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Abstract

Introduction: It has been suggested that patients with extreme body weight measurements and/or renal insufficiency may experience higher rates of bleeding with enoxaparin; the role of anti-Xa monitoring in these patient populations remains controversial. Hypothesis: Implementation of an anti-Xa monitoring protocol in high-risk patients will lead to a reduction in major bleeding events. Methods: This quasi-experimental retrospective study was approved by the Institutional Review Board at St. John Hospital & Medical Center, a 772-bed community teaching hospital in Detroit, Michigan. Data regarding major bleeding events for patients receiving therapeutic doses of enoxaparin was collected prior to (June 2010 – May 2011) and following (June 2011 – June 2012) anti-Xa monitoring protocol implementation. The protocol recommended monitoring anti-Xa levels in the following patient populations: pediatrics, pregnancy, total body weight > 100 kg or < 50 kg, creatinine clearance (CrCl) < 40 mL/min, or questionable drug clearance per pharmacist discretion. Anti-factor Xa levels drawn 3 to 5 hours following an enoxaparin dose were deemed appropriate for study inclusion (n = 34). Anti-Xa levels were classified as therapeutic between 0.6 – 1.0 unit/mL. Results: There were 988 patients who received enoxaparin in the pre-protocol period and 1188 patients who received enoxaparin following implementation of anti-Xa monitoring. Major bleeding events in patients receiving enoxaparin were significantly decreased following anti-Xa monitoring (n=3) compared to the pre-protocol period (n=11), 0.25% vs. 1.1%, respectively (p=0.026). Of the 34 appropriately drawn anti-Xa levels, 55.9% were reported as supratherapeutic. The indications for anti-Xa monitoring in patients with a supratherapeutic level were CrCl < 40 mL/min (36.8%), weight > 100 kg (31.6%), weight > 100 kg and CrCl < 40 mL/min (15.8%), and pharmacist discretion (15.8%). Conclusions: Implementation of the described anti-Xa monitoring protocol led to a reduction in major bleeding events at our institution. Anti-Xa monitoring should be strongly considered in patients receiving enoxaparin with extreme body weight measurements and/or renal insufficiency to prevent adverse events.