Immediate effects of whole blood donation on the endothelial surface layer and glycocalyx shedding

Background - The endothelium plays a pivotal role in regulating microvascular function, especially in situations associated with acute blood loss. Whether blood donation and the associated volume loss affects the dimensions of the endothelial surface layer (ESL) and glycocalyx integrity remains unknown. Materials and methods - This study was designed to determine real-time ESL and perfusion measurements of the sublingual microcirculation using sidestream dark field imaging performed in healthy subjects shortly before and after a donation of 500 mL whole blood. A novel image acquisition and analysis software (GlycoCheckT) automatically calculated the perfused boundary region (PBR), an inverse parameter for red blood cell (RBC) penetration into the ESL, in vessels between 5 and 25 mu m in diameter. Microvascular perfusion was measured by RBC filling percentage. Soluble glycocalyx components were determined in the peripheral circulation. Results - There was no significant immediate effect of whole blood donation on PBR and RBC filling percentage. Linear regression analysis revealed a distinct association between change in PBR and change in RBC filling percentage (regression coefficient beta: -0.040; 95% confidence interval: -0.049 to -0.030; p<0.001). A significant reduction in plasma heparan sulphate (1,329 +/- 316 vs 1,237 +/- 275 ng/mL, p=0.005) and hyaluronan (94 +/- 18 vs 90 +/- 16 ng/mL, p=0.002) was noted, while syndecan-1 levels (30 [23-50] vs 29 [24-46] ng/mL, p=0.282) remained unchanged. Discussion - Dimensions and integrity of the ESL appear to remain stable following a 500 mL whole blood donation and reflect its ability to ensure microvascular function and perfusion.