 This is a pilot study, including 10 ICU patients with severe sepsis with MFI 2,5 after fulfillment of a strict resuscitation protocol. At the start of the study, a baseline SDF measurement is made, when MFI 2,5 inclusion in the study is permitted and intravenous ketanserin administration is started and subsequently increased, guided by the effect on sublingual MFI, until a safe maximum dosage is reached. Safety margins for hypotension are defined in the study protocol. 