Effect of trauma-hemorrhagic shock on red blood cell deformability and shape.

Previous work in our laboratory has demonstrated a decrease in red blood cell (RBC) deformability in sepsis. This has not been studied following hemorrhagic shock. We tested the hypotheses that hemorrhagic shock, associated with soft tissue trauma, leads to decreased RBC deformability and that this is related to alterations in the resting shape of the RBC. Elongation index (EI), a measure of RBC deformability, was determined over a range of shear stresses from 0.3 to 30 Pa in 26 male rats before and at various times after 90 min of hemorrhagic shock. RBC resting shape was determined by scanning electron microscopy. The data demonstrate that EI decreased significantly at the end of shock (before resuscitation), and remained below normal throughout the 6-h postshock period. Eight of the 26 animals decompensated during shock, requiring return of a portion of the shed blood to maintain a mean arterial pressure of 30-40 mmHg. Four of eight decompensated animals died before the end of the study period, compared with none of the compensated rats. The decompensated rats had significantly lower EI at 0.3 Pa by the end of the shock period (0.050 +/- 0.009) than the compensated shock group (0.058 +/- 0.006; P < 0.05). RBC shape alterations were first demonstrated at the end of the shock period and persisted throughout the 6-h postshock resuscitation period. These data indicate that trauma and hemorrhagic shock cause RBC shape alterations and a significant decrease in RBC deformability, which becomes manifested during the shock period and persists for at least 6 h postshock. Additionally, a direct relationship appears to exist between the magnitude of the physiologic insult and the degree of RBC damage.