Levels of circulating microparticles in septic shock and sepsis-related complications: a case-control study

BACKGROUND: Microparticles (MP) have been largely studied as potential biomarkers in septic shock (SS) though their biological and clinical relevance is still unclear. This case-control study describes the trend of various MP subtypes during SS to evaluate their possible association with severity of illness and sepsis-related complications (disseminated intravascular coagulation [DIC] and acute kidney injury [AKI]). METHODS: Forty patients admitted to the Intensive Care Unit with SS and 40 matched healthy volunteers were recruited. AnnexinV+, E-selectin+, thrombomodulin (TM+), leukocyte-derived (CD45+, CD36+) and platelet-derived MP (PMP-expressed as PMP/platelets ratio) were measured by flow-cytometry at baseline, on day 1, 3 and 7 after diagnosis. Severity of illness was assessed by Sequential Organ Failure Assessment Score, duration of vasoactive support and mechanical ventilation. Sepsis-related complications were considered. RESULTS : Overall, septic patients showed higher levels of all MP considered compared to controls. TM+ MP were significantly lower in more severe sepsis, while CD36+ MP and PMP/platelets ratio were significantly increased in patients requiring longer vasoactive support and mechanical ventilation. As for sepsis-related complications, a higher PMP/platelets ratio in patients who developed DIC and increased E-selectin+ MP in subjects who developed AKI were observed. PMP/platelets ratio at baseline was significantly associated with longer vasoactive support (OR=1.59 [1.05-2.42]), longer mechanical ventilation (OR=1.6 [1.06-2.42]) and DIC occurrence (OR=1.45 [1.08-1.96]). CONCLUSIONS: A global response through extra-vesiculation of endothelial cells, leukocytes and platelets during the early stages of SS was confirmed. The cellular activation was detected until day 3 after diagnosis. PMP/platelets ratio at diagnosis may be useful to evaluate SS severity and DIC occurrence.