Local infections in the body can spread to the blood and cause sepsis. Sepsis is a serious condition that often leads to tissue damage in several major organ systems with high mortality rates. The body's immune system plays an important role in containing the infection, but at the same time causes damage to the blood vessels of tissues, resulting in plasma leakage. The blood vessels of the lungs are particularly vulnerable, leading to pulmonary edema and severe respiratory failure. A similar process has been observed in patients with severe Covid-19 disease in the current coronavirus pandemic. We have previously shown that proteins released from the storage vesicles of a group of white blood cells (neutrophil granulocytes) are strongly involved in reducing the barrier function of blood vessels during inflammation. We have also found that the harmful effect of these proteins on blood vessel permeability can be effectively counteracted by treatment with the heparin-like substance sevuparin. In the current project, we want to establish the therapeutic value of sevuparin treatment in severe infectious conditions. Blood plasma from sepsis and Covid-19 patients is analyzed for proteins that induce increased vascular permeability and edema formation, and the ability of sevuparin to inactivate these substances is evaluated. The results from these analyses will form the basis for planned clinical trials with sevuparin in severe infections.