Effect of volume expanders on the lysability of ex vivo thrombi in the rabbit.

The lysability of ex vivo thrombi before and after the infusion of dextran 70 (0.5 g/kg, 1.5 g/kg and 2 g/kg), dextran 40 (1.5 g/kg), albumin 5% (1.5 g/kg) and normal saline (0.3 g/kg) was studied in rabbits. All rabbits received 125I fibrinogen before the experiment. The thrombi were treated with plasmin or sodium chloride and the radioactivity released in the supernatant by the thrombus was determined. The thrombus weight was also recorded. A gradual increase in the lysability of thrombi after dextran 70 administration was observed and the maximum effect occurred 24 hours later. Increasing dose of dextran 70 did not potentiate the release of 125I fibrin degradation products in the supernatant, but did significantly decrease the thrombus weight during the first hours postinfusion, Dextran 40 was found to have a similar action but the effect was shorter and the lysability at 24 hours was similar to the preinfusion values. Albumin 5% and normal saline increase the radioactivity released from the thrombi to the supernatant but no change in the thrombus weight was observed. A similar result was obtained in the control group. The present investigation demonstrated that increasing doses of dextran 70 potentiate the effect on thrombolysis demonstrated by statistically significant decrease in the thrombus weight. Furthermore, albumin 5% and normal saline increase the release of 125I fibrin split products in the supernatant but did not have any effect on the thrombus weight and finally, the rabbit showed a marked spontaneous fibrinolysis probably related to the stress, anesthetic agent and surgical manipulation.