Resuscitation Strategies For Impact Thoracic Trauma With Acute Hemorrhagic Shock

PART ONEAn animal model of lung injury following impact thoracic trauma in ratsObjective To establish a novel animal model of impact lung injury in rats.Methods We induced lung contusion in anesthetized rats by dropping a 0.3-kg weight onto a precordial protective shield to direct the impact force away from the heart and toward the lungs.84 healthy Sprague-Dawley male rats were randomly divided into 7 groups to receive different percussion energy. The rats in group A were only anaesthetized, the rats in group B to group G were impacted by different energy from 2.7J to 0.9J. Blood pressure, heart rate and lung function were monitored during the experiment, arterial blood gases were measured at different time points. If the rats died, the causes of death were analyzed, the other rats were sacrificed, The heart and pulmonary morphology variation were observed after thoracotomy. We harvested the lung and recorded lung wet/dry weight ratios(W/D)to assess lung injury severity, and observed the changes of the pulmonary. Scores of pulmonary injury were assessed.Results The mortality of group B,C,D,E was 100%,75%,50%,50%, the cause of death including cardiogenic shock caused by heart damage, blood pneumothorax caused by pulmonary contusion and laceration, abnormal breathing caused by flail chest, unexplained irreversible respiratory arrest. Lung injury score, W/D of the survival rats showed a statistical significance with group F and G. The mortality of group F and G was 25% and 8.3%, after thoracotomy, typical changes of visual observation and pathological examination can be seen in group F, group G showed a slight degree of lung injury, while the control group was almost no change. Histology confirmed bilateral lung contusion without substantial cardiac muscle trauma.Conclusion The use of self-designed impact injury unit can produce a stable, satisfactory bilateral impact lung injury model easily, and is reproducible. With 1.2J combat energy, the mortality rates are low in rats, and bilateral lung injury is typical, so this can be used as study of the lung impact injury; with 0.9J combat energy, the bilateral lung injury is minor, can be used as an ideal lung injury animal model in combined injury.PART TWOResuscitation strategies for impact thoracic trauma with acute hemorrhagic shock in ratsObjective To compare the effects of Lactated Ringer's solution (LR),6.5% hydroxyethyl starch (HES),7.5% hypertonic solution (HS), hydrogen-rich saline solution (H2), Perfluorocarbon and 6.5% HES (PFC+HES) in a rat model of impact thoracic trauma with acute hemorrhagic shock, only the anesthesia, no injury, no recovery in the experimental group.Methods 46 healthy Sprague-Dawley male rats were randomly divided into 6 groups, the control group 6, only anaesthetized,8 in each group from group B to group F, were given different resuscitation fluid, LR group, HES group, HS group, H2 group, and PFC+HES group. Impact thoracic trauma was followed the methods of part one used 0.9J combat energy,5min later, the rats in the experimental group were exanguinated from femoral artery with a steady speed until mean arterial pressure lowered to 40 mmHg and maintenance for 50min, then different liquids were given through the femoral vein and then all rats were given oxygen. Two hours later, the survival rats were sacrificed, the blood samples were taken from the aorta, we harvested the lung and recorded lung wet/dry weight ratios(W/D)to assess lung injury severity, blood and BALF were centrifuged, and the supernatant is retained to measured IL-1β, SOD, TNF-a content. The W/D of the lung tissue is measured, and small intestine is taken for pathological examination.Results Two rats died of thoracic cavity hemorrhoea and extensive bleeding of one side of pulmonary and were excluded.120 minutes after resuscitation, blood lactate levels in HES group is significantly higher than the H2 group and PFC+HES group. Intestinal injury score in the control group is significant lower than the HS group, LR group (P<0.01), and PFC+HES group is significant lower than the control group (P<0.05), H2 group and HS group showed significant differences (P<0.01). The serum levels of IL-1βin H2 Group, PFC+HES group are significantly lower than the the control group, and HES group is significantly higher than PFC+HES group. The serum levels of TNF-a in LR and HES group are significantly higher than the control group and other groups. The serum levels of SOD in LR, HS, HES group are significantly higher than the control group and other groups. Pathological examination showed that the lung permeability index (LPI) in LR, HS, HES and control groups was significantly higher than the other groups, and significant interstitial edema, alveolar hemorrhage, atelectasis or pulmonary consolidation could generally seen in HS, HES and LR group.Conclusion H2, and PFC+HES have a better recovery resul in impact thoracic trauma with acute hemorrhagic shock rats, the degree of lung damage is relatively minor, and intestinal injury score, serum concentrations of inflammatory factors is low, so H2 or PFC +HES may be relatively good resuscitation fluid in the combined injury model.