Immediate effects of an intravenous fluid challenge on the endothelial glycocalyx in healthy anaesthetized cats.

Fluid overload accompanies critical illness, contributing to morbidity and mortality. The mechanism is multifactorial, involving microvascular and endothelial glycocalyx damage. Felines are prompt to fluid overload. Studies in other species suggest that IV fluid administration could damage the endothelial glycocalyx, contributing to fluid overload. Therefore, assessing the effects of IV fluids on the feline microcirculation is crucial to avoid such complications. This study evaluated whether a large-volume-short-duration IV fluid (fluid challenge) results in endothelial glycocalyx changes in cats, measured using sidestream dark field videomicroscopy and the Glycocheck™ software. Healthy anaesthetized cats (n = 29) randomly received 10 ml/kg/20 min of Hartman's solution, 6 % 130/0.4 tetrastarch, or no fluids. The GlycoCheck™ software calculated the perfused boundary region (PBR), an inverse estimate of endothelial glycocalyx thickness, from sublingual videomicroscopy images acquired before, during and immediately after intervention of microvessels with diameters 5-25 µm and 5-9, 10-19 and 20-25 µm subgroups. Packed cell volume was measured before and after intervention. We found that PBR did not increase significantly at the end of administration of either IV fluid, suggesting no immediate endothelial glycocalyx damage. Conversely, the PBR 10-19 µm increased over time in the control group (p = 0.029), indicating thinning of the endothelial glycocalyx. This suggests potential negative anaesthetic effects in this particular PBR subgroup. Since increases in this PBR were found in the control group not receiving IV fluids, these negative effects might have been mitigated by IV fluid administration in the other groups. Decreases in packed cell volume were associated with an increase in PBR 5-9 µm (p = 0.003). This study provides first insights into the feline endothelial glycocalyx response to IV fluids. Additional findings include potential anaesthetic effects on PBR and associations between PBR and packed cell volume.