The Influence of Heparin-Coated and Uncoated Extracorporeal Circuits on Blood Rheology During Cardiac Surgery

Abstract

The effect of heparin-coated perfusion circuits on blood trauma during clinical cardiopulmonary bypass (CPB) was studied in order to find out if traumatic changes in the blood could be minimized. Twenty-four patients undergoing coronary artery bypass surgery were randomized prospectively to CPB with heparin-coated circuits (HCC) or non-coated circuits (NCC). The trauma to blood was assessed by measuring damage to blood cells by estimating red and white cell rheology changes. These were measured as red cell filtration rate (RFR) and white cell filtration rate (WFR) using standard microfiltration methods. Furthermore, changes in plasma hemoglobin (P-Hb), whole blood and plasma viscosity were simultaneously assessed. The RFR was significantly reduced in both groups during CPB by 10% in the HCC and 32% in the NCC groups (p<0.01). When comparing the HCC and NCC groups, a significant difference was first seen after 30 minutes ofbypass (p<0.05) and increased at the end ofCPB (p<0.01). Similar results were seen regarding WFR (15% and 36%, p<0.01). After 30 minutes ofbypass, a significant difference was seen between HCC and NCC groups (p<0.05). Furthermore, a significant increase in P-Hb levels were seen during CPB in both patient groups. At the end of CPB, there was a significant difference in P-Hb levels (HCC 305±90 mg/L; NCC 455±78 mg/L, p<0.01) when comparing the two groups. When comparing HCC and NCC regarding corrected blood viscosity at shear rate 92 s-1, there were significantly higher viscosity values in the NCC group starting at 30 minutes of bypass (p<0.05). Plasma viscosity (PV) at shear rate 583 s-1 , showed similar results (p<0.05). This study suggests that heparin-coated extracorporeal circuits are less damaging to the rheological properties of blood and would therefore be better suited for clinical use during cardiac surgery using CPB.