ArticlesEffect of preoperative oral immune-enhancing nutritional supplement on patients at high risk of infection after cardiac surgery: a randomised placebo-controlled trial
Introduction
Elderly patients and patients with poor ventricular function who are undergoing cardiac operations with hypothermic cardiopulmonary bypass have increased postoperative morbidity and mortality rates.1 Host defence can be diminished by nutritional deficiencies, hypoperfusion, anaesthesia, and operative trauma. Immune function is also depressed by use of cardiopulmonary bypass and hypothermia.2 Results of studies have suggested that L-arginine can improve postoperative outcome in patients having cardiac surgery, and ω3 polyunsaturated fatty acids can restrict the postoperative generalised inflammatory response.3
Experimental studies have shown that the use of nutritional supplements containing L-arginine, ω3 polyunsaturated fatty acids, and nucleotides boost immune responsiveness after surgery or trauma.3 L-arginine is a semi-essential aminoacid and a precursor of nitric oxide, the most important endothelial vasodilator. In experimental studies,4, 5, 6 L-arginine improved wound healing, restored postoperative depressed macrophage function and lymphocyte responsiveness, and augmented resistance to infections. Arginine protected against ischaemia-reperfusion injury by increasing oxygen delivery upon reflow, thereby improving cardiac function. Intake of additional ω3 polyunsaturated fatty acids alters cell-membrane phospholipid content and prostaglandin synthesis.3, 7 This alteration might be an important factor in suppression of the generalised inflammatory response and subsequent immunosuppression and capillary leakage after major surgery.3, 8, 9 Purines and pyrimidines are semi-essential nutrients for rapidly dividing cells.10 Administration of nucleotides in the form of yeast RNA has improved the host immune response to infections.10, 11
These three immunonutrients have been combined into a single enteral feed. For trauma patients, critically ill patients, and those who are undergoing surgery for cancer, use of this immune-enhancing formula after surgery has improved immunocompetence, reduced infections, and shortened length of stay in hospital.12 The effect of postoperative immune-enhancing nutrition starts after 3 days and seems to be dose dependent.13 For this reason, an oral immune enhancing nutritional supplement before surgery might be beneficial. L-arginine, ω3 polyunsaturated fatty acids, and yeast RNA have been combined into a single oral immune-enhancing nutritional supplement. We aimed to ascertain whether this oral immune-enhancing nutritional supplement taken for at least 5 days before an operation in high-risk patients undergoing cardiac surgery improves preoperative host defence and subsequently reduces postoperative infections and organ dysfunction.
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Patients
We selected 50 patients who were scheduled to undergo cardiac surgery and met one or more of the following criteria: age 70 years or older, ejection fraction less than 0·40, or replacement of mitral valve. All patients gave written informed consent. Patients were excluded if they were younger than 21 years, were pregnant, had insulin-dependent diabetes mellitus, had severe renal or liver failure or both, had a known malignancy, used immunosuppressive medication, or used non-steroidal
Discussion
In this study, we investigated the effect of an oral immune-enhancing nutritional supplement on preoperative host defence, incidence of infections, and postoperative organ function. We recorded a significant increase in preoperative serum arginine concentration, indicating good substrate bioavailability and good compliance of patients to their supplemental diet. This increase in serum arginine concentration was close to concentrations previously reported.22 Our results show that intake of an
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