Infectious endocarditis (IE) and other severe infections are well-known to induce significant changes in the immune response including immune functionality in a considerable number of affected patients. In fact, numerous patients with IE develop a persistent functional immunological phenotype that can best be characterized by a profound anti-inflammation and/or functional anergy. This was previously referred to as injury-associated immunosuppression (IAI) by Pfortmüller et al., published in Intensive Care Medicine Experimental 2017. IAI can be assessed by measurement of cellular (functional) markers. Persistence of IAI is associated with prolonged ICU length of stay, increased secondary infection rates, and death. Immunomodulation to reverse IAI was shown beneficial in immunostimulatory (randomized controlled) clinical trials. CytoSorb® treatment is currently used as standard of care in some institutions in surgically treated IE patients. The investigators aim to investigate two accepted treatment protocols and aim to explore whether adsorption with a cytokine adsorption filter can increase immune competence in treated individuals.