Plasma Volume Expansion with 5% Albumin Compared to Ringer's Acetate during Normal and Increased Microvascular Permeability in the Rat

Background: It is believed that the effectiveness of colloids as plasma volume expanders is dependent on the endothelial permeability for macromolecules. The objective of this study was to test the hypothesis that the plasma volume expanding effect of 5% albumin relative to that of a crystalloid solution is reduced if microvascular permeability is increased. Methods: A control group was resuscitated with either 5% albumin (8 ml/kg) or Ringer's acetate (36 ml/kg) immediately after a hemorrhage of 8 ml/kg (n = 29). In a second group, permeability was increased by inducing sepsis through cecal ligation and incision (n = 28). Three hours after cecal ligation and incision, the animals were resuscitated with either 5% albumin in a ratio of 1:1 relative to the volume of lost plasma, or Ringer's acetate in a ratio of 4.5:1. Results: In the hemorrhage group, plasma volumes at 15 min after resuscitation with albumin or Ringer's acetate had increased by 9.8 +/- 2.6 ml/kg (mean +/- SD) and 7.4 +/- 2.9 ml/kg and were similar at 2 and 4 h. Plasma volume 3 h after cecal ligation and incision had decreased by approximately 7 ml/kg, and at 15 min after resuscitation with albumin or Ringer's acetate it had increased by 5.7 +/- 2.9 and 2.4 +/- 3.0 ml/kg, respectively (P < 0.05). At 2 and 4 h after resuscitation, plasma volumes did not differ between the groups. Conclusion: This study does not support the hypothesis that the plasma-volume-expanding effect of albumin relative to that of crystalloids is decreased under conditions characterized by increased permeability.