Is gastric malperfusion and endotoxemia one motor of the systemic inflammatory response syndrome following cardiac surgery?

We evaluated one group with low risk for developing SIRS (Group1: coronary artery bypass grafting without CHF) and a high risk group (Group 2: mitral valve surgery with CHF) with 10 patients each for clinical and laboratory signs of SIRS as defined by BONE. Intramucosal gastric pH, endotoxin was detected using a tonometric gastric tube (Baxter Inc.), TNFα and interleukin 6 (IL6) were measured with an ELISA at nine different times pre-, intra- and postoperatively.Groups were similar with regards to age and sex. Cardiac Index was lower in Group 2 (1.7 ± 0.3 l/min/cm3) than in Group 1 (2.8 ± 0.5 l/min/cm3; P < 0.05). In Group 2 the aortic cross clamping time was longer (Group 1: 59.6 ± 15.2 min, Group 2: 42.7 ± 19.4 min) and norepinephrine requirements for maintenance of vascular resistance were higher (8.2 ± 12.6 mg) than in Group 1 (1.7 ± 2 mg; P < 0.05).At the end of CPB gastric pH dropped to 7.33 ± 0.34 in Group 2 whereas the other group remained stable between 7.47 and 7.5 (P < 0.05). Endotoxin levels were significantly elevated and significantly higher in Group 2 (37.2 ± 3.2 pg/ml) than in Group 1 (20.6 ± 3.7 pg/ml; P < 0.05) after aortic cross clamp was opened. In Group 1 only in 1 of 3 patients (33%) with gastric acidosis endotoxin was detected, whereas in Group 2 8/9 patients (88%) endotoxemia occurred.TNFα was elevated in both groups during CPB and significantly higher in Group 2 at aortic declamping (Group 1: 19.6 ± 2.9 pg/ml; Group 2: 39 ± 4.8 pg/ml; P < 0.05) and after protamin application (Group 1: 27.3 ± 4.2 pg/ml; Group 2: 62.8 ± 8.1 pg/ml; P < 0.05). After protamin application IL6 raised postoperatively and was significantly higher in Group 2 (653 ± 75 pg/ml) than in Group 1 (547 ± 439 pg/ml). SIRS occurred more often in Group 2 (9/10) than in Group 1 (6/10) postoperatively. All patients with detected endotoxemia developed SIRS (13/13). (see Figure).SIRS is more common in patients with CHF undergoing CPB than in others. This seems to be related to a dr