Pencil & Paper method for calculating RhIg dosing...
NOTE: Often, the maternal blood volume is assumed to be 5L (5000 mL). More accurate TBV can be calculated using the weight/Hct (Calculator coming soon!)
Step 1: Determine the Kleilhauer-Betke %.
Let's say you find 50 fetal cells out a total of 2000 total cells counted.
KB% = # of fetal cells/2000 total cells counted
KB = 2.5%
Step 2: Convert KB% to Fetal whole blood volume
Fetal Blood Volume= KB% x 50 mL
= 2.5 x 50
FBV = 125 mL in this case
Step 3: Determine # of vials needed for coverage
# of vials = FBV/30 (avg RhIg coverage per vial)
=4.2 doses of RhIg to provide coverage
Step 4: Determine # of vials to administer:
To determine this, round the # of vials calculated in the previous step to the nearest whole number (round down if <5 in the tenths places. If 5 or above in tenths place, round up)
4.2 doses would round to 4
Then add 1 to this number. This provides a "safety dose" to make sure that all fetal blood cells are protected.
# of vials to administer= 4+1 = 5
Thus you would administer 5 vials
NOTE: This calculator automatically adds the 1 (safety vial) before rounding!
Thus, take whatever answer is on the calculator & round to the nearest whole number to determine the amount of vials to administer to the mother
Consult with your attending! This is not meant to provide medical advice.