Microcirculation disorders in patients with severe COVID-19 and development of bacterial sepsis

It is believed that microcirculation dysfunction in sepsis primarily caused by damage of the endothelium by infectious agents and pro-inflammatory cytokines. Mechanisms of impaired microcirculation in the severe course of COVID-19 and sepsis likely to be similar. However, there are few reports studied microcirculation disorders in patients with COVID-19, and their results are sometimes contradictory. Objective. To assess the microcirculation of patients with severe Covid-19 and the development of bacterial sepsis using nail bed microscopy and laser Doppler flowmetry. Materials and methods. 16 intensive care unit COVID-19 patients subsequently diagnosed with bacterial sepsis were examined. Patients underwent vital capillaroscopy and an occlusive test using laser Doppler flowmetry. The average rate of capillary blood flow, the size of the perivascular zone, the density of capillaries, the presence of intravascular aggregates, the increase in the amplitude of the maximum post-occlusive blood flow and the average value of postocclusive blood flow relative to the initial one were valuated. Additionally, the level of serum proadrenomedullin was evaluated. Studies were performed on the day of admission and in dynamics. Results. By the capillaroscopy analysis, microcirculation disorders were detected in the form of a decrease in the linear speed of capillary blood flow (<400 μm/s), an extention of the perivascular zone (>100 μm), the circulation of microaggregates; the absence of postocclusive hyperemia was determined by an occlusive test. Secondary bacterial infection led to an even greater aggravation of microcirculation disorders: an increase of the perivascular zone, the progression of intravascular aggregation resulting in microthrombosis with a decrease of the density of the capillary network (according to capillaroscopy), as well as a sharp decrease of amplitude maximal increment of blood flow of post-осclusive circulation at the time of an occlusive sample. We also revealed a trend of negative correlation between the level of serum proadrenomedullin and the maximum increase in blood flow during the occlusive test. Conclusion. The secondary bacterial infection in patients with COVID-19 leads to a significant aggravation of microcirculation disorders with the development of perfusion deficiency and interstitial edema. The increased plasma proadrenomedullin level supports the concept of the significant role of endothelial dysfunction in the pathogenesis of severe COVID-10 and bacterial sepsis.