A mathematical analysis of haemorheologic factors during cardiopulmonary bypass for congenital heart disease.

Abstract

Rheologic properties of blood are impaired by cardiac surgery using cardiopulmonary bypass. This study was set out to establish a mathematical model in order to assess seven known haemorheologic factors and evaluate their degrees of influence on blood rheology in cardiopulmonary bypass. Sixteen patients undergoing elective congenital cardiac surgery were studied. High shear blood viscosity, low shear blood viscosity, haematocrit, red blood cell filtration rate, red blood cell electrophoresis time, plasma viscosity and fibrinogen were monitored. The method for mathematical calculation was the stepwise regression analysis. The results showed that both high shear and low shear blood viscosity were mainly influenced by haematocrit and plasma viscosity. Red blood cell filterability contributed more than red blood cell electrophoresis time for low shear blood viscosity. The mathematical model was re-tested statistically and demonstrated that the selected factors in the model represented approximately 75% of rheologic changes during the surgery. Therefore, this mathematical analysis can be used to estimate the role of various possible haemorheologic factors and evaluate cardiopulmonary bypass techniques and therapeutic interventions.