OXYGEN FOR HEART PATIENTS

Evidence unclear on oxygen use for heart attack

Overview: Coronary heart disease is the leading cause of death in the UK, accounting for a third of all deaths in people aged 35 and over. Myocardial infarction occurs when the flow of oxygenated blood in the heart is interrupted for a sustained period of time. Supplementary oxygen, delivered by a face mask or cannula, is often given to a patient with acute myocardial infarction (AMI) with the rationale that it may improve the oxygenation of the ischaemic myocardial tissue and reduce pain, infarct size and consequent morbidity and mortality.Current treatment: Current evidence neither supports nor refutes the routine use of oxygen for patients with acute myocardial infarction. It is biologically plausible that oxygen is helpful but it is also biologically plausible that it is harmful. NICE recommends oxygen should not be routinely administered to patients with acute chest pain of suspected cardiac origin, but that oxygen saturation levels should be monitored and used to guide its administration. SIGN guidance only recommends oxygen use in hypoxaemia

New evidence: A Cochrane systematic review (Cabello et al 2010 Jun 16;6:CD007160) found three randomised controlled trials comparing the outcomes in patients given oxygen to those given normal air to breathe. It examined whether there was a difference in death, pain and complications.The results reaffirm the current uncertainty of the role of oxygen in patients with myocardial infarction, and the authors call for a large, definitive randomised controlled trial on which clinical practice guidelines can be more confidently based.
Commentary: "The rapid assessment and treatment of a patient with a heart attack is drummed into most medical students very early on in their training. ABC: airway, breathing, circulation. Part of that resuscitation is the delivery of oxygen to patients with a heart attack, mainly due to the fact that the flow of oxygenated blood in the heart is stopped for a period of time."We have moved from one set of guidelines based on expert opinion to another set of guidelines with a different set of recommendations, but the research evidence has not changed. As this recent Cochrane review highlights, there is still no conclusive evidence from randomised controlled trials to support the routine use of inhaled oxygen in patients with acute heart attack."As the reviewers rightly state, we urgently need a large scale trial to unpick the uncertainty. Potentially, if further research addresses the uncertainty in one direction or another, implications for public health and cost efficiency could be huge." - Carl Heneghan, Director of thNHS Evidence - cardiovasculare Centre for Evidence Based Medicine, GP and clinical lecturer at the University of Oxford.
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