Effects of mild hypothermic cardiopulmonary bypass on blood viscoelasticity in coronary artery bypass grafting patients

The purpose of this study was to determine the changes in blood viscoelasticity during and after coronary artery bypass grafting (CABG) and to identify correlations between blood viscoelasticity and patients' age, duration of cardiopulmonary bypass (CPB), and cross-clamp time. After Institutional Review Board approvals, patients (n = 10) who were subjected to mild hypothermic CPB were included in this study. Viscosity and elasticity were measured at strains of 0.2, 1, and 5 using a Vilastic-3 Viscoelasticity Analyzer. Arterial blood samples were collected preCPB, on normothermic CPB, hypothermic CPB, after rewarming, and after CPB. Viscosity and elasticity at strains of 0.2 and 1 were altered significantly during and after CPB compared to the pre-CPB (p < 0.01). In particular, elasticity of blood was diminished during normothermic bypass and could not be recovered after CPB (p < 0.01). Although there were strong correlations between blood viscoelasticity, duration of CPB, and cross-clamp time on normothermic CPB, only the patients' age showed a positive correlation between viscosity (r = 0.61, p = 0.05), and elasticity (r = 0.89, p < 0.001) after CPB. These results suggest that mild hypothermic CPB alters the blood viscoelasticity during and after CABG.