Changes of gut barrier function during anesthesia and cardiac surgery

The aim of this clinical study was to investigate the time sequence between intraoperative and postoperative endotoxemia, changes in intramucosal pH(I), mediator release, and acute phase proteins and their relationship to postoperative infections. In 60 patients (median age 61 [33-72] years, male/female: 50/10) plasma levels of endotoxin, endotoxin neutralizing capacity (ENC), leukotriene-C4 (LTC4), 6-ketoprostaglandin-F-1alpha (PGF), thromboxane-B2 (TxB2), interleukin-6 (IL-6), and C-reactive protein (CRP) were measured before, during, and after cardiac surgery. The intraluminal pH(I) of the stomach was assessed as a marker of splanchnic blood circulation. Patients were divided in one group with postoperative infections (group A, n = 8) and another groups without infections (group B, n = 52). Among all measured parameters, endotoxin plasma levels showed the most rapid changes. A significant increase of endotoxin plasma levels and a decrease in ENC appeared after the induction of anesthesia, culminating in a peak after reperfusion. Endotoxin showed a significantly higher increase in group A (14fold) compared to group B (sixfold, p<0.001), whereas ENC decreased by eightfold in both groups. The parameters of the arachidonic cascade increased and pH(I) decreased, however, there were no significant differences between both groups. The latest increase was observed for the acute phase proteins IL-6 and CRP. IL-6 levels peaked 6 hours postoperatively with a 20fold (group B) and 30fold (group A) increase (p < 0.001 vs baseline; no differences between groups), whereas CRP rose at the first postoperative day with a 21 fold (group B) and 25fold (group A) increase at day 2 (p<0.001 vs baseline, no difference between groups). Differences between both groups appeared at the second postoperative day for IL-6 (median values group A/B: 421/219 pg/mL; p <0.05) and at the fifth postoperative day for CRP (median values group A/B: 321/81 mg/L; p < 0.05). In conclusion, endotoxin seems to be the earliest trigger of the mediator cascade in acute phase response and may indicate infections in the postoperative course.