Protective effects of plasma replacement fluids on erythrocytes exposed to mechanical stress.

Haemoglobin release from 40 suspensions of packed red blood cells in modified fluid gelatin, 4% albumin solution, 6% hydroxyethyl starch and normal saline was investigated in vitro during circulation with a roller pump from a heart-lung machine for 120 min at a flow rate of 2.5 l.min-1 at room temperature. The lowest haemoglobin release was obtained with erythrocytes in modified fluid gelatin, whereas free haemoglobin concentrations became progressively higher with albumin, hydroxyethyl starch and normal saline [median free haemoglobin (interquartile range) after 120 min circulation: gelatin 493 (360-601) mg.l-1, albumin 692 (590-1111) mg.l-1, hydroxyethyl starch 1121 (692-1518) mg.l-1, normal saline 1178 (881-1757) mg.l-1, p < 0.001]. Modified fluid gelatin appears to have potent erythrocyte protective properties similar to those of albumin. This effect could decrease mechanical haemolysis during extracorporeal circulation or cell saver autotransfusion if modified fluid gelatin is used as part of a priming solution or as an additive in wash solutions.