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

INTRODUCTION: Enoxaparin prophylaxis prevents venous thromboembolism in surgical patients. Real time anti-Factor Xa monitoring for surgical patients on enoxaparin prophylaxis is increasingly common. PRESENTATION OF CASES: We report on three cancer patients with therapeutic or supratherapeutic anti-Factor Xa levels while on prophylactic doses of enoxaparin after surgical procedures. In all cases, elevated anti-Factor Xa levels were the result of blood specimens being removed from a heparinized chemoport. DISCUSSION: This case series highlights the importance of peripheral venipuncture or appropriate blood wasting from central access sites for anti-Factor Xa levels. CONCLUSION: Inappropriately drawn anti-Factor Xa levels may contribute to prophylaxis interruption or unnecessary workup for renal or liver failure.