title: Carbon dioxide and the critically ill--too little of a good thing?
abstract: Permissive hypercapnia (acceptance of raised concentrations of carbon dioxide in mechanically ventilated patients) may be associated with increased survival as a result of less ventilator-associated lung injury. Conversely, hypocapnia is associated with many acute illnesses (eg, asthma, systemic inflammatory response syndrome, pulmonary oedema), and is thought to reflect underlying hyperventilation. Accumulating clinical and basic scientific evidence points to an active role for carbon dioxide in organ injury, in which raised concentrations of carbon dioxide are protective, and low concentrations are injurious. We hypothesise that therapeutic hypercapnia might be tested in severely ill patients to see whether supplemental carbon dioxide could reduce the adverse effects of hypocapnia and promote the beneficial effects of hypercapnia. Such an approach could also expand our understanding of the pathogenesis of disorders in which hypocapnia is a constitutive element.
authors.affiliation: Department of Anaesthesia and Medical-Surgical Intensive Care Unit, Toronto General Hospital, University Health Network, University of Toronto, Ontario, Canada.
authors.forename: J G
authors.initials: JG
authors.lastname: Laffey
authors.forename: B P
authors.initials: BP
authors.lastname: Kavanagh
mesh_terms: D000138:Acidosis / Q000378:metabolism; D002245:Carbon Dioxide / Q000009:adverse effects / Q000502:physiology* / Q000627:therapeutic use*; D003422:Critical Care / Q000379:methods; D016638:Critical Illness / Q000628:therapy*; D006801:Humans; D006935:Hypercapnia / Q000139:chemically induced; D016857:Hypocapnia / Q000150:complications / Q000517:prevention & control; D010101:Oxygen Consumption; D012121:Respiration, Artificial
chemical_list: D002245:Carbon Dioxide