En Route and Critical Care Department, Naval Medical Research Center, Silver Spring, MD, USA; Department of Surgery, Uniformed Services University of the Health Sciences, Bethesda, MD, USA; The Henry M. Jackson Foundation for the Advancement of Military Medicine Inc., Bethesda, MD, USA.
En Route and Critical Care Department, Naval Medical Research Center, Silver Spring, MD, USA; The Henry M. Jackson Foundation for the Advancement of Military Medicine Inc., Bethesda, MD, USA.
Injury. 2022 Nov;53(11):3596-3604. doi: 10.1016/j.injury.2022.09.004. Epub 2022 Sep 15.
Traumatic brain injuries (TBI) represent a significant percentage of critical injuries in military conflicts. Following injury, wounded warfighters are often subjected to multiple aeromedical evacuations (AE) and associated hypobaria, yet the impact in TBI patients remains to be characterized. This study evaluated the impact of two consecutive simulated AEs in a fluid-percussion TBI model in swine to characterize these effects.
Following instrumentation, anesthetized Yorkshire swine underwent a frontal TBI via fluid-percussion. A hypobaric chamber was then used to simulate AE at simulated cabin pressure equivalent to 8000ft (hypobaria) in a 6 h initial flight on day 3, followed by a 9 h flight on day 6, and were monitored for 14 days. Animals in the normobaria group were subjected to the same steps at sea level while Sham animals in both groups were instrumented but not injured. Parameters measured included physiologic response, intracranial pressure (ICP), hematology, chemistry, and serum cytokines. Histopathology of brain, lung, intestine, and kidney was performed, as well as fluorojade staining to evaluate neurodegeneration. All animals were divided into sub-groups by block randomization utilizing a 2-way ANOVA to analyze independent variables.
Survival was 100% in all groups. Physiologic parameters were largely similar across groups as well during both 6 and 9 h AE. Animals exposed to hypobaria in both the TBI and Sham groups had elevated heart rate (HR) during the 6 h flight (p<0.05). Three animals in the TBI hypo group demonstrated leukocytosis with histologic evidence of meningeal inflammatory response. Expression of serum cytokines was low across all groups. No significant neuronal degeneration was identified in areas away from the site of injury.
Aeromedical evacuation in swine was not associated with significant differences in physiologic measures, cytokine expression or levels of neuronal degeneration. Histological examination revealed higher risk of meningeal inflammatory response and leucocytosis in swine exposed to hypobaria.
创伤性脑损伤（TBI）在军事冲突中占重伤的很大比例。受伤后，受伤的战士经常经历多次航空医疗后送（AE）和相关的低气压，但其对 TBI 患者的影响仍有待描述。本研究评估了在猪的流体冲击性 TBI 模型中连续两次模拟 AE 的影响，以描述这些影响。
在仪器化后，麻醉的约克夏猪通过流体冲击性接受额部 TBI。然后使用低压舱在模拟舱压下模拟 AE，模拟舱压相当于 8000 英尺（低气压），在第 3 天进行 6 小时的初始飞行，然后在第 6 天进行 9 小时的飞行，并监测 14 天。在正常气压组中，动物接受相同的步骤在海平面上，而在两组中的假手术动物都进行了仪器化但未受伤。测量的参数包括生理反应、颅内压（ICP）、血液学、化学和血清细胞因子。对脑、肺、肠和肾进行组织病理学检查，并进行氟优德染色以评估神经退行性变。所有动物均通过块随机化分为亚组，利用 2 路方差分析分析独立变量。
所有组的存活率均为 100%。在两次 AE 的 6 和 9 小时期间，各组的生理参数也基本相似。在 TBI 和假手术组中，暴露于低气压的动物在 6 小时飞行期间心率（HR）升高（p<0.05）。TBI 低气压组的 3 只动物出现白细胞增多，并伴有脑膜炎症反应的组织学证据。所有组的血清细胞因子表达均较低。在远离损伤部位的区域未发现明显的神经元变性。
在猪中进行航空医疗后送与生理测量、细胞因子表达或神经元变性水平无显著差异相关。组织学检查显示，暴露于低气压的猪脑膜炎症反应和白细胞增多的风险更高。
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