Pro-inflammatory Role of Blood Platelets in Critically Ill Patients With Septic Shock.

Inclusion Criteria:

* Patients aged over 18 years admitted to an intensive care unit for:

  * a septic shock evolving for less than 24h (defined by an increase in the SOFA (Sequential Organ Failure Assessment) score of at least 2 points related to an infection, a persisting hypotension requiring vasopressors to maintain MAP ≥65 mmHg and a serum lactate level \>2 mmol/L (18 mg/dL) despite adequate volume resuscitation)
  * Or a systemic inflammatory response syndrome (SIRS) evolving for less than 24h (defined as 2 or more of the following variables: fever of more than 38°C or less than 36°C, heart rate of more than 90 beats per minute, respiratory rate of more than 20 breaths per minute or arterial carbon dioxide tension (PaCO2) of less than 32 mm Hg, abnormal white blood cell count (\>12,000/µL or \<4,000/µL or \>10% immature forms).

Exclusion Criteria:

* Age \< 18 years
* Known history of constitutional thrombopathy (Bernard Soulier's disease, Glanzmann thrombasthenia, Gray's syndrome or dense granule disease)
* Myeloproliferative or myelodysplastic syndrome
* Autoimmune thrombocytopenic purpura
* Acute leukemia
* Haemorrhagic shock
* Platelet transfusion within 7 days prior to inclusion
* Antiplatelet medication (clopidogrel or ticagrelor taken within 5 days of inclusion, prasugrel or dipyridamole within 7 days of inclusion)
* Active HIV infection or known active hepatitis B or C
* Pregnant or breastfeeding woman
* Patients protected by the law, under guardianship or trusteeship, or deprived of liberty
* Patients without health insurance