Saving the zone of stasis in burns with recombinant tissue-type plasminogen activator (r-tPA): an experimental study in rats

Abstract

Hypercoagulability 2-3 h following scald injury and vessel thrombosis are well-known complications of burn injury. The present study was designed to determine the effect of recombinant tissue-type plasminogen activator (r-tPA) on vessels thrombosis in zones of stasis postburn. Twenty rats were assigned to experimental and control groups (N:10). After shaving the backs, a 'comb burn' was given bilaterally on the back of the rats 0.5 cm lateral and parallel to the midline by using a brass probe consisting of four rows (10 x 20 mm) and three interspaces (5 x 20 mm). Standardized full-thickness burns of the experimental group were treated with r-tPA via femoral veins 2 h after the burn, while the control group rats were infused the same volume of saline. Interspaces between the rows and vertical space area were evaluated as zone of stasis. The skin blood flow measurements of interspaces revealed a decreased level immediately and 2 h after the burn injury, averaging 11.3 and 9.8 perfusion units, respectively. On day 7, blood flow measurements of interspace and vertical space areas significantly differed between the groups, averaging 11.9 PU in the experimental and 1.8 PU in the control groups (P<0.05). To evaluate perfusion, each rat received 3 mCi of technetium-99m methoxyisobutylisonitrile on the first or seventh day postburn. After 30 min, the entire back skins including the panniculus carnosus muscle layer were dissected away. Gamma camera images revealed that in the experimental group the interspace areas took up 60-90 per cent more radioactivity than the burned areas while in the control group 20-50 per cent more activity was taken up by the interspace area when compared to burned areas. Autoradiography gave the exact borders of the necrotic and survived tissues. The percentage of live interspace and vertical space areas in the experimental group was 87.8 per cent on day 7, while it was 31.8 per cent in the control group (P<0.05). Dry/wet ratios did not reveal any significant difference at 24 h postburn. These results confirm that treatment with this selective fibrinolytic agent (r-tPA) after burn injury would have some benefits on saving the zone of stasis in burns.