Fact or Fiction: O2 for Myocardial Infarction? From the Publishers of CONSULT GUYS Fact or Fiction: O2 for Myocardial Infarction? COPYRIGHT © 2016, ALL RIGHTS RESERVED

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Dear Dynamic Duo: I was so impressed by your recent “myth busting” episode where in a brief 10 minute period you debunked the myths related to URI in the preoperative period, pseudo benefit of fish oil, and checking a urinalysis before joint replacement therapy. I am writing to see if you can settle a dispute at my hospital. It relates to the treatment of patients with ST segment elevation acute MI. Ever since I finished my training in 1978 its been my belief that supplemental oxygen should be given to all patients with suspected STEMI. It’s a basic principle of acute care medicine – if the heart is deprived of oxygen it is logical to augment myocardial oxygen supply to improve myocardial oxygenation by providing concentrated oxygen via face mask or nasal cannula. Our residents though have challenged me. They say that oxygen even in the STEMI patient should only be given to those who are hypoxic. My hope is that the “Dynamic Duo” aka Consult Guys can explore this one for me.

STEMI and O2 Therapy Questions Does supplemental oxygen increase myocardial oxygenation? Is supplemental oxygen beneficial to all patients with myocardial ischemia, myocardial infarction? Copyright © 2016

Gunnar RM, Bourdillon PV, Dixon DW, et al Gunnar RM, Bourdillon PV, Dixon DW, et al. Guidelines for the early management of patients with acute myocardial infarction: A report of the American College of Cardiology/American Heart Association Task Force on Assessment of Diagnostic and Therapeutic Cardiovascular Procedures (subcommittee to develop guidelines for the early management of patients with acute myocardial infarction). J Am Coll Cardiol. 1990;16(2):249-292. doi:10.1016/0735-1097(90)90575-A.

Committee Members, Ryan TJ, Anderson JL, et al Committee Members, Ryan TJ, Anderson JL, et al. ACC/AHA guidelines for the management of patients with acute myocardial infarction: A report of the American College of cardiology/American Heart Association Task Force on Practice Guidelines (Committee on Management of Acute Myocardial Infarction). J Am Coll Cardiol. 1996;28(5):1328-1419. doi:10.1016/S0735-1097(96)00392-0.

Antman, EM et al. ACC/AHA guidelines for the management of patients with ST-elevation myocardial infarction: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Revise the 1999 Guidelines for the Management of Patients with Acute Myocardial Infarction). Circulation. 2004 Aug 31;110(9):e82-292.

O'Gara PT, Kushner FG, Ascheim DD, et al O'Gara PT, Kushner FG, Ascheim DD, et al. 2013 ACCF/AHA Guideline for the Management of ST-Elevation Myocardial Infarction: A Report of the American College of Cardiology Foundation /American Heart Association Task Force on Practice Guidelines.  J Am Coll Cardiol. 2013;61(4):e78-e140. doi:10.1016/j.jacc.2012.11.019.

STEMI 2013 Oxygen therapy Few data exist to support or refute the value of routine oxygen in the acute phase of STEMI. Pooled Cochrane analysis of 3 trials shows a 3-fold higher risk of death for patients with acute MI treated with oxygen than for patients with AMI treated with room air. Oxygen therapy is appropriate for patients with hypoxemia (O2 saturation < 90%). Supplementary O2 may increase coronary vascular resistance.

RUSSEK HI, REGAN FD, NAEGELE CF RUSSEK HI, REGAN FD, NAEGELE CF. ONE HUNDRED PER CENT OXYGEN IN THE TREATMENT OF ACUTE MYOCARDIAL INFARCTION AND SEVERE ANGINA PECTORIS.  JAMA. 1950;144(5):373-375. doi:10.1001/jama.1950.02920050013003.

Rawles JM, Kenmure ACF. Controlled trial of oxygen in uncomplicated myocardial infarction. Br Med J. 1976 May 8; 1(6018): 1121–1123.

Stub D, et al. Air Versus Oxygen in ST-Segment-Elevation Myocardial Infarction. Circulation. 2015 Jun 16;131(24):2143-50. doi: 10.1161/CIRCULATIONAHA.114.014494. Epub 2015 May 22

Circulation 2015 Acute STEMI 441 pts O2 sat Room air > 94% Supplemental O2 (L/min) vs Room air

Circulation 2015 Hypoxemia was not common Only 7.7 % of patients allocated to RA had O2 sat < 94% No evidence that supplemental O2 improved Hemodynamics Symptoms Suggestion that supplemental O2 Increased acute myocardial injury (cardiac enzymes) Increased infarct size at 6 months (cardiac MR) Why? O2 reduces coronary blood flow O2 increases coronary vascular resistance

STEMI and O2 Therapy The Questions and the Answers Does supplemental oxygen increase myocardial oxygenation? Is supplemental oxygen beneficial to all patients with myocardial ischemia, myocardial infarction? There is evidence that in the patient with acute STEMI and O2 sat > 94% on room air supplemental O2 is: Not beneficial May increase acute myocardial injury and subsequent infarct size Reserve supplemental O2 for those with O2 sat < 94% Copyright © 2016

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