Hyperoxia and oxidative stress in anesthesia and critical care medicine

Abstract

Oxygen administ ration is part icularly relevant in pat ient s undergoing surgery under general anesthesia and in those who suffer from acut e or crit ical illness. Nevertheless, excess O2, or hyperoxia, is also known to be harmful. Toxicity arises from t he enhanced formation of react ive oxygen species (ROS) t hat, exceeding the ant ioxidant defense, may generate oxidat ive stress. Oxidat ive st ress markers are used to quant ify ROSt oxicity in clinical and non-clinical sett ings and represent a promising tool to assess t he opt imal FiO2 in anesthesia and crit ical care sett ing. Despit e controversial, the guidelines for the regulat ion of FiO2 in such sett ings suggest t he adopt ion of high perioperative oxygen levels. However, hyperoxia has also been shown t o be an independent mort ality risk fact or in crit ically ill pat ient s. In t his lit erat ure review, we discuss the biochemical mechanisms behind oxidative st ress and the available biomarkers for assessing the pro-oxidant vs ant ioxidant st at us. T hen, we summarize recent knowledge on the hyperoxia-relat ed consequences in the most common anest hesia and crit ical care sett ings, such as t raumat ic brain injury or cardiac arrest. To t his purpose, we searched the P ubMed dat abase according to the following combinat ion of key words: (“hyperoxia” OR“FiO2” OR“oxygen therapy”) AND (“oxidat ive stress” OR“ROS” OR“RNS” OR“lipid peroxidat ion”) AND (“anesthesia” OR“surgery” OR“int ensive care”). We focused in the result s from the past 20 years. Available evidence point s toward a conservat ive monitoring and use of oxygen, unless there is solid proof of it s efficacy.