| Thoracic firearm wounds are common in wartime, the incidence of which in wartime is over 12% in whole fireann wounds and 3%-4 1% in peacetime. In some countries where guns are not controlled strictly, the incidence of it can be as high as 23% in peacetime. Thoracic firearm wounds are severe and complex with a high morality and 60.1% of the cases die on spot or during evacuation. Therefore the early management on spot and during evacuation is of great importance. The experiments described in this paper used dogs as wound animals to study the mechanism of thoracic gunshot penetrating wound with an emphasis on the mechanism and change behavior of lung's injury with an aim to providing experimental foundation for clinic treatment. A total of 35 crossbreed healthy dogs were divided into 3 groups at random. In Group A (n=12, thoracic penetrating wounds group) thoracic penetrating wounds were made shot at the same site on low right breast in left lateral decubitus position with rifles (m=2.57g, d=5.S6rnm v=350 ?2Orn!s) from a distance of 10cm. In Group B (n=16, ligating intercostal artery before wound), the right intercostal artery near the spine was ligated before the shot and thoracic penetrating wound was made the same way as that of group A. In Group C (iv=7, ligating intercostal artery plus artificial pneumothorax before wound) the right intercostal artery near the spine was ligated and 600 70O ml air injected into the right thoracic cavity to make part of lung collapse before the wound was made the same as group A. Dogs in all groups were put in lateral recumbent position of the injured-side, the chest wall wounds were blocked, digital loop punctured to exhaust and closely drained instantly after wound. Dogs in each group were cannulated in right common carotid artery, right external jugular vein and tracheal before wound and the changes of respiratory rate, arterial pressure, venous pressure were observed continuously with an eight pathways physiological grapher before and after wound. The data of 5mm before wound, 5mm, 30mm, lh, 6h, 12h after wound were used for statistics analysis (the number of time points was determined by how long the animal could live). The dogs were dissected instantly if died, and killed 72h after wound if still lived. Changes of whole pathology were observed and lung were fixed routinely, observed with light microscope. Result: 1. Mortality and cause of death: Total mortality rate of Group A (group with thoracic penetrating wounds) was 83.3% and the mortality rate of 12h after wound was 58.3%. Total mortality rate of Group B (group with intercostal artery ligated before wound) was 37.5% and the mortality rate of 12h after wound was 18.8%. The mortality rate of Group C (group with intercostal artery ligated plus artificial pneumothorax before wound) was 0.00%. Among the 12h mortality of Group A, hemorrhagic shock was 100%. Among the 12h mortality of group B, hemorrhagic shock was 66.7% and ARDS was 33.3%. 2. Changes of respiration rate: Dogs in all groups were apneic for 5s after wound, then breathed deeper and faster. 1 h after wound, respiratory rates of group A and B were still faster than the normal while the respiratory rate of group C recovered to normal level. 3. Changes of airway pressure: Airway pressure of group A and B rose significantly after wound and was 2 times that before wound. The peek of airway pressure of Group C increased but not significantly. 30 mm after wound, the peek of airway pressure of Group A and B increased significantly and the peek of airway pressure of Group C decreased but still... |
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