Weight-Based Enoxaparin Achieves Adequate Anti-Xa Levels More Often in Trauma Patients: A Prospective Study

Multicenter study evaluating target attainment of anti-Factor Xa levels using various enoxaparin prophylactic dosing practices in adult trauma patients

STUDY OBJECTIVE

Enoxaparin is standard of care for venous thromboembolism (VTE) prophylaxis in adult trauma patients, but fixed-dose protocols are suboptimal. Dosing based on body mass index (BMI) or total body weight (TBW) improves target prophylactic anti-Xa level attainment and reduces VTE rates. A novel strategy using estimated blood volume (EBV) may be more effective based on results of a single-center study. This study compared BMI-, TBW-, EBV-based, and hybrid enoxaparin dosing strategies at achieving target prophylactic anti-Factor Xa (anti-Xa) levels in trauma patients.

DESIGN

Multicenter, retrospective review.

DATA SOURCE

Electronic health records from participating institutions.

PATIENTS

Adult trauma patients who received enoxaparin twice daily for VTE prophylaxis and had at least one appropriately timed anti-Xa level (collected 3 to 6 hours after the previous dose after three consecutive doses) from January 2017 through December 2020. Patients were excluded if the hospital-specific dosing protocol was not followed or if they had thermal burns with > 20% body surface area involvement.

INTERVENTION

Dosing strategy used to determine initial prophylactic dose of enoxaparin.

MEASUREMENTS

The primary end point was percentage of patients with peak anti-Xa levels within the target prophylactic range (0.2-0.4 units/mL).

MAIN RESULTS

Nine hospitals enrolled 742 unique patients. The most common dosing strategy was based on BMI (43.0%), followed by EBV (29.0%). Patients dosed using EBV had the highest percentage of target anti-Xa levels (72.1%). Multiple logistic regression demonstrated EBV-based dosing was significantly more likely to yield anti-Xa levels at or above target compared to BMI-based dosing (adjusted odds ratio (aOR) 3.59, 95% confidence interval (CI) 2.29-5.62, p < 0.001). EBV-based dosing was also more likely than hybrid dosing to yield an anti-Xa level at or above target (aOR 2.30, 95% CI 1.33-3.98, p = 0.003). Other pairwise comparisons between dosing strategy groups were nonsignificant.

CONCLUSIONS

An EBV-based dosing strategy was associated with higher odds of achieving anti-Xa level within target range for enoxaparin VTE prophylaxis compared to BMI-based dosing and may be a preferred method for VTE prophylaxis in adult trauma patients.

Creatinine Clearance May Predict Goal Enoxaparin Dose in Trauma

BACKGROUND

Guidelines for enoxaparin dosing after trauma recommend an initial dose of 40 mg twice daily for most patients and then adjusting by anti-Xa levels. Previous studies indicated higher enoxaparin doses are necessary with higher levels of creatinine clearance (CrCl). We sought to determine if the goal enoxaparin dose correlates with the admission CrCl to reduce the reliance on measuring anti-Xa levels.

STUDY DESIGN

A retrospective review was conducted of patients admitted to an urban, academic Level 1 trauma center from April 2017 to February 2020. Patients started on enoxaparin who reached goal anti-Xa trough levels were included, and patients were excluded if they did not reach goal anti-Xa levels. Data collection included patient demographics, injury characteristics, admission CrCl, and final enoxaparin dose. CrCl was then correlated with the final enoxaparin dose.

RESULTS

Of 421 patients included, the mean age was 46.6 years and 73% were male. The median goal enoxaparin dose was 40 mg twice daily. The mean CrCl significantly increased with increasing twice-daily doses of enoxaparin (20 mg: 69.2 mL/min; 30 mg: 89 mL/min; 40 mg: 112.8 mL/min; 50 mg: 140.5mL/min; 60 mg: 147.4 mL/min; and 70 mg: 140 mL/min; p < 0.01).

CONCLUSIONS

Admission CrCl may predict the enoxaparin dose required to achieve adequate anti-Xa levels. Our data indicate that CrCls of approximately 70, 90, 110, 140, and 150 mL/min may predict the twice-daily enoxaparin doses of 20, 30, 40, 50, and 60 mg, respectively. CrCl dosing guidance may reduce the time to goal anti-Xa levels and the frequency of anti-Xa measurements. Further research is necessary, and enoxaparin dosing should continue to be monitored by anti-Xa levels.

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.

One size does not fit all: Sex bias in pharmacologic venous thromboembolism prophylaxis

BACKGROUND

The optimal enoxaparin dosing strategy to achieve venous thromboembolism (VTE) prophylaxis in trauma patients remains unclear. Current dosing guidelines often include weight, age, and renal function but still fail to achieve appropriate prophylactic anti-Xa levels in many patients. We hypothesized that additional patient factors influence anti-Xa response to enoxaparin in trauma patients.

METHODS

This is a retrospective review of patients admitted to a Level 1 trauma center for ≥4 days from July 2015 to September 2020, who received enoxaparin VTE prophylaxis per protocol (50-59 kg, 30 mg/dose; 60-99 kg, 40 mg/dose; ≥100 kg, 50 mg/dose; all doses every 12 hours) and had an appropriately timed peak anti-Xa level. Multivariate regression was performed to identify independent predictors of prophylactic anti-Xa levels (0.2-0.4 IU/mL) upon first measurement.

RESULTS

The cohort (N = 1,435) was 76.4% male, with a mean ± SD age of 49.9 ± 20.0 years and a mean ± SD weight of 82.5 ± 20.2 kg (males, 85.2 kg; females, 73.7 kg; p <0.001). Overall, 68.6% of patients (n = 984) had a prophylactic anti-Xa level on first assessment (69.6% of males, 65.1% of females). Males were more likely to have a subprophylactic level than females (22.1% vs. 8.0%, p <0.001), whereas females were more likely to have supraprophylactic levels than males (26.9% vs. 8.3%, p < 0.001). When controlling for creatinine clearance, anti-Xa level was independently associated with dose-to-weight ratio (odds ratio, 0.191 for 0.5 mg/kg; p < 0.001; confidence interval, 0.151-0.230) and female sex (odds ratio, 0.060; p < 0.001; confidence interval, 0.047-0.072). Weight and age were not significant when controlling for the other factors.

CONCLUSION

Male patients have a decreased anti-Xa response to enoxaparin when compared with female patients, leading to a greater incidence of subprophylactic anti-Xa levels in male patients at all dose-to-weight ratios. To improve the accuracy of VTE chemoprophylaxis, sex should be considered as a variable in enoxaparin dosing models.

LEVEL OF EVIDENCE

Therapeutic/Care Management; Level III.

Effect of Delay and Disruption in Venous Thromboembolism Prophylaxis in Trauma Patients: Case-Control Study

BACKGROUND

Trauma patients are at high risk for venous thromboembolism (VTE) and bleeding. The purpose of this study was to characterize percentage of VTE chemoprophylaxis given to trauma patients with and without a VTE.

STUDY DESIGN

This retrospective case-control study evaluated trauma patients admitted to a Level I trauma center. Adult patients were included when hospitalized at least 2 days and had a head abbreviated injury score of 1 or less. Non-VTE patients were matched by decade of life and injury severity score (ISS). The primary outcome was percentage of VTE chemoprophylaxis received over the first 14 days of admission. Descriptive statistics, chi-squared test, Student's t-test, and Cox proportional hazard were used for analysis.

RESULTS

A total of 44 VTE patients were included with 125 matched non-VTE patients. Baseline demographics included age in years (50.7 ± 19.6 vs 49.6 ± 19.4), ISS (18.9 ± 11.3 vs 19 ± 11.6), and lower extremity fracture (54.5% vs 40%), for VTE and non-VTE groups, respectively. The primary outcome of VTE chemoprophylaxis doses given was significantly lower for VTE patients than non-VTE patients (49.3% vs 59.3%, p = 0.0069). Significant predictors of VTE were percentage of VTE chemoprophylaxis doses given (p < 0.0001) and weight (p = 0.0042) based on regression analysis. Notably, there was a 7% decrease in the hazard for VTE for every 1% increase in VTE chemoprophylaxis given.

CONCLUSIONS

Patients who developed VTE were more likely to have delays and disruptions in VTE chemoprophylaxis, even after controlling for age, sex, ISS, lower extremity fractures, and number of operations.

THE EFFICACY OF WEIGHT-BASED ENOXAPARIN DOSING FOR VTE-PROPHYLAXIS IN TRAUMA PATIENTS: A SYSTEMATIC REVIEW AND META-ANALYSIS

BACKGROUND

Trauma patients are at high risk of developing venous thromboembolism (VTE), and standard dosing enoxaparin regimens may be inadequate for prophylaxis. This meta-analysis was performed to clarify the efficacy of alternative dosing regimens for VTE prophylaxis in this high-risk group. The objective of this systematic review was to review the evidence regarding weight-based dosing of enoxaparin for VTE prophylaxis in trauma patients.

METHODS

A systematic database search was undertaken for studies comparing standard vs weight-based dosing of enoxaparin for VTE prophylaxis in adult trauma patients, aged ≥18 years. The primary outcome was the achievement of Anti-Factor Xa (AFXa) levels within the prophylactic range. Secondary outcomes included: sub-prophylactic AFXa levels, supra-prophylactic AFXa levels, VTE incidence and bleeding events. Meta-analysis was conducted using both fixed- and random-effects models, and presented as odds ratios (OR), risk ratios (RR) and risk differences (RD) with 95% confidence intervals (CI).

RESULTS

Four cohort studies were eligible for inclusion. Compared to standard dosing, weight-based enoxaparin prophylaxis dosing was associated with increased odds of prophylactic AFXa levels (OR = 5.85., 95%CI: 3.02-11.30, p < 0.00001) and reduced risk of sub-prophylactic AFXa levels (RR = 3.97, 95%CI: 3.02-5.22, p < 0.00001). Standard dosing was associated with a reduced risk of supra-therapeutic AFXa levels (RR = 0.23, 95%CI: 0.11-0.50, P = 0.0002), but this was not associated with a difference in risk of bleeding events (RD = -0.00, 95%CI: -0.02-0.01, P = 0.55). There was no statistical difference in incidence VTE between the two groups (RD = 0.01, 95%CI: -0.02-0.03, P = 0.64).

CONCLUSIONS

Compared with standard dosing, weight-based enoxaparin dosing regimens are associated with increased odds of prophylactic range AFXa levels. Further investigation is required to determine if this translates into improved VTE prophylaxis and reduced VTE incidence.

LEVEL OF EVIDENCE

Systematic Review, level III.

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.