JAMA logoHyperoxia refers to excess flow of oxygen which may be caused while breathing air or oxygen at atmospheric pressures greater than normal. According to a recent study by the Cooper University Hospital those patients who have excessive oxygen levels in arterial blood (hyperoxia) following resuscitation from cardiac arrest might have a higher rate of death in the hospital when compared to similar people without arterial hyperoxia.

The authors highlighted that generally after a sudden cardiac arrest patients may suffer from a cardiovascular disease. In cases where return of spontaneous circulation (ROSC) from cardiac arrest is successfully accomplished also almost 60 percent of patients apparently fail to survive hospital discharge.

The study authors added, “In the search for modifiable post-ROSC factors, the role of supplemental oxygen, which is often administered in high concentrations to patients after cardiac arrest, has come into controversy. Laboratory investigations suggest that exposure to hyperoxia after resuscitation from cardiac arrest may worsen anoxic brain injury; however, clinical data are lacking.”

J. Hope Kilgannon, M.D., of Cooper University Hospital, Camden, N.J., and colleagues conducted a study to ascertain if hyperoxia after ROSC from cardiac arrest was linked to lack of survival in the hospital. The collected data dated between 2001 and 2005 came from a critical care database of intensive care units (ICUs) at 120 U.S. hospitals. It should be noted that all the patients included in the study were above the age of 17 years. The authors also maintained they had faced nontraumatic cardiac arrest, cardiopulmonary resuscitation within 24 hours prior to ICU arrival. The arterial blood gas analysis was performed within 24 hours following ICU arrival.

The investigators cautioned, “While we acknowledge that association does not necessarily imply causation, these data support the hypothesis that high oxygen delivery in the postcardiac arrest setting may have adverse effects.”

On the basis of a measurement of oxygen in arterial blood all the patients were divided into 3 groups. Out of a total of 6,326 patients’, 1,156 patients had hyperoxia at 18 percent. 3,999 had hypoxia at 63 percent along with deficiency of oxygen in the blood and the remaining 1,171 had normoxia at 19 percent and displayed normal level of oxygen in the blood.

The authors then analyzed that a 63 percent rate mortality rate was enjoyed by the hyperoxia group. But the hypoxia group displayed 57 percent mortality rate and 45 percent by the normoxia group. Also in-hospital mortality rate was higher in the hyperoxia group when compared to the normoxia group displaying a difference by 18 percent and with the hypoxia group showing a dissimilarity of 6 percent.

They further shared that even among the hospital survivors hyperoxia showed a lower likelihood of independent functional status at hospital discharge compared with normoxia.

The study is published in the June 2 issue of JAMA.