Calculation of fresh frozen plasma amount to correct high international normalized ratio

Abstract

Introduction: Fresh frozen plasma (FFP) is the most widely-used blood component to correct high International
Normalized Ratio (INR). However, little is known about the amount of FFP needed to correct high INR and factors
related to normalized INR. Methods: A retrospective chart review study included 144 patients (96 warfarin and 48
nonwarfarin groups), aged over 18 years old, presenting high pretransfusion INR (PreINR; > 1.5) and receiving FFP
with INR values after transfusion (PostINR) between September 1, 2019 and November 30, 2020. ΔINR (PreINR
- PostINR) was calculated. Results: The median (range) PreINR was 2.67 (1.50-14.64) and median (range) ΔINR
was 0.87 (-0.09-12.81). The mean (±SD) amount of FFP was 2.2±0.6 units. The median (range) time from FFP
administration to PostINR testing was 4.59 hours (0-19). The median (range) time between PreINR and PostINR
testing was 11.55 hours (3-33). Vitamin K was administered to 88 patients. The formula ΔINR after FFP 2 units
= (0.91 x PreINR)-1.38 (R2 = 0.96 between predicted INR and actual improvement INR; p < 0.001). The factors,
correlated with normalized PostINR (INR < 1.5), were lower PreINR level (adjusted odds ratio [aOR] = 0.64, p =
0.017), intravenous vitamin K (aOR = 1.74, p = 0.025) and longer duration between PreINR and PostINR testing
(aOR = 1.30, p = 0.001). Conclusion: This formula may be used to predict INR after FFP transfusion. Factors
correlated with normalized INR after transfusion were lower pretransfusion INR, intravenous vitamin K and longer
duration between pre- and posttransfusion INR measurements