title: A novel calculation to estimate blood volume and hematocrit during bypass.
abstract: Patient blood volume impacts most facets of perfusion care, including volume management, transfusion practices, and pharmacologic interventions. Unfortunately, there is a wide variability in individual blood volumes, and experimental measurement is not practical in the clinical environment. The purpose of this study was to evaluate a mathematical algorithm for estimating individual blood volume. After institutional review board approval, volumetric and transfusion data were prospectively collected for 165 patients and applied to a series of calculations. The resultant blood volume estimate (BVE) was used to predict the first and last bypass hematocrit. The estimated hematocrits using both BVE and 65 mL/kg were compared with measured hematocrits using the Pearson moment correlation coefficient and the Bland Altman measures of accuracy and precision. There was a wide range of BVE (minimum, 35 mL/kg; mean +/- SD, 64 +/- 22 mL/kg; maximum, 129 mL/kg). Using BVE, the estimated hematocrit was similar to the measured first (24.7 +/- 6.4% vs. 24.5 +/- 6.2%, r = 0.9884, p > .05) and last (24.5 +/- 5.9% vs. 25.1 + 5.7%, r = 0.9001, p > .05) bypass hematocrit. Using 65 mL/kg resulted in a larger difference between estimated and measured hematocrits for the first (25.6 +/- 4.5% vs. 24.5 +/- 6.2%, r = 0.6885, p = .030) and last (23.8 +/- 3.6% vs. 25.1 +/-5.7%, r = 0.5990, p = .001) bypass hematocrits. Compared with using 65 mL/kg for blood volume, the BVE allowed for a more precise estimated hematocrit during CPB.
authors.affiliation: Geisinger Medical Center, Perfusion Services 20-15, 100 N. Academy Avenue, Danville, PA 17821, USA. cctrowbridge@geisinger.edu
authors.forename: Cody
authors.initials: C
authors.lastname: Trowbridge
authors.forename: Alfred
authors.initials: A
authors.lastname: Stammers
authors.forename: Myra
authors.initials: M
authors.lastname: Klayman
authors.forename: Nicholas
authors.initials: N
authors.lastname: Brindisi
mesh_terms: D000465:Algorithms; D001803:Blood Transfusion; D001810:Blood Volume; D001811:Blood Volume Determination / Q000295:instrumentation* / Q000379:methods; D002315:Cardiopulmonary Bypass / Q000379:methods*; D006400:Hematocrit; D006801:Humans; D008962:Models, Theoretical; D010477:Perfusion / Q000379:methods*; D019990:Perioperative Care; D011446:Prospective Studies