Development of a dosing algorithm in a nurse‐managed outpatient anticoagulation clinic

Purpose: To compare the effectiveness of an algorithm created for use in a nurse‐managed outpatient anticoagulation clinic with the use of clinical judgment without formalized guidelines. Data source: A search of the databases in Pub Med and the Cumulative Index to Nursing of articles published through November 2009 yielded 19 articles concerning warfarin, practice guidelines, and use of algorithms. Methods: A retrospective study was conducted comparing 179 consecutive patient visits in September 2007 with 206 consecutive patient visits in 2009 at the Johns Hopkins Outpatient Anticoagulation Clinic. An algorithm was created that incorporated “removeable causes” to aid nurses in decision making when, for example, additions and deletions of new medications are added that interact with warfarin (Coumadin). Results: In both years, there was a greater percentage of no change versus change in warfarin dose reflecting stable dosage patterns in both years. Chi‐square analysis showed no statistical significance in the relationship between dosing changes and year. A significant relationship was found, however, between removeable causes and year, suggesting improved documentation of removable causes in 2009. Implications for practice: Further study with a larger prospective randomized sample population is needed to more accurately assess the algorithm's effect on time in therapeutic range (TTR).