APTT Versus Anti Xa Monitoring of Unfractionated Heparin - a Retrospective Review of Clinical Outcomes

Abstract

AbstractAbstract 4391In May 2008, The William W. Backus Hospital changed the unfractionated heparin dosing protocol and the monitoring parameter for the treatment of thromboembolic disease. The original protocol utilized the Rashke's method (Bolus dose 80 units/kg and initial infusion of 18 units/kg/hour) monitored with aPTT (Therapeutic range 61–80.9 seconds). The newer protocol is a novel model utilizing a bolus dose of 26 units/kg and initial infusion rate of 15 units/kg/hour, calculated using the methodology designed by Rosbourough et al monitored with anti-Xa (Therapeutic range 0.3–0.7 anti Xa units). This is a retrospective study comparing of the efficacy and safety of each protocol. Methods:Data abstraction was completed through electronic medical record review of two hundred patients. Time point 0 was the date of changing to the new protocol. One hundred patients in reverse chronological order were reviewed for the original protocol and one hundred patients in chronological order with the new protocol. Data included demographics, duration of time prior to achieving therapeutic parameters, number of dosage changes, diagnosis of cancer, bleeding events and recurrent thrombotic events. Unpaired Student t tests were utilized to statistically analyze the differences between the cohorts. Results:Rashke MethodRosbourough MethodRecurrence Rate3%9%Cancer Diagnosis in Recurrent TE2/3 (67%)2/9 (22%)Mean Age61.7 (range 51–70)61.6 (range 35–90)Mean Weight males (kg)86.5 (range 77–96)88.64 (range 81–101.2)Mean Weight females (kg)103.2 (one patient)76.2 (range 51–94.5)Initial VTE provoked1/3 (33%)1/9 (33%)Genetic Predisposition1/3 (33%)1/9 (11%)Days to Recurrent VTE (mean)17.3 days17.4 daysMean Time Spent Subtherapeutic range within first 24 hours5 hours2.83 hours Conclusion:Both methodologies achieved therapeutic levels rapidly. The Rosbourough method required statistically significant less dosage changes when compared to the Rashke method. The incidence of major and minor bleeding was similar between the two dosing algorithms. Although not statistically significant, the incidence of recurrent thromboses was numerically higher with the Rosbourough method compared to Rashke method. This is concerning and suggests that the higher loading dose may be more appropriate. A prospective comparison of these two monitoring methods using Rashke dosing is planned. Disclosures:Off Label Use: Discuss alternative dosing and anti Xa monitoring of unfractionated heparin infusion.