Endogenous endotoxemia of intestinal origin during cardiopulmonary bypass. Role of type of flow and protective effect of selective digestive decontamination.

OBJECTIVE: To evaluate the possible related factors to endotoxemia and cytokine activation during the ischemic phase of extracorporeal surgery, and the effect of selective digestive decontamination (SDD) as a preventive measure. DESIGN: Prospective, open, randomized trial. SETTING: Two multidisciplinary ICUs (tertiary care hospitals). PATIENTS: One hundred consecutive patients undergoing cardiopulmonary bypass (CPB), randomly allocated to two groups; gut decontamination (group I = 50 cases) and controls (group II = 50 cases). INTERVENTIONS: Preoperative administration of oral non-absorbable antibiotics (polymyxin E, tobramycin and amphotericin B) versus no administration. MEASUREMENTS AND RESULTS: The assessment of decontamination by means of the bacteriologic control of rectal swabs. Determinations of gastric intramucosal pH (gastric pHi) and plasma endotoxin, tumor necrosis factor (TNF) aNd interleukin-6 (IL-6) before surgery and during the ischemic and reperfusion phases of bypass. Rectal aerobic Gram-negative bacilli (AGNB) were significantly reduced in the treated patients and in 56% total eradication was achieved. Endotoxin, TNF and IL-6 plasma levels were significantly lower in this group. By contrast, both endotoxin and TNF/IL-6 levels and gastric pHi correlated with the type of surgical flow (pulsatile versus non-pulsatile). CONCLUSIONS: SDD reduces the gut content of enterobacteria. This may explain the lower endotoxin and cytokine levels detected in decontaminated patients. In addition to SDD, the type of flow employed during bypass seems to influence endotoxemia and cytokine levels.

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.

Role of selective digestive decontamination (SDD) in the prevention of nosocomial pneumonia (NP): is gastric decontamination necessary?

In the course of a prospective selective digestive decontamination (SDD) trial to prevent nosocomial pneumonia (NP) during mechanical ventilation (MV), we carried out serial cultures of gastric aspirate to assess the importance of gastric colonization for potential respiratory pathogens and its relationship to the simultaneous gastric pH, to whether the patients were receiving Sucralfate or Ranitidine and to the nutritional biochemical parameters. If NP developed, a bronchial sample was taken by fibreoptic bronchoscopy to determine the causal organisms and its relationship to the previous gastric isolated. Results show: 1) Increase in aerobic Gram negative bacilli colonization during hospitalization. 2) Direct relationship between colonization level and gastric pH. 3) Greater pH in ranitidine vs sucralfate group. 4) Low incidence of NP (11%), the majority of these (66%) being early. 5) No bacteriological correlation between gastric colonization and aetiological agents of NP. 6) Close relationship between pharyngeal colonization and causative germs of pulmonary infection (40%).