Profound haemodilution during normothermic cardiopulmonary bypass influences neither gastrointestinal permeability nor cytokine release in coronary artery bypass graft surgery

Abstract

Background. Cardiopulmonary bypass (CPB) impairs intestinal barrier function and induces systemic inflammation after cardiac surgery. The objective of this study was to evaluate the effect of profound haemodilution (haematocrit 19-21%) during normothermic CPB on gastrointestinal permeability and cytokine release in comparison with a standard haemodilution (haematocrit 24-26%). Methods. This was a prospective, controlled, randomized pilot trial of 60 patients without gastrointestinal disease undergoing normothermic CPB (35.5-36°C) for coronary artery bypass graft surgery. Gastrointestinal permeability was measured by the triple-sugar technique (sucrose, lactulose, and mannitol excretion in urine) before and after CPB. Interleukin (IL)-6, IL-10, and tumour necrosis factor alpha (TNFα) were quantified using enzyme-linked immunosorbent assays. Results. Data from 59 patients (19-21% haematocrit, n=28; 24-26% haematocrit, n=31) were analysed. Data on gastrointestinal permeability were available for 47 patients (19-21% haematocrit, n=23; 24-26% haematocrit, n=24), blood samples for cytokine analysis from 59 patients. Mannitol excretion was normal before and after surgery without significant differences between the groups (after operation: 5.4% vs 2.9, P=0.193). Lactulose and sucrose excretion was within a normal range before surgery and increased afterwards without differences between the groups. IL-6, IL-10, and TNFα were elevated after surgery, but there was no difference between the groups [IL-6 (P=0.78), IL-10 (P=0.74), and TNFα (P=0.67)]. Conclusions. Profound haemodilution during normothermic CPB brought about significant changes neither in intestinal permeability nor in cytokine release. It may be concluded that a haematocrit of 19-21% during normothermic CPB does not impair intestinal barrier function and cytokine response in patients without gastrointestinal comorbidity.