Carbon monoxide poisoning – a review article

The incorporation of CO-oximeters in modern blood gas analyzers allows rapid determination of the amount of carboxyhemoglobin in blood. This, in turn, allows rapid diagnosis of carbon monoxide poisoning, the subject of a recently published review. 

This wide-ranging review article begins with consideration of the physical properties of carbon monoxide and the origins of its natural presence, at low concentration, in environmental air. There follows discussion of the quite normal endogenous production of carbon monoxide, and current understanding of the biological functions of this endogenously produced carbon monoxide. 

Attention then turns to carbon monoxide poisoning itself, which arises as a result of breathing air that is unnaturally polluted with carbon monoxide. The sources of this “artificial” carbon monoxide are listed under the general heading: “derived from incomplete combustion of carbon fuels”. They include among many others: motor vehicle exhaust, wood fires, gas fires, paraffin stoves and cigarette smoke. 

The potential sources of carbon monoxide pollution are so numerous and common that epidemiological evidence presented by the authors allows them to state that carbon monoxide poisoning is “unquestionably the leading cause of unintentional poisoning deaths in the Western countries”. 

A detailed discussion of the pathophysiology of carbon monoxide intoxication begins with a reminder that carbon monoxide is toxic principally because it binds with hemoglobin to form carboxyhemoglobin. Since carboxyhemoglobin cannot transport oxygen, tissues are deprived of oxygen. Much of the toxic effect results from tissue hypoxia, particularly in the brain and heart. 

A major focus of the article is the cardiac injury that can be associated with carbon monoxide poisoning, which is caused partly by hypoxia (ischemic damage), but also directly by carbon monoxide itself. This cardiac injury is addressed in terms of its pathophysiology, its acute clinical (symptomatic) consequence, and long-term deleterious effect. 

In further separate sections the authors deal with more general acute signs and symptoms of carbon monoxide poisoning; the role of laboratory testing in both diagnosis of carbon monoxide poisoning and determining the extent, if any, of associated cardiac injury; and finally, treatment options. This last section addresses the somewhat contentious issue of hyperbaric oxygen therapy. 

Along with its 96 references this review provides much detail about current understanding of carbon monoxide poisoning, as well as its diagnosis and treatment.