Poor microcirculatory flow dynamics are associated with endothelial cell damage and glycocalyx shedding following traumatic hemorrhagic shock

Background: Endothelial cell damage and glycocalyx shedding following trauma can increase the risk of inflammation, coagulopathy, vascular permeability and death. Bedside sublingual videomicroscopy may detect worse flow and perfusion associated with this endotheliopathy. We compared markers of endotheliopathy with physical flow dynamics following traumatic hemorrhagic shock (THS). Methods: Sublingual incident dark field video-microscopy was performed at three time-points following injury (<10h; 10–30h; and 30–50h). Values for microcirculatory flow index (MFI), Point Of carE Microcirculation assessment (POEM) score, proportion of perfused vessels (PPV), microcirculatory heterogeneity index (MHI), perfused vessel density (PVD), and total vessel density (TVD) were obtained. ELISAs were performed to measure concentrations of thrombomodulin and syndecan-1 as biomarkers of endothelial cell damage and glycocalyx shedding respectively. Flow parameters were dichotomised to above and below average, and biomarkers compared between groups; below average MFI, POEM, PPV, PVD, and TVD, and above average MHI were considered poor microcirculatory flow dynamics. Results: 155 sublingual video-microscopy clips corresponding to 39 time-points from 17 trauma patients were analysed. Median age was 35 (IQR 25–52); 16/17 were male. Within 10h of injury, syndecan-1 concentrations were significantly higher compared to 17 age and sex-matched healthy controls (30 (IQR 20–44) ng/ml) for worse TVD (78 (IQR 63–417) ng/ml); PVD (156 (IQR 63–590) ng/ml); PPV (249 (IQR 64–578) ng/ml); MFI (249 (IQR 64–578) ng/ml); MHI (45 (IQR 38–68) ng/ml); and POEM scores (108 (IQR 44–462) ng/ml) (all p<0.01). Thrombomodulin was also raised within 10 hours of injury when compared to healthy controls (2.9 (IQR 2.2–3.4) ng/ml) for worse PPV (4.1 (IQR 3.4–6.2) ng/ml) and MFI (4.1 (IQR 3.4–6.2) ng/ml) (both p<0.05). Conclusions: Endothelial cell damage and glycocalyx shedding are associated with worse flow, density, and heterogeneity within micro-vessels following THS. The clinical utility of these biomarkers and flow parameters at the bedside are yet to be elucidated. Study type / level of evidence: Prognostic study, Level III