Microvascular reactivity and endothelial glycocalyx degradation when administering hydroxyethyl starch or crystalloid during off-pump coronary artery bypass graft surgery: a randomised trial

The infusion of fluids to patients may affect tissue microcirculation and the endothelial glycocalyx. However, the effects of hydroxyethyl starch and crystalloid on endothelial glycocalyx degradation and microvascular reactivity have not been evaluated in detail. We hypothesised that hydroxyethyl starch may cause less endothelial glycocalyx degradation and better microvascular reactivity than that caused by crystalloid. We randomly allocated 120 patients undergoing off-pump coronary artery bypass graft surgery to receive up to 20 ml.kg^-1 of either hydroxyethyl starch 670/0.75 or crystalloid for intra-operative fluid resuscitation. Crystalloid was then infused to meet ongoing fluid requirements. During the peri-operative period, vascular occlusion tests were performed to assess microvascular reactivity, and serum syndecan-1 was measured as an index of endothelial glycocalyx degradation. The median (IQR [range]) fluid infused during surgery was significantly less in the hydroxyethyl starch group than the crystalloid group; 2800 (2150-3550 [1400-7300]) vs. 3925 (3100-4725 [1900-6700]) ml, respectively, p < 0.001. Vascular occlusion test parameters, including tissue oxygen saturation, occlusion and recovery slope did not differ significantly between the groups. Peri-operative changes in syndecan-1 were not significantly different between the groups. We conclude that, in patients undergoing off-pump coronary artery bypass graft surgery, compared with crystalloid, the use of hydroxyethyl starch 670/0.75 did not result in significant differences in microvascular reactivity or endothelial glycocalyx degradation.