Effects of transient intravascular volume overload on endothelial glycocalyx thickness in healthy anesthetized cats

IntroductionPrevious studies suggest that the endothelial glycocalyx is damaged by volume overload. This study assessed the effects of transient intravascular volume overload on estimated endothelial glycocalyx thickness in healthy cats, using sidestream dark field videomicroscopy and the Glycocheck™ software.MethodsThis was a prospective blinded cross-over single-center experimental study on twenty healthy cats. Cats were randomized to either receive 30 mL/kg/10 min of Hartman’s solution (volume overload group) or no fluids (control) with a washout of 7 days. Sublingual mucosa videomicroscopy images were acquired at T0 (baseline), T1 (immediately after intervention), T2 (3 h after end of intervention) and T3 (24 h after end of intervention) with three measurements performed per timepoint under propofol anesthesia. The perfused boundary region (PBR), an inverse estimate for endothelial glycocalyx thickness, for vessels with diameter of 5–25, 5–9, 10–19 and 20–25 μm, respectively, was then automatically calculated with the Glycocheck™ software. Packed cell volume (PCV) was measured at each timepoint. Data normality was assessed using the Shapiro–Wilk test and visual inspection. Linear mixed-effects regression modelling, with cat as a random effect, analyzed interactions between GlycoCheck™ and other parameters.ResultsPBR 5–25 μm, 5–9 μm and 10–19 μm increased over time, reaching significance at T2 (p = 0.001, p = 0.017 and p = 0.008, respectively). A significant group x timepoint interaction was identified for PBR 5–9 with decreased values at T2 (p = 0.028) and T3 (p = 0.010) in the volume overload group. Decreases in PCV were significantly associated with increases in PBR 5–25 μm (p = 0.003) and PBR 10–19 μm (p = 0.001).ConclusionThis study did not demonstrate decreases in estimated endothelial glycocalyx thickness after transient volume overload in healthy cats. The PBR did increase over time, suggesting potential anesthetic effects. Changes in PCV affected GlycoCheck™ parameters and this finding should be further explored. Further studies designed with understanding of feline volume kinetics are required to investigate the effects of IV fluids on the feline endothelial glycocalyx.