Venous thromboembolism chemoprophylaxis in plastic surgery: A randomized controlled trial of apixaban versus enoxaparin

Authors: Momeni A, Yesantharao PS, Meyer S, Posternak V, Shefren K, Przybylo V, Januszyk M, Pannucci CJ

Affiliation: Stanford University School of Medicine; Plastic Surgery Northwest

Journal: Plastic and Reconstructive Surgery, November 2025

PMID: 40327806.

Key takeaways

• In high-risk free-flap breast reconstruction patients, inpatient apixaban 2.5 mg BID had the same observed bleeding rate after prophylaxis initiation as enoxaparin 40 mg daily.

• No symptomatic VTE occurred in either arm at 90 days, so efficacy comparisons are not possible from these data.

• Chemoprophylaxis duration was inpatient only, averaging about 2.4 days, so this trial does not address extended prophylaxis strategies.

• Practical value: fixed-dose oral prophylaxis avoids injections and anti–factor Xa monitoring, and this study supports short-course safety, not superiority.

Background

Breakthrough VTE remains clinically meaningful in high-risk plastic surgery patients despite guideline-compliant enoxaparin (current gold-standard). Optimal LMWH dosing and adherence limited by and practical barriers including weight-based dosing, factor Xa monitoring, and subcutaneous injections.

Objective

Primary - Test safety of apixaban vs enoxaparin looking at clinically significant bleeding after starting prophylaxis

Secondary - Test efficacy of apixaban vs enoxaparin looking at symptomatic VTE in 90 days.

Methods

• Design: Single-center, blinded, randomized controlled trial with 1:1 randomization between study arms; Level II.

• Population: Adult women with breast cancer undergoing free abdominally-based freflap breast reconstruction and Caprini score 7 or higher.

• Key exclusions: Contraindication to study drugs, active bleeding, bleeding disorder/coagulopathy, HIT, liver or kidney disease, uncontrolled HTN, recent neurosurgery/ophthalmologic surgery, alcohol/substance abuse, therapeutic anticoagulation, postoperative flap takeback requiring heparin drip

• Interventions:

  • Apixaban 2.5 mg twice daily

  • Enoxaparin 40 mg daily

• Timing and duration: Started 12 hours after skin closure, continued inpatient until discharge.

• Co-interventions: SCDs periop and in bed; early mobilization POD1 per ERAS pathway.

• Primary endpoint: Clinically significant bleeding events after prophylaxis initiation through 90 days.

• Secondary endpoint: Symptomatic VTE within 90 days.

• Statistics: Intention-to-treat after exclusions, Chi-square and t-testing on normally distributed variables, nonparametric testing on non-normally distributed variables; odds determined using Fisher exact test with Firth penalized logistic regression with stepwise selection; noninferiority if the upper limit of 97.5% CI for apixaban event rate didn’t exceed 2% margin over enoxaparin event rate.

Results

• Enrollment: 86 screened; 79 enrolled; randomized – 37 to apixaban and 39 to enoxaparin after excluding 3 patients for takeback + heparin drip.

• Baseline and operative characteristics: Similar demographics, comorbidities (Caprini median 7 (in both arms), reconstruction characteristics; mean prophylaxis duration aligned with LOS (~ 2.4 days).

• Primary outcome, bleeding after starting prophylaxis: 1/37 (3%) apixaban vs 1/39 (3%) enoxaparin; OR (odds ratio) bleeding event 1 (99% CI 0.9-1.1, pseudo R²=0.91)

• Symptomatic VTE: 0 in both arms at 90 days.

• Other complications: Any 90-day complication 16% apixaban vs 13% enoxaparin; OR (odds ratio) other complication 1.1 (99% CI 0.9-1.1, pseudo R²=0.86)

Conclusion

In abdominally-based breast reconstruction high-risk (Caprini > 7) patients, short-course inpatient apixaban was noninferior to enoxaparin for post-initiation bleeding. No symptomatic VTE observed in either group.

Strengths

• Randomized clinical trial, with blinded assignment after surgery

Limitations

• This study does not answer the main clinical question: whether apixaban reduces VTE compared with enoxaparin. 0 symptomatic VTE events in both groups, trial not powered for VTE efficacy.

• Inpatient-only prophylaxis (2-3 d) limits generalizability to those using extended post-discharge prophylaxis.

• Single-center design and highly selected population excludes patients who declare themselves high-bleed-risk intraoperatively or early postoperatively, including those needing takeback with heparin infusion.

• Underpowered for bleeding detection, power justification references a high bleeding rate from a different oral Xa inhibitor experience with higher equivalent dose in patients also taking NSAIDs.

Clinical relevance

This study supports apixaban 2.5 mg BID as a reasonable safety-equivalent alternative to enoxaparin 40 mg daily with the presumed advantage of improved compliance with an oral agent. No VTE events were reported, so this study cannot weigh in on efficacy of VTE prevention, but prior studies suggest 2.5 m BID is an appropriate prophylactic dose. 

Editorial notes

• This trial shows short-course apixaban has similar bleeding rates to standard-dose enoxaparin after microsurgical breast reconstruction, but it was not able to compare VTE prevention.

• Apixaban 2.5 mg BID is a standard prophylactic regimen in other surgical fields (e.g., joint replacement). This study assumes comparable prophylactic-intensity anticoagulation versus enoxaparin 40 mg daily, but drug-specific anti–factor Xa levels were not measured to confirm equivalence.

• Apixaban may be an attractive outpatient prophylaxis option to avoid injections and potentially improve adherence. Outpatient safety, adherence, and VTE efficacy remain unproven in this study. Other specialties (notably ortho re: joint replacement) have evaluated apixaban 2.5 mg BID for post-discharge prophylaxis with acceptable outcomes.