Circulation profile of technetium-99m labeled liposome encapsulated hemoglobin in a 10% or 50% rat hypovolemic shock model.

The circulation kinetics and organ biodistribution of liposome encapsulated hemoglobin (LEH) was determined non-invasively in hypovolemic rats using a technetium-99m (Tc-99m) liposome labeling procedure. Rats with an indwelling catheter had either 10% or 50% of their blood volume removed and replaced with an equal volume of LEH labeled with Tc-99m (Tc-99m LEH). Mean arterial pressures and heart rates were monitored throughout the experiment. Gamma camera images were acquired during the first 90 minutes following infusion of the Tc-99m LEH and at 20 hours post-infusion. Blood capillaries were drawn at various times to monitor Tc-99m activity and the amount of LEH remaining in circulation. There were significant differences in the kinetics and biodistribution for the two groups. In the 10% group, the LEH was removed quickly from circulation with only 0.9% remaining at 20 hours, while the 50% group had 51.2% at 20 hours. The liver and spleen were the major organs responsible for LEH clearance. The 20 hour biodistribution by tissue sampling showed that the 10% group had 37.6% in the liver and 34.3% in the spleen, while the 50% group had only 18.4% in the liver and 14.6% in the spleen.