Surgical trauma leads to impairment of the interleukin (IL)-12/interferon-gamma (IFNγ) pathway, which is in turn associated with increased risk of nosocomial infection. Although cardiopulmonary bypass is known to modulate several systemic inflammatory responses, its effect on this cytokine pathway is not well-studied.
We measured IFNγ synthetic capacity in 43 patients scheduled for on-pump (Group 1; N=25) or off-pump (Group 2; N=18) open-heart surgery. Preoperative and postoperative whole blood was cultured for 18 hours with 0.01% fixed Staphylococcus aureus and plasma IFNγ levels were determined by ELISA.
Cardiac surgery was associated with a significant decline in IFNγ production, from a median of 400.0 pg/ml preoperatively (range 7.8–4912.0), to 13.5 pg/ml postoperatively (range 7.8–1825.2; N=43; P<0.001, Wilcoxon’s signed ranks test). There was no significant difference in preoperative or postoperative IFNγ production between Group 1 and Group 2. Interestingly, subjects under age 65 exhibited a significantly greater postoperative IFNγ synthetic capacity than those 65 years or older (P=0.007, Mann-Whitney’s U test). Sub-group analysis showed that this age-related difference was primarily found in Group 2 patients. Within Group 2, median postoperative IFNγ levels were 1005.0 pg/ml (range 36.9–1825.2; N=5) in subjects less than 65 years and 13.5 pg/ml (range undetectable to 383.5; N=13) in subjects age 65 and older (P=0.004).CONCLUSIONS: Elective cardiac surgery is associated with a significant decrease in IFNγ synthetic capacity in response to microbial stimuli. Our data suggest that post-surgical depression of IFNγ production is less severe in younger patients. This age-related preservation seems to be abrogated, however, by use of cardiopulmonary bypass.
Significant depression of IFNγ production in older patients undergoing cardiac surgery may contribute to the infectious complications seen in this population.
G.K. Yadavalli, None.