Supraprophylactic Anti–Factor Xa Levels Are Associated with Major Bleeding in Neurosurgery Patients Receiving Prophylactic Enoxaparin

• Published in: World neurosurgery Vol. 157; pp. e357 - e363
• Main Authors: May, Casey C., Cua, Santino, Smetana, Keaton S., Powers, Ciarán J.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.01.2022
• Subjects: Adult; Aged; Anticoagulants - administration & dosage; Anticoagulants - adverse effects; Anticoagulants - blood; Anti–factor Xa; Drug Monitoring - methods; Enoxaparin - administration & dosage; Enoxaparin - adverse effects; Enoxaparin - blood; Factor Xa Inhibitors - administration & dosage; Factor Xa Inhibitors - adverse effects; Factor Xa Inhibitors - blood; Female; Hemorrhage; Hemorrhage - blood; Hemorrhage - prevention & control; Humans; Low-molecular-weight heparin; Male; Middle Aged; Neurosurgery; Neurosurgical Procedures - trends; Obesity, Morbid - blood; Obesity, Morbid - surgery; Pre-Exposure Prophylaxis - methods; Pre-Exposure Prophylaxis - trends; Prophylactic anticoagulation; Retrospective Studies; Sex Factors; Venous Thromboembolism - blood; Venous Thromboembolism - prevention & control; anti-Xa; LMWH; DVT; tPA; PE; VTE; Anti–factor Xa; Low-molecular-weight heparin; Neurosurgery; Prophylactic anticoagulation; Hemorrhage; BMI
• ISSN: 1878-8750; 1878-8769
• DOI: 10.1016/j.wneu.2021.10.087

Prior studies demonstrated reduced risk for venous thromboembolism (VTE) in neurosurgical patients secondary to prophylaxis with both heparin and low-molecular-weight heparin. The ability to monitor low-molecular-weight heparin by obtaining anti–factor Xa (anti-Xa) serum levels provides an opportunity to evaluate safety and efficacy. The aim of this study was to describe characteristics of patients who have anti-Xa levels outside of the goal range (0.2–0.4/0.5 IU/mL) and investigate incidence of major bleeding and VTE. A single-center, retrospective, observational study was conducted on neurosurgical patients receiving enoxaparin for VTE prophylaxis between August 2019 and December 2020. Significance testing was conducted via Fisher exact test and independent samples t test. The study included 85 patients. Patients were less likely to have an anti-Xa level in the goal range if they were male, had a higher weight, or were morbidly obese. Three neuroendovascular patients (3.5%) experienced a major bleed. Serum anti-Xa levels were significantly higher in patients who experienced major bleeds compared with patients who did not (0.45 ± 0.16 IU/mL vs. 0.28 ± 0.09 IU/mL, P = 0.003). Patients with a supraprophylactic anti-Xa level (>0.5 IU/mL) were more likely to experience a major bleed (P = 0.005). One VTE event occurred: the patient experienced a pulmonary embolism with anti-Xa level at goal. Anti-Xa–guided enoxaparin dosing for VTE prophylaxis in neurosurgical patients may help prevent major bleeding. These data suggest that a higher anti-Xa level may predispose patients to major bleeding. Further evaluation is needed to identify the goal anti-Xa level for VTE prophylaxis in this population.