Microvascular alterations during cardiac surgery using a heparin or phosphorylcholine coated circuit

Abstract Objective Heparin biocompatible coating is frequently used to reduce inflammation and blood coagulation during cardiopulmonary bypass (CPB) in cardiac surgery. Whether heparin coating is protective or damaging to the vascular endothelium is however unclear. We investigated whether heparin-coated circuits are associated with better preservation of microcirculatory perfusion and glycocalyx dimensions compared to non-heparin phosphorylcholine-coated circuits. Design Prospective, randomized blinded study. Setting Tertiary university hospital. Participants A total of 26 adults undergoing elective coronary artery bypass graft surgery with CPB. Interventions Phosphorylcholine (PC, n=13) versus heparin-coated circuits (HC, n=13). Measurements and Main Results Sublingual microcirculatory perfusion was measured before, during and after CPB using side stream dark field imaging and analyzed for perfused vessel density and perfused boundary region, an inverse parameter for glycocalyx dimensions. Onset of CPB was associated with an increase in perfused boundary region in the PC group that continued until the 3rd postoperative day (2.0±0.2 to 2.5±0.2 µm; p=0.018). This was paralleled by increased plasma syndecan-1 levels in the PC group. Contrastingly, both parameters remained unaltered in the HC group compared to baseline levels. CPB decreased perfused vessel density in both groups (CPB vs pre-CPB: PC: 17±2 to 13±2 mm/mm2, p=0.006; HC: 16±2 to 11±2 mm/mm2, p=0.003) and remained equally altered in the first three postoperative days. Conclusion The use of a heparin-coated circuit is associated with better preservation of the endothelial glycocalyx compared to phosphorylcholine-coated circuits, whereas microcirculatory perfusion was equally disturbed in both groups. Hence, CPB-induced microcirculatory perfusion disturbances seem to be coating independent.