Can selective digestive decontamination avoid the endotoxemia and cytokine activation promoted by cardiopulmonary bypass?

Objective: To evaluate the effect of selective digestive decontamination on endotoxemia and cytokine activation during the ischemic phase of cardiopulmonary bypass surgery.

Design: Prospective, open, randomized, controlled trial.

Setting: Two multidisciplinary intensive care units in tertiary care hospitals.

Patients: Eighty consecutive patients randomly allocated to two groups: selective digestive decontamination (group 1, n = 40) and controls (group 2, n = 40).

Interventions: Preoperative administration of oral antibiotics (polymyxin E, tobramycin, and amphotericin B) vs. untreated controls.

Measurements And Main Results: Assessment of decontamination by bacteriologic evaluation of rectal swabs (colony-forming units [cfu]/mL) were made in each group, along with circulating endotoxin, tumor necrosis factor and interleukin-6 (IL-6) determinations before surgery, during ischemic and reperfusion phases of bypass, and at 4 hrs and at 24 hrs after surgery. Group 1 patients showed that rectal bacteria decreased ten-fold after treatment for 24 hrs, thousand-fold after 48 hrs, and registered 0 cfu/mL after digestive decontamination was administered for > 72 hrs. Endotoxin and IL-6 assays showed significantly lower values in this latter group vs. those circulating concentrations of control patients. On the other hand, both endotoxin and IL-6 concentrations correlated positively with the duration of surgical ischemia.

Conclusions: Selective digestive decontamination reduces the gut content of enterobacteria, with complete elimination after 3 days of treatment. This fact could explain the lower endotoxin and cytokine concentrations found in the blood samples of patients who had been fully decontaminated. Duration of aortic cross-clamping is an important factor in generating endotoxemia and in the activation of cytokines.