Limited effects of activated protein C on red blood cell deformability

BACKGROUND: Alterations of the microcirculation are common in critically ill patients and persistence of these alterations is associated with poor outcome. Infusion of high doses of activated protein C can ameliorate the microcirculation. Because red blood cells (RBCs) play an essential role in oxygen transport to the tissues, we studied the effects of activated protein C on RBC deformability in septic patients. METHODS: RBC deformability, assessed by ektacytometry (LORCA system) for shear stresses between 0.30 and 50 Pa, was compared in healthy volunteers and in septic patients before and during activated protein C infusion. RESULTS: RBC deformability was altered in septic patients compared to healthy volunteers. RBC deformability improved transiently during activated protein C infusion for shear stresses of 4.89 and 7.78 Pa, but the elongation index increased by just 3.4 and 3.2%, respectively. CONCLUSIONS: RBC deformability was altered in sepsis. Activated protein C had no clinically relevant effects on RBC deformability as assessed using ektacytometry.