How much FFP?
Dr. Sam Schulman from Karolinska Hospital, Stockholm, Sweden wrote an excellent review on "Care of Patients Receiving Long-Term Anticoagulant Therapy" in August 14, 2003 issue of NEJM. Part of article suggest formula for amount of FFP (Fresh Frozen Plasma) to correct INR upto desired level in a bleeding patient from over-anticoagulation.
Amount of FFP needed(ml) =(target level as percentage - present level as percentage) x Wt.(kg)
The "percentage" is prothrombin complex, expressed as a percentage of normal plasma, corresponds to the mean level of the vitamin K–dependent coagulation factors. It can be compute easily with following table:
INR 1 = 100 (%)
INR 1.4 - 1.6 = 40
INR 1.7 - 1.8 = 30
INR 1.9 - 2.1 = 25
INR 2.2 - 2.5 = 20
INR 2.6 - 3.2 = 15
INR 4.0 - 4.9 = 10
INR > 5 = 5 (%)
Example: In a 70 kg patient bleeding with INR of 7.5 and if our target is to bring INR down to 1.4, using above table:
Total FFP needed = (40 - 5) x 70 = 2450 ml
(One unit FFP usually contains 200-250 ml of FFP)
Reference: click to get reference
Care of Patients Receiving Long-Term Anticoagulant Therapy - NEJM - Volume 349:675-683, August 14, 2003
