Clinical factors influencing normalization of prothrombin time after stopping warfarin: a retrospective cohort study
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BioMed Central
Open Access
Original clinical investigation
Clinical factors influencing normalization of prothrombin time after stopping warfarin: a retrospective cohort study Sam Schulman*1, Rajae Elbazi2, Michelle Zondag1 and Martin O'Donnell1 Address: 1Department of Medicine, McMaster University, Hamilton, ON, Canada and 2Faculty of Pharmaceutical Science, Utrecht University, Utrecht, The Netherlands Email: Sam Schulman* - [email protected]; Rajae Elbazi - [email protected]; Michelle Zondag - [email protected]; Martin O'Donnell - [email protected] * Corresponding author
Published: 16 October 2008 Thrombosis Journal 2008, 6:15
doi:10.1186/1477-9560-6-15
Received: 4 September 2008 Accepted: 16 October 2008
This article is available from: http://www.thrombosisjournal.com/content/6/1/15 © 2008 Schulman et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract Background: Anticoagulation with warfarin should be stopped 4–6 days before invasive procedures to avoid bleeding complications. Despite this routine, some patients still have high International Normalized Ratio (INR) values on the day of surgery and the procedure may be cancelled. We sought to identify easily available clinical characteristics that may influence the rate of normalization of prothrombin time when warfarin is stopped before surgery or invasive procedures. Methods: Clinical data were collected retrospectively from consecutive cases from two cohorts, who stopped warfarin 6 days before surgery. An INR value of 1.6 or higher on the day of surgery or requirement for reversal with vitamin K the day before surgery were criteria for slow return (S) to normal INR. Results: Of 202 patients, 14 (7%) were classified as S. Eight of the S-patients required reversal with vitamin K one day before surgery and in another case surgery was cancelled due to high INR. Baseline INR was the only variable significantly associated with classification as S in stepwise logistic regression analysis (p = 0.003). The odds ratio for being in the normal group was 0.27 (95% confidence interval 0.12–0.62) for each unit baseline INR increased. The positive predictive value of baseline INR with a cut off at > 3.0 was only 15% and for INR > 3.5 it was 33%. Conclusion: Baseline INR, but not the size of the maintenance dose, is associated with the rate of normalization of prothrombin time after stopping warfarin, but it has limited utility as predictor in clinical practice. Whenever normal hemostasis is considered crucial for the safety, the INR should be checked again before the invasive procedure.
Background With increasing life expectancy, and thereby also increasing prevalence of atrial fibrillation, a larger proportion of the population is using vitamin K antagonists (VKA). It has been reported that 36% o
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