Hyperbaric
oxygenation prevents the development of delayed neuropsychological sequelae in
mild/moderately severe carbon monoxide poisoning.
Clinical Bottom Line:
1.
HBO decreased the incidence of delayed neuropsychological sequelae.
2.
The entry level of COHb was not predictive of DNS.
3.
All patients with DNS recovered to base-line scores during further follow-up.
Appraised
by: Mike Bennett, Dept of Diving and
Hyperbaric Medicine
Prince of Wales Hospital Sydney;
Friday 2nd October 1998
Clinical
Scenario: Adult with mild to moderate
carbon monoxide poisoning.
Three-part
Question: In patients with carbon
monoxide poisoning, does treatment with HBO in contrast to treatment with NBO,
result in a reduction in the incidence of delayed neurological sequelae?
Search
Terms: Carbon monoxide
poisoning/therapy, hyperbaric oxygenation
The
Study:
Non-blinded randomised
controlled trial with intention-to-treat.
Exposure to products of
combustion and/or high COHb level and/or symptoms and signs suggestive of CO
poisoning. Excluded if unconscious at any time or evidence of myocardial
compromise.
Control group (N = 32; 30
analysed): 100% oxygen via face mask until symptoms resolved, (ave 4.2 hours).
Experimental group (N = 33; 30
analysed): 100% oxygen as above until HBO instituted at 2.8ATA for 30 mins, then
2.0ATA for 90 mins, (ave total time 2.1 hours).
The
Evidence:
|
Outcome |
Time
to Outcome |
Control
Group Rate |
HBO
Group Rate |
Relative
risk reduction |
Absolute
risk reduction |
Number
Needed to Treat |
|
Diagnosis
of DNS |
4
weeks |
0.233 |
0 |
100% |
0.233 |
4 |
|
95%
Confidence Intervals: |
|
|
|
|
0.082
to 0.384 |
3
to 12 |
Comments:
1. HBO given early (<6 hours
from exposure in all cases).
2. All DNS patients eventually
recovered.
3. Greatest flaw of the study is
that it was not blinded.
Expiry date: September 2004
References:
Thom SR, Taber RL, Mendiguren II, Clark JM, Hardy KR, Fisher AB. Delayed
neuropsychologic sequelae after carbon monoxide poisoning: prevention by
treatment with hyperbaric oxygen.Ann Emerg Med. 1995 Apr;25(4):474-80.
