Sympathetic
blockade and hyperbaric oxygen exposure improved transcutaneous oxygen tension
in healthy volunteers.
Clinical Bottom Line:
1.The
combination of sympathetic block and hyperbaric oxygen administration improved
PtcO2 more than either administered alone in healthy volunteers.
Appraised
by: Mike Bennett, Dept of Diving and
Hyperbaric Medicine, Prince of Wales Hospital
Sydney; Saturday, 10 July 1999
Clinical
Scenario: A patient with peripheral
vascular disease presented with a problem wound. Three-part
Question: In patients receiving hyperbaric oxygen, does the administration
of a sympathetic block result in improved oxygenation of the tissues?
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Terms: hyperbaric oxygenation,
sympathetic block
The
Study:
Double-blinded concealed
randomised cross-over trial with intention-to-treat.
Healthy volunteers.
Control group (N = 10; 10
analysed): One injection of 20mls of isotonic saline surrounding the brachial
plexus via the axillary route prior to placement in the hyperbaric chamber.
Exposure was at 2ATA, breathing 100% oxygen for 60 minutes.
Experimental group (N = 10; 10
analysed): As above, but injection was of 20mls of 1% lignocaine.
The
Evidence:
Non-Event
Outcomes
Time to outcome
Saline group Lignocaine group
P-value
Increase
in PtcO2
on
compression
1 hour
130mmHg
350mmHg
<0.05
PtcO2
at 2ATA
1 hour
171mmHg
410mmHg
<0.05
Comments:
1. A rise in skin temperature
(1C) and axillary blood flow (23%) was noted in the lignocaine group prior to
compression.
2. The injection of placebo
solution may have had some effect on PtcO2 response on compression due to
reduction in axillary blood flow (reduced from 24 to 17ml/s).
3. It is not known if the
response shown would be reproduced in patients with abnormal peripheral vessels.
Expiry date: March 2003
References:
1. Thomas PS, Hakim TS, Trang LQ,
Hosain SI, Camporesi EM. The synergistic effect of sympathectomy and hyperbaric
oxygen exposure on transcutaneous PO2 in healthy volunteers. Anesthesia and
Analgesia 1999; 88:67-71.
