How to predict Hematocrit before starting Cardiopulmonary bypass (CPB)
You should know patient's blood volume : VpB = 1000 *f*wt where f is the proportion of body weight attributable to blood volume; f = 0.08 for infants and children up to 12 years of age, f = 0.065 for older patients. For example VpB = 1000 *0.065*80 = 5200 ml. ___________________________________________________ Than you shoud calculate the volume of patient's red cells: VpRBC = VpB * HCTp (patient's hematocrit) so : VpRBC = 5200 ml * 0.35 = 1820 ml ___________________________________________________ And finally calculation of hematocrit at the beginning of CPB : HCTpm = VpRBC / (VpB + VmB) where VmB is priming volume of CPB machine: HCT pm = 1820 / (5200 + 1300) = 0.28