Assessment of empiric body mass index-based thromboprophylactic dosing of enoxaparin after bariatric surgery: evidence for dosage adjustment using anti-factor Xa in high-risk patients

Incidence of Venous Thromboembolism Based on Caprini Score in Deep Inferior Epigastric Perforator Flap Breast Reconstruction

BACKGROUND

 Deep inferior epigastric perforator (DIEP) flaps are commonly used for autologous breast reconstruction, but reported rates of venous thromboembolism (VTE) are up to 6.8%. This study aimed to determine the incidence of VTE based on preoperative Caprini score following DIEP breast reconstruction.

METHODS

 This retrospective study included patients who underwent DIEP flaps for breast reconstruction between January 1, 2016 and December 31, 2020 at a tertiary-level, academic institution. Demographics, operative characteristics, and VTE events were recorded. Receiver operating characteristic analysis was performed to determine the area under the curve (AUC) of the Caprini score for VTE. Univariate and multivariate analyses assessed risk factors associated with VTE.

RESULTS

 This study included 524 patients (mean age 51.2 ± 9.6 years). There were 123 (23.5%) patients with the Caprini score of 0 to 4, 366 (69.8%) with scores 5 to 6, 27 (5.2%) with scores 7 to 8, and 8 (1.5%) patients with scores >8. Postoperative VTE occurred in 11 (2.1%) patients, at a median time of 9 days (range 1-30) after surgery. VTE incidence by the Caprini score was 1.9% for scores 3 to 4, 0.8% for scores 5 to 6, 3.3% for scores 7 to 8, and 13% for scores >8. The Caprini score achieved an AUC of 0.70. A Caprini score >8 was significantly predictive of VTE on multivariable analysis relative to scores 5 to 6 (odds ratio = 43.41, 95% confidence interval = 7.46-252.76, p < 0.001).

CONCLUSION

 In patients undergoing DIEP breast reconstruction, VTE incidence was highest (13%) in Caprini scores greater than eight despite chemoprophylaxis. Future studies are needed to assess the role of extended chemoprophylaxis in patients with high Caprini scores.

The efficacy of various Enoxaparin dosing regimens in general surgery patients: A systematic review

BACKGROUND

Patients undergoing surgical procedures are at an increased risk of venous thromboembolism events. A fixed Enoxaparin dosing regimen is the standard of care for chemoprophylaxis in most institutions; however, breakthrough venous thromboembolism events are still reported. We aimed to systematically review the literature to determine the ability of various Enoxaparin dosing regimens to achieve adequate prophylactic anti-Xa levels for venous thromboembolism prevention in hospitalized general surgery patients. Additionally, we aimed to assess the correlation between subprophylactic anti-Xa levels and the development of clinically significant venous thromboembolism events.

METHODS

A systematic review was conducted using major databases from January 1, 1993, to February 17, 2023. Two independent researchers screened titles and abstracts, followed by a full-text review. Articles were included if Enoxaparin dosing regimens were evaluated by anti-Xa levels. Exclusion criteria included systematic reviews, pediatric population, nongeneral surgery (defined as trauma, orthopedics, plastics, and neurosurgery), and non-Enoxaparin chemoprophylaxis. The primary outcome was peak Anti-Xa level measured at steady state concentration. The risk of bias was assessed using the Risk of Bias in Nonrandomized studies-of Intervention tool.

RESULTS

A total of 6,760 articles were extracted, of which 19 were included in the scoping review. Nine studies included bariatric patients, whereas 5 studies explored abdominal surgical oncology patients. Three studies assessed thoracic surgery patients, and 2 studies included patients undergoing "general surgery" procedures. A total of 1,502 patients were included. The mean age was 47 years, and 38% were males. The percentages of patients reaching adequate prophylactic anti-Xa levels were 39%, 61%, 15%, 50%, and 78% across the 40 mg daily, 40 mg twice daily, 30 mg twice daily, and weight-tiered, and body mass index-based groups, respectively. The overall risk of bias was low to moderate.

CONCLUSION

Fixed Enoxaparin dosing regimens are not correlated with adequate anti-Xa levels in general surgery patients. Additional research is warranted to assess the efficacy of dosing regimens based on novel physiologic parameters (such as estimated blood volume).

Effectiveness of Body Mass Index-Based Prophylactic Enoxaparin Dosing in Bariatric Surgery Patients

INTRODUCTION

Enoxaparin is administered for venous thromboembolic (VTE) prophylaxis in bariatric surgery patients. There is concern whether body mass index (BMI)-based enoxaparin dosing consistently achieves prophylactic targets in patients with severe obesity.

METHODS

This retrospective study included patients who underwent bariatric surgery at an academic medical center from Jan 2015-May 2021 and had an anti-Xa level drawn 2.5-6 h after ≥3 doses of BMI-based prophylactic enoxaparin. The primary outcome was the percentage of patients who achieved a target anti-Xa level. Secondary outcomes were prevalence of venous thromboembolic and bleeding events within 30 d post-operatively.

RESULTS

Overall, 137 patients were included. Mean BMI was 59.1 ± 10.4 kg/m², mean age was 43.9 ± 13.3 y and 110 patients (80.3%) were female. Target anti-Xa levels were achieved in 116 patients (84.7%); 14 (10.2%) were above target and 7 (5.1%) were below target. Patients with above target anti-Xa levels were significantly shorter in height than those within target range (167.1 versus 159.8 cm, P = 0.003). Five patients (3.6%) had a bleeding event; no thromboembolisms occurred. Anti-Xa levels correlated more strongly with enoxaparin dose per unit estimated blood volume (EBV) than dose per unit BMI (Rho = 0.54 versus Rho = 0.33).

CONCLUSIONS

Target range anti-Xa levels were achieved in 85% of patients using BMI-based enoxaparin dosing. Patients with above target anti-Xa levels were significantly shorter by nearly 3 inches, suggesting an increased risk of overdosing enoxaparin in shorter, obese patients. An EBV-based dosing regimen may better account for patient height and is supported by a greater correlation with anti-Xa levels with dosing based on EBV than BMI.

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

Guidelines for Perioperative Care in Bariatric Surgery: Enhanced Recovery After Surgery (ERAS) Society Recommendations: A 2021 Update

Background

This is the second updated Enhanced Recovery After Surgery (ERAS®) Society guideline, presenting a consensus for optimal perioperative care in bariatric surgery and providing recommendations for each ERAS item within the ERAS® protocol.

Methods

A principal literature search was performed utilizing the Pubmed, EMBASE, Cochrane databases and ClinicalTrials.gov through December 2020, with particular attention paid to meta-analyses, randomized controlled trials and large prospective cohort studies. Selected studies were examined, reviewed and graded according to the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system. After critical appraisal of these studies, the group of authors reached consensus regarding recommendations.

Results

The quality of evidence for many ERAS interventions remains relatively low in a bariatric setting and evidence-based practices may need to be extrapolated from other surgeries.

Conclusion

A comprehensive, updated evidence-based consensus was reached and is presented in this review by the ERAS® Society.