Oldham K M, Bowen P E
Mt Sinai Hospital Medical Center, Chicago, IL 60608, USA.
J Am Diet Assoc. 1998 Sep;98(9):1001-8. doi: 10.1016/S0002-8223(98)00230-2.
Reactive oxygen species (ROS) are constantly produced in human beings under normal circumstances. Antioxidant systems help defend the body against ROS but may be overwhelmed during periods of oxidative stress, which can cause lipid peroxidation, damage to DNA, and cell death. Critical illness, such as sepsis or adult respiratory distress syndrome, can drastically increase the production of ROS and lead to oxidative stress. Sources of oxidative stress during critical illness include activation of the phagocytic cells of the immune system (the respiratory burst), the production of nitric oxide by the vascular endothelium, the release of iron and copper ions and metalloproteins, and the vascular damage caused by ischemia reperfusion. Only indirect measurements of ROS are available, but the presence of oxidative stress in critical illness is supported by clinical studies. In general, serum antioxidant vitamin concentrations seem to decrease and measures of oxidative stress seem to increase in critically ill populations. Oxidative stress has been associated with sepsis, shock, a need for mechanical ventilation, organ dysfunction, acute respiratory distress syndrome, disseminated intravascular coagulation, surgery, and the presence of an acute-phase response. In addition, higher levels of oxidative stress seem to occur in patients with more notable injuries. Dietary supplementation with antioxidant vitamins seems to be the logical answer to decreasing serum antioxidant concentrations, but antioxidants may have adverse effects. The benefit of supplementing antioxidants in critically ill populations has not been shown and requires further study.
在正常情况下，人体会持续产生活性氧（ROS）。抗氧化系统有助于保护身体免受ROS的侵害，但在氧化应激期间可能会不堪重负，氧化应激会导致脂质过氧化、DNA损伤和细胞死亡。危重病，如脓毒症或成人呼吸窘迫综合征，会大幅增加ROS的产生并导致氧化应激。危重病期间氧化应激的来源包括免疫系统吞噬细胞的激活（呼吸爆发）、血管内皮产生一氧化氮、铁和铜离子及金属蛋白的释放，以及缺血再灌注引起的血管损伤。目前只能间接测量ROS，但临床研究支持危重病中存在氧化应激。一般来说，危重病患者群体中血清抗氧化维生素浓度似乎会降低，氧化应激指标似乎会升高。氧化应激与脓毒症、休克、机械通气需求、器官功能障碍、急性呼吸窘迫综合征、弥散性血管内凝血、手术以及急性期反应的存在有关。此外，损伤越严重的患者似乎氧化应激水平越高。通过饮食补充抗氧化维生素似乎是应对血清抗氧化剂浓度降低的合理方法，但抗氧化剂可能有不良影响。在危重病患者群体中补充抗氧化剂的益处尚未得到证实，需要进一步研究。
