REN and ischemia reperfusion injury: Sympathetic excitation of the body after hemorrhagic shock promotes the secretion of catecholamines, leukotrienes, angiotensin, and endothelin by the renin-angiotensin system (RAS), while the coagulation-fibrinolytic system is also activated, all of which promote pulmonary vasoconstriction, causing a decrease in pulmonary blood flow and affecting capillary permeability, leading to ischemia-reperfusion injury in the lungs [13, 14].