The co–primary end point was myocardial infarct size based on cardiac enzymes and other markers (mean peak creatinine kinase, mean peak troponin I, area under the curve of creatinine kinase and troponin I).
Patient characteristics in the groups were well-matched. The oxygen was appropriately administered, with 99.5% receiving oxygen via face mask in the prehospital and in-hospital setting, he said. In the no-oxygen group, 4.5% received oxygen prehospital for low oxygen saturations, 7.7% were treated during the procedure in the cath lab, and over 20% while on the ward.
This resulted in significant differences in oxygen saturation throughout the study, Stub noted. Cardiac arrest and cardiogenic shock occurred similarly between groups. Time from paramedic arrival on the scene to hospital arrival was approximately 55 minutes in both groups. Interestingly, they found no indication of symptomatic benefits of oxygen, with pain scores and administration of analgesics also similar in both groups, he pointed out. Details of the procedures were also not different between the study arms.
On the primary end point, they found a significant 25% increase in creatine kinase (CK)—"so the suggestion of increased myocardial injury in those delivered oxygen," Stub noted.