Release of bioactive interleukin 6 but not of tumour necrosis factor-α after elective cardiopulmonary bypass

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Abstract
This study examined whether the cytokine tumour necrosis factor-α (TNF) and interleukin 6 (IL-6) were released during and after elective coronary artery bypass grafting (CABG) in 13 patients. In five patients, arterial and coronary sinus blood samples were taken five, 10 and 30 minutes after aortic declamping to evaluate the possibility of release or trapping of the cytokines in the coronary circulation during reperfusion after cold cardioplegic arrest. TNF and IL-6 were measured by sensitive bio-assays. TNF bio-activity could not be detected in any sample during or after surgery in any patient. IL-6 was not detected in intra-operative blood samples, including those from the coronary sinus. However, postoperative IL-6 release was demonstrated in all patients, with peak values at eight hours postbypass. There was no correlation between I L-6 concentrations and the fever response (r = 0.42, p >0.05). A weak relationship was noticed between IL-6 and total operation time (r= 0.69, p <0.05). The IL-6 response was markedly depressed in one patient on long-term pre-operative steroid medication.