PB0997 - Patterns of supratherapeutic international normalized ratio reversal for patients receiving warfarin therapy: Real-world practice in a university-based hospital in Thailand

Background: Management of supratherapeutic international normalized ratio (INR) during warfarin therapy generally follows standard clinical practice guidelines (CPGs). However, real-world deviations from those CPGs are relatively common.

Aims: To explore the patterns of supratherapeutic INR reversal for adults undergoing warfarin therapy in Thailand.

Methods: Warfarin-associated supratherapeutic INR events during 2019-2021 were retrospectively reviewed. Using descriptive statistics and logistic regression, the primary (rate of treatments deviating from national/international CPGs) and secondary outcomes (post-reversal INR and INR normalization [ < 1.5], bleeding control, and factors associated with CPG-discordant treatments) were analyzed.

Results: Of 252 supratherapeutic INR events (median INR, 4.22; interquartile range, 3.61-5.99) in 125 patients (60% women; mean age 77.9 years; 78.4% requiring hospitalization), 33.3% were CPG-discordantly treated, either undertreated (20.6%) or overtreated (12.7%). In clinically relevant non-major bleeding (CRNMB; n=45) or major bleeding (MB; n=35), CPG-discordant treatments caused more INR prolongation and lower INR normalization rate at 48 hours post-reversal (Table 1). Although successful bleeding control rate was not different from the CPG-concordant group, fatality was only reported in the CPG-discordant group. CRNMB (adjusted odds ratio [aOR], 0.49; 95% confidence interval [CI], 0.22-0.87) and discretion made by in-training physicians (aOR, 0.30; 95% CI, 0.09-0.95) were significantly associated with CPG-discordant treatments. At 24 hours post-reversal, INR normalization rates between groups receiving oral vitamin K 1 mg or 2 mg were similar; however, intravenous vitamin K 1-2 mg led to lower INR levels compared with the oral equivalent dosages (P=0.02; Figure 1). Following intravenous vitamin K 5 mg or 10 mg, no significantly different effects or thromboembolic events were observed.

Conclusion(s): The rate of CPG-discordant reversal for warfarin-associated supratherapeutic INR is high, especially for CRNMB treated by in-training physicians, in Thailand. Despite no differences in bleeding control rates, real-world treatments deviating from CPGs potentially contribute to the failure to INR normalization at 48 hours post-reversal for CRNMB/MB.