Assessment of blood substitutes: I. Efficacy studies in anesthetized and conscious rats with loss of 1/3, 1/2 and 2/3 blood volume.

Acute and long-term recovery (14 days) studies were conducted in conscious rats bled 1/3, 1/2, and 2/3 blood volume, and in anesthetized rats bled 1/3 volume. Study I: bled 1/3 blood volume. Study Ia: Anesthetized rats bled 1/3 blood volume were in shock and most died within 1 hour; the group which received infusion of 3x volume Ringer's lactate regained blood pressure with 100% long-term recovery. Study Ib: In conscious rats bled 1/3 blood volume, blood pressure did not fall to shock levels, and the long-term recovery in both the control group and the group which received 3x volume Ringer's lactate was 100%. Study II: Bled 1/2 blood volume. In conscious rats bled 1/2 volume, the blood pressure of the control group was slightly above 70 mmHg. Infusion of 3x volume Ringer's lactate or 7 gm% human albumin in Ringer's lactate increased blood pressure to above 90 mmHg in the acute study. Long-term recovery and survival rate was 80% in both the controls and the Ringer's lactate group, and 100% in the albumin group. Study III: bled 2/3 blood volume. In conscious animals, loss of 2/3 blood volume resulted in fall of blood pressure to shock levels and death of the animal within 1 hour. Infusion of 3x volume Ringer's lactate did not increase blood pressure to above shock level. Stroma-free hemoglobin and polyhemoglobin increased blood pressure, and whole blood returned blood pressure to normal. In long-term recovery, poly-hemoglobin, but not SFHb, was as effective as whole blood with 100% long term recovery. Animal models in Study I and II are suitable only for studies of volume replacement. Animal models in Study III, especially using long-term recovery studies, are more suitable for studying both volume and red blood cells replacements.