Abstract-Potter and Damiano recently assessed the hydrodynamic dimensions of the endothelial glycocalyx in vivo (mouse cremaster muscle venules) and in vitro (human umbilical vein and bovine aorta endothelium cultured in perfused microchannels) using fluorescent microparticle image velocimetry (Circ Res. 2008;102:770 -776). Great discrepancy was observed, the glycocalyx presenting a zone of interaction extending Ϸ0.52 m into the vessel lumen in vivo, but only 0.02 to 0.03 m from cultured cells. In an accompanying editorial, Barakat cautioned that the difference in hydrodynamic interaction did not allow one to conclude that the cultured cells totally lack a physical cell surface layer capable of mechanotransduction (Circ Res. 2008;102:747-748 and of endothelial cells grown in culture in perfused microchannels by means of fluorescent microparticle image velocimetry. 1 A great discrepancy was observed between the 2 settings, the glycocalyx presenting a zone of interaction extending Ϸ0.52 m into the vessel lumen in vivo, but only 0.02 to 0.03 m from cultured cells. As pointed out in an accompanying editorial by Barakat, this very intriguing difference in apparent thickness of the glycocalyx does not allow one to conclude that the cultured cells totally lack a cell surface layer. 2 In fact, an appeal is made for some form of direct visualization of the glycocalyx. The studies of Potter and Damiano also do not address the issue of whether there are differences in the molecular thickness or composition of the glycocalyx between in vivo and in vitro endothelial cells. 2 Based on their results, Potter and Damiano caution against inferences made from in vitro studies in the areas of microvascular permeability, inflammation, mechanotransduction, and atherosclerosis, if results from such studies depend on the integrity of the endothelial cell surface chemistry. 2 However, whether the glycocalyx of human endothelial cells might show similar discrepancy between the in vivo and in vitro setting remained to be shown.A healthy vascular endothelium is coated by a variety of transmembrane-and membrane-attached molecules such as syndecans and glypicans, both carrying heparan sulfate and chondroitin sulfate side chains, which together constitute the scaffold of the endothelial glycocalyx. 3,4 The glycocalyx is also made up of many functionally important molecular components such as cell adhesion molecules, eg, integrins and selectins, 3 inflammatory regulators and adsorbed components, eg, of the coagulation system. 5,6 Interaction with plasma colloids conveys mechanosensitivity to the endothelium, contributing to the regulation of vascular tone. 7 Initially, the endothelial glycocalyx was believed to be an insignificant structure with a thickness of only a few tens of Original

Augmenting HTK with human albumin improves endothelial integrity and heart performance after 4 hr cold ischemia, because of a marked protection of the endothelial glycocalyx. For the prevention of acute and chronic graft failure, the glycocalyx might represent a new target.

AimsPatients referred to the cath-lab are an increasingly elderly population. Thermodilution (TD, gold standard) and the estimated Fick method (eFM) are interchangeably used in the clinical routine to measure cardiac output (CO). However, their correlation in an elderly cohort of cardiac patients has not been tested so far.MethodsA single, clinically-indicated right heart catheterization was performed on each patient with CO estimated by eFM and TD in 155 consecutive patients (75.1±6.8 years, 57.7% male) between April 2015 and August 2017. Whole Body Oxygen Consumption (VO2) was assumed by applying the formulas of LaFarge (LaF), Dehmer (De) and Bergstra (Be). CO was indexed to body surface area (Cardiac Index, CI).ResultsCI-TD showed an overall moderate correlation to CI-eFM as assessed by LaF, De or Be (r2 = 0.53, r2 = 0.54, r2 = 0.57, all p < .001, respectively) with large limits of agreement (-0.64 to 1.09, -1.07 to 0.77, -1.38 to 0.53 l/m2/min, respectively). The mean difference of CI between methods was 0.22, -0.15 and -0.42 (all p<0.001 for difference to TD), respectively. A rate of error ≥20% occurred with the equations by LaF, De or Be in 40.6%, 26.5% and 36.1% of patients, respectively. A CI <2.2 l/m2min was present in 42.6% of patients according to TD and in 60.0%, 31.0% and in 16.1% of patients according to eFM by the formulas of LaF, De or Be.ConclusionAlthough CI-eFM shows an overall reasonable correlation with CI-TD, the predictive value in a single patient is low. CI-eFM cannot replace CI-TD in elderly patients.

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