Preoperative hyperbaric oxygenation reduced psychometric dysfunction and some systemic inflammatory markers following cardiac bypass and surgery

1. Pre-operative HBOT was associated with a reduced chance of neuropsychiatric deficit when defined as a reduction of >1 standard deviation in two of seven tests
2.  HBOT may reduce the increase in some markers of systemic inflammation, including ICAM-1, CD-18 and heat shock protein 70,  but not others.

Citation:
1. Alex J, Laden G, Cale A, Bennett S, Flowers K, Madden L, Gardiner E, McCollum T, Griffin S. Pretreatment with hyperbaric oxygen and its effect on neuropsychometric dysfunction and systemic inflammatory response after cardiopulmonary bypass: A prospective randomised double-blind trial. Journal of Thoracic and Cardiovascular Surgery 2005;130(6):1623-30.

2. Alex J. Yogartnam JZ, Laden G, Cale ARJ, Bennett S, Guvendik L, McCollum PT, Griffin SC. Hyperoxic hyperbaric pre-conditioning induces neuroprotection and attenuates the systemic inflammatory response in a human model of ischemic reperfusion injury. European Journal of Hyperbaric Medicine 2005; 6(3):76-77.
Lead author's name and fax: Joseph Alex mrjosephalex@yahoo.co.uk

Three-part Clinical Question: For patients having cardiac operations using cardiopulmonary bypass, does pre-treatment with hyperbaric oxygen versus a standard approach result in a reduction in neuropsychiatric deficit and/or systemic inflammatory response?
Search Terms: Cardiac surgical procedures, neuropsychology, inflammation mediators

The Study:
Double-blinded randomised controlled trial with intention-to-treat.
The Study Patients: Adults without cerebrovascular disease or immunosuppresion having routine cardiac procedures using CPB
Control group (N = 31; 31 analysed): Sham procedure at 24, 12 and 4 hours before operation breathing air at 1.5 ATA for 60 minutes
Experimental group (N = 33; 33 analysed): 100% oxygen at 2.4 ATA on the same schedule

The Evidence:

Outcome

Time to Outcome

Sham group

HBO group

Relative risk reduction

Absolute risk reduction

NNT

>1 SD deterioration in two or more NPTs

4 months

0.52

0.27

47%

0.24

4

95% Confidence Intervals:

2% to 92%

0.01 to 0.48

2 to 95

 

 

Non-Event Outcomes

Time to outcome/s

Control group

Experimental group

ANOVA for CD-18 at pre-op, 2 hrs and 24 hours post-op within each group (units unknown). No between group comparison.

24 hours

P = 0.1

(63.6 to 83.8 at 2 hours)

P = 0.001

(63.3 to 77.5 at 2 hours)

 

Comments:
1. Numbers reaching follow-up not indicated, no sample size calculations or 95% CI for main outcome
2. There are practical difficulties with three pre-operative hyperbaric sessions

3. No direct comparison between groups for any inflammatory marker changes 

4. The impact on daily life of the overall decrement in neuropsychological testing is not clear
4. The zero time for inflammatory mediators is after HBOT, making interpretation difficult
5. Those with previous myocardial infarction were over-represented in the HBOT group (31% versus 10%) which may bias outcome, direction unknown.
6. There is information in the abstract that does not appear in the main text and no units for the inflammatory markers
7. Overall good methodological study with a result that is difficult to interpret

Appraised by: Sean Hopson, Antonia Edge & Mike Bennett, Diving and Hyperbaric Medicine, Prince of Wales Hospital, Sydney ; Friday, 26 May 2006
Email: m.bennett@unsw.edu.au
Kill or Update By:  August 2008