Pre-treatment of patients undergoing cardiopulmonary bypass with hyperbaric oxygen : a prospective randomised double-blind evaluation of inflammatory response and neurocognitive outcome
Over the past few decades, implementation of findings from scientific research and incorporation of technological advances into practice have produced a significant reduction in the morbidity and mortality from coronary revascularisation. Despite these improvements subtle neurocognitive impairment, from diffuse cerebral injury due to micremboli during cardiopulmonary bypass, continues to occur following cardiac surgery. Previous human and animal studies have shown that hyperbaric oxygen can reduce some of the mediators of inflammation. Evidence from animal experiments also suggest that pretreatment with hyperbaric oxygen can induce cerebral and spinal ischaemic tolerance. Using the prospective randomised double-blind method we set out to test the hypothesis that pretreatment with hyperbaric oxygen could reduce inflammatory mediators and neurocognitive dysfunction following cardiopulmonary bypass. 64 patients undergoing elective coronary revascularisation were either randomised to Group- A (air, 1.5 atmospheres absolute, n-31) or Group-B (hyperbaric oxygen, 2.4 atmospheres absolute, n-33). Both groups were comparable in terms operative and perioperative factors. Inflammatory markers were measured prior to anaesthesia and, 2 hours and 24 hrs after bypass. Neurocognitive assessment was performed 48 hours before the operation and 4 months after the operation. Neurocognitive impairment was defined as ≥1standard deviation (SD) decline in postoperative score in more than 20% of the neurocognitive tests. ANOVA, t-test and Chi-square tests was used as appropriate for statistical analysis. There was no difference in immediate postoperative clinical outcome. However analysis of variance revealed that the postoperative peak rise in the inflammatory markers soluble endothelial selectin (sE-selectin), heat shock protein-70 (HSP-70) and cluster differentiation antigen-IS (CD-IS) which was significant in group-A was not so in group-B. Analysis of data from the neurocognitive tests also revealed that the overall neurocognitive dysfunction was significantly higher in group-A compared to group-B. From our findings we concluded that pre-treatment with hyperbaric oxygen may have a potential beneficial role in reducing neurocognitive impairment and reducing some of the inflammatory mediators following cardiopulmonary bypass. Larger multi-centre prospective randomised trials are needed to further evaluate this form of therapy.