Summary We investigated microcirculatory perfusion disturbances following cardiopulmonary bypass in the early postoperative period and whether the course of these disturbances mirrored restoration of endothelial glycocalyx integrity. We performed sublingual sidestream dark field imaging of the microcirculation during the first three postoperative days in patients who had undergone on‐pump coronary artery bypass graft surgery. We calculated the perfused vessel density, proportion of perfused vessels and perfused boundary region. Plasma was obtained to measure heparan sulphate and syndecan‐1 levels as glycocalyx shedding markers. We recruited 17 patients; the mean ( SD ) duration of non‐pulsatile cardiopulmonary bypass was 103 (18) min, following which 491 (29) ml autologous blood was transfused through cell salvage. Cardiopulmonary bypass immediately decreased both microcirculatory perfused vessel density; 11 (3) vs. 16 (4) mm.mm −2 , p = 0.052 and the proportion of perfused vessels; 92 (5) vs. 69 (9) %, p < 0.0001. The proportion of perfused vessels did not increase after transfusion of autologous salvaged blood following cardiopulmonary bypass; 72 (7) %, p = 0.19 or during the first three postoperative days; 71 (5) %, p < 0.0001. The perfused boundary region increased after cardiopulmonary bypass; 2.2 (0.3) vs. 1.9 (0.3) μm, p = 0.037 and during the first three postoperative days; 2.4 (0.3) vs. 1.9 (0.3) μm, p = 0.003. Increased plasma heparan sulphate levels were inversely associated with the proportion of perfused vessels during cardiopulmonary bypass; R = −0.49, p = 0.02. Plasma syndecan‐1 levels were inversely associated with the proportion of perfused vessels during the entire study period; R = −0.51, p < 0.0001. Our study shows that cardiopulmonary bypass‐induced acute microcirculatory perfusion disturbances persist in the first three postoperative days, and are associated with prolonged endothelial glycocalyx shedding. This suggests prolonged impairment and delayed recovery of both microcirculatory perfusion and function after on‐pump cardiac surgery.

Background Microcirculatory dysfunction is associated with multiple organ failure and unfavorable patient outcome. We investigated whether therapeutically targeting the endothelial angiopoietin/Tie2 system preserves microvascular integrity during hemorrhagic shock. Methods Rats were treated with the angiopoietin-1 mimetic vasculotide and subjected to hemorrhagic shock and fluid resuscitation. Microcirculatory perfusion and leakage were assessed with intravital microscopy (n = 7 per group) and Evans blue dye extravasation (n = 8 per group), respectively. The angiopoietin/Tie2 system was studied at protein and RNA level in plasma, kidneys, and lungs. Results Hemorrhagic shock significantly reduced continuously perfused capillaries (7 ± 2 vs. 11 ± 2) and increased nonperfused vessels (9 ± 3 vs. 5 ± 2) during hemorrhagic shock, which could not be restored by fluid resuscitation. Hemorrhagic shock increased circulating angiopoietin-2 and soluble Tie2 significantly, which associated with microcirculatory perfusion disturbances. Hemorrhagic shock significantly decreased Tie2 gene expression in kidneys and lungs and induced microvascular leakage in kidneys (19.7 ± 11.3 vs. 5.2 ± 3.0 µg/g) and lungs (16.1 ± 7.0 vs. 8.6 ± 2.7 µg/g). Vasculotide had no effect on hemodynamics and microcirculatory perfusion during hemorrhagic shock but restored microcirculatory perfusion during fluid resuscitation. Interestingly, vasculotide attenuated microvascular leakage in lungs (10.1 ± 3.3 µg/g) and significantly reduced the required amount of volume supplementation (1.3 ± 1.4 vs. 2.8 ± 1.5 ml). Furthermore, vasculotide posttreatment was also able to restore microcirculatory perfusion during fluid resuscitation. Conclusions Targeting Tie2 restored microvascular leakage and microcirculatory perfusion and reduced fluid resuscitation requirements in an experimental model of hemorrhagic shock. Therefore, the angiopoietin/Tie2 system seems to be a promising target in restoring microvascular integrity and may reduce organ failure during hemorrhagic shock.

Background: Cardiopulmonary bypass (CPB) during cardiac surgery impairs microcirculatory perfusion and is paralleled by vascular leakage. The endothelial angiopoietin/Tie2 system controls microvascular leakage. This study investigated whether targeting Tie2 with the angiopoietin-1 mimetic vasculotide reduces vascular leakage and preserves microcirculatory perfusion in a rat CPB model. Methods: Rats were subjected to 75 min of CPB after treatment with vasculotide or phosphate buffered solution as control or underwent a sham procedure. Microcirculatory perfusion and leakage were assessed with intravital microscopy (n¼10 per group) and Evans blue dye extravasation (n¼13 per group), respectively. Angiopoietin-1,-2, and Tie2 protein and gene expression were determined in plasma, kidney, and lung. Results: CPB immediately impaired microcirculatory perfusion [5 (4e8) vs 10 (7e12) vessels per recording, P¼0.002] in untreated CPB rats compared with sham, which persisted after weaning from CPB. CPB increased circulating angiopoeietin-1,-2, and soluble Tie2 concentrations and reduced Tie2 messenger ribonucleic acid (mRNA) expression in kidney and lung. Moreover, CPB increased Evans blue dye leakage in kidney [12 (8e25) vs 7 (1e12) mg g À1 , P¼0.04] and lung [and 23 (13e60) vs 6 (4e16) mg g À1 , P¼0.001] compared with sham. Vasculotide treatment preserved microcirculatory perfusion during and after CPB. Moreover, vasculotide treatment reduced Evans blue dye extravasation in lung compared with CPB control [18 (6e28) mg g À1 vs 23 (13e60) mg g À1 , P¼0.04], but not in kidney [10 (3e23) vs 12 (8e25) mg g À1 , P¼0.38].