Validation of a linear dosing nomogram for enoxaparin anti-Xa levels

Purpose: Unlike heparin, enoxaparin is a low molecular weight heparin that does not require routine monitoring for safety and efficacy; however patient populations not prospectively studied in clinical trials may require anti-Xa level monitoring.  These populations include:  pregnant, cachectic, obese or pediatric patients, patients with significant burn injuries, recent trauma, renal failure, significant edema or coagulation factor disorders, and patients receiving therapeutic hypothermia.  Although not well studied, proposed target peak anti-Xa levels for enoxaparin are as follows:  prophylactic doses, 0.15-0.4 IU/mL; 1 mg/kg every 12 hour dosing, 0.5-1.0; 1.5 mg/kg every 24 hour dosing, 1.0-2.0.  For adult patients not in the appropriate anti-Xa level target range, no dose adjustment guidelines have been established.  Owing to the linear pharmacokinetics of enoxaparin, a dose adjustment nomogram was developed.  This study sought to compare the percentage of patients achieving target anti-Xa ranges when the novel dosing nomogram was used versus non-nomogram based dose adjustment.

Methods: Enoxaparin dosing nomogram-treated patients with anti-Xa levels obtained between May and September 2012 will be prospectively identified using a laboratory-generated report.  In addition, patients with anti-Xa levels obtained between June 2011 and March 2012, prior to the implementation of the dosing nomogram, were retrospectively identified.  Patients will be excluded if they are pregnant or less than 18 years of age.   Patients in the prospective cohort will be excluded if the dose adjustment nomogram was not followed or if peak anti-Xa levels were not drawn appropriately (3-5 hours post-dose, at steady state).  The following information will be collected for each patient: age, gender, height, weight, serum creatinine, indication for enoxaparin, enoxaparin dose(s), anti-Xa level result(s), time elapsed from dose to anti-Xa level collection, and bleeding or thrombotic events during index hospitalization. 

Results: Pending.  A chi-square test will be used to analyze the results for the primary endpoint. 

Conclusion: Pending.