胸段硬膜外阻滞对油酸致猪急性肺损伤时呼吸力学的影响

Change of respiratory mechanic variables in lung edema following acute lung injure induced by oleic acide

目的观察胸段硬膜外阻滞对油酸致猪急性肺损伤(ALI)时呼吸力学的影响。方法选健康家猪14只,肌内注射氯胺酮20mg/kg、阿托品0.05mg/kg,动物入睡后,建立耳缘静脉液路,静脉注射2.5%硫贲妥钠10mg/kg,经口气管插管,机械控制呼吸,维持正常的PaCO2。将油酸0.1ml/kg用0.9%氯化钠溶液稀释至20ml,经颈内静脉以40ml/h的速率持续静脉输注造模。造模成功后,将动物随机分S组(n=7):向硬膜外腔注入0.9%氯化钠溶液5ml;R组(n=7):向硬膜外腔注入0.25%罗哌卡因5ml。随后2组均持续泵入0.9%氯化钠溶液或0.25%罗哌卡因,观察4h。通过麻醉机气道压监测系统连续监测吸气峰压(PIP)、平均气道压(MPaw)、内源性呼吸末正压(PEEPi)作为基础值,并分别于ALI成功时(T0)及给罗哌卡因或0.9%氯化钠溶液1h(T1)、2h(T2)、3h(T3)、4h(T4)测定上述值。实验结束后,取肺组织,在光镜下观察肺组织病理变化。结果与基础值比较,ALI模型建立时2组PIP、Mpaw、PEEPi均升高(P<0.05),DLC降低(P<0.05)。2组基础及ALI模型建立时PIP、Mpaw、PEEPi和DLC差异无统计学意义(P>0.05),给药后各时间点R组PIP、Mpaw、PEEPi低于S组,DLC高于S组(P<0.05或<0.01)。光镜观察,R组肺组织病理学较S组明显减轻。结论胸段硬膜外阻滞可降低肺气道阻力,增加肺动态顺应性,改善肺组织的通气功能,对肺损伤有一定的保护作用。

Objective To observe the change of respiratory mechanic variables in lung edema following acute lung injure（ALI） induced by oleic acide. Methods Fourteen healthy piglets were used in this study. The catheter was inserted at T3.4 interspace and advanced 5cm into the epidural space cephalad. Oleic acid 0.1 ml/kg in 20ml of normal saline was infused via internal jugular vein. The ALl was considered to be successful according to PaO2/FiO2 〈 200 mm Hg. The PIP, Mpaw and PEEPi were measured before induction of ALI（ basline）, when ALl was induced （T0 ） and at 1,2,3,4 h after T0 （T1-4 ） , the animals were randomly divided into two groups： group A received 0. 25% ropavacine 5ml via thoracic epidural catheter at To followed by infusion of 0.25% ropivacaine 2ml/h for 4h, and group B received notmal saline instead of ropivacaine. The animals were killed at 4h after epidural ropivacaine, the histopathological changes of lungs were observed by light and electron microscopic. Results As compared with base values, the PIP, Mpaw, PEEPi were increased in both groups when the ALI models were established（ P 〈 0.01 ）, however, the DLC was obviously decreased （ P 〈 0.01 ）. There were no significant differences in PIP, Mpaw, PEEPi and DLC between the base values and the values when ALI model was established （ P 〉 0.05）, however, after administration the PIP, Mpaw, PEEPi in group R at different time points were significantly lower than those in group S,but DLC was significantly higher than that group S（ P 〈0. 05 or 〈 0.01 ）. The histopathological changes of lungs in group R were significantly lighter than those in group S. Conclusion The thoracic segments epidural block can reduce lung airway resistance, increase the dynamic compliance of lung,improve the ventilation function of lung tissues, as a resuh, which has certain protective effect on lung injury.