Oxygen therapy for acute myocardial infarction

Area of Science:

• Cardiology
• Emergency Medicine
• Respiratory Medicine

Background:

• Oxygen (O₂) is a common treatment for acute myocardial infarction (AMI), but its benefits and harms remain uncertain.
• Previous reviews, including a 2010 Cochrane review, found insufficient evidence regarding oxygen's effect on heart ischemia or infarct size.
• The lack of evidence since 2010 highlights the need for updated systematic reviews and further research on oxygen therapy in AMI.

Purpose of the Study:

• To evaluate the evidence from randomized controlled trials (RCTs) on the routine use of inhaled oxygen in patients with AMI.
• To determine if routine oxygen administration improves patient-centered outcomes, specifically pain and mortality.
• To assess the impact of oxygen therapy on heart ischemia and infarct size in AMI patients.

Main Methods:

• Systematic review of randomized controlled trials (RCTs) identified through comprehensive searches of multiple databases (Cochrane CENTRAL, MEDLINE, EMBASE, CINAHL, Web of Science, LILACS, PASCAL) up to July 2013.
• Inclusion criteria: RCTs involving patients with suspected or confirmed AMI (STEMI or non-STEMI) within 24 hours of onset, comparing inhaled oxygen to air.
• Data extraction and risk of bias assessment were performed independently by two authors. Primary outcomes included death, pain (analgesic use), and complications. Risk ratios (RR) with 95% confidence intervals (CI) were calculated.

Main Results:

• Four trials involving 430 participants were included in the updated review.
• A pooled analysis of 17 deaths showed a risk ratio (RR) of death of 2.05 (95% CI 0.75 to 5.58) in an intention-to-treat analysis, suggesting potential harm but with statistical uncertainty due to the small number of events.
• The pooled RR for analgesic use (as a proxy for pain) was 0.97 (95% CI 0.78 to 1.20), indicating no significant difference in pain perception between oxygen and air groups.

Conclusions:

• Current randomized controlled trial evidence does not conclusively support the routine use of inhaled oxygen in patients with acute myocardial infarction.
• The findings suggest a potential for harm with routine oxygen administration, although the evidence is not definitive.
• A large, definitive randomized controlled trial is urgently needed to resolve the uncertainty and address the discrepancy between clinical practice guidelines and the available trial evidence.