Supratherapeutic anti-factor Xa levels in patients receiving prophylactic doses of enoxaparin: A case series

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).

Current practices in pediatric hospital-acquired thromboembolism: Survey of the Children's Hospital Acquired Thrombosis (CHAT) Consortium

Background

A rise in hospital-acquired venous thromboembolism (HA-VTE) in children has led to increased awareness regarding VTE prophylaxis and risk assessment. Despite no consensus exists regarding these practices in pediatrics.

Objective

To describe common practices in VTE prophylaxis, VTE risk assessment models, and anticoagulation dosing strategies in pediatric hospitals that are members of the Children's Hospital Acquired Thrombosis (CHAT) Consortium.

Methods

An electronic survey of 44 questions evaluating practices surrounding pediatric HA-VTE risk assessment and prevention was distributed between August 9, 2021, and August 30, 2021, to the primary investigators from the 32 institutions within the CHAT Consortium.

Results

The survey response rate was 100% (n = 32). In total, 85% (n = 27) of the institutions assess HA-VTE, but only 63% (n = 20) have formal hospital guidelines. Within the institutions with formal guidelines, 100% (n = 20) include acute systemic inflammation or infection and presence of a central venous catheter (CVC) as risk factors for VTE. Pharmacologic prophylaxis is prescribed at 87% (28) of institutions, with enoxaparin being the most frequent (96%, n = 27). Variability in responses persisted regarding risk factors, risk assessment, thromboprophylaxis, dosing of prophylactic anticoagulation or anticoagulant drug monitoring. A majority of providers were comfortable providing thromboprophylaxis across all age groups. In addition, the global coronavirus disease 2019 increased the providers' use of prophylactic anticoagulation 78% (n = 25).

Conclusion

Practices among institutions are variable in regard to use of HA-VTE prophylaxis, risk assessment, or guideline implementation, highlighting the need for further research and a validated risk assessment model through groups like the CHAT Consortium.

Anti-Xa levels in critically ill children receiving enoxaparin for venothromboembolism prophylaxis

Venothrombolism (VTE) prophylaxis is increasingly utilized in pediatric intensive care units (PICUs). Enoxaparin, a low-molecular weight heparin, is frequently used for this purpose. Enoxaparin can also be used for therapeutic anticoagulation in cases of known thrombus. In such cases, monitoring involves obtaining serum anti- Xa levels with a target value of 0.5-1 units/mL. No monitoring recommendations currently exist for enoxaparin when intended for pediatric VTE prophylaxis. We hypothesize that a clinically important number of patients on VTE prophylaxis with enoxaparin have serum anti-Xa levels consistent with values targeted for therapeutic anticoagulation. We found that over 20% of patients on VTE prophylaxis with enoxaparin had serum anti-Xa levels consistent with true therapeutic anticoagulation (anti-Xa level 0.5-1 units/mL) during their enoxaparin course and 5% achieved values of supratherapeutic anticoagulation (anti-Xa level >1 units/mL). Serum anti-Xa level did not correlate with once versus twice daily dosing, body mass index (BMI), or creatinine level. Blood urea nitrogen (BUN) was found to have a positive odds ratio for an anti-Xa level ≥ 0.5 units/mL. We believe that this incidence of unintended therapeutic anticoagulation indicates a clinically significant number and therefore routine anti-Xa evaluation while on VTE prophylaxis is warranted within our population.