JOURNAL CLUBO2 in STEMI

By Nicholas NguaEmergency Unit

UHW

Air Versus Oxygen in ST-Segment Elevation Myocardial InfarctionAVOID Study

Published in Circulation. 2015 Jun 16;131(24):2143-50. doi: 10.1161/CIRCULATIONAHA.114.014494. Epub 2015 May 22

by Stub et al

Background

Oxygen therapy commonly used in initial treatment in STEMI – MONA Morphine Oxygen Nitrates Aspirin

There are a little evidence that suggest oxygen may do more harm than good

Cochrane review in 2013 conclusion: no conclusive evidence – suggest an RCT

Clinical Question

Among normoxic patients with STEMI, does supplemental oxygen therapy vs no supplemental oxygen therapy increase myocardial infarct size?

Design

Multicenter, randomised, open label, randomised N = 441

Oxygen (n=218) No oxygen (n=223)

Setting: 10 centers in Melbourne, Australia (24 hr PCI center)

Enrollment: October 2011 till July 2014 Follow up: 6 months Analysis: Intention to treat Powe : Witholding O2 may influence myocardial injury by

20%, -level set at 0.01α

Population

Inclusion Criteria ≥ 18 yr old Chest pain <12 hours Prehospital ECG –

STEMI

Exclusion Criteria SpO2 < 94% Bronchospasm

requiring neb with O2 O2 prior to

randomisation Altered conscious

state Transport to non

studied hospital

Intervention Facemask 8L/min – continued until transfer to

cardiac care ward

Control No oxygen unless O2 fell below 94% - NC

4L/min or Facemask 8L/min

Both groups initiated on aspirin 300mg by paramedics

Results (Primary)

Geometric Mean Peak Trop I Oxygen 57.4 mcg/L No Oxygen 48 mcg/L (p=0.18)

Geometric Mean Peak CK Oxygen 1948 U/L No Oxygen 1543 U/L (p=0.01)

Results (Adverse Events)

Death by Hospital Discharge Oxygen 1.8% No Oxygen 4.5% (p=0.11)

Recurrent MI Oxygen 5.5% No Oxygen 0.9% (p=0.006) NNH = 21

Major Cardiac Arrthymia Oxygen 40.4% No Oxygen 31.4% (p=0.05)

Results (CMR)

32% underwent CMR Oxygen 65 No Oxygen 74

Median Infarct Size Oxygen 20.3g No Oxygen 13.1g (p=0.04)

% Infarct of LV Oxygen 12.6% No Oxygen 9.0% (p=0.08)

Conclusion

In normoxic patients, routine O2 administration was not associated with reduction in symptoms accompanied by harm as reflected by

significant CK rise larger infarct size by CMR at 6 months

Questions

Does the primary outcome reflects infarct size? Does infarct size reflects clinical outcome? What are the current guidelines on STEMI

regarding oxygen supplements? What are your practices with STEMI or even NSE-

ACS? Assuming the conclusion of the study is not a

Type I error, how can you explain in terms of pathophysiology

Questions

Does the actual PaO2 matters? Are you convinced after this paper regarding

switching of practice of not giving routine oxygen supplementation?

Questions

What is the primary outcome of this study? Do you think this is appropriate?

What is intention to treat analysis? Give two advantages and two disadvantages of this method of analysis.

At the end of this journal club, Dr Jo Mower asks you whether it should be introduced in your department. Give reasons to support your stand.

THANK YOU

Thank Prof for editing the slides

Next Journal Club on 9 September 2015

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