Models of Holland and Brooks for Predicting the Impact of Fresh Frozen Plasma (FFP) Transfusion on the INR

 

Size of FFP units:

(1) adult: 500 mL (collected by apheresis, comparable to about 2 units derived from single donor units)

(2) children: 250 mL

 

For an adult:

 

change in INR after 1 unit FFP (500 mL) =

= (0.37 * (pretreatment INR)) - 0.47

 

Since the change in INR = (pretreatment INR) - (posttreatment INR)

 

posttreatment INR =

= (0.63 * (pretreatment INR)) + 0.47

 

For an child:

 

change in INR after 1 unit FFP (250 mL) =

= (0.29 * (pretreatment INR)) - 0.37

 

posttreatment INR =

= (0.71 * (pretreatment INR)) + 0.37

 

Since FFP units are given in sequence and the INR after one unit of FFP is the pretreatment INR for the next unit, the following relationship can be seen (with "x" indicating the initial INR, "a" indicating the slope of the line and "b" the intercept for an adult or pediatric patient)

Units FFP	Post-Treatment INR
1	(a * x) + b
2	(a^2 * x) + (a * b) + b
3	(a^3 * x) + (a^2 * b) + (a * b) + b
4	(a^4 * x) + (a^3 * b) + + (a^2 * b) + (a * b) + b
5	(a^5 * x) + (a^4 * b) + (a^3 * b) + (a^2 * b) + (a * b) + b
6	(a^6 * x) + (a^5 * b) + (a^4 * b) + (a^3 * b) + (a^2 * b) + (a * b) + b
7	(a^7 * x) + (a^6 * b) + (a^5 * b)+ (a^4 * b) + (a^3 * b) + (a^2 * b) + (a * b) + b
8	(a^8 * x) + (a^7 * b) + (a^6 * b) + (a^5 * b)+ (a^4 * b) + (a^3 * b) + (a^2 * b) + (a * b) + b

 

The authors found that there was often little if any improvement in the INR when FFP is transfused to a patient with the initial INR < 1.7.