The Role of Serotonin in Intensive Care Patients

ICU-PATIENTS Inclusion criteria: * Active treatment of sepsis, septic shock, cardiac arrest with ROSC or severe multiple trauma. * Age over 18 years * Written consent from the patient or preliminary consent from the next of kin. * Receiving mechanical ventilator treatment upon inclusion. * Arterial and central venous cannulas present. Exclusion criteria: * Withdrawal of consent * Serotonergic carcinoid syndrome, short bowel or other considerable comorbidity altering serotonin content in blood. * Intoxication prior to ICU admission. HEALTHY CONTROLS Inclusion criteria: * Age over 18 years and signed written consent. * Conformed to diet and activity restrictions. Exclusion criteria: * Any acute illness or injury * Ongoing autoimmune, malignant, infectious, or other inflammatory disease. * Severe psychiatric disease or drug abuse. * Use of any medication except oral contraceptives last two weeks. * Withdrawal of consent. ICU CONTROLS Inclusion criteria: * Status epilepticus, encephalitis, stroke, or other localized neurological disease. * Age over 18 years * Written consent from the patient or preliminary consent from the next of kin. * Receiving mechanical ventilator treatment upon inclusion. * Arterial and central venous cannulas present. Exclusion criteria: * Withdrawal of consent * Clinical signs of infection with focal symptoms or temperature over 38,0°C. * Biochemical signs of infection or inflammation with leukocytes \> 11 x 10\^9/l, CRP \> 15 mg/l, or PCT \> 0,10 μg/l. * Respiratory failure with PaO2/FiO2 ratio \< 40 kPa. * Circulatory failure with MAP \< 60 or need for pressor treatment prior to sedation. * Thrombocytopenia or thrombocytosis with platelets \< 100 or \> 400 x 10\^9/l. * Serotonergic carcinoid syndrome, short bowel or other considerable comorbidity altering serotonin content in blood. * Extracranial autoimmune or malignant disease. * Severe psychiatric disease or drug abuse. * Intoxication or physical trauma prior to ICU admission.