Red blood cell deformability in patients with sepsis: a marker for prognosis and monitoring of severity.

Sepsis in different states of severity (sepsis, severe sepsis, septic shock and adult respiratory distress syndrome (ARDS)) is associated with microcirculatory blood flow abnormalities leading to decreased red blood cell's (RBC's) deformability, impaired oxygen delivery to tissues and organs failure. The main goal of the present study, was to first determine the values of RBC's deformability, in the course of patients treated in an Intensive Care Unit (ICU) for basically sepsis and then deteriorated states and secondly to establish the prognostic efficiency of the test. For this purpose a filtration method and the hemorheometer, was used to determine experimentally the RBC's deformability, by measuring the RBC's Index of Rigidity (IR). Our results indicated that the IR was significantly increased in all patient groups and it was found to be approximately 51% higher in patients with sepsis, 229% in patients with severe sepsis, 1285% in patients with septic shock and 923% in patients with ARDS than in the healthy donors. The relationships between IR and Simplified Acute Physiology Score II (SAPS) and IR and Projected Mortality (PM) were found to be IR = 2.0237(SAPS) - 58.807 (r=0.731) and IR = 1.0671(PM) - 5.9829 (r=0.726) respectively. Our findings imply a significant impairment of the membrane's deformability possibly due to changes in its structure. It seems that the RBC's deformability is a useful mechanical parameter to estimate the prognosis and monitor patients suffering from different severity levels of sepsis.