Hyperbaric
oxygen may reduce mortality following myocardial infarction in a heterogenous
group of patients.
Clinical Bottom Line:
1.
There is significant reduction in early mortality by the addition of
hyperbaric oxygen, after
adjustment for severity of clinical condition.
Appraised
by: Mike Bennett, Dept of Diving and
Hyperbaric Medicine
Prince of Wales Hospital,
Sydney; Thursday, 17 December, 1998
Clinical
Scenario:
A 56 year old man with an acute myocardial infarction.
Three-part
Question: In patients with recent acute
myocardial infarction, does the addition of hyperbaric oxygen in addition to
standard care, result in any reduction in mortality rate in the early
post-infarction period?
Search
Terms: Hyperbaric oxygenation,
myocardial infarction.
The
Study:
Non-blinded randomised
controlled trial with intention-to-treat.
Patients under seventy where
there was a strong clinical suspicion of MI occurring within 24 hours of
presentation and without specific contraindication to HBO.
Control group (N = 105; 105
analysed): Full orthodox coronary care regime including oxygen by mask at
6l/min. No sham treatment.
Experimental group (N = 103; 103
analysed): As above but patients were given oxygen 100% at 2ATA for two hours,
followed by air for one hour in a repeating cycle for 48 hours.
The Evidence:
|
Outcome |
Time
to Outcome |
Control
Rate |
HBO
Rate |
Relative
risk reduction |
Absolute
risk reduction |
NNT |
|
Mortality |
3
weeks |
0.23 |
0.17 |
28% |
0.064 |
16 |
|
95%
CI: |
|
|
|
-19%
to 75% |
-0.04
to 0.17 |
NNT=
6 to INF NNH= 23
to INF |
Non-Event
Outcomes
Time to outcome
P-value
Regression
of mortality
on
HBO and severity
score
3 weeks
0.03
Comments:
1. Patients of widely differing
severity were included and when the mortality is adjusted for severity (using an
index), there may be an important effect of hyperbaric oxygen.
2. 23 patients in the HBO group
did not actually receive HBO for a variety of reasons, mainly claustrophobia.
3. 12 patients initially entered
were excluded due to misdiagnosis or wrong age.
Expiry
date:
October 2004
References:
1. Thurston GJ, Greenwood TW, Bending MR, Connor H, Curwen MP.
A controlled investigation into the effects of hyperbaric oxygen on mortality
following acute myocardial infarction. Quarterly Journal of Medicine 1973;
XLII:751-770.
