Albumin, HES 120 and dextran 70 as adjuvants to red blood cell concentrates: a study on colloid osmotic pressure changes in vitro.

An in vitro model of surgical bleeding was developed to simulate continuous blood loss and replacement therapy with plasma substitutes and red cell concentrates. The model was used to determine the lowest colloid concentration in vitro for each of the plasma substitutes that sustains colloid osmotic pressure above 2.4 kPa (or 18 mmHg) when used up to the recommended maximal total dose. Plasma, supernatant separated from red cell concentrates and dextran 70, hydroxyethyl starch 120 or albumin were mixed to create dilutions imitating plasma composition in the course of clinical blood loss and replacement therapy. The relative volume of each component was calculated according to the model when the bleeding was equal to multiples of 10% of blood volume up to a blood loss of 120%. Our measurements indicate that the colloid concentrations of 5.0% for albumin, 4.0% for hydroxyethyl starch 120 and 3.5% for dextran 70 preserve colloid osmotic pressure above 2.4 kPa.