Correlation of the change in the International Normalized Ratio and decreasing the Coumadin dosage following total joint arthroplasty

This retrospective pilot study determined whether a change in the daily International Normalized Ratio (INR) correlates with a decrease in Coumadin (DuPont Pharma, Wilmington, Del) dosage. Four hundred seventeen patients yielded 1167 pairs of INR values and Coumadin doses. An increase in INR > 0.4 units correlated 81% with a decrease in the Coumadin dose (P < .05). In patients aged > or = 70 years, the correlation fell to 70% compared to an 89% correlation in patients aged < 70 years (P < .05). The correlation fell to 78% in women, while men exhibited an increase to 87% (P < .05). Although this is a pilot study, when managing postoperative Coumadin anticoagulation for orthopedic patients, an increase in INR > 0.4 units correlates highly with the need to decrease the Coumadin dose. A prospective study is needed to test the usefulness of this parameter.