Platelet function in sepsis

Coagulation abnormalities and thrombocytopenia are common in severe sepsis, but sepsis-related alterations in platelet function are ill-defined.

The purpose of this study was to elucidate the effect of sepsis on platelet aggregation, adhesiveness, and growth factor release.

Agonist-induced platelet aggregation was measured in platelet-rich plasma separated from blood samples collected from 47 critically ill patients with sepsis of recent onset. Expression of platelet adhesion molecules was measured by flow cytometry and the release of vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) was measured by ELISA in the supernatant of platelet aggregation.

Septic patients had consistently decreased platelet aggregation compared with controls, regardless of the platelet count, thrombin generation, or overt disseminated intravascular coagulation (DIC) status. The severity of sepsis correlated to the platelet aggregation defect. Adhesion molecules, receptor expression (CD42a, CD42b, CD36, CD29, PAR-1), and alpha-granule secretion detected by P-selectin expression remained unchanged but the release of growth factors was differentially regulated with increased VEGF and unchanged PDGF after agonist activation even in uncomplicated sepsis.

Sepsis decreases circulating platelets' hemostatic function, maintains adhesion molecule expression and secretion capability, and modulates growth factor production. These results suggest that sepsis alters the hemostatic function of the platelets and increases VEGF release in a thrombin-independent manner.