Septic shock is a major cause of mortality and morbidity worldwide. Serotonin (5-HT) is released by activated platelets into the circulation, and is mediator of endothelial dysfunction. 5-HT metabolism is known in immune system via specific 5-HT receptor, also in effects on the peripheral nervous system. Kinetic of 5-HT, tryptophan, kynurenine, MAO activity and IDO activity in human septic shock was never investigated.

Inclusion Criteria:

• Age above or equal to 18 years

• Strong presumption clinical sepsis

• Need for mechanical ventilation

• Body temperature above 38°C or below 36°C

• Heart rate above 90 bpm

• Systolic blood pressure of <90mm Hg despite adequate fluid replacement or a need for vasopressors less than 3 hours

• Presence of at least one of the following criteria:

  • Ratio of arterial oxygen tension over inspired fraction of oxygen of less than 300 mm Hg
  • Urinary output below 0.5 mL per kg of bodyweight per h or below 30 mL/h (for at least 1 h)
  • Arterial lactate concentration above 2 mmol/L

• Consent signed

Exclusion Criteria:

• Age below 18 years
• Pregnancy
• Underlying disease with a poor prognosis, a life expectancy of less than 24 hours
• Depression or melancholy
• Neuropsychiatric diseases: Seizure, manic psychosis, Migraine, or Drug addiction
• Neuroendocrine tumors
• Obstructive cardiomyopathy or acute myocardial ischaemia
• Pulmonary embolism
• Advanced stage cancer, malignant haemopathy, or AIDS with a decision to withhold or withdraw aggressive therapies
• Inclusion in another clinical trial
• Patient who receive before inclusion one of the following treatment known to modify serotonin level: almotriptan, amitriptyline, amoxapine, citalopram, clomipramine, clozapine, desipramine, dihydroergotamine, dolasetron, dosulepin, doxepin, eletriptan, ergotamine, flunarizine, fluoxetine, fluvoxamine, granisetron, imipramine, indoramin, interferon Alfa, interferon alfacon-1, interferon beta, iproniazid, maprotiline, methysergide, mianserin, Milnacipran, mirtazapine, moclobemide, naratriptan, olanzapine, ondansetron, oxetorone, paroxetine, pizotifen, risperidone, sertraline, sumatriptan, tianeptine, trimipramine, tropisetron, venlafaxine,viloxazine, zolmitriptan.
• No consent

Patients who were 18 years of age or older and had been hospitalized in our ICU were prospectively enrolled in the study if they met all eligibility criteria. Inclusion criteria were clinical evidence of infection, evidence of a systemic response to infection, and the onset of shock within the previous 3 hours.