INTENSIVE CARE AND RESUSCITATION: Edited by Marek BrzezinskiOxygen in the critically ill friend or foe?Damiani, Elisaa; Donati, Abelea; Girardis, Massimob Author Information aAnesthesia and Intensive Care Unit, Department of Biomedical Sciences and Public Health, Università Politecnica delle Marche, Torrette di Ancona bDepartment of Anesthesia and Intensive Care, University Hospital of Modena, Modena, Italy Correspondence to Professor Massimo Girardis, Anesthesia and Intensive Care Unit, Department of Anaesthesia and Intensive Care, University Hospital of Modena, Via del Pozzo 71, 41124 Modena, Italy. E-mail: [email protected] Current Opinion in Anaesthesiology: April 2018 - Volume 31 - Issue 2 - p 129-135 doi: 10.1097/ACO.0000000000000559 Buy Metrics Abstract Purpose of review To examine the potential harmful effects of hyperoxia and summarize the results of most recent clinical studies evaluating oxygen therapy in critically ill patients. Recent findings Excessive oxygen supplementation may have detrimental pulmonary and systemic effects because of enhanced oxidative stress and inflammation. Hyperoxia-induced lung injury includes altered surfactant protein composition, reduced mucociliary clearance and histological damage, resulting in atelectasis, reduced lung compliance and increased risk of infections. Hyperoxemia causes vasoconstriction, reduction in coronary blood flow and cardiac output and may alter microvascular perfusion. Observational studies showed a close relationship between hyperoxemia and increased mortality in several subsets of critically ill patients. In absence of hypoxemia, the routine use of oxygen therapy in patients with myocardial infarction, stroke, traumatic brain injury, cardiac arrest and sepsis, showed no benefit but rather it seems to be harmful. In patients admitted to intensive care unit, a conservative oxygen therapy aimed to maintain arterial oxygenation within physiological range has been proved to be well tolerated and may improve outcome. Summary Liberal O2 use and unnecessary hyperoxia may be detrimental in critically ill patients. The current evidence supports the use of a conservative strategy in O2 therapy to avoid patient exposure to unnecessary hyperoxemia. Copyright © 2018 YEAR Wolters Kluwer Health, Inc. All rights reserved.