Carrie Wilmer, PharmD, BCPS
Clinical Pharmacist
VA Pittsburgh Healthcare System, United States
Disclosure information not submitted.
Xinhua Zhao, PhD
Data Analyst
Center for Health Equity Research and Promotion, United States
Disclosure information not submitted.
Sherrie Aspinall, PharmD, MSc, BCPS
Clinical Pharmacy Specialist
VA Center for Medication Safety/Pharmacy Benefits Management Services, United States
Disclosure information not submitted.
Title: Supratherapeutic Unfractionated Heparin Anti-Xa Levels Due To Treatment-Dose Enoxaparin Exposure
Introduction: Intravenous unfractionated heparin (UFH) is a routine option for anticoagulation in hospitalized patients. Therefore, accurate laboratory results are essential, including minimizing variables that affect UFH monitoring. Anti-factor Xa (anti-Xa) monitoring may be subject to drug-laboratory elevations.
Methods: This study was a single-center retrospective review of patients who were administered UFH with anti-Xa monitoring to assess the incidence of supratherapeutic anti-Xa levels (greater than 0.7 international units per milliliter) between three subgroups, defined as recipients of prophylactic-dose enoxaparin, treatment-dose enoxaparin, and no enoxaparin within 24 hours prior to initiation of UFH therapy.
Results: Initial supratherapeutic anti-Xa levels were present in 8 of 81 (9.9%) patients without enoxaparin prior to UFH, 2 of 16 (12.5%) in the prophylactic-dose enoxaparin group and 5 of 6 (83.3%) in the treatment-dose enoxaparin group (p=0.0002). There was no significant difference in the incidence of initial supratherapeutic anti-Xa levels between the subgroups who received prophylactic-dose enoxaparin and when enoxaparin was absent (p=0.67).
Conclusions: This study suggests that a high percentage of initial anti-Xa levels for UFH monitoring may be supratherapeutic in
the setting of exposure to treatment-dose enoxaparin.