title: Does the duration of cardiopulmonary bypass or aortic cross-clamp, in the absence of blood and/or blood product administration, influence the IL-6 response to cardiac surgery?
abstract: Cardiopulmonary bypass (CPB) induces a systemic inflammatory response characterized by release of proinflammatory cytokines, including interleukin 6 (IL-6). Recent reports suggest that plasma IL-6 is increased after CPB. Previous studies evaluating the influence of duration of CPB and/or aortic cross-clamp time on the release of IL-6 are conflicting. Infusion of blood and blood products during these studies may have influenced plasma concentrations of proinflammatory cytokines by inducing host cell (monocyte) activation and IL-6 release. The purpose of our investigation was to determine, in an environment free from blood and/or blood product administration, the influence of duration of CPB and/or aortic cross-clamp on the magnitude of the IL-6 response in patients undergoing cardiac surgery. We prospectively evaluated plasma IL-6 levels preinduction (T0) and at sternal closure in 16 patients undergoing CPB (coronary artery bypass grafting, n = 9; valvular cardiac surgery, n = 7) to determine whether there is a correlation between the absolute increase in IL-6 and the duration of CPB or aortic cross-clamp time. None of the patients received blood and/or blood products during the study to control for the introduction of additional activated cells and soluble mediators, including IL-6. The results demonstrate that the magnitude of the IL-6 response to CPB is positively correlated with the duration of CPB but not with duration of aortic cross-clamp. It seems that induction of IL-6 release is part of a normal response to CPB and does not depend on activation of host cells during prolonged aortic cross-clamp. The activation or presence of inflammatory cytokines associated with administration of blood and/or blood products could have influenced previously published investigations relating the influence of duration of CPB and/or aortic cross-clamp time to the magnitude of the IL-6 response.
  
  
  CONCLUSIONS
  This study found a positive correlation between the magnitude of the interleukin 6 response to cardiopulmonary bypass and duration of cardiopulmonary bypass (but not duration of aortic cross-clamp) when measurements were made in the absence of blood/blood product transfusion. Future studies evaluating strategies to reduce cytokine responses to cardiopulmonary bypass should therefore control for cardiopulmonary bypass duration.
authors.affiliation: Department of Anesthesiology and Pain Management, University of Texas Southwestern Medical Center at Dallas 75235-9068, USA. cwhitt@mednet.swmed.edu
authors.forename: C W
authors.initials: CW
authors.lastname: Whitten
authors.forename: G E
authors.initials: GE
authors.lastname: Hill
authors.forename: R
authors.initials: R
authors.lastname: Ivy
authors.forename: P E
authors.initials: PE
authors.lastname: Greilich
authors.forename: J M
authors.initials: JM
authors.lastname: Lipton
mesh_terms: D000328:Adult; D000368:Aged; D001011:Aorta / Q000502:physiology; D002315:Cardiopulmonary Bypass; D005260:Female; D006801:Humans; D015850:Interleukin-6 / Q000097:blood*; D008297:Male; D008875:Middle Aged; D013997:Time Factors
chemical_list: D015850:Interleukin-6