We’ve all seen the patients roll in with EMS nasal cannula snug against their nares. “Why are they on oxygen?” EMS response, “I don’t know he was having chest pain.” EKG shows STEMI! The last thing you’re thinking is whether their nasal cannula should be adjusted but maybe they don’t need the oxygen at all.
According to the AVOID Trial 2015 (an RCT in 441 patients) oxygen may actually make things worse. The authors compared 8L/min of O2 to no O2 in STEMI patients. Their primary endpoint was measuring the myocardial infarct size based on surrogate markers–>cardiac enzymes troponin and CK. They did not find a significant difference in peak troponins but did find those who received oxygen had significantly higher peak CK levels.
Their secondary outcomes found: (1) increase in recurrent MI at hospital discharge in the O2 group [5.5% versus 0.9%; P=0.006], (2) increase in frequency of cardiac arrhythmia in the O2 group (40.4% versus 31.4%; P=0.05), (3) increase in myocardial infarct size found on cardiac magnetic resonance @ 6 months in the O2 group [20.3 versus 13.1 g; P=0.04)
Their research was based on earlier RCTs that showed a possible deleterious effect of O2 on compromised cardiac tissue most likely 2/2 to: (1) increase coronary vasoconstriction–>decreased coronary blood flow (2) increased production of reactive oxygen species (ROS)–>reperfusion injury and increased vasoconstriction
No significant difference found in adverse events in the 2 groups at 6 mos (although there were more events in the O2 group 21.9% vs no O2 group 15.4%).
In Recap: I probably will opt for no O2 in my STEMI patients but for those other AMI patients stay tuned for the DETO2X-AMI Study!
- Stub, D., Smith, K., Bernard, S., Nehme, Z., Stephenson, M., Bray, J. E., … & Meredith, I. T. (2015). Air versus oxygen in ST-segment elevation myocardial infarction. Circulation, CIRCULATIONAHA-114.
- Bradford, C. 2015. AVOID Trial. The Bottom Line. http://www.thebottomline.org.uk/summaries/icm/avoid/