Immunonutrition in patients who underwent major abdominal surgery: A comprehensive systematic review and component network metanalysis using GRADE and CINeMA approaches.

Background: The benefits of immunonutrition in patients who underwent major abdominal surgery have been recently established, but the optimal combination of immunonutrients has remained unclear. The aim is to clarify this point.

Methods: A systematic search of randomized clinical trials about immunonutrition in major abdominal surgery was made. A frequentist random-effects component network meta-analysis was conducted, reporting the P score and odds ratio or mean difference with a 95% confidence interval. The best components and best plausible strategies were described. The critical endpoints were morbidity and mortality rates. The important endpoints were infectious complication rate and length of stay.

Results: The meta-analysis includes 87 studies and 8,375 patients. The best approach for morbidity rate, with a moderate grade of certainty, was the use of perioperative enteral/oral immunonutrition with arginine, glutamine, and polyunsaturated fatty acids (odds ratio 0.32; 0.10 to 0.98; P score of 0.93). The mortality rate was reduced by postoperative enteral immunonutrition with RNA, arginine, and polyunsaturated fatty acids (odds ratio 59; 0.29 to 1.22; P score 0.84) but with a low grade of certainty. No significant heterogeneity or incoherence is observed. The length of stay and infectious results are "at risk" for high heterogeneity or network meta-analysis incoherence. The component analysis confirmed that postoperative oral/enteral use of 2 or 3 components is crucial to reducing morbidity rate.

Conclusion: The oral/enteral immunonutrition in the postoperative period, with multiple immunonutrients, can reduce the morbidity rate in patients undergoing major abdominal surgery. The effect of immunonutrition on mortality, infectious disease, and length of stay is unclear.