Morphologic changes of red blood cells during hemorrhagic shock replicate changes of aging

Blood loss leads to the reduction in vitality of red blood cells (RBCs). Ho wever, the changes in morphology at different stages of hemorrhagic shock h ave not been studied. Thus, the aim of this study was to identify and quant itate the sequence of morphological changes in RBCs during hemorrhage. This study was performed on 15 adult inbred dogs. Blood samples were taken befo re hemorrhage, when the mean arterial pressure reached 40 mm Hg (initial st age of shock), and at a mean arterial pressure level of 20 mm Hg (decompens ated stage of shock). The volume of blood removed averaged 33.6 +/- 8.9 and 55.1 +/- 6.9 mL/kg, respectively. Evaluation of RBC morphology was perform ed by computerized light microscopic morphometry and scanning electron micr oscopy. At the early stage of hemorrhage the number of "young-appearing" RB Cs with large visible surface areas (41-50 mum(2)) increased from 17.7% +/- 3.1% to 26.6% +/- 3.5% (P < 0.05). Concomitantly, the number of "old-appea ring" RBCs with small visible surface area (20-30 <mu>m(2)) significantly d ecreased from 5.3% +/- 2.7% to 2.7% +/- 2.3% (P < 0.01). At the stage of de compensated blood loss, the opposite phenomenon was observed. The number of "old-appearing" RBCs increased to 8.2% +/- 1.1% (P < 0.01), whereas the nu mber of "young-appearing" RBCs decreased to 12.3% +/- 4.2% (P < 0.01). The changes in visible surface area of RBCs was accompanied by significant alte rations in their shape. The percentage of abnormal shaped RBCs increased fr om 8.9% +/- 1.1% before the hemorrhage to 36.4% +/- 5.8% at the stage of de compensated hemorragic shock (P < 0.01). Thus, during the late decompensate d stage of hemorrhagic shock, RBCs assume shape and surface area changes th at are similar to those seen in aging. These changes in RBC size and shape may be due to the effects of shock-induced oxidative stress.