Cerebrovascular cytokine responses during coronary artery bypass surgery: Specific production of interleukin-8 and its attenuation by hypothermic cardiopulmonary bypass

Brain dysfunction after cardiopulmonary bypass (CPB) is common, and it has been hypothesized that this injury might be due partly to activation of inf lammatory processes in the brain. We measured juguloarterial gradients for interleukin-1 beta, interleukin-6, and interleukin-8 (IL-8) as indices of l ocal proinflammatory cytokine production in the brain and studied the effec t of temperature during CPB on these changes. Twelve patients undergoing co ronary artery bypass graft surgery (normothermic CPB n = 6, hypothermic CPB n = 6) were studied. Cytokine levels were measured in paired arterial and jugular bulb samples obtained before, during, and after CPB. Although syste mic levels of all three cytokines increased during and after CPB, increases in juguloarterial cytokine gradients were observed only for IL-8. Juguloar terial IL-8 gradients started to increase 1 h post-CPB and were significant ly elevated 6 h post-CPB (P < 0.05). At this time point, the median (interq uartile range) juguloarterial IL-8 gradients were significantly larger in t he normothermic CPB group (25.81 [24.49-39.51] pg/mL) compared with the hyp othermic CPB group (6.69 [-0.04 to 15.47] pg/mL; P < 0.05). These data impl y specific and significant IL-8 production in the cerebrovascular bed durin g CPB and suggest that these changes may be suppressed by hypothermia durin g CPB. Implications: Using juguloarterial gradients to measure cerebrovascu lar cytokine production is novel in the setting of cardiopulmonary bypass a nd implicates the cerebral activation of inflammatory processes, which may contribute to brain dysfunction. Hypothermia during cardiopulmonary bypass may significantly attenuate this response.