Skin microcirculation reactivity to local thermal hyperaemia in patients with COVID-19 - A pilot observational study.

BACKGROUND: Endothelial dysfunction and microvascular disturbances are suggested to play a key role in higher morbidity and worse prognosis in patients with COVID-19 and cardiometabolic diseases. OBJECTIVE: Study was aimed to establish relationships between the skin microcirculation parameters and various clinical and laboratory indicators. METHODS: The study included 18 patients with moderate disease according to WHO criteria. Skin microcirculation measurements were performed by laser Doppler flowmetry using a heating test on the hairy skin of the right forearm. RESULTS: Baseline perfusion only correlated with C-reactive protein (Rs = 0.5, p = 0.034). Microcirculation indices characterising the development of hyperaemia during the first minute of heating (LTH1 and AUC60) showed significant correlations (Rs from 0.48 to 0.67, p <  0.05) with indices of general blood analysis and blood coagulation (fibrinogen, D-dimer, haemoglobin, erythrocyte count and haematocrit). Indexes characterising the dynamics of hyperaemia development over longer time intervals showed correlation with the glomerular filtration rate (Rs = 0.6, p = 0.009). CONCLUSION: Known COVID-19 risk factors (haemorheological parameters, age) are correlated with the microvascular reactivity to heating in patients with COVID 19. We suggest that, prospectively, the method of laser Doppler flowmetry could be used for non-invasive instrumental assessment of microcirculatory disorders in patients with COVID-19.