Free radicals and surgical stress

Free radicals have at least one unpaired electron. Some of them have very high reactivity and harmful to cells and tissues. O2-. and HO. are generated during re-perfusion phase of shock. Both induce lipid peroxidation and this attack initiates auto-continuing injury of membrane lipid by lipid peroxide. This may result in damage of membrane function and permeability alteration. NO is an another type of free radical and huge amount of NO is generated by inducible NO synthase with variety of stimulation. NO decreases vascular tonus and may be related with hyperdynamic circulatory status in sepsis. NOx and ONOO- which are NO derivatives, deteriorate mitochondrial function. Free radicals are one of major agents which damages patients under surgical stress, however, they also have important rules in our defense system. In this sense, control rather than suppression may be important to ameliorate injury caused by surgical stress.