Postoperative morbidity following cardiopulmonary bypass may be attributed to endotoxemia

Introduction

Increased concentrations of endotoxin (ET) have been measured in the plasma of patients undergoing cardiopulmonary bypass (CPB), however the significance of the increase is uncertain. Using a new rapid, reliable, whole blood method for ET detection, we sought to determine the prevalence of endotoxemia in a group of patients undergoing CPB, and describe the relationship between endotoxemia and postoperative morbidity.

Design

Prospective, observational trial in a Canadian tertiary medical centre.

Subjects

Twenty-seven patients undergoing coronary artery bypass graft surgery (CABG) or valvular heart surgery.

Methods

Whole blood samples (1 ml) were drawn at arterial line insertion, immediately postoperative, and at 24 h. Known pre-operative risk factors were assessed and subjects were assigned a mortality risk score [1]. MOD [2] scores and APACHE II scores were calculated at 24 h or at discharge from CVICU.

Results

Fourteen patients had CABG, 8 had mitral valve repair, 5 had aortic valve repair. Two patients died >48 h postoperatively. 22/27 patients (81%) had preoperative ET levels >50 pg/ml. All 5 pre-op ET negative patients had levels >50 pg/ml following surgery. There was no correlation between pre-op ET levels and indication for surgery, degree of left ventricular function or preoperative mortality risk score. Postoperative mean ET levels were significantly different from baseline levels (195.2 ± 224.0 vs 399.7 ± 282.8 pg/ml [P = 0.003]). Using univariate linear regression analysis, postoperative ET levels were associated with increased MOD score at 24 h (P < 0.05) and prolonged hospital stay (P < 0.05).

Conclusion

We found that patients undergoing cardiac surgery and CPB have high mean baseline ET levels. ET levels significantly increased following CPB and were associated with measures of increased morbidity such as MODS and hospital length of stay. Measuring ET using a rapid reliable assay, identifies a group of patients where perioperative treatment with an anti-endotoxin strategy, or alterations in perfusion related factors may be beneficial.