Study on characteristics of blast-fragment combined injury in dogs

It is known that blast wave and fragments are the primary causes of casualties from explosive weapons. To study the characteristics of blast-fragment combined injuries, functional and morphological changes were investigated in three groups of anesthetized dogs with blast injury, high velocity fragment extremity injury, and combined injuries of both types. The same parameters were also examined in a control group. Several of the functions investigated were systemic pressure, mean pulmonary arterial pressure (PAP), oxygenic partial pressure of arterial blood (Po2), thromboxane B2(TXB2), and 6-keto-prostaglandin F1 alpha (6-keto-PGF alpha). The morphologic study included gross, light microscopic, and transmission electronic microscopic observations. In the blast injury group, Po2 decreased and PAP, levels of blood plasma 6-keto-PGF alpha and level of TXB2 increased after injury, whereas PAP and level of 6-keto-PGF alpha decreased 24 hours after injury. The levels of 6-keto-PGF alpha and TXB2, in lung tissues, lung/body weight index were higher than those of the control group 24 hours after injury. The TXB2/6-keto-PGF alpha level in blood plasma increased slightly after injury, but showed no difference in lung tissue 24 hours after injury compared with the control group. The morphological changes showed that most of the animals sustained moderate lung injury. In the fragment injury group, Po2 decreased slightly and PAP increased slightly after injury; the levels of 6-keto-PGF alpha, TXB2 and TXB2/6-keto-PGF alpha in blood plasma increased after injury and were higher in lung tissue than in the control group 24 hours after injury. The lung/body weight index was nearly equal to that of control group. The morphological changes showed that only a few animals suffered from mild lung injury. In the combined injury group, Po2 and PAP changed in a manner similar to those of the other two injury groups but were more significantly. The level of blood plasma 6-keto-PGF alpha decreased gradually, whereas that of TXB2 increased permanently; thus, the levels of TXB2/6-keto-PGF alpha obviously increased after injury and were much higher than those in the other injury groups. The level of TXB2 in lung tissue was higher than that of the control group 24 hours after injury, but that of 6-keto-PGF alpha showed no change compared with that of the control group, and the level of TXB2/6-keto-PGF alpha was higher than in the other three groups. The morphological changes showed that most of animals sustained severe lung injury. It is concluded that extremity injury from high velocity fragment will aggravate lung blast injury. Changes in the levels of PGI2 and TXA2, can be used to determine the extent of injury in the three kinds of wounds. This may be useful for early diagnoses and rational treatment of the victims of explosion.