The 2022 American Society for Metabolic and Bariatric Surgery (ASMBS) issued an updated position statement on perioperative venous thromboembolism (VTE) prophylaxis in bariatric surgery. The panel highlighted the ongoing lack of high-quality evidence concerning the safety, effectiveness, dosing, and duration of pharmacologic thromboprophylaxis during the peri-operative period. The complexity of dosage and timing further complicate the formulation of guidelines due to substantial variations. Pharmacoprophylaxis has not been extensively studied within the obese population, leading to uncertainties about the pharmacokinetics of these agents. Current recommendations advocate for BMI-stratified dosing, typically using low-molecular-weight-heparin (LMWH) 40 mg every 12 hours for patients with a BMI ≤50 kg/m² and a higher dose of 60 mg every 12 hours for those with a BMI >50 kg/m². This extended high-dose regimen for 10 to 14 days post-discharge has been shown to be safe without an increased risk of clinically significant bleeding. However, a significant concern noted is the potential inadequacy of standard fixed dosing, particularly in patients with severe obesity. Anti-Xa level monitoring is increasingly recognized as an important tool to ensure therapeutic efficacy. Studies cited show that a substantial proportion of patients (e.g., 21-31% in one study) did not reach the target prophylactic anti-Xa range (generally accepted as 0.2 to 0.4 IU/mL at peak) with standard fixed doses, necessitating individual dose adjustments. This monitoring is especially recommended for higher-risk patients, such as those with very high body weight (e.g., >150 kg) or higher lean body mass, who are on extended prophylaxis, as pharmacokinetics can be variable. Currently, there is no consensus or robust data regarding the optimal choice, dosing regimen, and duration of pharmacoprophylaxis after bariatric surgery. While conflicting data exist in the literature concerning the preferred type of pharmacoprophylaxis, various strategies involving single-agent and combined therapies of unfractionated heparin (UFH) and LMWH have been proposed. [1]
A 2022 systemic review and meta-analysis (N= 15) summarized studies evaluating the use of VTE prophylactic regimens to determine optimal dosing, duration, and agents of use. Both LMWH and fondaparinux may be effective in reducing VTE risk without increasing major bleeding or mortality risk (odds ratio [OR] 1.02; 95% confidence interval [CI] 0.14 to 7.39), but supporting evidence for this claim was rated low-quality. Pooled estimates suggest augmented LMWH dosing may both increase bleeding in comparison to standard dosing (OR 3.03; 95% CI 0.38 to 23.96) and show no added benefit in reducing VTE incidence (OR 0.57; 95% CI 0.07 to 4.39). Based on the incidence of post-surgery VTE events following discharge in observational studies, extended prophylaxis may show merit in patients who exhibit a higher VTE risk, but there is insufficient high-quality data to support this observation. There was no evidence regarding the efficacy of oral anticoagulants as peri-operative pharmacoprophylaxis in bariatric surgery. [2]
A review conducted in 2020 outlined an approach to preventing VTE after surgery. This review examined the assessment of postoperative VTE and bleeding risks in patients, as well as the delicate balance required to create an effective VTE prophylaxis plan. The appropriate dosing of heparin for obese patients remains uncertain. While therapeutic heparin dosage is typically determined based on a patient's total body weight, it is not as clear whether the standard prophylactic heparin doses offer adequate VTE protection for obese individuals. In bariatric surgery, research has suggested that higher doses of LMWH or low-dose UFH could slightly improve effectiveness in patients with significant obesity without a notable rise in bleeding risks. A summary of VTE prophylaxis recommendations following bariatric surgery can be found in Table 1. [3]
A 2014 literature review analyzed the appropriate enoxaparin dose for VTE prophylaxis in patients with extreme obesity by evaluating eight studies, six of which focused on bariatric surgery patients. The studies assessed fixed-dose regimens ranging from 30-60 mg subcutaneously (SQ) every 12 hours, as well as weight-based dosing strategies, including 0.5 mg/kg/day. Three investigations prioritized the incidence of VTE as the primary endpoint, while the others concentrated on achieving optimal anti-Xa levels. Findings indicated that higher-than-standard enoxaparin doses were necessary to attain target anti-Xa levels more consistently. Notably, a 2008 prospective, nonrandomized study further compared 40 mg and 60 mg SQ every 12 hours, demonstrating that the higher dose resulted in greater attainment of therapeutic anti-Xa levels (0.43 U/mL vs. 0.21 U/mL; p<0.001), though major bleeding events were uncommon. Additionally, another study observed a population of patients with a BMI >50 kg/m2 undergoing bariatric surgery for their therapeutic levels of anti-Xa after three doses of 60 mg enoxaparin SQ given every 12 hours. Four hours after the third dose, 69% of patients achieved the desired therapeutic anti-Xa levels, compared to 79% of patients with a BMI ≤50 kg/m2 who received 40 mg enoxaparin. When the VTE incidence and bleeding risk were assessed, only one patient had a confirmed deep vein thrombosis (DVT) after discontinuation of enoxaparin, and five major bleeding incidences were recorded. However, all events, except one bleeding incident were from the 40 mg cohort, causing authors to question whether enoxaparin was truly the cause of bleeding. Across all studies, enoxaparin doses exceeding conventional regimens were more frequently associated with optimal anti-Xa levels, with a potential reduction in VTE risk, particularly for bariatric surgery patients, although further large-scale, randomized trials are warranted to refine dosing recommendations in this population. [4]
Another 2014 systematic review and meta-analysis was conducted to determine whether a weight-based thromboprophylactic dosing regimen of heparin products is safe and effective in the post-operative period for obese patients undergoing bariatric surgery. Enoxaparin was used in three studies with a dosing regimen of enoxaparin 30 mg q12h, enoxaparin 40 mg q12h, or enoxaparin 60 mg q12h. Patients receiving weight-adjusted prophylactic doses of heparin products had an in-hospital rate of VTE of 0.54% (95% CI 0.2 to 1.0%) compared to 2.0% (95% CI 0.1 to 6.4%) in patients receiving fixed doses. Of all patients included in the study, the highest incidence of VTE was seen in those receiving a fixed dose of enoxaparin 30 mg q12h (Table 2). Rates of major bleeding were similar for patients receiving weight-adjusted dosing and fixed-dosing (1.6% vs 2.3%). Authors concluded that weight-adjusted dose for prophylaxis of VTE after bariatric surgery showed a non-significant trend to a lower rate of inpatient VTE complications without an increased risk of major bleeding. [5]
A 2025 review provided a summary of recent guidelines recommendations regarding VTE prophylaxis in bariatric surgery (see Table 2). Furthermore, a short discussion was presented regarding the role of direct oral anticoagulants (DOACs) in the post-operative setting. Rivaroxaban has been considered due to its oral dosing and pharmacokinetic studies showing stability in obesity. A 2023 RCT found a 7-day course of rivaroxaban 10 mg daily was effective. However, concerns about potential post-surgical absorption changes lead current guidelines to still favor LMWH for high-risk patients, and the application of DOACs in Asian populations requires specific study due to lower average body weight and a higher genetic risk of bleeding complications. [6]
A 2025 meta-analysis of seven studies concluded that DOACs are a safe and effective option for post-operative thromboprophylaxis in bariatric surgery patients. The pooled analysis found a low incidence of thrombotic events (0.23%), major bleeding (0.33%), and minor bleeding (1.27%), with rates that appeared favorable compared to cited data on enoxaparin. Regarding dosing, the included studies primarily evaluated regimens of rivaroxaban 10 mg once daily (for 7 to 30 days post-discharge) and apixaban (at prophylactic doses, typically 2.5 mg twice daily), when dosing was mentioned in the study. However, the analysis could not definitively establish a single optimal dose or duration, as protocols varied. The authors highlight that while pharmacokinetic studies support the stability of drugs like rivaroxaban in obesity, the current evidence is limited by a lack of head-to-head comparative trials with enoxaparin. Therefore, they recommend DOACs as a viable alternative but call for future randomized controlled trials to establish definitive guidelines on the optimal prophylactic agent, dose, and duration. [7]