa dose adjustment also suggested no VTE reduction (OR 0.68, p = 0.08).

CONCLUSIONS

Patients with higher anti-Xa levels are less likely to experience VTE, and anti-Xa guided chemoprophylaxis increases anti-Xa adequacy. However, dose adjustment, including anti-Xa guided dosing, may not reduce VTE.

LEVEL OF EVIDENCE

Level IV; Systematic Review Meta-Analysis.

Complications Associated with Administration of Post-operative Weight-Based Enoxaparin in Orthopaedic Trauma Patients

Background

In orthopedic-specific patients, limited evidence exists in regard to prophylactic weight-based enoxaparin dosing in the obese population. We examined the clinical outcomes of administering weight-based enoxaparin to obese orthopedic trauma patients.

Methods

This retrospective study involved 679 patients who underwent orthopedic trauma surgery and were admitted from 1/2016 to 6/2020 at a single institution. Of those patients, 156 patients met our inclusion criteria. Inclusion criteria included BMI>35 kg/m² and received weight-based enoxaparin post-operatively (defined as any singular dose >40 mg at any time). Blood transfusion, documented hematoma, deep vein thrombosis (DVT), and return visits to the OR after the administration of weight-based enoxaparin were the primary endpoints assessed. Age, BMI, weight, injury severity score (ISS), sex, post-operative time to the first dose of enoxaparin, the total daily dose of enoxaparin, operating room (OR) blood loss, OR time, patient co-morbidities, and pre/post-operative hemoglobin were evaluated for a potential relationship with the primary endpoints.

Results

One hundred and eighty-five surgeries were performed on a total of 156 patients. Thirty-six of the 185 (19%) surgeries required post-operative blood transfusion after weight-based enoxaparin was given. Higher ISS score, lower pre-operative hemoglobin, and lower post-operative hemoglobin were significant predictors of blood transfusion. Only increased post-operative time to the first dose of enoxaparin was significantly associated with DVT formation. Thirteen of the 156 patients (8.3%) had a post-operative hematoma after administration of enoxaparin, and four of the 13 patients required return to the OR for bleeding complications. ISS was the only significant predictor of post-operative hematoma formation.

Conclusion

Patients with a higher injury severity score are at an increased risk of adverse bleeding and may benefit from lower doses of enoxaparin administered earlier post-operatively.

Comparison of Anti-factor Xa Levels in Female and Male Patients with Obesity After Enoxaparin Application for Thromboprophylaxis

Purpose

Venous thromboembolic events (VTEs) are common complications after bariatric surgery, and enoxaparin is commonly used to prevent VTEs. The risk for VTEs is sex-specific. Whether enoxaparin application results in similar anti-factor Xa activities (aFXa) in males and females with obesity remains to be determined. We investigated whether our dosage regimen of enoxaparin resulted in similar serum aFXa levels in female and male patients undergoing bariatric surgery.

Materials and Methods

We administered enoxaparin twice daily in patients undergoing bariatric surgery. Patients with a body mass index (BMI) > 60 kg/m² (n = 11) received 60 mg enoxaparin (group 2), and patients with lower BMI (n = 86) received 40 mg per dose (group 1). Peak aFXa levels were measured 3 days after surgery. The primary outcome was the aFXa level. As a secondary outcome, we detected VTEs and major bleeding events and explored the possible influencing factors of aFXa.

Results

Women had higher aFXa than men, but after matching for anthropometric values, the two groups were similar (females: 0.17 ± 0.08 U/ml; males: 0.18 ± 0.08 U/ml). Linear regression revealed a moderate relationship between weight and aFXa levels. The 3-month follow-up was attended by 94.9%, at which one patient had pulmonary embolism.

Conclusion

Individual enoxaparin dosage regimens for men and women do not seem to be required. Weight-based dosing regimen seems to be a more reasonable choice.

Graphical abstract

Monitoring of Enoxaparin during Hemodialysis Covered by Regional Citrate Anticoagulation in Acute Kidney Injury: A Prospective Cohort Study

Background: Current guidelines recommend the monitoring of anti-factor Xa (anti-Xa) levels to avoid an accumulation of low-molecular-weight heparins in patients with acute kidney injury, but there is no evidence on how to proceed with such monitoring during continuous renal replacement therapy. Against this background, we investigated the potential accumulation of enoxaparin administered subcutaneously for venous thromboembolism prophylaxis in critically ill patients during continuous renal replacement therapy covered by regional citrate anticoagulation. Methods: Anti-Xa levels were measured at baseline (≤12 h before renal replacement therapy) and on three consecutive days (A to C) when enoxaparin had reached trough levels. Supplementary testing included modified assays of rotational thromboelastometry known to be highly sensitive for low-molecular-weight heparins. Results: The 16 men and 13 women included were adults comparable in age, body mass index, thromboembolism risk assessment, and clinical severity of the disease. Throughout the four examinations, the median trough levels of anti-Xa remained below the detection limit of the test (<0.1 IU mL⁻¹), with interquartile ranges of <0.1 to 0.14 IU mL⁻¹ at baseline and <0.1 to 0.16 IU mL⁻¹ on days A/B/C. All rotational thromboelastometry parameters of clot initiation and clot formation dynamics did not significantly change from baseline to day C. Conclusions: Neither anti-Xa levels nor modified assays of rotational thromboelastometry revealed any accumulation of enoxaparin administered for thromboprophylaxis during continuous renal replacement therapy covered by regional citrate anticoagulation. Although generally recommended in patients with acute kidney injury, monitoring of anti-Xa levels should be questioned in this defined setting.

Venous Thromboembolism Chemoprophylaxis in Trauma and Emergency General Surgery Patients: A Systematic Review

BACKGROUND

Appropriate venous thromboembolism (VTE) chemoprophylaxis in trauma and emergency general surgery (EGS) patients is crucial.

OBJECTIVE

The purpose of this study is to review the recent literature and offer recommendations for VTE chemoprophylaxis in trauma and EGS patients.

METHODS

We conducted a literature search from 2000 to 2021 for articles investigating VTE chemoprophylaxis in adult trauma and EGS patients. This study was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines.

RESULTS

Our search resulted in 34 articles. Most studies showed low-molecular-weight heparin (LMWH) is similar to unfractionated heparin (UFH) for VTE prevention; however, LMWH was more commonly used. Adjusted chemoprophylaxis dosing did not change the VTE rate but the timing did. Direct oral anticoagulants (DOACs) have been shown to be safe and effective in trauma and traumatic brain injury (TBI)/spinal cord injury (SCI). Studies showed VTE prophylaxis in EGS can be inconsistent and improves with guidelines that lower VTE events.

CONCLUSIONS

There may be no benefit to receiving LMWH over UFH in trauma patients. In addition, different drugs under the class of LMWH do not change the incidence of VTE. Adjusted dosing of enoxaparin does not seem to affect VTE incidence. The use of DOACs in the trauma TBI and SCI setting has been shown to be safe and effective in reducing VTE. One important consideration with VTE prophylaxis may be the timing of prophylaxis initiation, specifically as it relates to TBI, with a higher likelihood of developing VTE as time progresses. EGS patients are at a high risk of VTE. Improved compliance with clinical guidelines in this population is correlated with decreased thrombotic events.

Fixed-dose enoxaparin provides efficient DVT prophylaxis in mixed ICU patients despite low anti-Xa levels: A prospective observational cohort study

BACKGROUND

Deep vein thrombosis (DVT) is a serious but preventable complication of critical illness with a reported incidence from 4 to 17%. Anti-Xa activity in critically ill patients achieved with standard dosing of low-molecular-weight heparins (LMWH) is often below the target of 0.2-0.5 IU/mL. However, the clinical significance of this finding is unclear. The quality of thromboprophylaxis also strongly impacts the incidence of DVT. We performed a prospective observational study to evaluate the incidence of DVT in a mixed medical-surgical-trauma intensive care unit (ICU) using a thromboprophylaxis protocol with a fixed dose of enoxaparin. We also explored the relation between DVT incidence and anti-Xa activity.

METHOD

All consecutive patients with expected ICU stay ≥72 hours and without evidence of DVT upon admission were included. They underwent ultrasound screening for DVT twice a week until ICU discharge, death, DVT or pulmonary embolism. Peak anti-Xa activity was measured twice a week. Patients received 40 mg of enoxaparin subcutaneously (60 mg in obese, 20 mg in case of renal failure). Graduated compression stockings were used in case of LMWH or another anticoagulant contraindication.

RESULTS

A total of 219 patients were enrolled. We observed six cases of DVT (incidence of 2.7%). The agreement between expected and delivered DVT prophylaxis was 94%. Mean peak anti-Xa activity level was 0.24 (SD, 0.13) IU/mL. There was no significant difference in anti-Xa activity in DVT and non-DVT group.

CONCLUSION

A low incidence of DVT was achieved with meticulous adherence to the standard prophylactic protocol. The low incidence of DVT was observed despite low levels of anti-Xa activity. Our findings suggest that enoxaparin dose adjustment based on regular monitoring of anti-Xa activity is unlikely to result in further reduction of DVT incidence in a mixed ICU population.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03286985.

Impact of antithrombin III and enoxaparin dosage adjustment on prophylactic anti-Xa concentrations in trauma patients at high risk for venous thromboembolism: a randomized pilot trial

The impact of antithrombin III activity (AT-III) on prophylactic enoxaparin anti-factor Xa concentration (anti-Xa) is unknown in high-risk trauma patients. So too is the optimal anti-Xa-adjusted enoxaparin dosage. This prospective, randomized, pilot study sought to explore the association between AT-III and anti-Xa goal attainment and to preliminarily evaluate two enoxaparin dosage adjustment strategies in patients with subprophylactic anti-Xa. Adult trauma patients with Risk Assessment Profile (RAP) ≥ 5 prescribed enoxaparin 30 mg subcutaneously every 12 h were eligible. AT-III and anti-Xa were drawn 8 h after the third enoxaparin dose and compared between patients with anti-Xa ≥ 0.1 IU/mL (goal; control group) or anti-Xa < 0.1 IU/mL (subprophylactic; intervention group). The primary outcome was difference in baseline AT-III. Subsequently, intervention group patients underwent 1:1 randomization to either enoxaparin 40 mg every 12 h (up to 50 mg every 12 h if repeat anti-Xa < 0.1 IU/mL) (enox12) or enoxaparin 30 mg every 8 h (enox8) with repeat anti-Xa assessments. The proportion of patients achieving goal anti-Xa after dosage adjustment were compared. A total of 103 patients were included. Anti-Xa was subprophylactic in 50.5%. Baseline AT-III (median [IQR]) was 87% [80-98%] in control patients versus 82% [71-96%] in intervention patients (p = 0.092). Goal trough anti-Xa was achieved on first assessment in 38.1% enox12 versus 50% enox8 patients (p = 0.67), 84.6% versus 53.3% on second assessment (p = 0.11), and 100% vs. 54.5% on third trough assessment (p = 0.045). AT-III activity did not differ between high-risk trauma patients with goal and subprophylactic enoxaparin anti-Xa concentrations, although future investigation is warranted. Enoxaparin dose adjustment rather than frequency adjustment may be associated with a higher proportion of patients achieving goal anti-Xa over time.

A Weight- and Anti-Xa-Guided Enoxaparin Dosing Protocol for venous thromboembolism Prophylaxis in intensive care unit Trauma Patients

BACKGROUND

Trauma patients are high risk for venous thromboembolism (VTE) and the optimal dosing strategy for prophylactic enoxaparin remains unknown. The purpose of this quality improvement project was to evaluate a weight-based and anti-Xa-guided enoxaparin dosing protocol in intensive care unit (ICU) trauma patients and to determine if the protocol led to reduced clinical VTE rates.

MATERIALS AND METHODS

Adult trauma patients admitted for ≥ 48 hours to our surgical or neurosurgical ICUs who received ≥ 3 consecutive weight-based enoxaparin doses were eligible for inclusion into this pre-post implementation cohort study. Enoxaparin 30 mg every 12 hours was used for weight 50 to 100 kg and body mass index (BMI) < 40 kg/m² and enoxaparin 40 mg every 12 hours for weight ≥ 100 kg or BMI ≥ 40 kg/m². PRE cohort patients did not routinely receive anti-Xa level monitoring, while in the POST cohort, dosing was subsequently titrated to peak anti-Xa levels of 0.2 to 0.4 IU/mL.

RESULTS

A total of 110 and 113 patients were included in the PRE and POST cohorts, respectively. Clinical VTE rates were similar between groups. In the POST cohort, 75% of patients achieved goal anti-Xa levels without dose titrations, while 12% of higher weight patients and 9.1% of lower weight patients required adjustment. When comparing weight quartiles, patients > 100 kg were more likely to have sub-prophylactic anti-Xa levels than those ≤ 69 kg.

CONCLUSIONS

Our enoxaparin dosing protocol was safe and frequently achieved initial anti-Xa levels within goal, indicating that weight-based dosing alone may be sufficient. However, patients > 100 kg may benefit from anti-Xa monitoring as they are highest risk for sub-prophylactic levels despite higher initial enoxaparin dosing.

Timely Venous Thromboembolism Prophylaxis in Trauma: A Team Approach to Process Improvement

Venous thromboembolism is a significant complication in trauma. Multisystem injury, advancing age, surgery, and blood transfusion all contribute to the risk of venous thromboembolism in trauma patients. Our Level I trauma center was identified as an outlier with compliance in timely venous thromboembolism prophylaxis in the Michigan Trauma Quality Improvement Program, a statewide collaborative for improving trauma care. The purpose of this study was to provide an evaluation of a performance improvement project to increase the timely administration of venous thromboembolism prophylaxis in admitted trauma patients. Using a Plan-Do-Study-Act method of quality improvement, we initiated a focused, goal-directed team approach that emphasized education, tracking, and feedback. This approach resulted in improved and sustained compliance rates. Resolute focus, audit, and feedback moved our center from a low- to high-performing center for timely venous thromboembolism prophylaxis.

Venous thromboembolism prophylaxis in the trauma intensive care unit: an American Association for the Surgery of Trauma Critical Care Committee Clinical Consensus Document

Venous thromboembolism (VTE) is a potential sequela of injury, surgery, and critical illness. Patients in the Trauma Intensive Care Unit are at risk for this condition, prompting daily discussions during patient care rounds and routine use of mechanical and/or pharmacologic prophylaxis measures. While VTE rightfully garners much attention in clinical patient care and in the medical literature, optimal strategies for VTE prevention are still evolving. Furthermore, trauma and surgical patients often have real or perceived contraindications to prophylaxis that affect the timing of preventive measures and the consistency with which they can be applied. In this Clinical Consensus Document, the American Association for the Surgery of Trauma Critical Care Committee addresses several practical clinical questions pertaining to specific or unique aspects of VTE prophylaxis in critically ill and injured patients.

Prevention, diagnosis, and management of venous thromboembolism in the critically ill surgical and trauma patient

PURPOSE OF REVIEW

Venous thromboembolism (VTE), which encompasses deep vein thrombosis and pulmonary embolism, is common among trauma patients and critically ill surgical patients admitted to the ICU. Critical care surgical patients are at an extremely high risk for VTE and the related morbidity and mortality associated with it. The present review aims to provide an overview of the importance of identifying risk factors, prescribing effective prohylaxis, accurate diagnosis, and timely appropriate treatment for trauma and critically ill surgical patients with VTE in the ICU.

RECENT FINDINGS

VTE is a healthcare burden among critically ill surgical patients that is mostly preventable through adherence to prophylactic protocols that aim to recognize VTE risk factors while simultaneously providing guidance to appropriate timing and administration prophylaxis regimens. Newer pharmacologic therapies for prophylaxis and treatment, diagnostic modalities, and indications for therapy of VTE have continued to evolve.

SUMMARY

Critical care surgical and trauma patients represent a population that are at a heightened risk for VTE and associated complications. Appropriate screening, prevention strategies, accurate diagnosis, and timely administration of appropriate treatment must be utilized to reduce morbidity and mortality.

Venous thromboembolism in burns patients: Are we underestimating the risk and underdosing our prophylaxis?

BACKGROUND

Burns patients exhibit all factors of Virchow's triad and are thus at high theoretical risk of venous thromboembolism (VTE). At our tertiary referral burns unit, a standard dose of low molecular weight heparin, which acts primarily by inhibiting Factor Xa, is given for thromboprophylaxis. However, the pharmacokinetics of enoxaparin are altered following a burn injury, and thus burns patients are likely underdosed on their thromboprophylaxis. The objectives of this study were to determine the incidence and risk factors for VTE among burns patients at the Victorian Adult Burns Service (VABS) and to determine the adequacy of the current enoxaparin thromboprophylaxis regimen through measurement of anti-factor Xa (AFXa) levels and comparison with established reference ranges.

METHODS

This study consisted of two parts. In part 1, the Burns Registry of Australia and New Zealand (BRANZ) was reviewed for cases of VTE in burns patients admitted to the VABS from 2013 - 2018. Part 2 was a prospective study that determined peak and trough AFXa levels in patients admitted to the VABS with >10% total body surface area (TBSA) burns.

RESULTS

Part 1. Totally, 1,475 patients were admitted to the VABS between 2013 - 2018. There were 20 cases of VTE (1.36%). Percent TBSA of burn (OR = 1.04, 95% CI: 1.03 - 1.06), full thickness burns (OR = 2.78, 95% CI: 1.15 - 6.73), ICU admission (OR = 15.08, 95% CI: 5.01 - 45.44), mechanical ventilation (OR = 10.62, 95% CI: 4.05 - 27.91), operative procedures (OR = 1.43, 95% CI: 1.29 - 1.59), and a longer hospital stay (OR = 1.05, 95% CI: 1.04 - 1.07) were all associated with an increased VTE risk. Part 2. A total of 20 participants with >10% TBSA burns were recruited to the prospective study. Peak anti Factor Xa (AFXa) levels were measured for all 20 participants with 15% recording an initial prophylactic peak AFXa level within reference range. Upon subsequent measurements, 50% of participants reached a prophylactic peak AFXa level. Trough AFXa levels were measured for 17 participants with no participant recording an initial or subsequent trough AFXa level at or above the prophylactic threshold.

CONCLUSION

Our study demonstrates a high incidence of VTE among burns patients at the VABS, especially among the major burns patients, and a thromboprophylaxis protocol that is ineffective in achieving prophylactic levels of AFXa level. The evidence suggests a need to evaluate different dosing protocols among burns patients in order to improve AFXa levels, with the aim of decreasing incidence of VTE in high-risk patients.

Venous thromboembolism in critically ill COVID-19 patients receiving prophylactic or therapeutic anticoagulation: a systematic review and meta-analysis

Many aspects of care such as management of hypercoagulable state in COVID-19 patients, especially those admitted to intensive care units is challenging in the rapidly evolving pandemic of novel coronavirus disease 2019 (COVID-19). We seek to systematically review the available evidence regarding the anticoagulation approach to prevent venous thromboembolism (VTE) among COVID-19 patients admitted to intensive care units. Electronic databases were searched for studies reporting venous thromboembolic events in patients admitted to the intensive care unit receiving any type of anticoagulation (prophylactic or therapeutic). The pooled prevalence (and 95% confidence interval [CI]) of VTE among patients receiving anticoagulant were calculated using the random-effects model. Subgroup pooled analyses were performed with studies reported prophylactic anticoagulation alone and with studies reported mixed prophylactic and therapeutic anticoagulation. We included twelve studies (8 Europe; 2 UK; 1 each from the US and China) in our systematic review and meta-analysis. All studies utilized LMWH or unfractionated heparin as their pharmacologic thromboprophylaxis, either prophylactic doses or therapeutic doses. Seven studies reported on the proportion of patients with the previous history of VTE (range 0-10%). The pooled prevalence of VTE among ICU patients receiving prophylactic or therapeutic anticoagulation across all studies was 31% (95% CI 20-43%). Subgroup pooled analysis limited to studies reported prophylactic anticoagulation alone and mixed (therapeutic and prophylactic anticoagulation) reported pooled prevalences of VTE of 38% (95% CI 10-70%) and 27% (95% CI 17-40%) respectively. With a high prevalence of thromboprophylaxis failure among COVID-19 patients admitted to intensive care units, individualised rather than protocolised VTE thromboprophylaxis would appear prudent at interim.

Elevated eosinophil count is related with lower anti-factor Xa activity in COVID-19 patients

Despite prophylactic anticoagulant treatments, thrombotic complications may develop in patients with coronavirus disease 2019 (COVID-19). This study aimed to evaluate the factors influencing anti-factor Xa activity in COVID-19 patients receiving low molecular weight heparin (LMWH). We prospectively evaluated 80 COVID-19 patients, diagnosed using polymerase chain reaction test, who were admitted to our clinic and administered LMWH; LMWH (enoxaparin) was applied according to the weight, D-dimer levels, and clinical condition of patients. Anti-factor Xa activity in blood, drawn 4 h after the 3rd dose of LMWH, was measured and an activity of < 0.2 IU/mL was considered subprophylactic. Patients were followed up clinically, and anti-factor Xa activity was re-examined before discharge. Groups 1 and 2 included 13 and 67 patients with subprophylactic (mean ± SD: 0.18 ± 0.06) and prophylactic (mean ± SD: 0.43 ± 0.23) anti-factor Xa activity, respectively. The proportion of eosinophils in patients was significantly higher in group 1 than in group 2 (mean ± SD; 2.96 ± 2.55 vs 0.90 ± 1.28; p = 0.001). At the time of discharge, the eosinophilic proportion of patients was significantly higher (eosinophil %, mean ± SD; 3.06 ± 1.49 vs 2.07 ± 1.92; p = 0.001), but the activated partial thromboplastin time was significantly lower (22.34 ± 1.38 vs 24.38 ± 3.58; p = 0.01) in group 1 than in group 2. Of 14 patients with eosinophil content > 4%, 6 were in group 1 ((6/13) 46.2%), while 8 were in group 2 ((8/63) 11.9%); (p = 0.009), and all had a D-dimer level < 1 μg/mL (p = 0.03). ROC analysis for the presence of anticoagulation at subprophylactic level revealed an area under curve of 0.79 (95% CI: 0.64-0.93); p = 0.001). In conclusion; Elevated eosinophil count is related to lower anti-factor Xa activity in patients with COVID-19 receiving LMWH. The clinical significance of the subprophylactic anti-factor Xa activity should be studied in COVID-19 patients (NCT04507282).

The Timing of Symptomatic Pulmonary Embolism in Patients With Nonwarfarin Anticoagulants Following Elective Primary Total Joint Arthroplasty

BACKGROUND

The purpose of this study is to investigate the incidence and timing of postoperative, symptomatic pulmonary embolism (PE) in patients receiving nonwarfarin treatment following primary total joint arthroplasty (TJA), to clarify the appropriate duration of postoperative VTE prophylaxis.

METHODS

We retrospectively reviewed the medical records of 11,148 patients who underwent primary TJA, including total knee arthroplasty and total hip arthroplasty at our institution between January 2012 and March 2019. The median postoperative day of diagnosis of symptomatic PE and the interquartile range for day of diagnosis were determined. Multivariate Cox proportional hazards modeling was used to test the difference of timing for PE based on demographics and comorbidities.

RESULTS

The overall 90-day rate of symptomatic PE was 0.71%. The median day of diagnosis for symptomatic PE was 3 days postoperatively (interquartile range, 2-7 days). Factors showed statistical significance on multivariate analysis in association with earlier timing of PE occurrence in patients with atrial fibrillation, diabetes mellitus, coronary heart disease, and history of stroke.

CONCLUSION

The vast majority of symptomatic PE occurs in the early postoperative period after TJA, and atrial fibrillation, diabetes mellitus, coronary heart disease, and history of stroke were independent factors affecting the timing of symptomatic PE.

Supplementation with antithrombin III ex vivo optimizes enoxaparin responses in critically injured patients

BACKGROUND

The high incidence of venous thromboembolism (VTE) following trauma persists in spite of aggressive thromboprophylaxis strategies. Approximately half of VTE patients do not achieve the recommended anti-FXa response to enoxaparin anticoagulation (0.1-0.4 IU/mL), however, research to explain or correct this phenomenon is lacking. We hypothesized that antithrombin III (AT) deficiency is associated with poor enoxaparin responsiveness in trauma patients that develop VTE which can be reversed through supplementation with AT.

METHODS AND FINDINGS

A retrospective cohort study was performed on plasma collected from trauma patients who did and did not develop pulmonary embolism (PE) as well as healthy volunteers. AT levels, thrombin generation, and anti-FXa levels were measured in the collected plasma at baseline and in response to supplementation with AT concentrate at 120-200% or plasma (30% volume). A total of 54 PE patients and 46 non-PE patients were enrolled in this study for analysis. Compared to healthy volunteers, trauma patients had lower levels of AT, elevated thrombin generation, and lower anti-FXa levels in response to enoxaparin. Moreover, thrombin generation was higher and responses to enoxaparin were lower in patients who developed PE compared to those who did not develop PE. We found that supplementation with AT, but not plasma, increased AT levels and improved enoxaparin-mediated inhibition of thrombin generation.

CONCLUSIONS

Supplementation with AT may provide a novel adjunct therapy to increase the effectiveness of enoxaparin thromboprophylaxis and reduce the incidence of VTE in the trauma population.

The ATLANTIC study: Anti-Xa level assessment in trauma intensive care

OBJECTIVE

To quantify the pharmacodynamic (PD) activity of daily subcutaneous (SC) enoxaparin as venous thromboembolism (VTE) prophylaxis in high-risk trauma patients admitted to the intensive care unit (ICU).

METHODS

This was a prospective observational PD study conducted in the ICU of a state-wide major trauma referral centre. The study cohort included adult patients admitted to the ICU with a high risk of VTE, as defined by at least one of the following: age > 40 years, prior VTE, spinal cord injury (SCI), traumatic brain injury (TBI), major venous injury, pelvic fractures, spinal fractures requiring treatment, severe lower limb injuries, and major surgery >2 h in duration. Standard prophylactic enoxaparin dosing was 40 mg SC daily, unless amended by the treating clinician. Plasma anti-Xa activity was measured approximately 60 min before dosing (trough activity), and at 3-5 h after dosing (peak activity). Target peak and trough activity were defined as >0.2 IU/mL and >0.1 IU/mL respectively. Clinical data including the development of VTE and haemorrhagic complications were collected.

RESULTS

Twenty-five patients were enrolled. Median [IQR] age, weight, and plasma creatinine were 59 years [36,70], 85 kg [76.5,93.5] and 70μmol/L [60.5,109] respectively. Median APACHE III and Injury Severity Score were 54 [42.5,66.5] and 27 [17,34] respectively. Thirteen patients suffered a TBI, in 12 cases surgery extended beyond two hours, and five patients had spinal fractures requiring treatment. Twenty-two patients received enoxaparin 40 mg SC daily, two 60 mg, and one 20 mg. Median peak and trough anti-Xa activity was 0.21 IU/mL [0.125,0.25] and 0.01 IU/mL [0,0.05] respectively. Twelve (12/25; 48%) patients had low peak activity ≤0.2 IU/mL. Twenty-one (21/23; 91%) patients had low trough activity (≤0.1 IU/mL) and in six (6/23; 26%) cases, these were undetectable. Eight (8/25; 32%) patients had documented VTE of whom seven had low trough activity. There were no major haemorrhagic complications.

CONCLUSIONS

In a cohort of high risk critically ill trauma patients receiving daily SC enoxaparin as VTE chemoprophylaxis, measured peak and trough plasma anti-Xa activity was inadequate in a significant proportion. On this basis, further systematic investigation concerning dose optimisation in this patient population appears warranted.

Platelet-derived extracellular vesicles released after trauma promote hemostasis and contribute to DVT in mice

BACKGROUND

Traumatic injury can lead to dysregulation of the normal clotting system, resulting in hemorrhagic and thrombotic complications. Platelet activation is robust following traumatic injury and one process of platelet activation is to release of extracellular vesicles (PEV) that carry heterogenous cargo loads and surface ligands.

OBJECTIVES

We sought to investigate and characterize the release and function of PEVs generated following traumatic injury.

METHODS

PEV content and quantity in circulation following trauma in humans and mice was measured using flow cytometry, size exclusion chromatography, and nanoparticle tracking analysis. PEVs were isolated from circulation and the effects on thrombin generation, bleeding time, hemorrhage control, and thrombus formation were determined. Finally, the effect of hydroxychloroquine (HCQ) on PEV release and thrombosis were examined.

RESULTS

Human and murine trauma results in a significant release of PEVs into circulation compared with healthy controls. These PEVs result in abundant thrombin generation, increased platelet aggregation, decreased bleeding times, and decreased hemorrhage in uncontrolled bleeding. Conversely, PEVs contributed to enhanced venous thrombus formation and were recruited to the developing thrombus site. Interestingly, HCQ treatment resulted in decreased platelet aggregation, decreased PEV release, and reduced deep vein thrombosis burden in mice.

CONCLUSIONS

These data demonstrate that trauma results in significant release of PEVs which are both pro-hemostatic and pro-thrombotic. The effects of PEVs can be mitigated by treatment with HCQ, suggesting the potential use as a form of deep vein thrombosis prophylaxis.

A comparison of different modes of pneumatic compression on muscle tissue oxygenation: An intraparticipant, randomised, controlled volunteer study

Intermittent pneumatic compression (IPC) to the lower limbs is widely used as a mechanical means to prevent deep vein thrombosis in hospitalised patients. Due to a theoretical concern about impairing blood flow, thromboembolic-deterrent stockings and IPC are considered contraindicated for patients with peripheral vascular diseases by some clinicians. This study assessed whether IPC would alter peripheral limb muscle tissue oxygenation (StO2), and whether such changes were different during 10 minutes of sequential and single-compartment compressions. Twenty volunteers were randomised to have their left or right arm treated with a sequential or single-compartment IPC for 10 minutes, using the contralateral arm without compression as an intraparticipant control. After a five-minute wash-out period, the procedure was repeated on the same arm using the alternative mode of IPC. Both hands’ thenar muscles StO2 was monitored every two minutes for 10 minutes using the same near-infrared spectroscopy StO2 monitor. Both sequential (3.5%, 95% confidence intervals (CI) 2.7–4.2; p < 0.001) and single-compartment IPC (1.6%, 95% CI 0.4–2.8; p = 0.039) significantly increased muscle StO2 within 10 minutes compared to no compression; and the increments were higher during sequential compressions compared to during single-compartment compressions (2.1%, 95% CI 0.7–3.5; p = 0.023). This mechanistic study showed that both modes of IPC increased upper limb muscle StO2 compared to no compression, but the StO2 increments were higher with the multiple-chamber sequential compressions mode. Contrary to the theoretical concern that IPC may impair peripheral limb tissue oxygenation, our results showed that IPC actually increases oxygenation of the peripheral limb muscles, especially during the sequential compressions mode.

Determining the impact of culture on venous thromboembolism prevention in trauma patients: A Southwestern Surgical Congress Multicenter trial

INTRODUCTION

Venous thromboembolism (VTE) remains one of the principal causes of morbidity and death in trauma patients that survive the first 24 h. Recent literature on VTE prevention focuses on choice of chemoprophylaxis, specifically unfractionated heparin (UFH) versus low molecular weight heparin (LMWH). This singular focus on a multifactorial process may be inadequate to fully understand the optimal approach to VTE prevention. We hypothesized that variations in care between trauma centers could be used to identify key components of VTE prevention associated with better outcomes.

METHODS

A 50 question survey of VTE management for years 2014-2016 was sent to 15 trauma centers. The survey included: demographics of the trauma centers, type and timing of chemoprophylaxis, ambulation expectations, and complementary services (geriatric trauma service (GTS), mobility teams, physical and occupational therapy (PT/OT)). Each center submitted their American College of Surgeons Trauma Quality Improvement Program (TQIP) Benchmark Report for Spring 2017. TQIP data included: mortality, observed rates of deep vein thrombosis (DVT) and pulmonary embolus (PE), and time to VTE prophylaxis. The survey and TQIP reports were blinded for analysis; descriptive statistics were utilized. The top DVT & PE TQIP performers were used to identify potential aspects of better care on the survey responses. The institutions' DVT and PE rates were then compared for these responses using Wilcoxon-Rank-Sum test.

RESULTS

Fifteen trauma centers (13 Level-1, 2 Level-2) completed the survey; the centers admitted 1050-7200 trauma patients per year (median 3000). The majority of centers were University-affiliated (11 of 15) with general surgery residencies (14 of 15), Acute Care Surgery or Surgical Critical Care Fellowships, (9 of 15) and critical care boarded-surgeons only on-call (9 of 15). Few have geriatric trauma services (3 of 15) or mobility teams (1 of 15). Half the trauma centers have dedicated PT/OT teams for trauma or weekend coverage. With a total of 20,878 TQIP patients analyzed, the average observed DVT and PE rates were 1.27% (range 0.1-5.2%) and 0.68% (range 0-1.6%), respectively. Weekly lower extremity surveillance duplex (2 of 15) increased DVT detection (4.15% vs 0.80%, p = 0.034) but did not decrease PE rates (1.05% vs 0.62%, p = 0.229). Great variance was seen in choice, dosing and timing of chemoprophylaxis: UFH,⁴ LMWH daily,¹ LMWH twice-daily,⁵ LMWH weight-based dosing,⁴ and LMWH anti-Xa dosing.¹ The top 3 performers for DVT and PE all used different types of chemoprophylaxis. These top performers had a prominent culture of mobility: dedicated PT/OT teams for trauma or weekends and an expectation to ambulate 3-times per day. Weekend PT/OT teams were associated with lower DVT rates (median 0.40%, range 0.10-1.10% vs 1.30%, 0.60-5.20%, p = 0.018), and ambulation 3-times per day was associated with lower PE rates (median 0.20%, range 0.00-0.20% vs 0.80%, 0.40-1.60%, p < 0.005).

CONCLUSIONS

Considerable variation in VTE chemoprophylaxis exists among trauma centers. "Best practices" in this area requires further investigation. An expectation of mobility and investment in mobility resources may serve to decrease VTE rates in trauma patients compared to a singular focus on type of chemoprophylaxis administered.